Cayman S 987 Gen 2 — track day geometry?

[jcarruthers]

I'm getting my geometry checked/done next week in readiness for a track day.

The question was asked "road or track geometry"

I have PASM.

Opinions on this?


James

[mrdemon]

You cannot get a track geo with stock parts,
Just get them to max out the movment available in the top mounts have no front toe and fit some front spacers.

[IREvans]

jcarruthers said:

I'm getting my geometry checked/done next week in readiness for a track day.

The question was asked "road or track geometry"

I have PASM.

Opinions on this?


James

There isn't a lot of adjustment possible on the 987S, but I'd be inclined to ask your garage to set it up for track. This will mean adjusting the front camber up to around -1 degree by moving the top mounts inwards. Make sure front toe is parallel. The downside of track geometry is that your car may feel a little more busy on the road (due to the increased front negative camber), but you may prefer it..?

Not sure if you've been on lots of track days or not, but the biggest effect on the car's handling you can have on the day is to adjust the tyre pressures during the day as they get hotter. Just remember to re-inflate them before you drive home..!

[edc]

I don't know whether this can be done for a 987 but for both my 986 the top mount slots have been drilled/ground out by a further ~5mm. This allows you some extra negative camber. My current car runs a little over -2 deg at the front like this.

[vee5]

..and on the subject of tyre pressures, I'm about to track my Michelin-shod 987S for the first time so without prior experience was going to start with standard road pressures and then take it from there - interested to hear others opinions on what presures they've found to work well?

[Trev450]

I find with my 987S which is also Michelin shod that starting on stock pressures (32 F, 36 R) is fine, but after about 3 to 4 laps (depending upon track length), you need to drop them back down as they rise quite a bit.

[gtsralph]

IREvans said:

There isn't a lot of adjustment possible on the 987S, but I'd be inclined to ask your garage to set it up for track. This will mean adjusting the front camber up to around -1 degree by moving the top mounts inwards. Make sure front toe is parallel. The downside of track geometry is that your car may feel a little more busy on the road (due to the increased front negative camber), but you may prefer it..?

Thanks for the above, but what about the rear settings, leave at stock?

[vee5]

Thanks Trev450. Do you find that dropping hot tyres to "cold" pressure values avoids too much damage to the outside of the tyre?

[mrdemon]

You will kill the outside of the tyres, the stock cars roll and you cannot combat all that with camber.

Stock pressures on the R is 30/31 any way so much lower than the 36 talked about.

Also don't drop them 1st you will scrub the tyres, go out for a few laps come in and then drop them.

[Trev450]

vee5 said:

Thanks Trev450. Do you find that dropping hot tyres to "cold" pressure values avoids too much damage to the outside of the tyre?

As mrdemon says, you won't avoid destroying the outer edges, but dropping to cold pressures afer a few laps will allow you to stay out longer before the tyres 'go off'.

[Trev450]

[quote=mrdemon]
Stock pressures on the R is 30/31 any way so much lower than the 36 talked about.
[quote]

Why should that be?

[mrdemon]

Not sure, my mates cayman s is listed as 30/31 also it seems porsche dropped them a lot

Spyders also 30/31

[Trev450]

mrdemon said:

Not sure, my mates cayman s is listed as 30/31 also it seems porsche dropped them a lot

Spyders also 30/31

Is that a 987.2 as well? Mine's a 987'1 and the pressures given on the inside of the door slam are definately 32F, 37R.

[mrdemon]

Yes his is a gen 2 ,

What's your wear like ? If it' s a bit bolder in the middle try a few psi lower.

[Trev450]

mrdemon said:

Yes his is a gen 2 ,

What's your wear like ? If it' s a bit bolder in the middle try a few psi lower.

No the rears wear very evenly across the whole width. The fronts as we've already established destroy ther outer shoulder, but apart from that they wear evenly too.

[jcarruthers]

Thanks all for your replies.

@IREvans — I've always set up my (classic) cars with more camber on the front so that works for me. My worry is tyre wear when most of the mileage is going to be road. Not too worried about slightly more twitchy handling. I've done quite a few track days now — I have a tyre pressure gauge and IR temp gun at the ready. I usually drop them down only a couple of PSI before going out if the ambient temp is reasonable as in the past I've always had them warming up fairly quickly. I'm interested to see how helpful the TPMS is!

@mrdemon — my 987.2 is 32 and 34 on 19" wheels (I think!) — pretty sure none of the pressures are as low as you're stating.

Edited by jcarruthers on Saturday 12th July 09:33

[Far Cough]

I tracked my CR and made some changes to mitigate the outside shoulders getting a hammering. Firstly as mentioned , the stock suspension wont let you change the camber enough to stop the outside edge wear. Modifications to the top mount can be made but even when that is maxed out it still is not really enough if you are pushing on track. Modifications can be made at the lower end of the suspension and new Lower Coffin Arms which are adjustable can be fitted but they are far more expensive than a simple "Dremel and Geo" job !However they will allow much more adjustment to the track setup.

I went the top mount route which is pretty invisible to all but the geekiest of Porsche experts and didnt want to ruin the on road handling - I was after a compromise that meant I didnt have to put 2 new tyres on it after every trackday !

Mine was MPSS shod and at Spa I played with the pressures and found the following results. All these pressures are hot pressures and enabled the tyres to "stay in shape" rather than deform and roll onto the shoulder increasing the rate of wear. This was with std geo.
40F 40R - Understeery
40F 38R - neutral
40F 37R - oversteery

I also found that 38 front and back hot gave more traction and the car was neutral in handling but I could see the wear starting to happen.
Once the Camber had been changed I was able to run 32F and 35R which gave a good balance on the shorter UK circuits

Hope that helps and gives you food for thought

[jcarruthers]

Far Cough said:

I tracked my CR and made some changes to mitigate the outside shoulders getting a hammering. Firstly as mentioned , the stock suspension wont let you change the camber enough to stop the outside edge wear. Modifications to the top mount can be made but even when that is maxed out it still is not really enough if you are pushing on track. Modifications can be made at the lower end of the suspension and new Lower Coffin Arms which are adjustable can be fitted but they are far more expensive than a simple "Dremel and Geo" job !However they will allow much more adjustment to the track setup.

I went the top mount route which is pretty invisible to all but the geekiest of Porsche experts and didnt want to ruin the on road handling - I was after a compromise that meant I didnt have to put 2 new tyres on it after every trackday !

Mine was MPSS shod and at Spa I played with the pressures and found the following results. All these pressures are hot pressures and enabled the tyres to "stay in shape" rather than deform and roll onto the shoulder increasing the rate of wear. This was with std geo.
40F 40R - Understeery
40F 38R - neutral
40F 37R - oversteery

I also found that 38 front and back hot gave more traction and the car was neutral in handling but I could see the wear starting to happen.
Once the Camber had been changed I was able to run 32F and 35R which gave a good balance on the shorter UK circuits

Hope that helps and gives you food for thought

Thanks for all this. How many degrees of camber are you running?

I have heard of using GT3 LCA — do they allow adjustment?

[mrdemon]

yes GT3 LCA or RSS or the GT3 pattern non branded part

[Far Cough]

jcarruthers said:

Thanks for all this. How many degrees of camber are you running?

I have heard of using GT3 LCA — do they allow adjustment?

I managed to get just about -2 degrees on the front after the modification to the top mount. You are limited on one side by the presence of a bulkhead so although in theory one will go more they need to be the same each side and the limiting factor is how far you get elongate the slot.

This setting hardly made any difference to the road manners or showed any increase on the inside of the tyre. If I was pushed I would say the front end was more pointy but not the extent it would throw you into the ditch on a bumpy road.

The cost of this was approximately half the cost of one RSS adjustable coffin arm !! and I could have gone further by adding wheel spacers but didnt feel the need too. The result was unchanged road handling and less wear on the front tyres when on track which was the compromise I was after.