Chipseal vs Hotmix

[slofox]

Whilst I may not have the correct technical terms for these two types of road surface, I am sure you all know what I mean by each.
Usually we ride around on chipseal - that very abrasive, noisy stuff with lots of little stones sticking up out of it that is cheap(er) to put down and leaves lots of loose stones after application for bikers to arse off on...(like SH bloody 22 last Sunday)..... On occasion, we are treated to short lengths of hotmix - no stones, nice and smooth and a lot quieter but dear(er) to put down.
What I am interested in is the relative grip that each provides in wet conditions, all other things being equal (to stop all you bloody hair splitters....) Anyone know?

Just as a sideline I also wonder why (like on the Waikato Expressway) you will get about 1km of hotmix in the middle of a 17km run of chipseal? Who the hell decides that? And why? "Ahhhh I'm sick of this bloody chipseal - let's chuck in a km of hotmix, just to wake the drivers up :zzzz:....."??? Bizarre......:weird:

[Okey Dokey]

My personal experience overseas was that hotmix provided considerably less traction in the rain than the rough chip & tar used in NZ.

[sunhuntin]

not knowing anything at all about the two different types aside from difference in looks and noise, id say the chip seal would be better for wet weather braking, provided its been swept of loose stones. the hotmix [smooth stuff?] just seems like its got no grip to it. its due to this assumption that i am always careful going into otaki in the wet, as the road in from the north is lovely and smooth. having the stones sticking up on the chipseal just seems like itd be grippier. [like sand paper compared to normal paper]

in saying that, i love the hot mix by otaki. perfect road right there.

[Big Dave]

Hot mix is laid own as ready mixed asphalt and compressed as such.

Chip seal has bed of tar laid down and then loose stones adhered to and squashed on top of it.

The main reason Australian bikers wear less protective gear is because the roads are made from hotmix and are far less likely to 'betray' them.
Chip seal would just melt over there too.

Hotmix is SIGNIFICANTLY safer for motorcyclists. Provides better wet weather adhesion - because of the uniform surface and greater contact area - and has no likelihood of its surface wearing off and exposing slippery black death.

I was told It is more expensive to lay and more importantly - maintain - in NZ conditions.

$58 million on flow control for the onramps ya know.

[nodrog]

grip is all about surface contact area, as long as there is no standing water hotmix will provide better traction than chipseal.

[davebullet]

From my limited experience, asphalt (hotmix) feels more grippy than chipseal (metal).

There seems to be two types of "flat" road surface. There is the black asphalt and grey ... ?

[slofox]

grip is all about surface contact area, as long as there is no standing water hotmix will provide better traction than chipseal.

Standing water being different from just 'wet'?

[slofox]

The main reason Australian bikers wear less protective gear is because the roads are made from hotmix and are far less likely to 'betray' them.

OH! I see.....I thought they were just.......errrrr.......never mind.....

[Spyke]

Hotmix is SIGNIFICANTLY safer for motorcyclists. Provides better wet weather adhesion - because of the uniform surface and greater contact area - and has no likelihood of its surface wearing off and exposing slippery black death.


I think you hit the nail on the head with that one! :drinknsin

[slimjim]

O crap ...there goes the thread....bloody roo busters...i like hotmix.:drool:..fuck what it costs...i voted national...they'll sack alot of public service people...so they have heaps of spare dosh to send on sticky shit..:lol:

[nodrog]

Standing water being different from just 'wet'?

yes

_________

[Maha]

Chip seal has bed of tar laid down and then loose stones adhered to and squashed on top of it.


Too Technical for me :eek:

See I would have thought stone chip would have the better grip?
While hotmix is nicer to ride/drive on, would it not bleed quicker in hoter conditions? and form ice quicker in colder conditions? than stone chip?

Interesting to read others take on the matter.

[MSTRS]

Generally speaking, the hotmix/asphalt type provides more grip than chipseal. Because of its lower noise, it is often used in higher speed zones adjacent to houses. It is almost always used on roundabouts, because it provides that better grip*, and lasts longer than chip seal. It does tend to get 'pushed' outwards into increasingly large humps (always on our line, of course).

* I have been told by roading people that there are different grades, offering a variety of skid resistance. Of course, the more expensive ones are better, so contractors often use the cheaper one/s despite Transit specs (and prolly charge the higher amount).

[MSTRS]

See I would have thought stone chip would have the better grip?
While hotmix is nicer to ride/drive on, would it not bleed quicker in hoter conditions? and form ice quicker in colder conditions? than stone chip?



No. To all of those.
Why are race tracks laid with some sort of hotmix/asphalt/bitumen? Quite simply, it is superior to chipseal.
It doesn't bleed cos it was never liquid. And it is less likely to ice up, because it is smoother and doesn't retain water (unlike chipseal, where water sits in all the hollows between the individual chips)

[Devil]

See I would have thought stone chip would have the better grip?
While hotmix is nicer to ride/drive on, would it not bleed quicker in hoter conditions? .

Hotmix doesn't bleed like chip seal does. It's much more resilient to temperature and lasts long.
As all ready stated it's all about contact patch. Both types need adequate drainage either way.
Gimme hotmix and lots of it.

[Maha]

Generally speaking, the hotmix/asphalt type provides more grip than chipseal. Because of its lower noise, it is often used in higher speed zones adjacent to houses. It is almost always used on roundabouts, because it provides that better grip*, and lasts longer than chip seal. It does tend to get 'pushed' outwards into increasingly large humps (always on our line, of course).

* I have been told by roading people that there are different grades, offering a variety of skid resistance. Of course, the more expensive ones are better, so contractors often use the cheaper one/s despite Transit specs (and prolly charge the higher amount).

An intersting observation up thisa way John is, most of the stone chip road resealing does not last that long, maybe a year before it starts to flake away. They closed the brynderwyns a couple of weeks back for a day to reseal in Hotmix...went over them last weekend and all they have done is patch here and there, same with the Mangawhai road, surely it would more cost effective to get right the first time, or is it that, if they get it right there wont anything for them to do in a few years? Keeps them employed I guess.

[Maha]

No. To all of those.
Why are race tracks laid with some sort of hotmix/asphalt/bitumen? Quite simply, it is superior to chipseal.
It doesn't bleed cos it was never liquid. And it is less likely to ice up, because it is smoother and doesn't retain water (unlike chipseal, where water sits in all the hollows between the individual chips)


Hotmix doesn't bleed like chip seal does. It's much more resilient to temperature and lasts long.
As all ready stated it's all about contact patch. Both types need adequate drainage either way.
Gimme hotmix and lots of it.

Some days, this place is way better than school use to be!!!

[MSTRS]

...surely it would more cost effective to get right the first time....

Like barriers?
These are quasi-govt departments we are talking about...'nuff said.

Some days, this place is way better than school use to be!!!
And just as pointless?

[nodrog]

Some days, this place is way better than school use to be!!!

except you cant swap your sammies for some better ones

[Maha]

except you cant swap your sammies for some better ones

Hot Chip sammies? :confused:

[BOGAR]

grip is all about surface contact area, as long as there is no standing water hotmix will provide better traction than chipseal.
You could have a chip seal with polished stone giving the look of a good road surface (plenty of chip sticking up) but poor or very poor breaking characteristics.
AC is now mainly used because the process is less disruptive to traffic, quieter and the surface is less likely to fail under turning stress.
But reasons why it is used in one place and not another may just come down to the individual who is in charge.
The surface texture of a pavement-wearing surface is one of the primary contributors to tyre-pavement friction. Both macrotexture and microtexture affect the friction characteristics. As dose pavement smoothness and geometry. :done:

[slofox]

...they'll sack alot of public service people...

Who will then go on the dole and use MORE money than has been saved...:2thumbsup

[slofox]

Keeps them employed I guess.

You got it in one........!!

[Forest]

It's fairly well known that the coarse chip-seal used in the South Island wears down bike tyres quicker than other road surfaces.

Doesn't that meant that chip-seal has better grip?

[Pussy]

It's fairly well known that the coarse chip-seal used in the South Island wears down bike tyres quicker than other road surfaces.

Doesn't that meant that chip-seal has better grip?

No, it just means it's coarser and shreds your tyres!
I totally agree with the positive comments about hotmix/asphalt... superior grip in dry or wet, and no tar bleeding. I'd be happy to see every road surfaced in hotmix

[Forest]

No, it just means it's coarser and shreds your tyres!
I totally agree with the positive comments about hotmix/asphalt... superior grip in dry or wet, and no tar bleeding. I'd be happy to see every road surfaced in hotmix

I don't think that's right.

Chip-seal has a greater resistance to skidding in the wet because it has a higher level of grip than hotmix. Even the road-code acknowledges this:

http://www.ltsa.govt.nz/roadcode/about-driving/road-surface.html

[Pussy]

It is right. You don't see chip seal racetracks, do you? Far better grip with hotmix.... not to be confused with flushing tarseal

[R6_kid]

What is the stuff on the Newmarket fly over? Seems to be a 'coarse' hot mix?

[Forest]

It is right. You don't see chip seal racetracks, do you? Far better grip with hotmix.... not to be confused with flushing tarseal

No. However you do see rather a lot of race-track crashes when it is wet.

I think chip-seal provides superior grip in wet conditions. If anyone has evidence to the contrary, please feel free to post it.

[Forest]

What is the stuff on the Newmarket fly over? Seems to be a 'coarse' hot mix?

I know the answer to this question!

The Newmarket viaduct is suffering from a really bad case of concrete cancer. So they've resurfaced it with a lighter coloured material (I think it is greywacke from the South Island) to prevent it from heating up during summer. That's why it has a different colour to the rest of the Auckland motorway system.

Within the next few years they will build a new viaduct beside the existing one, transfer traffic to the new viaduct, and tear down the old one (the old one doesn't meet the current regulations for seismic resistance).

[Sketchy_Racer]

I don't think that's right.

Chip-seal has a greater resistance to skidding in the wet because it has a higher level of grip than hotmix. Even the road-code acknowledges this:

http://www.ltsa.govt.nz/roadcode/about-driving/road-surface.html

You believe them?

The definition of grip is the amount of friction one can make between two objects. chip seal with its high points and valleys create an illusion of more grip because "its a rough surface" therefore should create more friction. In some ways true, but it also has a lot lower surface area for the tyres to contact on, meaning less available friction between the two.

Why do you think racing tyres are bald or "slick" .. It's to create the maximum amount of area for the tyre to create friction with track. The grooves in your tyres actually reduce the available grip in dry conditions, at a compromise that it helps with water dispersion in the wet.

Hotmix has a much smoother surface giving a much larger area for your tyres to make contact with, therefore creating more grip.

What oil residues on those surfaces change things altogether but for this argument, lets say they are perfectly clean.

[Forest]

You believe them?

The definition of grip is the amount of friction one can make between two objects. chip seal with its high points and valleys create an illusion of more grip because "its a rough surface" therefore should create more friction. In some ways true, but it also has a lot lower surface area for the tyres to contact on, meaning less available friction between the two.

I'm more than happy to agree that hotmix has superior grip in dry conditions.

However I'm inclined to believe that chip-seal has superior grip in the wet.

[Sketchy_Racer]

I'm more than happy to agree that hotmix has superior grip in dry conditions.

However I'm inclined to believe that chip-seal has superior grip in the wet.

Fair enough, what makes you believe that?

I did used to think the same, until I realised what made me think that Chip seal had more grip was a mental thing (I thought it did, therefore I felt that it did when I was riding) Until I thought about it in more 'scientific' way and the funny thing is now with more riding experience and getting to feel how a bike reacts when pushed hard on different surfaces I feel that asphalt has a much higher grip level in the wet.

[Pussy]

I'm more than happy to agree that hotmix has superior grip in dry conditions.

However I'm inclined to believe that chip-seal has superior grip in the wet.
If you're happy to believe that, all is good!
I, however, would much rather ride on hotmix in the dry AND the wet, and much prefer the better grip on hotmix in the wet

[Big Dave]

Whatever perfect world you care to therorise in, and the conclusions you draw, it bears little resemblance to the imperfect condition of the seal on NZ's roads.

I would prefer hotmix in any conditions. real world consistency of the surface/grip being the key.

Then there is tyre wear.

[Big Dave]

A minister in the former government told me that they could fix the road surface in NZ - but it would be expensive.

He wanted 'someone' to research what the human and medical cost of the current chip sealed state was - and compare it to the cost of actually fixing the piles of loose crap and the shiny black death.

I kinda glazed over at the enormity of the task and now the govt has changed.

[Forest]

It's fairly well known that the coarse chip-seal used in the South Island wears down bike tyres quicker than other road surfaces.

Doesn't that meant that chip-seal has better grip?

I found some information which relates to the size of the chip in the chip-seal.


21. Is a road with big chip safer than a smoother road?

No, not at all. What makes a road safe is how much grip (skid resistance) vehicle tyres have on the road. This is a combination of how big the chips are in terms of whether they stick out of the bitumen, and how the surface of the chip looks.

Some of the chips are very, very small, like the relatively soft volcanic andacites. But even though the chip is small it has a high skid resistance. Transit keeps monitoring skid resistance and uses the standards that are used in the United Kingdom. There's no simple rule that 'big chips give you better grip'.

What does matter is the way the road is built. If you keep building a road out of big chips on top of big chips on top of big chips, layer after layer, every 10 to 12 years, then eventually you will probably get a pudding of black bitumen with big stones in it.

From here (http://www.transit.govt.nz/about/faqs.jsp#21)

[SpeedMonger]

I can give you some details on this being a "roading person".

This is actually a fairly complex issue.

But to clear up some definitions;

Tar - "tar" a derivitive of coal has not been used on NZ roads for decades.

Bitumen - Bitumen is what is left from crude oil once all of the useful things have been extracted from it such as fuels and light oils. It come in different grades for different applications. They an be modified with polymers and other additives to improve performance.

Sealing Chip - is a crushed aggregate product (98% minimum) that comes in six different grades or sizes (specified by Transit NZ). The aggregate used must meet several durability criteria including resistance to polishing "PSV" which relates to skid resistance on the road.

Asphalt - Also known as Hotmix, is a blend of various sized aggregates and bitumen put through a specialised blending / heating plant. There are different varieties for different purposes ranging from wearing, structural and water dispersing etc.

Skid resistance is measured by spraying water on the road in front of a wheel that has a force applied to the point of skidding, the more force = more skid reistance.

Chip Seal Pavements

A chip seal pavement is constructed by spraying bitumen over the new pavement or existing seal and spreading sealing chipover the top, which is then rolled to embed the chip into the bitumen. It is critical to get the right application rate for the size of chip to be used, too much and you geed bleeding or too little and chip loss can occur. There are many types of seals for different purposes. Firstcoats on new roads use large chip, and subsequent reseals generally use smaller chips that fill in the gaps between the larger stones. The PSV of the aggregate dictates what scenario the aggregate can be used in, ie a high speed corner requires a higher PSV than a straight section of the same road. The PSV is dependant on the microtexture fn the stones themselves. An aggregate that polishes with traffiking will have low microtexture and lower skid resistance. High PSV aggregates have rougher surfaces and larger grain sizes that abrade with traffiking giving consistent high skid resistance over time but are less durable.

Chipseals have high macrotexture (gaps between the stones), this means it can disperse water easily and therefore should have better wet weather grip than a asphalt made from the same aggregate.

The bitumen used is generally cutback with diluents to make it easier to spray and for ductility under various weather conditions. they also have adhesion agents added to help make the stones stick. Different additives are required depending on the aggregate's chemistry makeup. When a bitumen is used that is diluted too far for a given climate, it's softening point will be too low meaning it soften to the point where stones can be plucked out - this is called "flushing", you then just get left with the black slippery bitumen. If the bitumen does not adhere to the stones because they are dirty or incompatible you also get flushing.

Asphalt

Asphalts fall into two types, open graded and dense graded. Dense graded mixes generally have relatively low surface texture (macrotexture) as they are designed to compact well and interlock for strength and durability. Open grade mixes are designed to drain surface water and are laid over the top of a dense mix. They have high macrotexture but little microtexture, so they have improved wet skid resistance but potentially less dry skid resistance.

Asphalt is more expensive to produce and is logistically more difficult to deliver and apply as it has strict temperature control requirements and requires specialised plant.

So to summarise, in the dry there is no real difference between the two types, an asphalt should be better because of the increased contact patch to microtexture but when water is added then the surface with the best combination of macrotexture and microtexture should win ie a high PSV chip seal - as the water acts as a barrier between the rubber and the stone microtexture on a dense asphalt.

Still awake?? lol.:shit:

[Big Dave]

Flushing. Apt name for that crap!

[Forest]

So to summarise, in the dry there is no real difference between the two types, an asphalt should be better because of the increased contact patch to microtexture but when water is added then the surface with the best combination of macrotexture and microtexture should win ie a high PSV chip seal - as the water acts as a barrier between the rubber and the stone microtexture on a dense asphalt.

Still awake?? lol.:shit:

Thanks - I was fairly certain that was the case.

It appears that chip-seal really does offer better grip in wet conditions.

[Bass]

I'm with Forest here.
We all know that the "shiny patches" (excess bitumen) have almost no adhesion in the wet. Asphalt, hot mix, whatever, of necessity has all the stone coated with bitumen.
The grip (resistance to sliding) is proportional to the perpendicular contact force and the coefficient of friction.
The "shiny patch" syndrome says to me that the coefficient of friction is higher between tyre and wet stone than it is between tyre and wet bitumen.

In the dry, I suspect that surface condition is more important than surface content.

[Okey Dokey]

I cannot compete with all this technical talk. I will repeat, however, that I certainly found better grip on chip & tar roads in the wet than on hotmix. In a light drizzle the hotmix was okay, but a soon as it rained it was as if the entire road was covered in standing water. It was perfect for aquaplaning and not very nice to ride on. In the "real world" I would much rather be on the chip type surface.

I also agree with the poster who mentioned the amount of crashing that occurs in bike races on hotmix when it rains. I'm sure that if these top guys experience loss of traction, than we humble mortals should take note.

I also suspect that hotmix is used here on roundabouts not because it provides superior grip, but because it copes better with the pressures of heavy vehicles turning.

[MSTRS]

... lighter coloured material (I think it is greywacke from the South Island) to prevent it from heating up during summer. That's why it has a different colour to the rest of the Auckland motorway system.
...

I would hope that greywacke is not used. It is known colloquially as Rotten Rock. There is a good reason for that. It is a particular type of sedimentary stone, that was formed in layers that have a high clay content (I think). It is as hard as hell UNTIL it is exposed to the elements. Then it quickly breaks down and becomes very crumbly. Not at all suitable for roading chip.

[racerhead]

Ok Ive been reading over the last few pages and from what I have seen one of the big benefits of hotmix is its consistency. Example, with hotmix the surface is very uniform in its grip levels in either the wet or dry but with the chipseal the surface grip can change rapidly due to a varying amount of chips/bitumen. So IMO hotmix wins in the dry and hotmix wins in the wet even though it has less grip than chipseal but it does have consistency which will give you the confidence to corner at or near the limits of grip.
Example: Taking a wet corner on hotmix will be easier to hold a bike on its grip limit while with chipseal you can have the bike on its grip limit but you hit a patch with less chips and less grip so you get a slide which will mess with your head.

[Big Dave]

Thanks - I was fairly certain that was the case.

It appears that chip-seal really does offer better grip in wet conditions.

Then there is the reality, flushed with adhesion.
The last time I rode hwy 4 - 20% of the surface was gone in long sections.

[Bass]

Then there is the reality, flushed with adhesion.
The last time I rode hwy 4 - 20% of the surface was gone in long sections.

Ah...... true, but that is a whole different discussion.

[Big Dave]

Ah...... true, but that is a whole different discussion.

No it innit. It's the whole point! Were it hotmix it (surface) would still be there and would offer significantly better safety & grip.

The discussion says that a chip seal is theoretically better in the wet. I don't agree, because the reality is it is inconsistent and more prone to failure.

[The Stranger]

Skid resistance is measured by spraying water on the road in front of a wheel that has a force applied to the point of skidding, the more force = more skid reistance.



So do you have any information which could be used to compare the various types. Would be interested to know what sort of variation we see.

[Bass]

No it innit. It's the whole point!

I disagree.
The original point was which surface is inherently better.
Now we are talking about which surface requires more maintenance.
If you want to go down that road then there are all sorts of other factors, like how slick hot mix gets with a little bit of rain after a long hot dry spell.

Having said that however, I too will take hot mix over BADLY MAINTAINED chip seal, wet or dry. Give me chip seal in good order though, and my wet riding is not much different from the dry.

[MSTRS]

So do you have any information which could be used to compare the various types. Would be interested to know what sort of variation we see.

Any results would be meaningless where we are concerned...since it is unlikely that bikes are ever tested.

[Bass]

Any results would be meaningless where we are concerned...since it is unlikely that bikes are ever tested.

I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

[Big Dave]

I disagree.
The original point was which surface is inherently better.


Hotmix every time - refer previous posts.

[MSTRS]

I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

Not necessarily. Not all rubbers are created equal. Just like road surfaces.
A guide, perhaps, but not an absolute.

[Bass]

Not necessarily. Not all rubbers are created equal. Just like road surfaces.
A guide, perhaps, but not an absolute.

Ah but it's not an absolute we want, it's a relative measurement. We are not asking "how good is it", we are asking, "which one is better" and for that, any old rubber will do.

[Bass]

Hotmix every time - refer previous posts.

Not so O large Australian, camera wielding, cycle testing, 6 string plucker, fucker.:innocent:

The evidence says that chip seal IN GOOD ORDER, is better in the wet

refer previous posts

[Big Dave]

The evidence says that chip seal IN GOOD ORDER,

No - that would by a hypothesis as said condition has never been encountered.

Even brand new it is strewn with its own detritus and it begins to fail from there.

[MSTRS]

The evidence says that chip seal IN GOOD ORDER, is better in the wet



No - that would by a hypothesis as said condition has never been encountered.
Even brand new it is strewn with its own detritus and it begins to fail from there.

The condition 'in good order' is such a brief one. In fact, on some roads it may be measured in days....

[Bass]

No - that would by a hypothesis as said condition has never been encountered.

Even brand new it is strewn with its own detritus and it begins to fail from there.

I suggest that you exaggerate, but it has to be said, that in NZ at least, there is more than a modicum of truth in what you say.

You (I think) mentioned earlier in this thread that the roads in OZ were predominately hot mix.
You may be aware that earlier this year, I did around 18,000 km in Oz and while most of it was "in the dirt" a fair chunk was also on the seal. I had read herein, on several occasions that the roads in Oz were better than here because higher grade materials were used and in particular, the bitumen was higher melting point. Consequently I took an interest.
My observations were:
1. The vast majority of the seal was chip seal. Hot mix only appeared on major arterial routes or around metropolitan areas.
2. There may be some truth to the rumours of higher grade materials because while it did occur, bitumen bleed was less prevalent than here and the daytime temperatures we encountered got into the low to mid 40's.
3. This was in the middle of winter and so the temperatures get a lot higher than we encountered.
4. We passed through Marble Bar which routinely records the highest summer temp's of any Oz town. The roads were all chip seal and in good to very good order

So Dave, while I take your point that (and as others have also said) reliability of grip is part of the overall question, it seems that it can be done with chip seal because I have seen it so and for many, many kilometers.


The condition 'in good order' is such a brief one. In fact, on some roads it may be measured in days....

John,
Sadly, as above there is some truth in what you say.

[Big Dave]

I still like hotmix better than perfick order chip seal in the wet. nothing will change that opine.

Aus depends on the state, shlre, geology and logistics. Most place I lived were hotmixed - as in the shizzle comes out of the truck all mixed up - rather than the stuff dumped on top.

[sunhuntin]

An intersting observation up thisa way John is, most of the stone chip road resealing does not last that long, maybe a year before it starts to flake away. They closed the brynderwyns a couple of weeks back for a day to reseal in Hotmix...went over them last weekend and all they have done is patch here and there, same with the Mangawhai road, surely it would more cost effective to get right the first time, or is it that, if they get it right there wont anything for them to do in a few years? Keeps them employed I guess.

the local roadies recently resealed a corner that was badly pot holed. its not much used by cars, but a LOT of stock feed trucks use that corner at all hours of the day. im picking about 20 trucks a day, maybe more? so 20 sets of tyres, all hitting the same line daily. that reseal lasted about 2 days, and now its twice as bad as before. im actually avoiding that road when im on the bike, its that badly damaged. and there seems to be no sign of proper repair. they used hotmix over chip seal, which may have had something to do with it, as they didnt remove the old road first.

[Big Dave]

And seriously - The only issue with this is that so many people I know - and me for that matter - have dumped bikes because of accumulated piles of loose chip seal stones - or lost it on the flushed surface.

[Bass]

And seriously - The only issue with this is that so many people I know - and me for that matter - have dumped bikes because of accumulated piles of loose chip seal stones - or lost it on the flushed surface.

Ummm.......me included

[SPman]

The main reason Australian bikers wear less protective gear is because the roads are made from hotmix and are far less likely to 'betray' them.
Chip seal would just melt over there too.

Hotmix is SIGNIFICANTLY safer for motorcyclists. Provides better wet weather adhesion - because of the uniform surface and greater contact area - and has no likelihood of its surface wearing off and exposing slippery black death.

.

The predominant surface out of Perth is Chipseal - big hunks of sharpened granite that grind through leather like 5 grit sandpaper through pine! - (if you have the opportunity to test it...). Toodyay Rd has had some patches of hotmix put on it, and the official reaction was to lower the speed limit to 80kph (temporarily, of course...) until the "dangerous, slippery hotmix sections" have been expunged! (apparently, WA drivers fall off hotmix when it rains....)
The chipseal doesnt seem to melt like it does in NZ - its the traffic that seems to do it - pushing the chip into the seal and creating nice slippery grooves........

With good tyres, hotmix has better grip in the dry, and similar grip in the wet, but, chip seal is half the price.

[Big Dave]

My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

[Bass]

My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

It's the other way round mate. The heater in a distillation column is at the bottom and your lowest temp fraction comes off the top.
Normally the lighter fractions are the more valuable and the heavies are by-products. However, to get a really good bitumen may involve refining the lights out to a degree that is really high cost in energy terms.

Not sure about used engine oil.

I would have thought that it would have to be polymerised somehow to get enough heavies to make bitumen recovery worthwhile, but there could well be catalysts around that will handle that by now

[SPman]

Wasn't there something about making the roads from recycled engine oil in WA?

I thought they did - straight from the trucks to the road,,,,,,,,,

[The Stranger]

the local roadies recently resealed a corner that was badly pot holed. its not much used by cars, but a LOT of stock feed trucks use that corner at all hours of the day. im picking about 20 trucks a day, maybe more? so 20 sets of tyres, all hitting the same line daily. that reseal lasted about 2 days, and now its twice as bad as before. im actually avoiding that road when im on the bike, its that badly damaged. and there seems to be no sign of proper repair. they used hotmix over chip seal, which may have had something to do with it, as they didnt remove the old road first.

20 trucks a day is a lot.
Sounds like the southern motorway, or perhaps Stanley st.


What's the problem?
The rougher the better, keeps you awake and on your toes. Means you have to work for your ride.

[Titanium]

Hot mix (asphaltic concrete) is 5 times more expensive than tar and chip seal. Is typicall more robust and when laid in a deep lift scenario is even better than concrete roads.

Also limitations around what raw material (asphaltic PAP 7mm percentage All Passings, as opposed to a TNZ40 Grade specification chip) there is to use in certain areas of new zealand and the location of ashphalt plants vs tar supplies.... greywackey vs basalt vs limestone all have different characteristics.

AC is also very quiet as a running surface and can be used where road noise is an issue (built up areas). Gives superior ride quality as well.

AC is typically more robust as a driving surface and can take a lot more punishment than a chipseal surface. AC takes a lot less R&M over full life but the upfront cost is nearly prohibitive at the moment. AC has probably a lower full lifecycle cost also can be recycled back into a roading surface where chip and tar can only be recycled back into a sub base using a hoe.

Surface resistance is not really taken into account when specifying which product to use.

Of course there are also differences in economies when preparing the subgarde for each of the products and also areas where one product may not be suitable to use.

The Americans use a lot of concrete in their roads, so does Australia.

[cooneyr]

Where to start with this lot. Firstly hotmix will be better in the dry due to the larger contact area similar to what a poster said about why racers use slicks. Thing of the other extreme - knobblies and what that does to traction on the same length of surfacing. The problems arise where there is a friction modifier in place i.e. water, especially whey the water cannot be dispersed quickly. I dont have figures but I suspect that it is much of a muchness when both are wet. If things freeze however chipseal wins hands down.


I would hope that greywacke is not used. It is known colloquially as Rotten Rock....

I'm not sure what part of the country you are from but crushed canterbury greywacke is the second best bar crushed volcanic rock chip in the country. You are right in that it will not stay as a solid mass but once it has erroded and worked its way down a river - the waimak say - only the hardest stone remains. The north island really struggles to get its hands on good chip due where as we souf islanders have an excess of it.


I can give you some details on this being a "roading person". ..... Still awake?? lol.:shit:

Well said. That is about as much detail as needed here.


No it innit. It's the whole point! Were it hotmix it (surface) would still be there and would offer significantly better safety & grip.

The discussion says that a chip seal is theoretically better in the wet. I don't agree, because the reality is it is inconsistent and more prone to failure.

As mentioned above getting hold of good chip and good pavement materials for that matter is hard in the norf island. As a result your roads tend to fall appart much quicker than those in the souf island. The higher traffic volumes don't help. Logic then says use a surfacing that will hold together better but if used correctly it actually acts as a structural member of the pavement as well. Overall hotmix will be a better product for most high traffic volume roads in the norf island, however the cost of hotmix is such that you just have to put up with crappy chipsealed roads in many locations.


I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

Called a British Pendulum. Lump of rubber on a pendulum of known weight and you measure how high the pendulum swings once skimming the surface. Good as a relative measure but pretty average as an absolute measure.


My guess is the further up the fractional distillation tower they get the base material from - the higher the melting temperature.

Wasn't there something about making the roads from recycled engine oil in WA?

There are predominantly two grades of bitument used in NZ and I'm buggered if I can remember what they are, 80/100 and 180/200 I think? The problem with these grades is that their softening temperature and freezing (such that they start loosing grip on the chip) are too close together. This becomes an issue in places like the McKenzie country where the surfacing temperatures can range from -10 to +50. To attempt to get around this polymers (sort of glue) are added however this normally is done to deal with the cold and it cannot help with the hot.

If the temp gets close to the softening point of the bitumen (of whatever grade) and then a heavy vehicle turns on it the heavy rolls the stones and brings the bitumen to the surface which leads to flushing. Bleading however is when the temps are so hot that the bitumen softens and the stones are punched down into the bitumen. The net result is the same - bitumen on top of the stones. This is not good for any vehicle the next time and every time after when it rains.

In short well maintained chipseal with good products is a very good solution for most of the roads in NZ. Poor products, poor maintenance poor pavement design or high traffic volumes really calls for hotmix.

Cheers R

[Ixion]

They are both crap. The only decent thing to make a road out of is concrete. There are miles and miles of concrete road, laid down in the 1930s, with cars still driving on them. Except the idiots have covered the concrete with a thin layer of asphalt stuff.

Take a gander when they are doing repairs to some of the older roads, Mt Wellington Highway, Ellerslie Highway, Onewa Road, lots of others. When they strip the top couple of inches off, underneath is the old concretae raod.

Concrete. That's what we want. Or gravel. Why do the roads have to be sealed at all?

[Big Dave]

They are both crap. The only decent thing to make a road out of is concrete. There are miles and miles of concrete road, laid down in the 1930s, with cars still driving on them. Except the idiots have covered the concrete with a thin layer of asphalt stuff.

Take a gander when they are doing repairs to some of the older roads, Mt Wellington Highway, Ellerslie Highway, Onewa Road, lots of others. When they strip the top couple of inches off, underneath is the old concretae raod.

Concrete. That's what we want. Or gravel. Why do the roads have to be sealed at all?

The raod in Lange wuth meny a winding tern.

[Ixion]

No, the other sort.

[SpeedMonger]

So do you have any information which could be used to compare the various types. Would be interested to know what sort of variation we see.

Yep, aggregates in NZ vary in PSV from low 40's up to mid 60's.

For example Blackhead Quarry in Dunedin is one of the lowest in the mid 40's, it is hard, fine grained and polishes easily. Canterbury Greywacke (more durable than Nth Island greywacke) is around 55, Auckland Basalt's are in the high 50's low 60's, Melter slag is also used from the steel mill up there it is in the mid 60's and the highest material used is Calcine Bauxite (imported) which is up in the 70's - this is generally only used on braking sections of road, there is some around Auckland - not sure of locations though. Quarries have to have their sealing chip tested every two years, most fall in the 50 - 55 range. Contractors are then supposed to apply chip of the approriate PSV for the section of road they are sealing, so they may need to haul high psv aggregate over large distances just to seal certain bends and use local materials for straight sections.

[SpeedMonger]

I disagree here too, mate.
Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.


yep you are right here, the basic machine used is a British Pendulum which has a rubber pad at an offset angle that is draged over the surface as the pendulum swings through it's arc. The distance it swings after passingover the pavement gives the psv reading. the more friction the less follow through there is. The rubber pad is a specific standard material but obviously cannot replicate all the different tyres/componds out there.

The one Transit refer to in the earlier post is the Scrim tester which is a large truck that drives along measuring as it goes. In NZ we have trailer mounted grip testers that use an offset wheel.


All three have differnet results as they are empirical test procedures but they correlate to one another. there is a test section of road here in Canty that all three were used on for comparison purposes.

Oops should have read last posts first, CooneyR is on the money

[Bass]

Yep, aggregates in NZ vary in PSV from low 40's up to mid 60's.


What does PSV stand for?

something something value presumably?

[Big Dave]

What does PSV stand for?



Eindhoven.


_____

[Bass]

Eindhoven.


_____

It was actually a serious question, but I guess I asked for that.
I'm not a soccer fan (lawn snooker as my father used to call it) and so I even had to google it to find out what you were on about.

[sunhuntin]

20 trucks a day is a lot.
Sounds like the southern motorway, or perhaps Stanley st.


What's the problem?
The rougher the better, keeps you awake and on your toes. Means you have to work for your ride.

yes, 20 a day is a lot, but the factory must get at least that. so really its like 40 trucks, cos each truck that comes in also has to go out again. each truck is generally a truck and trailer. very few solo trucks come in.
i dont mind a bit of a rough road, but right on a corner like that could be dangerous, as there are usually large stones that have been flipped out of the holes by the trucks. im having to relearn that line to avoid the holes, which almost puts me on the footpath.

[jrandom]

Roads are obviously dangerous things, and should be banned.

[slofox]

One of my pet hates about chipseal is what I have dubbed "Road Eczema"...where the top layer of chipseal has parted company with the next layer down....so you get what are basically shallow potholes all over a road surface.....plays hell in corners, especially if you are moving along a little......one of the worst I hit was in a long sweeping left hander...didn't see it coming...the bike skipped closer and closer to the centre line and the oncoming traffic....fortunately the eczema ran out before I ran out of road.....but it did cause my knees to fell a little strange for a wee while afterwards.....

[cooneyr]

They are both crap. The only decent thing to make a road out of is concrete. There are miles and miles of concrete road, laid down in the 1930s, with cars still driving on them. Except the idiots have covered the concrete with a thin layer of asphalt stuff.

Take a gander when they are doing repairs to some of the older roads, Mt Wellington Highway, Ellerslie Highway, Onewa Road, lots of others. When they strip the top couple of inches off, underneath is the old concretae raod.

Concrete. That's what we want. Or gravel. Why do the roads have to be sealed at all?

I agree with the gravel but I'm not so sure about the concrete. Yes concrete makes a good structural element of the pavement but it is damn expensive. The lifecycle costs are pretty high given the hugh upfront investment costs. Also concrete polishes pretty badly hence the hotmix over the top. Lastly bumpedy bumpedy bumpedy is bloody annoying - I'd rather ride on Chip seal (well gravel actually). This is another reason for mixing the surfacing.

There are a few sections of concrete road around Chch as well if you know where to look for them. Listen out for rythmic bumps next time you travel between Chch and Rolleston or between Kaiapoi and Pine Acres.

Cheers R

[Forest]

If anyone is interested in doing some further reading, there is a huge amount of information at the following link:

http://www.transit.govt.nz/technical/surfacefriction.jsp

[Forest]

What does PSV stand for?

something something value presumably?

PSV = Polished Stone Value

This is a laboratory measurement of skid resistance for an individual aggregate. It is measured by subjecting the aggregate to a standard polishing process and then testing the aggregate with a Portable Skid Resistance Tester. The polishing procedure basically simulates what happens to aggregate that is laid on the road surface - so the PSV is basically a measurement of how much grip will be left after the road surface has been worn down by a couple of years worth of traffic.

The testing procedure and description of the testing process are set out in British Standard 812:Part 114.

[Bass]

PSV = Polished Stone Value



A sensible respose on KB.
It sometimes happens if I wait long enough.
Thanks mate

[slofox]

So much for grip in wet or dry conditions.
Next question: Does the grip vary with temperature and if so, how so?

Over to you Forest.........

[Big Dave]

A sensible respose on KB.
It sometimes happens if I wait long enough.
Thanks mate


brown nose.:laugh:

[Bass]

Does the grip vary with temperature and if so, how so?



Mate, there's an old riddle that claims that the difference between pink and purple is the grip.
So yeah, if she's hot................

[Bass]

brown nose.:laugh:

Brown arms:clap:

[Forest]

So much for grip in wet or dry conditions.
Next question: Does the grip vary with temperature and if so, how so?

Over to you Forest.........

I am not an expert. But from what I've read, the temperature of the air/tyre/road-surface all combine to affect the level of surface grip.

Generally speaking, rubber softens as it warms up and this increases the level of grip.

However at some point (depending on which materials were used to build the road surface) the bitumen will start to liquefy and the grip will start to decrease.

[slofox]

Mate, there's an old riddle that claims that the difference between pink and purple is the grip.
So yeah, if she's hot................

You're a grubby bastard, y'know that......? :rofl:

[Bass]

guilty............:innocent:

[Moki]

Hotmix is best. If it's laid properly-and to correct spec - there should be sufficient surface drainage to ensure adequate contact area for traction in the wet. As this wears down though, drainage properties also reduce.

[motorbyclist]

The definition of grip is the amount of friction one can make between two objects. chip seal with its high points and valleys create an illusion of more grip because "its a rough surface" therefore should create more friction. In some ways true, but it also has a lot lower surface area for the tyres to contact on, meaning less available friction between the two.

Why do you think racing tyres are bald or "slick" .. It's to create the maximum amount of area for the tyre to create friction with track. The grooves in your tyres actually reduce the available grip in dry conditions, at a compromise that it helps with water dispersion in the wet.

and how well do slicks do in the wet? they dont, the water can't go anywhere between the flat surfaces of slicks and hotmix and you aquaplane right into last place.

that said, i don't trust knobblies on the road either as there is too little contact area. (and wrong compounds too)

hotmix is mint in the dry, chipseal less so but i trust it to provide adequate grip if it's nice chipseal

in the wet (not just moist, i mean wet), hotmix has a film of water (and oil etc) between you and the road, and when you roll over it at 50-100kph the water has to get out of the way before you can make contact. it's going to go out and into your tread. on chipseal it will easily go out through the chips, thus giving more useful contact

chipseal also digs into a tyre just that little bit to help hold you on the road. also annihilates bike fairings/pegs/bars/tanks etc plus leather/codura/skin/meat/bone by the same mechanism.

hotmix is used where there is braking or heavy traffic turning as the chipseal stones just get pulled off. mind you both surfaces often get those waves forming from braking vehicles or turning vehicles with locked diff's

so in a 100-0 "omfg how did you not see me coming you f---wit" braking test in the rain, i'd prefer to take the good quality chipseal thanks :)

of course so many roads are in such varied conditions it's a pretty frivolous argument. in a car i prefer the quiet surface.



Data is data and all we are talking about is a coefficient of friction test. It doesn't even have to include a vehicle at all. A bit of rubber, a weight and a spring balance will give potentially useful results.

a moving vehicle on a wet road has issues where is takes time for the water to get out from between the rubber and the road, so any test pushing a stationary object until it moves isn't going to be very accurate



so, of course, if anyone is willing to do a test of two identical corners, in the rain, to see if the chipseal or hotmix offer better traction over a range of tyre choices i'm willing to accept those results:)

[Okey Dokey]

in the wet (not just moist, i mean wet), hotmix has a film of water (and oil etc) between you and the road, and when you roll over it at 50-100kph the water has to get out of the way before you can make contact. it's going to go out and into your tread. on chipseal it will easily go out through the chips, thus giving more useful contact

chipseal also digs into a tyre just that little bit to help hold you on the road.

hotmix is used where there is braking or heavy traffic turning as the chipseal stones just get pulled off.


Thank you, you have just restated my thoughts precisely on both aquaplaning on hotmix and why hotmix is used at roundabouts.

[Pixie]

Asphalt (hotmix) is superior.
Tyre compounds are designed to run on asphalt as few countries use crap to seal their roads,this provides lower wear and better grip.
Ashalt in good condition has a degree of porosity that reduces standing water.
Chipseal suffers tar flushing.
The agregate smooths over.
It is preferable to NZ roading authorities because,above all, it is cheap.
Like WRB's

[Pixie]

No it innit. It's the whole point! Were it hotmix it (surface) would still be there and would offer significantly better safety & grip.

The discussion says that a chip seal is theoretically better in the wet. I don't agree, because the reality is it is inconsistent and more prone to failure.

I agree.
I've yet to see asphalt turn into a total fluid tar slick 2 weeks after it was laid,as I did when the corner of Peak rd and SH16 was resealed recently

[MSTRS]

I agree.
I've yet to see asphalt turn into a total fluid tar slick 2 weeks after it was laid,as I did when the corner of Peak rd and SH16 was resealed recently

It shouldn't at all. If 'proper' seal was used, with appropriate materials prepared and laid properly.
But this is NZ...the land that common sense emigrated from....

[NZsarge]

I have been told by roading people that there are different grades, offering a variety of skid resistance.

There is a good example of this in the main street of Dannevirke, two distinctly different grades of hot mix laid down, one for the road itself and another in the parking area's right next to the road.

[motorbyclist]

back at my old high school some f---wit decided to chipseal the new carpark


loose stones EVERYWHERE for months!

[Big Dave]

>>i don't trust knobblies on the road either<<

TKC88 are fantastic road tyres - wet or dry. srsly

[BOGAR]

Reading the book “Handbook of Road Technology” a possible answer to dose grip increase with temp.
Winter gives high values due to the colder temp and rain weathering the surface back
Summer often gives low values due to the surface polishing under the action of tyres on the dry, hot surface
Trucks also have the same effect approximately as 18 cars.
Actually getting results for the different skid resistances of chip and Hotmix are rather hard to come by but I am still looking.

[Titanium]

Actually getting results for the different skid resistances of chip and Hotmix are rather hard to come by but I am still looking.

They are out there though! A rig is here on the east coast at the moment measuring surface resistance and the quality of the recent pavement recycling contract.

SCRIM - This is implemented by Transit NZ and some RCA's on New Zealand roads to evaluate the surfaces skid resistance. It involves using a modified water tanker which can complete approximately 60 km of non- stop self wetting skid testing. The tanker is fitted with two wheels, one for each tyre path per lane. The test wheels are treadless, pnumatic tyres with there own load and suspension. they are angled 20 degrees to the direction of the tankers travel. The tyres are lowered onto the wet surface and freely able to rotate as the vehicle moves forward causing it to scuff the road in a sideways manner. The ratio of the sideways force is measured and stored over 10 metre intervals. This is known as the sideways force co-efficient or SFC. The data is inserted into a road network database to assist with road maintenance and research. This method is supposed to closely simulate a wet roads skid resistance offered to a vehicles tyres.

79 pages of light reading http://www.landtransport.govt.nz/research/reports/295.pdf