Tire pressures for track days

[kyliesmith.com]

Doing a few laps next weekend at our local racing park with the Lotus club, just sprints and nothing too dramatic!! But I want to know if people are using a lower pressure than the recommended 32psi for the track. I used to run dot performance tires on the 89 Turbo and got the temps even across the surface of each tire when measured hot after loads of testing and mucking around, but cold temps meant these were down to 28psi cold and yes ok they were smaller tires with a taller profile. How do pirellis perform under extreme heat? I have P-Zero neros on the front and Rossos on the rear in 285 rather than the specd 295's from new. I admit the rears are hard as rocks and I hope to throw these in the bin soon, so I want to make sure I have an even temp across the tire to maximise my grip.

I know most of you have tracked your 350's so opinions please

[MPx]

Unless its really cold Kylie, isn't it more normal to put pressures up a few pounds for track use? I get my (narrow) 235s really hot with an extra 3-5LB in on track and get great grip. Have only gone softer in the rain etc. when the tyre needs help to warm up.

Mike

[Daniel]

I've not tracked the 350 yet (YET) but I've done loads and loads of track days in Esprits Exige's and Elises, not to mention years of bike racing.

When I do track the 350, because it's a car I've not driven before on tyres I've never used, I'll be dropping the standard pressures, certainly at least on the rears, by maybe up to 4 PSI. Simple reason is that I'll get better feedback but maybe sacrificing overall grip. You can feel the tyre scrabbling earlier.

Depending on the weather, I'll probably do that for 1 maybe 2 sessions, then up the pressures gradually.

I'll certainly be doing my first 350 track day on a circuit I know well.

Check out your ride heights too, PM me if you need the standard settings.

Let me know how you get on.

[andydclements]

When I did the driver training day, which is admittedly more tight cornering than a normal track, I had to nearly double the pressure just to stop the car from destroying its own tyres. At normal road pressure they were rolling over so badly it was scuffing the side wall.

Andy

[kyliesmith.com]

Unless its really cold Kylie, isn't it more normal to put pressures up a few pounds for track use? I get my (narrow) 235s really hot with an extra 3-5LB in on track and get great grip. Have only gone softer in the rain etc. when the tyre needs help to warm up.

Mike

Well being summer here it dosent get colder than 15 deg c at night and 26 during the day

A friend of mine has a car like yours with factroy specd tires and he made the mistake of putting his pressures up cause someone said so. He did so many spins and frustrated as hell. After talking to him that his Geo set-up was perfect and other driving factors we took some air out of his tires and he got his grip back on the next outing. But again I warned him that my experience was with race dot performance tires only and I had no experience in his car set up. That is why I am on here as I know how critical it is to set up the tires to minimise you having an "OFF"

I've not tracked the 350 yet (YET) but I've done loads and loads of track days in Esprits Exige's and Elises, not to mention years of bike racing.

When I do track the 350, because it's a car I've not driven before on tyres I've never used, I'll be dropping the standard pressures, certainly at least on the rears, by maybe up to 4 PSI. Simple reason is that I'll get better feedback but maybe sacrificing overall grip. You can feel the tyre scrabbling earlier.

Depending on the weather, I'll probably do that for 1 maybe 2 sessions, then up the pressures gradually.

I'll certainly be doing my first 350 track day on a circuit I know well.

Check out your ride heights too, PM me if you need the standard settings.

Let me know how you get on.

Hi Yep am hoping Mike, RobC or some of the other diehard track day guys will chim in. I might email them and let you know. Re ride height did you check with two people sitting in the car or not necessary? I can always drag the neighbour over!! Will have to measure that later on tonight, as Simon and I replaced the drive shaft seals yesterday so will need to let the rear suspension settle down.

[oneshot]

Did a run in Germany with my brother (he was in his Porche 928GTS) and we upped the pressure by 2psi.

The owners handbook says that for a standard V8 the tyre pressure should be upped from 2.0bar to 2.5bar for sustained speeds over 149mph BUT the handbook says for the sport 350 in ALL conditions pressure should be 2.2bar

[Daniel]

Re ride height did you check with two people sitting in the car or not necessary?

Lotus set it with two people and half a tank of fuel, so that's what I did.

[mike_sekinger]

Hi Kylie,

The Sport350 was designed with track work in mind, so I

[kyliesmith.com]

Geday Mike thanks for the advice, with the tires I was told they were Pirellis, but when I got the car here to NZ closer look unveiled Rossos on the rears. The Neros on the front have heaps of good tread and only a few years old, they feel quite good and not hard. However the Rossos are down to 4mm and gone quite hard but have even wear. I am hoping to replace these with some Neros later on this year I hate mismatched rubber and these rears will be a bit skiddy hence getting the correct psi in theme.

Re extra power yeah ive got more power than I can shake a stick at - for me anyway!! I will be really careful here and hope to be in 3rd on the only hair pin corner and just torque it out rather than that extra punishment on second, I have nothing to prove to anyone so I am not fussed if other V8 owners will be peeling out quicker times.. Its only a 1.3km high speed track with minmal twisties and will be doing four laps each outing with a tire warm up lap and come off for 3/4 break before going back on again. Plenty of time for brakes and engine to cool down. Usually I will do around 4 sets for the day but can do up to six if I want. I tend not to do the last ones as I am usually feeling mentally and physically stuffed so a good time to finish up and watch the others.

Ill focus on smooth gear changes, no dumping the clutch and careful of releasing 5 gear down to 4th and top end speeds. Ive the got the camera mounted already its all go.

[Günter]

as you know, I'm only a beginner as as you also may know I'm simple minded -so after all i was on the Hockenheim racetrack ("das Beste Ostern 2007 Hockenheim LCD" as seen in youtube...) with my 235/285 Dunlop Sport 9000 road tires and the overpressure setting from long distance/ fuel efficiency "Autobahn calculations". I run normally 2.5 bar -and more!

That was just to much for perfect traction and grip. Even after a few runs , i could hold my hand on the wheels.

But maybe i was simply so slow as i have a lag of race experience: missed the Sport 350 reference time by 15 (!)seconds (reference is the Sport Auto car test from 9/99 , witch was won by the sport 350 against the F355 ! )

[kyliesmith.com]

Gunter all I know is temperature of the tires is critical to overall grip on the entire surface of the tread while on the track. I used to have access to a infra red digital scanner when I was working in a Lab and meansured the tires ASAP after four laps on track each time. Initially the tires were piping hot in the middle and 3/4 the way across towards the outer edges were alot colder by heaps as expected, as the tires simply balloon up. So I let a little air out and after two more adjustments I pretty much got the inside within a few deg C to the outer measurement. Ideally this needs to be measured actually while the car is running as the tires a constantly trying to cool, but in my case by feel and a little tweaking. The difference was night and day performance wise and so much more better grip. For road use I put them back up up to 4 psi as they will naturally operate colder in cruise mode .

Edited March 27, 2008 by kyliesmith.com

[Günter]

after all experience from those days , i would say : Yes , not more than 2.3bar (even less )with cold tire

the others (from the Club meet) gave me also the advice to reduce my pressure. Otherwise i wouldn't be happy on the track .... .

All i can say -i was more outside from the ideal line, and grabbed up much from the hot *slick*-rubber that the others(Elise's, Cup exiges, Alpines, R5 -Turbos ...) lost at the grid. And that cools down immediately at my much colder tires - and produces a "rough ride" ...

[neal]

[all pressures are quoted with cold tyres]

On the road I go with the stock pressures 29psi at the front and 28psi at the rear (I use 28psi instead of 29psi at the rear since going from 285s to 295s to achieve the same loading - I guess the S350 specifies 29psi for the rear due to the extra downforce from the wing).

I've now done a couple of dry track days since fitting my new rubber (Potenze RE050A). I found that the rears were running nicely hot. However, the fronts were pretty cool. So I had to reduce the fronts to 26psi and that brought them up to temperature in line with the rears.

I agree with Mike that the fronts are a bit oversized. Alas, you can't get a 225/40/R17. You can get a 225/45/R17 but the diameter would be 14mm greater than stock which would look odd and might rub the wheel well. You can also get a 215/45/R17 which would only be 5mm greater diameter than stock but a 215 tyre is a bit too small for an 8.5 wheel.

[kyliesmith.com]

Hi Neal this is interesting. Was on track yesterday with 32psi (recommended for S350 set-up), I felt were a little too much and I really wanted to let some air out!!!! I felt like I was in the drift squad!!! I checked the tyres as soon as I came into the pits using an infrared heat temperature scanner and the tyres were hotter in inside as expected with the camber and temps were not even on the midde and outer edge.

My tires went off after the first lap (unauable and slippery), so will be binning the old rears that are on them. I might just just consider getting a second set for the track, and go the smaller sizes as well. I was running 225's and 255's on the 89 Turbo with dot performance Toyos and was dialled in perfectly for grip and handling. A comprimise to both of these sizings would be good.

[neal]

Where did you get the 32psi all round (normal usage) figure for the S350 - the owner's manual? There's nothing about it in my service notes, which covers the S350 in other specific areas, e.g. brakes and wheels/tyres so I presumed it used the standand V8's 29psi all round. I also think I read recently on a different thread that a S350 owner checked with Lotus Technical and they told him 29psi.

I don't want to be too specific about my geometry settings since I have an adjustable suspension with my own spring and damper rates (though I've kept the stock ride height for now) but I did use the standard geometry as a starting pointing. After lowering the tyre pressure the fronts were fine - evenly heated across the tyre, but like you the rears were a lot hotter on the insides. I might expect a little warmer on the insides due to the straight line acceleration wearing against the negative camber but not that much. So I've reduced the rear camber from -1.5' to -0.5' and now get even heating (and pretty neutral handling)...

Edited March 31, 2008 by neal

[cweeden]

Hi Neal this is interesting. Was on track yesterday with 32psi (recommended for S350 set-up), I felt were a little too much and I really wanted to let some air out!!!! I felt like I was in the drift squad!!! I checked the tyres as soon as I came into the pits using an infrared heat temperature scanner and the tyres were hotter in inside as expected with the camber and temps were not even on the midde and outer edge.

My tires went off after the first lap (unauable and slippery), so will be binning the old rears that are on them. I might just just consider getting a second set for the track, and go the smaller sizes as well. I was running 225's and 255's on the 89 Turbo with dot performance Toyos and was dialled in perfectly for grip and handling. A comprimise to both of these sizings would be good.

Hi Kylie,

Did you measure the pressures when you came into the pits? I had a similar experince (on Toyo proxies BTW) at Bedford Autodrome last year. The front would understeer on the tighter corners but I didn't have a problem with the rear (nothing unexpected anyway). The pressures after a session had risen by about 10psi when hot. I adjusted them down to around 30-32psi which may no end of difference.

Neal,

32psi (2.2bar) is recommended in the handbook for the Sport350.

Incidentally I have a set of wheels with Goodyear F1's and a set with Toyo proxies. The proxies were on the spare set I bought and wouldn't have been my first choice. I think both tyres are very similar but I would still favour the Goodyear's if I had to buy another set. I had some time at the Nurburgring in those in torrential conditions and they were excellent. I also had some laps at Goodwood in the dry and they did go off after a few laps causing some mild drifting but still very managable and Goodwood is an abrasive track anyway.

cheers

-Chris

[Fred Basset]

If its hot I always reduce the pressue by 3-4psi in each wheel, pressure increases with heat so if you put them up they go up much more when you drive on track because they get hotter than on the road. I was first alerted to this by the guy who looks after my Evo, he used to be a mechanic for Dave Brodie in the Run baby run days and after that Tony Pond. Theory is that if the pressure is too high then you end up driving on the centres and have little grip.

That said I remember Matthew Becker and Gavan Kershaw's advice when I did a lotus experience day in a V8 GT and SE at Silverstone back in 98. They told me to keep the standard pressure for track work.

I don't track the Esprit much as it's too precious to me, the Evo does get used quite a bit and is very easy on its tyres with this pressure drop.

Regards

Fred

[kyliesmith.com]

Hi Kylie,

Did you measure the pressures when you came into the pits? I had a similar experince (on Toyo proxies BTW) at Bedford Autodrome last year. The front would understeer on the tighter corners but I didn't have a problem with the rear (nothing unexpected anyway). The pressures after a session had risen by about 10psi when hot. I adjusted them down to around 30-32psi which may no end of difference.

Neal,

32psi (2.2bar) is recommended in the handbook for the Sport350.

Incidentally I have a set of wheels with Goodyear F1's and a set with Toyo proxies. The proxies were on the spare set I bought and wouldn't have been my first choice. I think both tyres are very similar but I would still favour the Goodyear's if I had to buy another set. I had some time at the Nurburgring in those in torrential conditions and they were excellent. I also had some laps at Goodwood in the dry and they did go off after a few laps causing some mild drifting but still very managable and Goodwood is an abrasive track anyway.

cheers

-Chris

Hi Chris, yeah as soon as I got out of the car I measured them ASAP, not ideal but gives me an idea anyway.

I have never tried the T proxies (you referring to the T-1R?) on any of my cars but heard positive things with T1R's on our 350s and V8 set ups. I had an indepth discussion with my friend yesterday who has P-Zero Nero's on his V8 and he does not rate them at all, and he tracks his V8 a few times each yr over the last few yrs. He also said his 89SE used to lap faster through the corners on Goodyears and bringing in slightly quicker times than the V8, purely because he struggled getting the grip.

One of the S350 gents on here who has done some testing on the recommended P-Zero Neros, say the quality made today is not as good as what was previoulsy produced 8-9 yrs ago. My friend can back that up, but I like to experience these things first hand. Like as I say id still like to shod the car in Pirelli as speced from the factory for weekend cruising but like to get an extra set of race wheels with proper stickies for the occasional blat on the track. Failing this I am very keen to look into Ultra performance T-1R or Goodyears. Ive got some decisions to make Not easy. The best thing though is sharing real time experiences for track use to help everyone make better choices.

If its hot I always reduce the pressue by 3-4psi in each wheel, pressure increases with heat so if you put them up they go up much more when you drive on track because they get hotter than on the road.

Hi Fred, yep did heaps of testing with my 89 running Toyo RA-1's (stickies) and got them down to 26psi (cold). This worked a treat on the set-up I had for this car only so know about the theory well. However my first outing in the S350 on track I wasnt about to argue with what was recommended and really didnt want to tweak anything as you can imagine. Having old tyres that went off didnt help, but from what I know from measuring myself I will let a little air out next time and compare notes.