trackday tyre pressures - up, down, or road?
Discussion
hi all, i've done about 7-8 trackdays now and generally start with my tyre pressures just a few psi over road settings to stop them falling over round corners (car weighs just under 1000kg, i run at about 26-28psi on the road).
this seems to do me ok, i get pretty even wear across the tyre (currently using hankook RS2) and grip and response are good.
but i know that some people (in the same car) whack the pressures up (by like 10psi), i guess to stop the tyre falling over and also to lessen the overheating by not allowing the tyre to move about so much*. and others take their pressures down to allow for the fact that the tyre temp will increase beyond what you'd get on the road and so overall pressure will go higher (tho i guess it's a bit sloppy on track until things do warm up!).
so who is right, or does it depend on whether you are using trackday type tyres or not?
or do i just need to invest in a tyre thermometer so that i can monitor tyre temps, and simply adjust so that temps are as even as possible across the tyre?
thanks in advance
this seems to do me ok, i get pretty even wear across the tyre (currently using hankook RS2) and grip and response are good.
but i know that some people (in the same car) whack the pressures up (by like 10psi), i guess to stop the tyre falling over and also to lessen the overheating by not allowing the tyre to move about so much*. and others take their pressures down to allow for the fact that the tyre temp will increase beyond what you'd get on the road and so overall pressure will go higher (tho i guess it's a bit sloppy on track until things do warm up!).
so who is right, or does it depend on whether you are using trackday type tyres or not?
or do i just need to invest in a tyre thermometer so that i can monitor tyre temps, and simply adjust so that temps are as even as possible across the tyre?
thanks in advance
- is this assumption correct!? a tyre with high cold pressure will run cooler than one with low cold pressure?
Edited by skinny on Monday 25th February 17:33
For OEM tyres start with std pressures and work up / dowm depending on balance and whats happening with the tyre. There is no right answer as different drivers will use different cold pressures simply because one may work the tyres more so will generate different hot pressures.
Some tyres need alot of air to keep their profile, others can be run at much lower pressures to maximise grip.
Also if you change camber settings you get the opportunity to review pressures again.
oh and the wider the tyre the more critical pressures are, i run 315mm sections on the rear of mine and i run at least 15psi lower than std. For example.
Bit of a black art - i think
Some tyres need alot of air to keep their profile, others can be run at much lower pressures to maximise grip.
Also if you change camber settings you get the opportunity to review pressures again.
oh and the wider the tyre the more critical pressures are, i run 315mm sections on the rear of mine and i run at least 15psi lower than std. For example.
Bit of a black art - i think
my CSL runs 33-34 road pressure cold on PS2 but then with Cups (think they have stronger side walls) i run hot 32-34 on track which on a warm day cools to about 26-28 PSi.
So comparing like for like with a 1440kg car on cups i reduce my psi by about 6 psi for track
My old M5 E39 used to have the psi ramped up on track by about 4-6 psi.
So comparing like for like with a 1440kg car on cups i reduce my psi by about 6 psi for track
My old M5 E39 used to have the psi ramped up on track by about 4-6 psi.
I think that with R-compound track tires the pressures on track are likely to vary less from road pressures owing to the stiffer sidewall.
On standard road tires I always find myself increasing the pressure considerably to get even tyre wear.
At the 'Ring in my brother's 250 bhp Cooper S we were running about 38 PSI hot on 215/18/35s (Yokie Parada Spec 2) with 2 degrees negative camber on the front & we were getting considerable shoulder wear. Someone commented that looking at the tyre wear we could probably afford about 3 degrees on the front.
Bottom line - the stiffer the sidewall the less pressure required.
On standard road tires I always find myself increasing the pressure considerably to get even tyre wear.
At the 'Ring in my brother's 250 bhp Cooper S we were running about 38 PSI hot on 215/18/35s (Yokie Parada Spec 2) with 2 degrees negative camber on the front & we were getting considerable shoulder wear. Someone commented that looking at the tyre wear we could probably afford about 3 degrees on the front.
Bottom line - the stiffer the sidewall the less pressure required.
Penguinracer said:
Bottom line - the stiffer the sidewall the less pressure required.
Pretty good summary.But the only real way is to experiment. It's as much to do with how you drive as the physics of temperature/pressure/shear/angle of slip and all that cobblers. Find what works best for you and your car and ignore the theorists!
Interesting to see so many differing opinions...
I was always taught that handling was most important on trackdays, and to decrease PSI by 2-3 below normal road pressures.....
Yes increasing the pressure may mean more even wear and mean they may last longer, but the idea of trackdays is handling and cornering and being stuck to the road, not whether your tires last 8,000 or 10,000 road miles surely..... ?
I was always taught that handling was most important on trackdays, and to decrease PSI by 2-3 below normal road pressures.....
Yes increasing the pressure may mean more even wear and mean they may last longer, but the idea of trackdays is handling and cornering and being stuck to the road, not whether your tires last 8,000 or 10,000 road miles surely..... ?
I remember many years ago back in NZ taking a heavily modified Rover SD1 to the track (Toyota Supra 'box, Quaife diff, big brakes, modded engine etc) under the guidance of a racing driver who had been a front runner at Bathurst in M3's back in the Group A days of the late '80s.
He told us to whack our 205/60/14s up to between 40 & 44 PSI COLD. Okay - these weren't track tyres - but the point stands - you don't want too much sidewall flex or distortion in the shape of the footprint. Think of your tyres as shoes - if they're under inflated it's like attempting a 100 sprint on runners four sizes too big for you!
He told us to whack our 205/60/14s up to between 40 & 44 PSI COLD. Okay - these weren't track tyres - but the point stands - you don't want too much sidewall flex or distortion in the shape of the footprint. Think of your tyres as shoes - if they're under inflated it's like attempting a 100 sprint on runners four sizes too big for you!
Nurburgsingh said:
Start High and come down.
Dont start low and hope that you'll heat them up enough to get the pressures right, you'll damaage the side walls of the tyres quicker than you think. more so when the track temp is a low as its likely to be around about now
I would have said start at normal road pressures & drop them down as they heat upDont start low and hope that you'll heat them up enough to get the pressures right, you'll damaage the side walls of the tyres quicker than you think. more so when the track temp is a low as its likely to be around about now
Even in the cold & wet at Oulton on Friday, mine were way too high (38/40) after only a few laps. (I run 32/36 F/R in the wet on T1-R's in the 944) Once I dropped them down they stayed consistent through the rest of the day.
edh said:
Nurburgsingh said:
Start High and come down.
Dont start low and hope that you'll heat them up enough to get the pressures right, you'll damaage the side walls of the tyres quicker than you think. more so when the track temp is a low as its likely to be around about now
I would have said start at normal road pressures & drop them down as they heat upDont start low and hope that you'll heat them up enough to get the pressures right, you'll damaage the side walls of the tyres quicker than you think. more so when the track temp is a low as its likely to be around about now
Even in the cold & wet at Oulton on Friday, mine were way too high (38/40) after only a few laps. (I run 32/36 F/R in the wet on T1-R's in the 944) Once I dropped them down they stayed consistent through the rest of the day.
all very well to say dont go out underinflated but by default it is impossibe not to if you want to run hot at optimum psi.
if the tyres cool and pressure drops by say 2-3 psi or more when you are off track then all you do is go out and run 1-2 laps of session light and easy to get tyres up to pressure
otherwise if you run col at optimum psi you will have to come in to let down tyres which is just not practicable.
just dont go out too low or drive too heavy on cooled tyres
if the tyres cool and pressure drops by say 2-3 psi or more when you are off track then all you do is go out and run 1-2 laps of session light and easy to get tyres up to pressure
otherwise if you run col at optimum psi you will have to come in to let down tyres which is just not practicable.
just dont go out too low or drive too heavy on cooled tyres
Question here: My Megane RS265 runs 30f and 33r according to Renault's guidence for road use. Sticking with this on track the fronts will heat up quicker than the rears and so evening out the overall pressures. It makes sense to me but then so does higher pressures at the front due to the engine weight and weight transfer under braking. Also, reading above, what indicates softer/harder tyre walls? (I rum MPSS in the fronts)
Impossible to say without a tyre pyrometer. I'd love one but haven't found a cheap one yet. I've got an infrared pyrometer which isn't anywhere near as accurate, but apparently good enough to ball park it.
Usually you'll want to go a little lower than the recommended cold pressures, as the tyres will be getting hotter than during road use, and so they'll come back up to the recommended pressure anyway. The goal is to have the maximum contact patch, and drive smoothly enough so as not to overheat the surface of them.
If you're too far out of the sweet spot either way, you'll feel it as they slip. An under pressure kind of slip you can sometimes hear or feel, and it will be there from the start. And over pressure slip usually gets worse the longer you're out there, and feels less juddery.
If you find that a few laps of pushing in, where you're being smooth and not sliding the car, the tyres start to die a little bit, it usually means you need to drop a pound or two out of them, as when they get hot, the pressures are going too high.
But if you're just sliding around a lot, the pressures might be fine, but instead you're just overheating the surface.
This only really applies to a decent set of well regarded sports tyres that are well matched to the car, otherwise they might just plain overheat and slide regardless of what you do.
Either way, don't make your decision until a few laps in, and while you need to lean on them to bring them up to temperature, do it smoothly, and load them up firmly, but progressively.
With a tyre pyrometer, and an accurate gauge with a bleed valve, you can nail the tyres AND get a direction on where you need to go with camber. I wish there was a basic £50 probe type tyre pyrometer.
Usually you'll want to go a little lower than the recommended cold pressures, as the tyres will be getting hotter than during road use, and so they'll come back up to the recommended pressure anyway. The goal is to have the maximum contact patch, and drive smoothly enough so as not to overheat the surface of them.
If you're too far out of the sweet spot either way, you'll feel it as they slip. An under pressure kind of slip you can sometimes hear or feel, and it will be there from the start. And over pressure slip usually gets worse the longer you're out there, and feels less juddery.
If you find that a few laps of pushing in, where you're being smooth and not sliding the car, the tyres start to die a little bit, it usually means you need to drop a pound or two out of them, as when they get hot, the pressures are going too high.
But if you're just sliding around a lot, the pressures might be fine, but instead you're just overheating the surface.
This only really applies to a decent set of well regarded sports tyres that are well matched to the car, otherwise they might just plain overheat and slide regardless of what you do.
Either way, don't make your decision until a few laps in, and while you need to lean on them to bring them up to temperature, do it smoothly, and load them up firmly, but progressively.
With a tyre pyrometer, and an accurate gauge with a bleed valve, you can nail the tyres AND get a direction on where you need to go with camber. I wish there was a basic £50 probe type tyre pyrometer.
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