I thought it might be useful to start a thread on suspension settings, which seems to be a learning process for all new owners, particularly of GT4s. We all know the GT4's limited adjustability is frustrating so perhaps an exchange of facts around what is possible and how to expand the possibilities might be the most useful focus for contributions.
Whilst the GT4 has suspension more adjustable than the 'cooking' versions, there are constraints particularly at the rear where the GT4 rear toe control arm (tca) has adjustment limited by the eccentric nut and which is exactly the same dimensions as the standard part. The GT4 rear top mount is offset (i.e. the damper attaches off centre) and this is different to the standard arrangement. This became evident when Centre Gravity were installing an adjustable set-up on my CS including GT4 top mounts, these created additional neg. camber and because of the angles, moved the tyre too close to the diagonal control arm (dcc) when running 11.0" wheels. As of today, my (car's) rear has Tarett central top mounts and 997RS wishbones with shims (with RSS tca) and clearances are OK. The front has RSS wishbones with shims, GT3 top mounts, GT4 roll bar and Tarett drop links. Dampers are Damptronics with Eibach helper and main springs, the spring rates being 51 and 63 N/mm. The GT4's are 45 and 80 N/mm per Evo AP video.
Anyway having explained where my car is 'coming from' and on the basis that there must be some commonalities across the 981 Cayman platform..
I had been running with a lot of neg. camber (3:20 F and 3:12 R) with 0:02 F total toe and 0:20 R total toe and (GT4) roll bars set to the mid position. There was no tramlining, rear was a little light on trail braking and a little squirrelly on heavy breaking from high speed. Otherwise the car was very stable and faster than previously with 2:00 F and 1:75 R camber, and H&R roll bars set to soft on the rear. Tyres then and now are MPSS 245 and 295 on 8.5" and 11.0" wheels.
Talking with Chris, it seemed a good idea to keep front : rear camber similar, but reduce from the previous high levels, to slightly increase toe, and to go soft on the rear roll bar. Camber changes were to balance out grip v tyre wear, toe to help braking stability and with roll bar, to help with traction on a few occasions where it could be improved. The car was set up with 90kg 'driver' weights, full fuel tank and 7kg luggage loading, cross weights were 780kg each diagonal. Ride height was set at 103mm/130mm and 0.5 degree rake.
The car now has front 2:30 neg camber and 0:04 total toe, and rear 2:12 neg camber and 0:30 total toe. I have not been on track yet so I won't really know how it feels in extremis until March 22/23 at Silverstone and Goodwood, respectively.
It'll be interesting to hear how well David's changes work at Donnington and to get some tyre temp/pressure data. Whilst my car and MPSS are a different package, his and my experiences will give some ranging data which might inform and encourage others' developments.
Finally, the picture below shows the base settings for the Clubsport (on 18" slicks of course but interesting nevertheless).
Contributions welcome!
Whilst the GT4 has suspension more adjustable than the 'cooking' versions, there are constraints particularly at the rear where the GT4 rear toe control arm (tca) has adjustment limited by the eccentric nut and which is exactly the same dimensions as the standard part. The GT4 rear top mount is offset (i.e. the damper attaches off centre) and this is different to the standard arrangement. This became evident when Centre Gravity were installing an adjustable set-up on my CS including GT4 top mounts, these created additional neg. camber and because of the angles, moved the tyre too close to the diagonal control arm (dcc) when running 11.0" wheels. As of today, my (car's) rear has Tarett central top mounts and 997RS wishbones with shims (with RSS tca) and clearances are OK. The front has RSS wishbones with shims, GT3 top mounts, GT4 roll bar and Tarett drop links. Dampers are Damptronics with Eibach helper and main springs, the spring rates being 51 and 63 N/mm. The GT4's are 45 and 80 N/mm per Evo AP video.
Anyway having explained where my car is 'coming from' and on the basis that there must be some commonalities across the 981 Cayman platform..
I had been running with a lot of neg. camber (3:20 F and 3:12 R) with 0:02 F total toe and 0:20 R total toe and (GT4) roll bars set to the mid position. There was no tramlining, rear was a little light on trail braking and a little squirrelly on heavy breaking from high speed. Otherwise the car was very stable and faster than previously with 2:00 F and 1:75 R camber, and H&R roll bars set to soft on the rear. Tyres then and now are MPSS 245 and 295 on 8.5" and 11.0" wheels.
Talking with Chris, it seemed a good idea to keep front : rear camber similar, but reduce from the previous high levels, to slightly increase toe, and to go soft on the rear roll bar. Camber changes were to balance out grip v tyre wear, toe to help braking stability and with roll bar, to help with traction on a few occasions where it could be improved. The car was set up with 90kg 'driver' weights, full fuel tank and 7kg luggage loading, cross weights were 780kg each diagonal. Ride height was set at 103mm/130mm and 0.5 degree rake.
The car now has front 2:30 neg camber and 0:04 total toe, and rear 2:12 neg camber and 0:30 total toe. I have not been on track yet so I won't really know how it feels in extremis until March 22/23 at Silverstone and Goodwood, respectively.
It'll be interesting to hear how well David's changes work at Donnington and to get some tyre temp/pressure data. Whilst my car and MPSS are a different package, his and my experiences will give some ranging data which might inform and encourage others' developments.
Finally, the picture below shows the base settings for the Clubsport (on 18" slicks of course but interesting nevertheless).
Contributions welcome!
so 8mm shims up front and new tarret Rear toe links to go on. with locking plates also.
