718 GT4 Track Tyre Pressures

[Sut0l]

Firstly apologies if this has been discussed elsewhere in the forum. Please direct me otherwise.

I have Cup 2s on my car and was wondering what hot tyre pressures you would recommend. Previously I have used 33psi all round. I have done 5 track days on the current set and in the last outing I did experience more understeer. So it would be useful to know how others have found this as the tyres are used on track numerous times. TIA Chris

 

[Twinfan]

I've been running 32psi all round when hot which I've found great. A friend runs slightly lower front at 30psi with 32psi rear. I think if you're in this kind of ballpark, which you are, then all is good. The odd psi here and there doesn't make a huge amount of difference.

Your understeer could be down to driving style or geo settings?

 

[AndrewCS]

FYI ...

Michelin PS Cup 2`s ... info | Porsche Forum from Porsche Club GB

 

[Twinfan]

Awesome info, cheers!

 

[Sut0l]

FYI ...

Michelin PS Cup 2`s ... info | Porsche Forum from Porsche Club GB

Thank you Andrew that's brilliant So it looks like I've been on the money re hot pressures.

I've run my car at Goodwood for each of my 5 track excursions (clockwise circuit) and the tyre wear reflects this. I was wondering if this has increased the understeer.

 

[ralphmusic]

I've run my car at Goodwood for each of my 5 track excursions (clockwise circuit) and the tyre wear reflects this. I was wondering if this has increased the understeer.

Where at Goodwood are you experiencing understeer?

 

[Sut0l]

I've run my car at Goodwood for each of my 5 track excursions (clockwise circuit) and the tyre wear reflects this. I was wondering if this has increased the understeer.

Where at Goodwood are you experiencing understeer?

Madgewick and Fordwater. Fordwater mainly, used to be 120-125, now 115-120. Lap times dropped from 1:28 to 1:32 (big drop). Maybe just me getting older

 

[Twinfan]

After a number of heat cycles you may be finding that the Cup2s are past their best. I've done a similar number of days on a set and while they've got plenty of tread left they've started to lose grip for me at the rear and I'm oversteering out of corners.

If you've regularly been turning them blue, so that the oils are escaping, you may be in a similar situation to me?

 

[ralphmusic]

I've run over 30 times at Goodwood and get slower each year, but I am on my 4th 3 year licence extension.

My track coach suggested I take a later turn-in to Fordwater and get on the power earlier and for me Madgewick is about getting the best line but with that corner's camber I can see how you might get understeer. Do you not have understeer at Lavant?

What are your alignment settings, mine are below:

Note the "before", particularly rear toe where small differences can have a noticeable effect.

I am going back to Center Gravity in July to have motorsport rear toe control arms fitted which will allow more camber with a little more ride height (both axle's camber is constrained by the OEM rear toe adjustability) as this second PDK GT4 with the same alignment as my earlier manual one, seems to hit the bump stops too easily.

 

[Sut0l]

After a number of heat cycles you may be finding that the Cup2s are past their best. I've done a similar number of days on a set and while they've got plenty of tread left they've started to lose grip for me at the rear and I'm oversteering out of corners.

If you've regularly been turning them blue, so that the oils are escaping, you may be in a similar situation to me?

Not noticed blueing but did notice quite extensive feathering after the first couple of td's.

 

[Sut0l]

I've run over 30 times at Goodwood and get slower each year, but I am on my 4th 3 year licence extension.

My track coach suggested I take a later turn-in to Fordwater and get on the power earlier and for me Madgewick is about getting the best line but with that corner's camber I can see how you might get understeer. Do you not have understeer at Lavant?

What are your alignment settings, mine are below:

Note the "before", particularly rear toe where small differences can have a noticeable effect.

I am going back to Center Gravity in July to have motorsport rear toe control arms fitted which will allow more camber with a little more ride height (both axle's camber is constrained by the OEM rear toe adjustability) as this second PDK GT4 with the same alignment as my earlier manual one, seems to hit the bump stops too easily.

Yes Lavant naturally as off camber, careful if damp!

Admission - the car is on its stock setup, re aero and geo. I think I'll get the cars geo checked and maybe get a fast road setup put on it, if it's not on it already. Thanks for the info

 

[JamesBall]

I don't have hard evidence but I belive Cup 2s go off after about 5 or 6 track days. They seem to go hard then last for ever. Great for saving money but not so good for grip (and lap times)

 

[Sut0l]

I don't have hard evidence but I belive Cup 2s go off after about 5 or 6 track days. They seem to go hard then last for ever. Great for saving money but not so good for grip (and lap times)

Now that is interesting as that just about describes my situation! Also the tyres are no longer feathered but are roughened and do feel harder. There is still plenty of tread on them though, so it looks like I will haveto sacrifice 4s a lap for the time being. I do have another set waiting to go on which I bought when Michelin were doing a cashback deal.

 

[Twinfan]

Yep, that's what I was alluding to. It's all about the heat cycles.

I'm not interested in lap times but I am interested in having confidence and good grip! I'm swapping to a fresh set in a couple of weeks prior to Silverstone in July.

 

[AndrewCS]

For road use ... I found that it takes quite some time - miles for them to scrub in

What pre track preparation do `you` do ?

 

[ralphmusic]

Now that is interesting as that just about describes my situation! Also the tyres are no longer feathered but are roughened and do feel harder. There is still plenty of tread on them though, so it looks like I will haveto sacrifice 4s a lap for the time being. I do have another set waiting to go on which I bought when Michelin were doing a cashback deal.

You say feathered?

These are from one Silverstone GP track day even after driving 200 miles home - I removed over 800 grams of OPR off the four tyres. Hot days and others' slicks or really soft rubber can do this.

 

[Twinfan]

For road use ... I found that it takes quite some time - miles for them to scrub in

What pre track preparation do `you` do ?

Nothing specific, just try to get some miles on them to remove the release compound. First sessions of every day I always take easy anyway so they have plenty of time to scrub in.

 

[ralphmusic]

Bit like F1 [8D]

 

[JamesBall]

I've used brand new tyres, fitted in the pit lane, on track days. The first lap was like driving on ice but after two or three laps I was able to give it full beans (although this was ZZR extremes, on a Caterham)

 

[Sut0l]

Now that is interesting as that just about describes my situation! Also the tyres are no longer feathered but are roughened and do feel harder. There is still plenty of tread on them though, so it looks like I will haveto sacrifice 4s a lap for the time being. I do have another set waiting to go on which I bought when Michelin were doing a cashback deal.

You say feathered?

These are from one Silverstone GP track day even after driving 200 miles home - I removed over 800 grams of OPR off the four tyres. Hot days and others' slicks or really soft rubber can do this.

that almost looks like pickup rubber from the track. What I call feathering is if you imagine a pine cone, run your fingers over it one way and it's smooth, the other way rough. Hope that makes sense?