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FROSTY
15th September 2005, 22:11
Just a lil reminder
Our modern good quality tyres are fantastic at keeping the bike right side up.
But as they get stickier they also leak more air.
Checking tyre pressures regularly is essential to keeping the shiney side up

Right Charlie
15th September 2005, 22:19
Hmm, i think ill fill mine up with Nitrogen, bigger molecules stay in longer.

They use it in our Aircraft, just have to be carefull, 180psi Air System i beleive, as oppsed to the 60psi at your garage, it packs a whallop.

FROSTY
15th September 2005, 22:26
charlie--you have ready access to nitrogen (he says with his ears perked up)

k14
15th September 2005, 22:32
Hmm, i think ill fill mine up with Nitrogen, bigger molecules stay in longer.

They use it in our Aircraft, just have to be carefull, 180psi Air System i beleive, as oppsed to the 60psi at your garage, it packs a whallop.
Huh?? Nitrogen molecules are actually smaller than oxygen (and only by the smallest amount). The atmosphere is made up of over 80% nitrogen anyway so its mostly that in your tyres when you pump them up at the petrol station. AFAIK the reason people use nitrogen to pump up tyres is because it expands less due to heat, so the cold to hot pressures don't vary as much.

Right Charlie
15th September 2005, 22:55
Huh?? Nitrogen molecules are actually smaller than oxygen (and only by the smallest amount). The atmosphere is made up of over 80% nitrogen anyway so its mostly that in your tyres when you pump them up at the petrol station. AFAIK the reason people use nitrogen to pump up tyres is because it expands less due to heat, so the cold to hot pressures don't vary as much.


For years, over the road truckers, auto racers and the U.S. military have been filling tires on their vehicles with pure nitrogen. Here's why. In a tire filled with compressed air, the oxygen molecules tend to "migrate" through the wall of the tire over time. That's why, when you open the garage to check on your aunt's dust-covered 1980 Pontiac the tires are often flat. But nitrogen molecules migrate 3 to 4 times more slowly than oxygen, so tires stay properly inflated longer. There are other benefits. Nitrogen retains less heat than oxygen and therefore allows tires to run cooler.

While nitrogen is dry and benign and will not combine chemically with other materials (the metal in tire rims, for instance), compressed air contains trace amounts of water and the oxygen tends to combine with other materials, causing rust and corrosion. If you were to see the inner face (the part enclosing and sealing the inside of the tire) of some fancy aluminum wheels you would be surprised at how corroded they become due to oxidation.

Tour de France bicyclists fill their tires with nitrogen. So do NASCAR, Indy and Formula One racing teams, over-the-road truckers, some fire departments and the U.S. military.


An oxygen molecule is 0.29 nanometers in diameter and a nitrogen molecule is only slightly bigger: 0.31 nanometers

Lord Bless Google ;)

Right Charlie
15th September 2005, 22:57
charlie--you have ready access to nitrogen (he says with his ears perked up)

Thats Nitrogen, Pure Nitrogen, not Nitrous Oxide which i suspis you are after
:motu:

TwoSeven
15th September 2005, 23:10
I check mine every day mainly because I notice the difference in a couple of PSI (it depends on how lazy I am whether I actually adjust the pressure or not tho). Over the years I've gotten into the habbit of sticking the pressure guage on - its always close by the bike. Its just part of my pre-ride check I do each day.

On the krappisaki I have leaky valves, so after a week it drops down to 20 or so psi on each tire and I really do have to reinflate them (they are tubed).

FROSTY
15th September 2005, 23:11
nope dude--nitrogen for my tyres -keeps em cool -etc etc

Right Charlie
15th September 2005, 23:25
nope dude--nitrogen for my tyres -keeps em cool -etc etc

The problem being to inflate them with nitrogen one must first deflate the tire of air.

If the tire becomes unseated i dont have the know how to re-seat it. The nitrogen supply is in the hangar.

Flyingpony
15th September 2005, 23:45
I notice the loss of 2psi (or more) so end up inflating every two weeks.
Have a ratio of check typre pressure against fill her up between 2:1 & 4:1.
I'm one of those frequent visitors who rarely tanks, as it appears.

Car tyres get done every month with spare every 2nd.
Air pressure loss on bike is higher than car but then bike travels more km.

Gremlin
16th September 2005, 00:35
From my observations I have found that I seem to lose less air if the bike is ridden daily, and if the bike sits for a week it loses more...

Is this actually true??

And boy did I find out the value of air. One ride I went on by myself I hadn't checked the pressure for a week and a bit, and I can only surmise that that was the cause of my handling problems. The ride was very uncomfortable and everything simply felt wrong...

TwoSeven
16th September 2005, 02:13
Generally when a tire goes thru a heat cycle it will have lost air when its cooled again. Its unusual to lose much pressure for a tire thats not changed in pressure much (ie. cold) apart from a small amount caused by a leaking valve.

bugjuice
16th September 2005, 10:09
I thought tyres run best when they're hot, to make them sticky..?? If they're cool, then surely they'd loose what little heat they would build up..?

FROSTY
16th September 2005, 10:30
Different issue entirely BJ --Yea tyres at opperating temp work best but there is also optimum tyre PRESSURE. what using nitrogen does is reduce pressure variations during the heat cycle so the tyres stay at optimum pressure.
Also I notice around a 4-5 psi drop in my race bike tyres between meetings
5 psi over 3 weeks

Biff
16th September 2005, 10:30
I run my tyres a few (2-3) PSI below the manufacturers recommended pressure. I find it improves the handling on my bike.

FROSTY
16th September 2005, 10:40
well its a bit of a black art --grip/tyre roll/longevity --all come into play

TwoSeven
16th September 2005, 12:03
I run my tyres a few (2-3) PSI below the manufacturers recommended pressure. I find it improves the handling on my bike.

I assume thats the sidewall pressure youre talking about.

I usually find road tires for me work best in the mid 30s (34/36) being about the average. Its enough to keep the tread pattern open and not use the tire as suspension, but not too hard as every single bit of grit on the road shows thru the bars.

I think everyone has their different preference, but I'd suggest dont make the tires so soft that they deform around bumps rather than lift the wheel over them.

Pathos
16th September 2005, 12:21
How do you check the pressure?

i just use the pumps at the station but they are useless.

I probably rode all the way home from palmy with the wrong pressure for all I know.

bugjuice
16th September 2005, 12:26
I assume thats the sidewall pressure youre talking about.
I always took that as being the max the tyre can operate at (safely or not, I don't know). I never run it at that pressure.. it's often like 40psi +!!

SuperDave
16th September 2005, 12:34
I run my tyres a few (2-3) PSI below the manufacturers recommended pressure. I find it improves the handling on my bike.

That's interesting as I now run 30 front and 33PSI on the rear after the recommendation of the guys at cyceltreads. My manual says 27 front and 29 rear and after going up to the higher PSI front and back I've certainly noticed improved handling.

Although I guess it all depends on what kind of compound the tyre's are, the size and the bike they are fitted to.

Flyingpony
16th September 2005, 12:37
I run my tyres a few (2-3) PSI below the manufacturers recommended pressure. I find it improves the handling on my bike.
Run my tyres 1-2 psi over the bike ownership manual. Handling is better though grip in wet is probably worse, as if it's flash to start with.
Also have difficulty-getting front/rear respectively at 27(25?)/29 psi, so run it at 28/30 psi. Only do short range commuting, so not worried if it's slightly over because tyres never get hot.

FROSTY
16th September 2005, 12:44
How do you check the pressure?

i just use the pumps at the station but they are useless.

I probably rode all the way home from palmy with the wrong pressure for all I know.
For road bikes what I used to do is stop at a servo close to home on my way HOME from a ride and deliberately over inflate my tyres by about 5 psi
when I got home I would drape my tyre pressure guage over the seat
next time I wanted to ride I'd just drop the pressure to the pressure i wanted.
Probably one of the best investments you can make for your bike is a good quality tyre pressure gauge.
Mine I bought from Kendle raceing supplies and it cost about $60.00
its got a pressure bleed button and the gauge itself is wrapped in a rubber sheild so it cant get damaged if dropped.

Tyre pressure is a bit of a black art.
if you really want to know the pressures that work for YOU on YOUR bike with a particular set of tyres you need to do some testing.
check the tyre pressures cold then check them hot.
The pressure variation between hot and cold should be around 2 PSI

vifferman
16th September 2005, 13:00
I assume thats the sidewall pressure youre talking about.

I usually find road tires for me work best in the mid 30s (34/36) being about the average. Its enough to keep the tread pattern open and not use the tire as suspension, but not too hard as every single bit of grit on the road shows thru the bars.

I think everyone has their different preference, but I'd suggest dont make the tires so soft that they deform around bumps rather than lift the wheel over them.
Y'know, I get the feeeling that tyre pressures have become sort of a combination of "macho bullshit" and weird urban myth. So many sprotsbike riders seem to indicate by the things they say that they believe that if you don't run low, low pressures, then you aint hardcore, and can't cut it in the racing department. So, they end up running low pressures on the road, because someone who does the occasional track day tells them they should, and belittles them if they don't.
Me? I'll start with the manufacturer's recommended pressures, and adjust from there. Incidentally, I've found on my last few bikes that the recommended pressures (or no less than a couple of PSI below) gave the best feel. Anytime the pressure dropped below that, the bike wandered on coarse chip seal, felt unsettled, and - worst of all - sufffered accelerated wear, due to excessive tread flex, as exhibited by cracking next to the tread blocks.

Here's another urban myth: run lower pressures to get better grip in the wet. Nup.
Causes the tread blocks to close up slightly, giving less water clearance. Plus tyres wear faster in the wet, so that's not the time to be further accelerating wear by dropping the pressure.
The tyre's footprint size is the same regardless. All lowering the pressure does is allow the tyre to flex more, and flex causes internal friction, which heats the tyre compound. Ultimately, too much flex/heat wrecks the tyre by causing cracking or delamination.

Sensei
16th September 2005, 14:50
Having Shaun Harris at my finger tips in the Naki is excellent to get his point of view about tyre pressures . Put a Supercorsa on the other week & He told me to run it at 29 psi that is what the tyre people told him they are surppose to be not what the bike manufacturer's tell you . Tryed it but was to soft for Road use maybe Ok on the track when you could ride like he can but went back & told him wasn't good for me , He know how fast ride so we worked out a presssure that would help with the suspenion settings we put on my bike . The main thing is that the tyre is getting to its correct heatcycle so it can work correctly like it has been designed too . Track & road differ alot as on the Track the tyre is subjected to alot more heat build up so this has to be taken into count & the road has more varied surfaces which effect the tyres as well . As above a good Tyre gauge is something that is very handy to have on ya bike once you have you own Pressures sorted

Kickaha
16th September 2005, 15:42
charlie--you have ready access to nitrogen (he says with his ears perked up)

I know at least a couple of the Firestone stores in Orcland have the equipment for nitrogen filling

FROSTY
16th September 2005, 16:11
The main thing is that the tyre is getting to its correct heatcycle so it can work correctly like it has been designed too . Track & road differ alot as on the Track the tyre is subjected to alot more heat build up so this has to be taken into count & the road has more varied surfaces which effect the tyres as well . As above a good Tyre gauge is something that is very handy to have on ya bike once you have you own Pressures sorted
Yup what he said.
From personal experience i can tell ya --a bike set up to handle well on the track is gonna feel like a wheelbarroew full of bricks on the road -and a good road setup feels like a spungy pud on the track.
BUT -even if you run very low tyre pressures ya still gotta check em

k14
16th September 2005, 17:13
Lord Bless Google ;)
Do you care to share your source for that info?? Yes I may have been wrong but I find it very hard to believe that 0.02nm difference changes things at all. From my searchings it seems that the reason for using nitrogen in aircraft tyres is due to the fact that atmospheric air has a moisture content, aircrafts travel in temperatures much below 0 thus the moisture in the tyres will freeze at these temps.

Also (as i said in my first post), the atmosphere is made up of around 85% nitrogen anyway so there's already alot of it in your tyres. Pretty sure racing teams use it due to ease of application and nothing else.

TwoSeven
16th September 2005, 23:04
The reason given to me many years ago by some factory tire dude guy was that nitrogen keeps the heat in the gas stable, so the heat is only generated by the tire itself. Whereas air, is affected by the heat from the tire and acts to further warm up the tire and so is more unpredictable in what it does. Something like that anyhow.

Don't know the science in it, dont care. I use air and I measure what happens in differing weather and surface conditions - so it doesnt bother me.

Only reason i'd ever consider using nitrogen is in a 45 min race or a long endurance race, and being an unfit, stone broke lazy bastard, there is currently a million to one chance of that ever happening :)

FROSTY
18th September 2005, 14:12
I know at least a couple of the Firestone stores in Orcland have the equipment for nitrogen filling
Thanks kick--its more of a case of--MMMM hes right on my doorstep and hes got nitrogen. I'm interested to see what effect itll have on my tyres whilst racing.

Racey Rider
8th March 2008, 10:06
Thanks kick--its more of a case of--MMMM hes right on my doorstep and hes got nitrogen. I'm interested to see what effect itll have on my tyres whilst racing.

Did you experiment with this in the end Frosty?
Are you still using it in your race bike?
Care to share your thoughts if you have any info to add?

Racey

FROSTY
8th March 2008, 10:13
No can do -Haven't seen my racebike in a bloody long time

dipshit
8th March 2008, 12:25
How do you check the pressure?

i just use the pumps at the station but they are useless.


Get yourselves a half decent and easy to read tyre pressure gauge and a foot pump. It doesn't have to be a flash foot pump. You can get them quite cheaply. Better to spend more of the money on a better quality pressure gauge.

Now you can check and adjust your tyres at home before you go on a ride when they are cold.

dipshit
8th March 2008, 12:51
Just a lil reminder
Our modern good quality tyres are fantastic at keeping the bike right side up.
But as they get stickier they also leak more air.
Checking tyre pressures regularly is essential to keeping the shiney side up

Indeed! I had a good lesson about this just the other day.

A couple of days ago on a ride - somehow the bike just didn't feel right. Couldn't get into my usual rhythm and flow like I usually do on a familiar bit of road. Just put it down to being "one of those days" at the time.

However the next day I happened to check my tyre pressures and both ends were down 4 psi...! (32 psi instead of 36) Readjusted and went for another ride and everything felt good again.!

That will teach me for not checking for a few weeks.

Sharry
8th March 2008, 14:11
Indeed! I had a good lesson about this just the other day.

A couple of days ago on a ride - somehow the bike just didn't feel right. Couldn't get into my usual rhythm and flow like I usually do on a familiar bit of road. Just put it down to being "one of those days" at the time.

However the next day I happened to check my tyre pressures and both ends were down 4 psi...! (32 psi instead of 36) Readjusted and went for another ride and everything felt good again.!

That will teach me for not checking for a few weeks.

I checked my tyres, for the first time since I bought Jade on the 31 Jan, on the AWNR last week. They were down more than I thought they would be (both under 30) and pumped them up to what I was recommended (40 in the rear and 35 in the front).
I was surprised to find the difference it made. There had been a couple of times that I thought the whole frame was wobbly and didn't know what to blame this on, this has not happened since I put the right pressure in.
I will therefore check it weekly as recomended to me.

moT
8th March 2008, 16:09
Its a waste of time running low pressures on the road especialy with soft tyres you just wear out the middle of the tyre anyway so when rideing on the road i go for longevity i run the tyres at almost maximum psi like 38psi each and use nytrogen gas makes the tyres run cooler and increases tread life. (if any of you guys out there have good tyres only worn in the middle please give them too me) but on the other hand at the race track i run much lower and i change the pressures to the situations eg: cold day i run 26-28 at taupo and on a hot day 30-32 (these are just estimates i normaly check tyre pressures after each session make sure the hot pressure is 2psi above cold pressure so cold pressures can vary)