Aims of tyre pressure (semis)

[BlitZ]

Is my aim to get the pressures the same all round when its hot?

next question... ideal semis tyre pressure (more specific ; wakie), when hot..

and what pressure is required to achieve that when cold...

[tinkerbell]

i start my 15in Toyo R888's at 27 psi front 29psi rear COLD at wakie in the cooler months...

i personally aim for 34 psi hot f/r and adjust from there depending on circuit surface traction...

[JCE]

I believe that "ideal" tyre pressures would depend entirely upon the suspension setup and therefore the amount of force exerted upon the tyre.

Ideal pressure for one setup may not be the same for the other.

[Jingers]

although i understand to a point what too much pressure or too less pressure does to a cars handling

can someone just quickly list the pros and cons of both under pressure and over pressure?

[BlitZ]

although i understand to a point what too much pressure or too less pressure does to a cars handling

can someone just quickly list the pros and cons of both under pressure and over pressure?

Lower tyre pressure
better grip
more tyre wear on sides
more sidewall flex
top end not as good (slighty)

higher pressure
better side wall
better top end
no as well in traction..
last longer

[Jingers]

http://www.turnfast.com/tech_handlin...pressure.shtml

Good site

[l3vnd1]

Bumping an old thread in preperation for Decembers track day (yes I know a while away)

I will be running Toyo R888's on stock DC2R sussy.

I have read that pressures depend on suspension, and Tinkerbell has advised not to go over 34PSI hot...

Is this applicable to stock suspension as well? Does it change much?

Also - would the drive down scrub them in or would you need to devote session 1 entirely to doing this?

[fatboyz39]

we aim for 32 HOT for R888. We ran 38 HOT on the R888 (38 works well on RE55s) before research and they were junk. So 32-34 HOT is on the ball. As for scrubing them in, just do it on the track. Shouldnt take more then a few laps.

[Elwood]

I was on 32psi cold, and 37 hot..

Too much, so i ran roughly 35.

I was getting noise from the rear left, and turned out it was on 17psi for some reason..

...4dlulz.

[ChargeR]

I run 34 psi hot at all four corners on 205/55 16 RE55s with stiff coilovers. When I was on stock suspension I used to run a touch higher simply because it felt better but there was nothing I could do to stop my car riding on the outer shoulders of the tyres as I simply had too little camber and too much body roll.

It might be worth getting a friend with a tyre pyrometer to sit at the pit wall and if you do a quick pit half way through a session they can take your tyre temps and record them. That will give you a better idea of what your tyres are doing.

[Elwood]

I think the problem is most of us arnt experienced enough to:

-Notice a problem with the cars performance,
-Realise it is due to the tyre pressures and not suspension settings etc
-Rectify that problem by either increasing or decreasing those pressures (or suspension for that matter).

[FunkyR]

Here's a good article on tyre pressures that pretty much summaries the previous link into a page.

http://wp.circuitclub.com.au/wp-cont...uit/Issue7.pdf

[ChargeR]

I think the problem is most of us arnt experienced enough to:

-Notice a problem with the cars performance,
-Realise it is due to the tyre pressures and not suspension settings etc
-Rectify that problem by either increasing or decreasing those pressures (or suspension for that matter).

I agree. I only have a vague idea of what I am doing when I set my pressures, which is why it is nice to have some temperature data to back up your driving impressions.

[tinkerbell]

Also - would the drive down scrub them in or would you need to devote session 1 entirely to doing this?

i have de-mouldreleased tyres on the way to wakie... but still needs a session before they are at their best...

build them (and yourself!) up gradually to speed and you will be happy and comfortable...

[KEVSY]

when i bought my semis i spoke to the tyre tech he said 36 hot max temp , start off with 32 do a run and reset pressures. i found that camber was an issue , tyre would wear outside edge with stock suspension. i used to run 38-40 hot but could feel tyre sliding across track , car felt nervous , car running 34-36 so much more grip less understeer. i would run my semi on the road to and from track days that would scrub them nicely and you would cycle some temp through tyres.