Cayman GTS track focused modifications

[Motorhead]

Hi Carl,

Some more dedicated track day fans will be able to offer more useful advice than I can provide, but just be aware that any modifications have the potential of invalidating your warranty. I suppose you could claim that by using GT4 LCAs you’re using a Porsche approved part which your dealer will be able to supply [with the Club 10% discount], or you could try Design911 who also give a 10% discount to Club members [see Porsche Post].

As far as I’m aware it’s not possible to change the rear suspension camber, the only adjustment being toe-in.

I’d be inclined to get a good geometry set-up from someone like Centre Gravity with the standard components and then put the car on track to see where you are and take it from there.

Please keep us updated on your journey.

Jeff

 

[Ryan9729]

Hi all,

I would like to get my CGTS a little more track focused as I plan to do quite a few track days this year coming,

Planned modifications:

• 1st on the list would be some GT4 Lower control arms in order to achieve around -2.0 camber at the front. (has anyone got a good link of where to purchase these?)
• I’d also like to run a set of dedicated track wheels and tyres, I’m just thinking of some secondhand 19s with Nankang‘s AR1’s 245 & 275/35/R19. Does anyone know of any TPMS systems that will connect without coding?
• I believe the rear in stock form can get to -2.0 camber so I don’t believe I need any modifications here? anyone know any different?
• lastly what pads to folk run on track, do stock hold up or is it best to run with something else

ultimately it’s still a road car so don’t want to induce NVH, but any other suggestions welcome.

thanks

 

[Ryan9729]

Jeff,

Thanks for reply, I'll keep everyone updated as I'm sure a lot of folk are interested in this route for track-days. As far as I can I'm going to be using all OEM parts, so whilst not the cheapest way to do things it should keep NVH down to a minimum and help not to invalidate any warranty although I know this is a risk.

I'll be in contact with Design 911 regarding the 991 GT3 Lower Control Arms, I think the part numbers compatible with the 718 are:

[ul][*]Left 99134104187[*]Right 99134104287 [/ul]If anyone knows any different let me know, the plan once I get these is to get alignment done, I'll ask the guys to give me the max camber on the OEM set up as that is good to know for everyone but I believe this to be around -1 degrees of camber and I'm going to need -2 degrees really for which the GT3 parts are good for.

 

[ralphmusic]

Is it not generally understood that the main camber constraint on the 981/718 platform is the rear toe control arms? Fitting split front wishbones will not address that issue although getting camber from wishbones is far better than relying on top mount adjustment.

Has the OP spoken to someone versed in suspension design and set up?

For what it is worth, my modified 981 Cayman was equipped thus:

Dampers: Bilstein B16 Damptronics Coil Overs

Springs: Eibach

FRONT

Main - ERS H 170-60-60 (343)

Helper - ERS 40-60-40 (229)

REAR

Main - ERS H 140-60-80 (457)

Helper - ERS 40-60-50 (286)

Length mm-Diameter mm - Nm/mm

Front Suspension: GT3 top mounts, RSS front wishbones, PF caster pucks, Tarett drop links and GT4 ARB

Rear Suspension: Elephant Racing top mounts, GT3RS wishbones, OEM drop links, RSS Toe Arms and GT4 ARB

Settings with 90kg 'driver' weights, full fuel tank and 7kg luggage:

F -3:20 camber, 0:02 total toe in, ARB 2 of 3 (medium)

R -3:12 camber, 0:20 total toe out, ARB 2 of 3 (medium)

Cross weights 768kg each diagonal

Total (EU) weight 1536kg inc. 90kg & 100% fuel

Car only (DIN) weight 1445kg inc. 100% fuel

Ride height 104mm/145mm

If you want Porsche rear toe control arms, use the Motorsport versions.

On pads, OEM parts now have reduced copper content and (on 992 GT3) are no so good as the 991 versions, laying down deposits under heavy track use that make the disc feel like it has warped. Best to fit after market (lots of personal preferences) or get some older type OEM pads.

 

[Ryan9729]

Jeff,

It surprised me somewhat when you said there is no adjustment for Camber in the rear so I popped under and had a look, it looks like I can add a bit more to the current alignment setting with the use of that eccentric bolt.

 

[Motorhead]

Carl,

I think you’ll find that the eccentric bolt will only give you toe adjustment, and as far as I know the strut top fixing has no adjustment, so not much to play with at the rear.

Jeff

 

[Ryan9729]

Jeff,

No mate that is definitely for the camber, the toe bar to the rear also has an adjustment bolt, I've attached a photo for reference for anyone else.

 

[ralphmusic]

Rear toe adjustment is limited and when maximisng camber you run out of toe adjustment

 

[Ryan9729]

Your right, the way Porsche have configured the set up means future adjustment is limited but still good to optimise what we have, when I get the alignment done I'll get the chaps to give indicative maximum numbers for camber and toe for the stock set up, this would be good information for all those wanting track there cars a bit more and have bit more of a tyre friendly set up.

As with all MacPherson set ups there is no roll recovery for camber meaning when the car rolls the degrees in which camber is dialed in reduces, this can have an adverse effect on handling and more importantly for those doing recreational track days is a lot of shoulder wear on tyres. Your superior GT4 set up being double wish bone does not suffer from this.

 

[ralphmusic]

I wish the GT4 did have double wishbones but it’s the same basic architecture albeit better camber adjustment limited by rear toe control arms.

 

[Motorhead]

Jeff,

No mate that is definitely for the camber, the toe bar to the rear also has an adjustment bolt, I've attached a photo for reference for anyone else.

That’s interesting Carl. I run a 987.2 CS which as far as I’m aware only has rear toe adjustment, so it looks as though a useful additional level of adjustability is available for the 718, even as Ralph has pointed out there’s a degree of conflict between the two adjustments.

Jeff

 

[AndrewCS]

Jeff

As attached ... you should have similar to the 981 and 982 / 718 ...

 

[Ryan9729]

Little bit of an update; for those that don't know factory PASM -20mm alignment values are:

Front Axle:

Left/ Right Toe: -0.02' to +0.04'

Total Toe: -0.03' to +0.07'

Camber: -1.05' to -0.35'

Caster: +7.50' to +8.50'

Rear Axle:

Toe: +0.03' to +0.13'

Camber -2.05' to -1.35'

Without any vehicle modifications the maximum Camber at the front you can achieve whilst remaining with stock settings for Toe and Caster is 1.65' and c2.15' at the rear.

In the end I went for the upper end of Caster at +8.50' with -1.60' Camber at the front and -2.05' Camber at the rear. All Toe is within factory specifications.

The stance of the car looks much better and initial thoughts are a more positive turn in, but lets see how it goes on a proper outing before I give feedback. Anyway I thought that would be useful information to some.

 

[MrDemon]

you always run more camber at the front vs the rear on these cars.

you will just wear your inners now on the rear and have less traction esp as the GTS as thinner tyres than a GT4 as that car will never get to roll onto the tyre contact patch at the rear. The cars really need to be at least -2.2 front and about -1.8 rear as starting point depending on driing style, some people goto -2 at the rear I tend not to need it. And with the toe needed you need front LCA and rear toe links and look at GT4 ARB's. track -2.6/ -2.2 is what I ran at Spa but I am back to -2.2 just for road use even it's mega.

car will push like a bitch on track set up like that. the car will roll you will run out of front camber as the rear starts to find grip and thus the car will really push killing the front tyres and over heating them, after 3 laps the front will get too hot and you might even bend the rubber at the edges.

track driving is a bitch, you need to spend the money to SAVE a lot of money on tyres and get the enjoyment from a car which works on track.

 

[ralphmusic]

Interesting discussion, I have always run with more camber (between 0.5 to 0.75 degrees) at the front. GT4 Clubsport race cars (albeit with amongst other differences much stiffer springs, different dampers and slicks) are similar with front camber 0.4 degrees greater than rear as below for 981 version.

But with my latest Center Gravity set-up having fitted rear Motorsport TCAs to allow more rear camber without the previous ride height reduction, rear camber was increased to 2:25 matching the front, with toe remaining at 0.02' and 0.13' each side, front and rear respectively. Ride height was raised c10mm front and rear See reasons here Post #176

On track at Castle Combe earlier this week with the new set-up, I felt the car was lacking a little front end grip. Tyre pressures increased more evenly front/rear matching my road driving experience with the rears not overheating as they had on previous track days. I should have taken my pyrometer to check tread temps across the tyres but will on the next days.

Questions; am I getting better tyre heat management/pressures because of (i) greater suspension damper travel, (ii) the more even front/rear camber relationship, (iii) the driver getting slower with less confidence in the front, or (iv) something else? I have never seen rears not heat up significantly more than fronts, whether in the GT3 or the GT4s.

I have Thruxton and Goodwood in the next three weeks and then I'll decide whether I want more front camber or just leave it as it is.

 

[MrDemon]

Only way you will know is with a pyro now what to do next, I find too many drivers lean on abs and PTV so this makes heat, better drivers don’t let ABS cut in or lean on PTV, so again depends on skill levels and how one drives, I have seen people with much hotter rears than fronts and visa virsa. A good geo just gives you confidence and also helps you get a few extra days from tyres. I have seen people with bent treds as a modern porker will push and push like hell, but PTV will still get you round to a point, issue is 1 track day your tyres are shot.

again every one wants a race geo then drives too slow to use it. I am much slower these days, I had -2.6 at the front and did not use it, the rear outters were way to cold. it ment I just was slower even though the setup might have been faster driven by a pro. I am back to -2 or -2.2 and -1.8 at the rear the car feels much better to me and brakes better. I even have more steering feel as more tyre on the road more of the time which again helps with confidence to go faster.

goto most track days though and peoples front outters are too hot and rear outters too cold.

and after doing maybe 40 tracks days I aM the only one who seems to have a pyro, most people don’t really care and use ABS, PTV and PDK to get round fast enough at the cost of pads and tyres. And I mean pretty poor drivers can do ok ish laps in modern cars with all this tech.

I remember one guy who did lap fast but then has to change rear disks every 3 track days and tyres every one. I have never had to change a set of rear disks ! And I would hope to get 8 days from a set of cups. After Spa and a bit of road use my tyres look like new again and have even wear across the tyre. Shame I am just slow now lol.

 

[Ryan9729]

Well I did a trackday with the set up above, the car behaved very well, the balance was slightly out so I need a bit more camber up front or reduce the rear, I haven't decided which way I'm going to go yet, I'll probably end up fitting GT3/4 LCA's up front to get the fronts to -2.2 degrees, that appears to be the accepted for these cars. The factory alignment is definitely set up for understeer as my fronts were -0.50 at the fronts and -2.05 degrees at the rear front factory.

I've contacted Porsche and they allow the fitment of Cup 2 tyre on the 718 as long as they are the Porsche N rated tyre, so pondering on whether to go for the following set ups.

Stock - F235 & R265

Hybrid - F245 & R265

GT4 - F245 & R295

All tyres will fit as our wheels are 8.5J Front and 10.5J Rear.

Has anyone gone this route before? Would welcome the feedback.

KR

Carl

 

[JohnCRS]

Hi Ryan

You are on an interesting journey with this. Please keep posting your experiences as you progress through the various options.

As to the TPMS, I would just accept the dashboard light and not fit sensors if you are using track only wheels / tyres. It stops flashing and becomes a steady light after a minute or so.

Good luck, John

 

[kegly8]

What did you end up doing Ryan?

 

[MrDemon]

I would go AD09 tyres 255/285 on 19" rims and ds2500 pads and a geo, that's it and see what it's like.

Adding LCA is a slippy slope to wanting a GT4.