[galaxy]

I just read an article on tire pressure that said to check/adjust tire pressure when completely cold...makes sense. Then, when the tire is warmed up to it's normal or highest temperature, check it again. There should have been an increase of 6-7 psi. If so, you are running the correct pressure. If it increases more than that, the initial pressure setting was too low. If it doesn't increase enough, the initial pressure was too high. Makes sense to me, I had just never heard this before. Seems like it would be tough to do outside of the race track...with daily varying conditions such as air/road temps, riding conditions (commuting, cutting up the twisties, etc) traffic, etc. Guess you would have to find a happy medium hu?? Just curious if anyone does or had seen this before.

 

[MikeM]

Interesting... I learned the 10% rule and it's been around a while. Properly inflated tire will warm by 10% or about 3 lbs.

 

[xseal]

I was just at the track this weekend. 3lbs difference (29/32F, 26/29R) b/t 60 degrees (ambient) and 135 degrees with tire warmers.

 

[Herbivator]

The 10%F/20%R rule does not apply to radials.

 

[dug]

Hm. How interesting. Dave Moss just gave a suspension seminar in Folsom and he spoke of a 5-7 psi increase for properly inflated tires and adjusted suspension. I don't remember if he specified track or not.

 

[Chuckracer]

Yeah, that's pretty much racetrack stuff. The team I was working for was running Dunlop slicks and we looked for a 4psi rise, but that depends on so many varibles, including rider preference.


When it comes to chassis set-up, nothing is concrete. All of it is a good starting point, but that's all it is. There is no such thing as one true "right" set-up.

 

[mals900ss]

what if you are running nitrogen in your tyres... something that is becoming more popular.. also known as tyre gas??? I heard this stuff doesn't fluctuate with temp.

Mal

 

[galaxy]

I was just at the track this weekend. 3lbs difference (29/32F, 26/29R) b/t 60 degrees (ambient) and 135 degrees with tire warmers.

Tire warmers are up to 135, but don't the tires reach temps of 200+, depending on conditions/rider of course, out on the track??

 

[hank]

Personally, I have recently started taking 3 readings:

1) Cold (ambient temp)
2) While on warmers (fully heated at mid-temp setting)
3) Immediately after a session

I don't have enough info at this time to make any quasi/pseudo intelligent observation but there really is a difference between number's 2 & 3 above.
Clearly #2 is easier to measure in terms of consistency.

I find that the front increases about 10% and the rear increases about 12.5% from cold to hot... makes sense since the rear tire volume is greater but then again.... I'm shooting in the dark about this stuff!

 

[xseal]

Pirelli recommends warming their slicks to 135. Different manufacturers recommend different "starting" warm pressures, Dunlop is around 195.

I didn't measure when we got off, interesting question will check the next time. My hunch is it varies a bit based on grip of track, ambient temp, whether the sun is out, etc. That's why Pirelli recently started recommending setting pressures at warmed temp, rather than cold. There is a 3 lb different in their warm and cold recommendations, though.

 

[hank]

Pirelli recommends warming their slicks to 135. Different manufacturers recommend different "starting" warm pressures, Dunlop is around 195.

I didn't measure when we got off, interesting question will check the next time. My hunch is it varies a bit based on grip of track, ambient temp, whether the sun is out, etc. That's why Pirelli recently started recommending setting pressures at warmed temp, rather than cold. There is a 3 lb different in their warm and cold recommendations, though.

Do you have a link to the Pirelli site that mentions recommended air pressures?

 

[fraz]

what if you are running nitrogen in your tyres... something that is becoming more popular.. also known as tyre gas??? I heard this stuff doesn't fluctuate with temp.

Mal

I was waiting for somebody to mention this. I have been out of the bike race scene for a little while but nitrogen being new? We have used it in our race cars for years and I typically run it in my street bike tires too. It's not that nitrogen doesn't fluctuate, it is _almost_ devoid of the water component present in oxygen. Meaning nitrogen is a drier gas than oxygen (it's a gas too). It is the water that causes the wild fluctuations in tire stagger and I know when you have 4 tires it is next to impossible to get a consistent setup on a race car with tire stagger moving all over the place. Yes nitrogen filled tires will grow too but they grow/shrink at a consistent rate and are very predictable. Don't forget, some tires from different manufacturers also grow/shrink at different rates too so keep your eyes on it.

Nitrogen is cheap and I highly recommend it. I have a small cylinder of it in my garage that I use for tires and air tools at the track. The water component causes friction/heat buildup and that is the root of the problem. The other cool thing about nitrogen is you can fit so much more at a much higher PSI into a cylinder. With my small cylinder you can get like 600PSI of oxygen/air. Using nitrogen I can get 2000PSI in the same cylinder.

 

[mals900ss]

Thanks Fraz.. I knew it wasn't new... like you said we were using it years ago.. I did suggest it was becoming more popular.. Quite a few tyre shops now have Tyre Gas available in OZ and charge about 4 bucks a tyre to inflate your new car tyres with it...

thanks for the info though.. looks like I was mislead oh so long ago.. or didn't understand!!

Mal