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Tyre pressures on track days - advice please

Johnny H

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Joined
23 Jun 2008
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Any advice out there re above,. Several other drivers have said I should let pressure right down once tyres have heated up, but should they not be just dropped to the recommended level as shown on car?
 
Regular road tyres as supplied on car (on 2nd rear set) 295/30 ZR19 (100Y) rear 235/35 ZR19 (87Y) front.
 
I've been messing with pressures on exactly the same size tyres. Generally a drop of 4lb/in² in front and rear have not been too bad for me on a cool day. When the track temp is higher as it was in Spa this year and it was 30 deg in the sun, 4lb/in² was not enough.

The rears, even though were reduced to 40 cold, ended up being 50 when hot!! It wrecked the tyre too easily....

I think 3-34 front (HOT) and 37-38 rears (HOT), but have yet to try that combination.
 
Thanks for the tips, also that other thread reminded me that the left tyres wear faster on a clockwise track (as I discovered at Mondello). Track use seems to fairly shred the road tyres!

Also noticed the item about the torque wrench for checking the wheel nuts (my own nuts usually tighten at the first corner!). The right torque settings I guess are in the owner's manual.
 
Johnny H said:
Thanks for the tips, also that other thread reminded me that the left tyres wear faster on a clockwise track (as I discovered at Mondello). Track use seems to fairly shred the road tyres!

Also noticed the item about the torque wrench for checking the wheel nuts (my own nuts usually tighten at the first corner!). The right torque settings I guess are in the owner's manual.

I believe the torque is pretty much standard on all Porsches - 130 nm.

p.s. I see that you've not been a member here for long, so welcome to the madhouse :thumbs:
 
Thanks for the welcome, I have to say I've found out more on these forums to help me get ready for 2nd visit to the 'Ring next week then anywhere else.

I think I have contracted a full-blown case of "obsessedwith911s-itis"!
 
I now tend to taske an educated guess, depending on the track, direction, day (temp) and type of bends -urr a little high, do one session to warm up and the bleed them down to about 38 ish hot. As I don't drive much between trackdays, often don't alter them inbetween either!
 
I drop mine by 3 psi on track vs the std road going PSI level
 
wizard993 said:
I drop mine by 3 psi on track vs the std road going PSI level

Is that all round? The reason I ask is that I've measured increases in my rears of up to 8 psi on track on a hot day. And the fronts have only gone up by half that. Hence I end up taking more air out of my rears by than my fronts.
 
Average conditions /dry(short bursts on track) - I drop them by the same amount all round.

If it's mega hot(which is not that often in jockland) I take another 1/2psi out the backs but NEVER ever anymore.

Once a 911 starts rolling about on it's rears you can chuck in the towel.

I know it's not easy deciding what to run them at but mine never has less than 37psi(18" wheels) in the rears under any circumstances.
 
wizard993 said:
I know it's not easy deciding what to run them at but mine never has less than 37psi(18" wheels) in the rears under any circumstances.

Must have been a slow day in the wet! Try Spa in the middle of summer and your 37psi will be hitting 47-50psi with a very squirmy rear end ;)
 
"Must have been a slow day in the wet! Try Spa in the middle of summer and your 37psi will be hitting 47-50psi with a very squirmy rear end "

Those GT3 drivers must be the best-of-the-best :worship: as I get 43/44PSI in the wet/dry when nicely warmed up....never had any traction/grip issues on full chat/pushing hard....but then again, I ain't been to Spa.

....I have often wondered why it's usually GT3 or Turbos that leave the road/tracks going backwards(wet or dry) :floor:
 
At Silverstone yesterday evening I had yet another go with pressures. I ended up with 32 in the front (HOT) an 38 in the rear (HOT).

The front tyres after a 5 or six leap stint were not every warm at all almost perfect I would say and turn in was a little better. I guess I could have raised them to 34 (HOT) without much difference.

The rears did get a little hotter and seemed to manage okay also, but I think a couple more lb's perhaps, maybe 36/37, but now I'm splitting hairs aI think.
 

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