Tire pressure help

[zer0]

I have a 2001 748 that I mainly use for aggresive canyon runs and some freeway sprints . What are some recommendations on tire pressure specs. PSI measured

[karter18]

What brand and type of tire are you running?

[Chuckracer]

Freeze! Keep you hands where I can see 'em! Alright, slowly turn around and face me.

Do you know why I've stopped you? Take a look at your profile...I don't see anything there, do you? No city/state at all. Hmm. How about a Sig line with the details about your ride in there...nope, nothing.

I'm gonna let you off with a warning, cause I'm in a good mood...but get that taken care of ASAP. If I see you around here again and that's not fixed, I WILL take you downtown and you can explain it to the judge.

He looks just like me.

[zer0]

im running dunlop sportmaxs

[Chuckracer]

Thanx bro!

I'd run 35 for highway and around town, 31 for canyon slamming.

[thatkidchris]

Close, but i run mine a little lower.

Speaking of which, isnt the pressure for Power Race's real wierd. Like 29 front/24 rear. Im thinking of getting a set for the bike.

[Chuckracer]

Yeah, I think that's it. I wouldn't run those pressures on the street though. I like my rims round!

[zer0]

Originally Posted by Chuckracer

Thanx bro!

I'd run 35 for highway and around town, 31 for canyon slamming.

its 31 in the rear then how bout the front?

[MilleRrrr]

Are you looking for max traction or maximum life.

I run mine at a higher pressure on the street vs the track, as the street encompases both Highway & twists. If I was going at track speeds on the street I'd probably be dead by now. Additionally, you are not gaining that much traction by having the lower air pressure but you are losing out on tire life.

For street I start out 33 f 35 r
Track 31f / 30 r Diablo Corsas

Originally Posted by me

Tire Pressure:

You'll get a lot of opinions on what tire pressure to run, but the correct tire pressure for you is not a matter of polling other rider's opinion. Here are the basics you'll need to decide for yourself. "Dennis Smith of Dunlop's Sport Tire Services recommends an increase of two to four pounds in front tires and six to eight in the rear (sportsrider.com)". While the most scientific means of determining if a particular pressure is the use of a pyrometer to assess whether the rubber has reached the manufacturer's recommended temperature, charting the pressure increase of a tire after track sessions will give a good impression of how hard a tire is working.

Stamped on the outside of many of your tires is a recommended tire pressure range. (At least an upper limit.) For longest tire life it is my recommendation that you strive to keep them at the higher limit of those recommendations (regardless of what your motorcycle owner's manual might say to the contrary.) Further, this pressure should be determined while the tires are cold - meaning, have not been used for a couple of hours.

Start with the bike manufacturer's recommendation in the owners manual or under-seat sticker. This is the number they consider to be the best balance between handling, grip and tire wear. Further, if you're running alloy wheels on poor pavement, consider adding 2 psi to the recommended tire pressure just to reduce the likelihood of pothole damage. Just as you would for a car, increase the pressure 2 psi or so for sustained high speed operation (or 2-up riding) to reduce rolling friction, increase tire life, and casing flexing.

In order to get optimum handling a tire has to get to its optimum temperature, which is different for each brand of tire and different uses. Most of us don't have the equipment needed to measure tire temperature directly so we measure it indirectly by checking tire pressure since tire pressure increases with tire temperature. Tire temperature is important to know because too much flexing of the casing of an under-inflated tire for a given riding style and road will result in overheating resulting in less than optimum grip. Over-pressurizing a tire will reduce casing flexing and prevent the tire from getting up to the optimum operating temperature and performance again suffers.

Street

A technique for those wanting to get the most out of their tires on the STREET is to use the 10/20% rule.

First check the tire pressure when the tire is cold. Then take a 30-40 minute ride on your favorite twisty piece of road to get your tire temperature up, then measure the tire pressure immediately after stopping.

If the pressure has risen less than 10% on the front or less than 20% on the rear, the rider should remove air from the tire (to increase heating affect of carcass flex). So for example, starting at a front tire pressure of 32.5 psi should bring you up to 36 psi hot. Once you obtain this pressure increase for a given rider, bike, tire, road and road temperature combination, check the tire pressure again while cold and record it for future reference.

Each manufacturer is different. Each tire model is different.

A tire design that runs cooler needs to run a lower pressure (2-3 psi front) to get up to optimum temperature. Remember carcass flex to generate additional heat.
The rear tire runs hotter than the front tire on both road and track. So the rear tire cold-to-hot increase is greater.
Dropping air pressure has the additional side effect of scrubbing more rubber area, and can additionally add more traction at the cost of a little stability
As an example for 2004 Aprilia RSV Mille the recommended starting temperatures for STREET use are.

Front Tire 34.8 deg. Cold which in turn should be approximately 37.5 -38.5 deg Hot (3-4psi increase)
Rear Tire 39.4 deg Cold which in turn should be approximately 45-47 deg Hot (7-9psi increase)
Please note that these numbers tend to be too high for maximum traction but in turn increase the life of the tire.

Track

Track tire pressure is a different animal altogether. With track requirements the tire pressure is a +/- game which has a goal to getting to the proper temperature and pressure to maximize grip, feel, and stability.

Too much pressure leads to less contact patch and reduced grip
More pressure tends to give feeling of more stability (less rear wiggle)
Too much pressure leads to non-optimum tire Traction
Too little pressure leads to overstressed carcass and excessive heat (blueing of tire)
Too little or too much pressure leads to non-optimum tire temperature
For the track you'll have to drop the cold tire pressures an additional 10/20%. Track operation will get tires hotter (increasing the cold-to-hot pressure range) so starting at say 32/30 psi now should bring you up to the proper opreating temperature AND create enough tire pressure to maximize contact patch AND create enought feel and stability for the track. With these goals in mind the tire should be approximatly 35/36 psi when fully heated (at optimum tire temperature).

Since track riding put tremendous stresses on a "STREET" tire the tire heats up more than if it was on the street. "Race" tires will have different heat capabilities and are able to withstand the higher forces of a track better (ie cooler) than a street tire. The lower the tire pressure the more the tire deforms. The more the tire deforms, the more friction there is between the tire and the road surface. The more friction, the more heat. The more heat, the greater the opportunity the tire has to regenerate itself by shedding the 'used' layers of rubber (to a point). This deformation of the tire also creates a bigger contact patch at the cost of a little stability (ex rear wiggle).

Different riders have differerent starting pressures. You have two riders, 'super fast john', and 'average joe' go out on the recommended 31psi pressure and 'averages joe's' tires come in with the correct hot pressure (lets say 34-35 psi for example using Pirelli's reccommended hot pressure) you can bet that because that 'superfast John' will be working the tire harder, spinning it more and his tire might come in reading 37psi.

This would mean that to reach the target pressure of 34 psi which is the pressure and also temp that the tire works the best, 'superfast john' will need to take 3psi out of his tires and be starting at 28psi cold.

[OldBaldy]

Some tires like more pressure than what seems normal -even for the track. Diablo Corsa recommendations for the track are 34/35 psi - no lower. They have very soft sidewalls. Pilot Powers also like pressure maybe 1 psi lower than the Corsas.
The Power Races recommendation for the track is 31F/22-24R, due to the very stiff rear tire sidewalls.