718 GT4 Track Tyre Pressures

[Sut0l]

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

What pre track preparation do `you` do ?

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

What pre track preparation do `you` do ?

None what so ever regrettably. Doing it properly would mean getting the tyre temps up to say 80C letting them fully cool down and repeat. That's possible on a track day if you have a spare set of wheels handy

 

[Sut0l]

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)

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)

Avon ZZRs are a great tyre which I use on my VX220 but require respect in the wet. They have always remained consistent and wear economically.

 

[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.

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?

Mine was not feathering….just showing another on track tyre damage issue

 

[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?

Mine was not feathering….just showing another on track tyre damage issue

The more I think about it, I'm thinking a geo is necessary

 

[ralphmusic]

I have never had a car from Porsche where the alignment was in spec. and consistent across each axle. With new ones I do around 1k running in miles including one track day and with the suspension settled plus experience of track behaviour, I take it to CG 250 miles away to have the car set up properly.

It will be interesting to see your alignment “befores” and whether they have contributed to your understeer.

 

[JamesBall]

I have never had a car from Porsche where the alignment was in spec. and consistent across each axle. With new ones I do around 1k running in miles including one track day and with the suspension settled plus experience of track behaviour, I take it to CG 250 miles away to have the car set up properly.

I've never had a 'fun' car I haven't had the geo done pretty much as soon as I've bought it (and every 1 or 2 yrs thereafter). The idea of spending £££££££ on something and it not driving quite right for the sake of a few hundred pounds on a geo seems like madness to me, regardless of track days.

 

[AndrewCS]

Ralph ...

Where are the ride height measurements taken at please ?

 

[ralphmusic]

Andrew,

At the proper measurement points, I don't know where these are but google may be of more help than me...

Ralph

 

[AndrewCS]

Andrew,

At the proper measurement points, I don't know where these are but google may be of more help than me...

Ralph

pp Rennlist ... believing that 981 and 718 are the same

Noting from GT4 Service Information : 2016 Technik Introduction | Porsche Forum from Porsche Club GB

Before adjusting the vehicle height/wheel loads, remove all suspension/stabilizers on the front and rear axles. The effects of the high turning forces of the stabilizers can falsify the measurement

 

[MrDemon]

cups are past their best after 15 heat cycles, but still usable. Depends what you are after, it won't cause more under steer as the rears will also have gone off, they will just be slower laps with said grip levels so you have to slow down.

if you are after times fit AO52's and leave all the other GT4's for dead on track with cups on ;-)

If you feather the edges you are driving too hard into the bend or don't have enough camber, below -2.5 seems pointless for track and a waste of time and money imo the way prices are going inc tyres etc.

-2.5/2.6 seems the max limit with out having caster pucks fitted. I see many people push the car though under steer and it just wrecks the tyres. these modern cars will let you abuse the tyres but the tyres will give up if driven incorrectly.

you will get round but will kill and even bend the tread blocks, which is very common with miss driven cars on track under steering every where. Not saying this is the case but it's very common to see wrecked tyres at track days. Electronics will get you round at the price of a set of tyres.

 

[Sut0l]

Thx MrDemon for that info, all useful stuff. When you say heat cycles, I was under the impression that you get the tyres upto say 80degC and then let them cool down to ambient which counts as one cycle. Your interpretation would seem to somewhat different. Could you explain please.

Got these photos. If you can see anything out of the ordinary let me know. Should be noticeable which is front and rear. You can see the feathering I was talking about. Tyres are down to 5mm tread front and 3mm rear. All track work done at Goodwood. I have another set of tyres ready to go on, which after fitting will be followed by a geo check/adjustment. Apologies if all this is a bit anal but I want to understand the science behind it all. I'm not complaining about the tyre wear just curious to know that the setup is all ok and any abnormalities are down to my driving style..

After 1st track outing

https://photos.app.goo.gl/bUkwxvrJFdPwfZr16

After 5 track outings

[link]https://photos.app.goo.gl/tWvJHCLkz9ZtvG7P6[/url]

 

[MrDemon]

I don't like running mine too hot. You can tell if the blocks have warped/bent over as you will get a vibration though the steering wheel.

1: what is your camber atm, do you get vibration though the steering wheel now ?

the tyres just about look ok just a slight bending at the end of the tread block maybe over driving though the understeer. I don't track these days (1 a year for a go) but only stay out 6 laps ish and you can feel the tyres go greasy/hot.

here is a tech PDF for the R spec hard core CUP R

Technical Bulletin_PSC2R.pdf (michelin.co.uk)

I used to set my PSI after a proper pyro heat gun mesurment. but no one seems too do this for some reason now days.

I think 82oc is max grip on a Cup2.

 

[Sut0l]

I don't like running mine too hot. You can tell if the blocks have warped/bent over as you will get a vibration though the steering wheel.

1: what is your camber atm, do you get vibration though the steering wheel now ?

the tyres just about look ok just a slight bending at the end of the tread block maybe over driving though the understeer. I don't track these days (1 a year for a go) but only stay out 6 laps ish and you can feel the tyres go greasy/hot.

here is a tech PDF for the R spec hard core CUP R

Technical Bulletin_PSC2R.pdf (michelin.co.uk)

I used to set my PSI after a proper pyro heat gun mesurment. but no one seems too do this for some reason now days.

No vibration. The car is as per factory settings, but as others have said that doesn't mean they are correct! I don't get anywhere near 100%, probably 80%. The increasing laptimes is not a worry it's just good to stretch the car once in a while. As I will be getting the new tyres fitted in makes sense to check that the setup is correct in any case.

 

[MrDemon]

buy a pyro, I think the max grip is 82 oc for the Cup2 then it looses grip.

go get-2.6 camber up front and buy some rear Cup toe links maybe circa -2.2 at the rear.

this is doable without top mounts and will also increase your front track which is good. Swap out oem pads also they are dire for track work.

I run Manthey Pads but they do make a bit of noise when you nanny them.

 

[MrDemon]

PS. or buy cup 2 connects they have more grip than a normal cup2 and they tell you what PSi to run and when they are too hot.