Chipseal vs Hotmix

[Bass]

guilty............

[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:Me]

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.

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