Hello guys,
I today had alot of upgrades performed to my cayman. I installed some ohlins road and track coilovers, tarret drop links front and rear, vorshlag camber plates, and tarett rear toe links. I recently purchased a set of new wheels and tires from this website which are 295 rear and 245 on the front. Alignment is set to -2.5 degrees of camber on the front and -2.15 in the rear. Front toe in is 0.03 and rear toe is 0.11. I took the car out for a test drive and the car seems to have grip until it doesn’t. One incident of oversteer was when I was leaving a roundabout and getting on the gas aggressively, the rear of the car stepped out quite suddenly. 10 minutes later I was on a backroad I know quite well, was pushing pretty hard and was leaving a corner getting on throttle, rear stepped out quite a bit while I was going 55mph. That one was quite scary as it was very sudden with little warning and took a very quick correction. I’ve done both of these things before the car had any upgrades and the rear always planted predictably without stepping out. I find it quite weird a 275hp flat 6 seems to be able to break loose 295 section width tires. I don’t know if it is a driver problem as I’ve done this stuff before these mods with no issues. Any advice would be appreciated.

 

Ironically, I've just done much the same modifications with a more aggressive alignment. I had the same experience a few years back right after an alignment. My first guess is the installers did not torque down the rear toe links totally and it is moving. I would jack up the rears and check to see if there is movement in or out on toe side. Second guess is that rear alignment is off on one side.

 

A 50 drop F/R (295 to 245) is a lot. If anything, it should amplify the car's inherent tendency to understeer. Maybe when you're getting into oversteer situations, it becomes all or none and you get snap. You should be able to get at least 255's in the front and possibly 265s. I run a 20 drop (275 to 255) and it's rock solid on track with little understeer or oversteer tendency and no snap. I've done this in both a turbo 4 718 (tuned to 430 HP) where the torque came on suddenly at low rpm and now a 981 (340 HP, smoother NA torque curve). Even with that power, the rear of my 718 wouldn't step out unless I made a couple of simultaneous mistakes on a difficult piece of track (heavy throttle foot while not unwinding wheel enough tracking out on a sharp turn over a crest). Suspension mods were very simliar to yours. I don't know if this is any help to you, but tire sizes are something to consider.