The first track outing was another trip to Streets of Willow. In order to get more caster, the front wheel is pulled forward. A benefit is the wheelbase is increased slightly, but the front is slightly lowered too. I noticed the lower front-end because I was scraping the air deflectors in front of the front tires more easily. Too much caster though, and the front tire can be pulled forward enough where the tire rubs away the wheel well inner liner; that is potentially around 10+ degrees of caster. Also, I manually set the rear spoiler into the ‘up’ position for track days. Otherwise, it goes up and down over the course of a lap.
With the new front alignment of -3.0 degrees camber, 9.5 degrees caster, and 0 degree toe, tire wear across the front was much more even. This is the right front tire after another 100 track miles. With the old alignment, I guarantee the outside shoulder would have been worn smooth whereas there is just a smidge of thread depth left. Yes, the E-Motion suspension components are not cheap, but they will reduce tire costs as I can now get full use out of the tires instead of them dying a premature death. I’ve seen pictures of a 911 on stock alignment destroy a set of tires in two track weekends. I’m talking down to the cords on the shoulders while there remained a ton of thread on the rest of the tires. Considering the cost of a set of tires is pushing $2k mounted, the return on investment compared to trying to track the car on factory suspension will not take long due to savings in tire costs.
This is the right rear set to -2.5 degree camber and 2mm toe-in per side. The wear is looking pretty good across the face of the tire.
So how well does the car handle after all the mods? My buddy David, who has a S2000 track car, hopped into the Cayman and pulled 1.33-1.40G lateral; this is on one year old tires with 4600 miles and a few prior track days on them mind you. I don’t think David has ever driven a Cayman before either which tells me the handling is set up well for balance. The previous lateral G record in my car was held by Dave Coleman at 1.19-1.23G on the previous alignment. The session before David got into the car, I did have the rear of the car slide out sideways twice on turn-in; I had the car in PSM Sport mode all day which allows some slip compared to having the full stability controls on and it leaves on the auto rev matched downshifts; PSM completely turned off also turns off the auto rev matching. The max G force up to that point in the day I had attained was 1.33G. So, I adjusted the rear rebound settings in the DSC to reduce the oversteer on turn-in. I wanted to get the balance how I liked it before handing the keys to David. Like I said way back, who needs PTV? A proper alignment and some suspension calibration tweaks has the car turning in just fine, thank you very much. As for the new -1.33G max braking acceleration, I would attribute that to the DSC controller.
My buddy Andres snagged this sweet photo of the car entering the skid pad after coming down the main straight. With the new alignment, the maximum grip is increased due to the better utilization of the tires. Another benefit is that I no longer had to drive in a point-and-shoot manner to try to preserve the front tires. I was able to take more traditional lines and the tires stayed much more consistent instead of the fronts overheating. For tire pressures, I started out at 2.0 bar cold and the tires would warm up to 2.4 bar at all four corners. Looking at this picture, you can see how soft the stock suspension is which is why I say it’s too soft for serious track use chasing fast lap times. But for a dual-purpose street and track car, I think stock SPASM is pretty good.
11 comments
Great update. Any plans to go to a dedicated DOT-at wheel/tire set up for the track?
I’m planning on 19″ wheels and RE-71s (245/275 vs current 235/265) after I wear out these tires. Save a little mass. With the stock springs, I don’t think they can handle that much more grip.
The rear toe arms on your car are the non-GT4 Tarett ones. They’re just a different length than the GT4 ones due to different subframe and hubs. Your front tie rods look like Emotion, slightly different design.
Just did a very similar setup on my T with Dundon front tension arms (shims as well) and Tarett control arms. Curious how Emotion got the factory rear tension arms to work the their puck, which only has a center hole. I had to use the eccentric hole due to the factory tension arm not having enough machined off the LCA mount to avoid interfering with the edge of the puck in the center position. Wonder if they just machined it further out to fit. Trying to avoid either throwing off the toe curve with the eccentric or losing the T brake duct by going to an aftermarket rear tension arms.
Also didnt realize that the narrow 991 GT3 style LCA inners worked on our cars.
Cheers – always enjoy hearing about your project
I added some pictures for you and the parts list for the car. The front tie rods are E-motion parts. They don’t make their own rear toe links because there’s no real reason too with the various options already available. I had bought TPC rear toe links for the 718 Cayman, but they didn’t fit as the E-motion setup required GT4 compatible parts. So E-motion ordered up what I believe are the Tarrett parts.
Thanks so much for the photos! Finally got the car back together (didn’t realize that all the subframe bolts for the front sway bar were torque to yield, so took a bit to get new ones).
Seeing the sharpie mark on your trailing arm really helped. That was marking how far out they had to remove material from the inside of the flange, which was machined for the narrow metal interface on the rubber bushing vs the full width on the aftermarket solid pucks. Took a Dremel with a fine sanding bit and got a pretty nice result.
I had the pleasure of driving Khiem’s 718 at Streets of Willow CW (thanks Khiem!). Although I have limited seat time in Porsches, I agree with his comments on it being a well balanced setup for both track and street use. I’m excited to see the ride difference with the E-Motion Engineering spherical bearings and links installed! Any plans on increasing spring or roll bar stiffness? Looking forward to another track day soon!
Maybe coilovers…..
Hi Khiem,
Curious if you are considering upgraded Anti-Sway bars for this project or not. I have a GTS that came with single hole non adjustable bars and considering a second hand set from a GT4 that have three holes so I can adjust the bias front or rear. Still working on how thick my current ones are vs the GT4 bar.
Good job on the project so far, I love the tech and reading all of the articles. Looking forward to the next installment
Jeremy
I’m content with factory bars. I would typically use adjustable bars to tweak the handling balance, but I can do that effectively with the DSC.
Update: on my GTS I have now installed a set of used GT4 swaybars.
On the track I used to have to wait for the car to take a set into the corner, now it can just turn.
Still playing with the multiple holes of adjustment and feeling how the balance changes front to rear.
The front for our non GT4 cars require a shorter end link, the rears links work as they are.
I also have the DSC but don’t yet know how to go about making these changes as the DSC is based on velocity tables.
Thanks for the update! You can adjust the low speed rebound settings in the DSC to tweak the handling balance.
Agree on the stock suspension, especially in normal mode, needing to wait for the car to take a set. This is really evident in a slalom. I’m content enough with my DSC tuning for sport mode in that regard.