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Cayman - reducing understeer on track

13K views 40 replies 15 participants last post by  Brian C in Az 
#1 ·
So I have a base '07 Cayman (2.7) with 17" rims - 205/55 6.5J ET55 front, 235/50 8J ET40 rear. On the track it just pushes through the corners too much and needs some more front end grip. Lowering the pressures on the front helped a bit but not enough. I've been thinking about a few things.

1. As much negative camber on the front as I can - not sure how much that is with stock setup - not much I'm guessing?
2. Change the wheels for 18" 996 Carrera rims - these are 8J ET57 235/40 front 10J ET58 265/40 or 275/35 rear. The 275/35 seems easier to find than the 265/40 when it comes to moving to track day tyres, hence the reason for looking at 10J rims rather than the normal 18x9J. (Wheels can be had for about £1000 with fairly new tyres. So the wheels would be about £600 of that plus any spacers)
3. Changing front LCA to enable greater negative camber - budget won't allow for both this and the wheels, not sure how much labour cost is involved in changing the LCAs

So my questions, firstly does this seem rational given the problem I am trying to fix?
Secondly will they fit, the spec Cayman 18" are 8J ET57 and 9J ET43 so the front are fine but I'm wondering if anyone runs the 10J ET58 rears and what sort of spacer they require, at a guess it looks like about 15mm?

Also doing this is likely to add 8-10lb per wheel is that going to be a noticeable drop in performance given this is only the "baby" Cayman.

Any comments people have from their experience will be very helpful
 
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#4 ·
Tyres are Good Year Eagle F1 Aysm all round. Don't find much choice in the 17" of appropriate sizes.
Not sure what the temps are in the tyres on track - it was a cold day 6C, pressures initially rose from 27PSI to 33 on the first session, and I then returned then to 27.
Geo was check recently by somewhere I trust when they change one of the track rods.

thanks
 
#3 ·
You'll be lucky to get -0.8 in the front with stock suspension, instead of lca try a set of camber plates which may give you another -1. It's a cheaper alternative to lca. Might want to try stiffer rear sways to add more oversteer as well. I don't think wider rear tires and or wider rear track is a good idea if you're trying to reduce understeer.
 
#5 ·
I admit I had the same thought about increasing the rear but running staggered wheels seems to be the right thing on these cars - don't feel like I should go too far off spec.

Camber plates are an interesting idea - anyone got any opinion for how much difference a couple of degrees on negative camber would have? Is the fit a reasonably easy DIY? (I assume you need a full geo afterwards)
 
#6 ·
Really, you don't need to do much except learn to drive the car at (or just beyond) the limits of available grip. I drove my '07 cayman 2.7 for 8 years on track. It went from bone stock, to having all the usual track mods, and (mostly) back again. In the end, I was running stock 17" wheels and N-spec MPS2 tires, with Cayman R suspension, and a Guard limited slip differential. Alignment was per the aggressive end of Cayman R specs -going by memory here- (F/R:) -1.5/-2.0 degrees camber, and 0/-1/32 inch toe in, with hot tire pressures of 36/38. Believe me when I say it's really fun to drive once you learn to gently slide the car through turns, at the edge of traction, without punishing the tires. And guess what? I was driving in the PCA instructor run group (but giving a lot of point-bys to the bigger toys.) One of my best friends (and fellow instructor/PCA club racer,) who had run with me for years through the car's many iterations, summed it up after observing me sliding the car around on stock rubber by stating that I "must be comfortable with the speed." My point being: In the end, it's mostly about learning to get the most out of yourself, and safely exploring the edges of your car's performance envelope. Be safe, and have fun with your car!

Sent from my SM-N910V using Tapatalk
 
#8 ·
Really, you don't need to do much except learn to drive the car at (or just beyond) the limits of available grip. I drove my '07 cayman 2.7 for 8 years on track. It went from bone stock, to having all the usual track mods, and (mostly) back again. In the end, I was running stock 17" wheels and N-spec MPS2 tires, with Cayman R suspension, and a Guard limited slip differential. Alignment was per the aggressive end of Cayman R specs -going by memory here- (F/R:) -1.5/-2.0 degrees camber, and 0/-1/32 inch toe in, with hot tire pressures of 36/38. Believe me when I say it's really fun to drive once you learn to gently slide the car through turns, at the edge of traction, without punishing the tires. And guess what? I was driving in the PCA instructor run group (but giving a lot of point-bys to the bigger toys.) One of my best friends (and fellow instructor/PCA club racer,) who had run with me for years through the car's many iterations, summed it up after observing me sliding the car around on stock rubber by stating that I "must be comfortable with the speed." My point being: In the end, it's mostly about learning to get the most out of yourself, and safely exploring the edges of your car's performance envelope. Be safe, and have fun with your car!
That sounds like a good story to learn from. (36PSI on the front sounds high - that's not a typo is it? before I go and experiment!) I'm certainly not looking to spend money I don't need to. Certainly agree these are fun cars - was happily keeping a couple of Carrera S drivers at bay on my last track day much to their surprise/frustration. I was just finding that the tendency to understeer was fairly high, while inducing over steer required some quite violent actions, I know some people like it that way. I'm looking to make it easier to have fun and slide predictably rather than huge sticky tyres and suspension setup for outright cornering speed. Sounds like I'll play with the tyre pressures a bit more at the next track day and maybe get some camber plates fitted.
 
#7 ·
-2 would get you pretty good bite in the front. Reducing camber in the rear would help too. I can take off the front suspension in about an hour but it depends on your wrenching skills. You will have to disassemble the front struts, to take off the oem strut mount to replace with camber plate. Just need a spring compressor and it's pretty easy to do. There is an article here on how to take off the struts.
 
#9 ·
36 PSI in the front is not high, my car sweet pressure is around 37 PSI all around. Tires move up in size in recent years so there aren't much options for 17-in. You want to move up to 18-in and if you stick to stock size of 235/40 and 265/40 you have the option of RE-11, R-S3, AD08R and these will make a huge different. You can push the front to 245/40 and it will work fine without messes up the electronic.

Do the tires first. If it's not satisfactory then I would try to get more negative camber, then fine tune the characteristic with sway bar. Important!!! Change only one thing at a time.
 
#10 ·
Thanks, this has all been great advise. The only reason I thought 36 seemed high on the front was in comparison to the stock pressure on the door plate, and my experience that having the fronts up at 33 when hot last week was causing heavy wear to the edges of the centre tread rings, lowering the pressures back to 27 seemed to help. I guess different tyres will behave differently. I'll try to get an open pit lane event for my next track day to allow me to come in and out more and have time to monitor and experiment with the tyre pressures more. Probably keep an eye out on ebay for some 18" cayman/boxter rims too, just to get the greater range of tyres when I come to get my next set.
 
#11 ·
So I thought I'd update this with what I have done/found. I started simple - I got some 18" wheels off ebay (standard Porsche 987.1) fitted with 265rear/245front Michelin Pilot Super Sports. This has made a big difference. It was a damp/wet and fairly cold UK day so getting much temperature into them was difficult, but running pressures of 43rear and 35 front them felt nice. Much sharper turn in, far less understeer and more neutral and balanced feel through the corners. Real test will be when I get them on a dry day but definitely a step in the right direction. Down side is that on the road they are noisy and give a harsh ride so will switch back to the 17" 235/205 setup when not on the track.
 
#12 · (Edited)
You have it backwards.

Increasing front pressure will reduce understeer. Increasing the back will reduce oversteer.

You need to try 40 hot front and 33 hot back.

With the stock suspension on my 981 2.7 boxster, I found getting 245/40/20 front tires instead of 235/35/20 helped a lot. Also lots of negative camber. 37 front hot and 35 rear hot works well.

i am getting x73 suspension soon. This is supposed to get rid of all understeer and make it slightly oversteer...then you can tinker with tire pressure to get it just right.
 
#19 ·
I am referring to larger sidewall (+5) and width (+10). Keep in mind the tire width is kind of irreverent because the wheel width is what controls contact patch. If you get wider tires, you must run them with lower tire pressure so the inside and outside tread blocks properly make road contact...putting a chalk line on the tire is good a way to test this...if the outside tread blocks don't make proper contact, handling and steering feel is greatly reduced.

Larger front tires is possible on stock suspension on 981 due to clearance, but wouldn't be on sports suspension. I plan on front 235/35 and 275/30 rear tires with x73.
 
#24 ·
Curious but what model is your car? I genuinely ask this because last few times I test drove a Porsch (granted I was on the street in an unfamiliar car) but the last thing I thought the car would react especially in a mid engine car would be with understeer.

But Augie's advice is correct. Driving style change is the first thing I would work on. Usually I exhaust every possible option to manage the car's handling by changing my driving style first before I resort to tweaking the car. That's what I did in my 09 M3 before I swapped it for the Spyder. It was a heavy car so it was easy to make it understeer and once I figured out entry speeds in to various corners so I wouldn't understeer then next was oversteer and the M dynamic mode TC settings from slamming in like an anvil and upsetting the car when trying to power out of the corner. I learned to reduce the steering angle and not STAB at the throttle to let the car's tires hook up on the road and thus stop the TC dropping in. Funnily enough my speeds went up! Experimenting is fun!
 
#23 ·
I don't think you'll be able to run 43 lbs. in the rear on a hot dry day. The tires will not like it and neither will you. You have adequate size tires now. I would go with 36-38 front and back; then start learning to drive differently. Understeer with your set-up means you are trying to force the tires to do to much. Your driving style is over taxing the tires. One basic of driving faster is "slow in, fast out". Keep that in mind and you will be a better, faster driver. Also remember to ask your car to do one thing at a time; accelerate, brake, turn-in, accelerate. Try it - you will like the results.
 
#25 · (Edited)
I'll agree with the previous posts that mention adjusting your driving style before modding the car. I don't know the experience of the OP, but if you're a novice, you might be coming into corners too hot, or not transitioning from braking to turning smoothly (i.e., unloading the front before turning). If that's not the problem, do you trail brake? That can (and should) be used to help a car turn.

Also, you didn't mention if the understeer is present in all turns, just fast ones (unlikely), just slow ones, etc. Often there's a trade-off and you can have a car that understeers in slow corners but is well-balanced in high-speed turns. If you try to fix the slow-corner understeer too much, the car might end up neutral in slow corners but have oversteer in fast corners (not something I like). We need more details.
 
#28 ·
Ever since switching my 987.2S to 255/35-18 front and 275/35-18R, understeer has NOT been a problem! In fact, I had to put on a GT3 front swaybar to keep from spinning every time I entered a corner or transition. I put these wheels on 986S at one point and found it really helped balance that car better, too.

Very good article on how driving style can create/exacerbate understeer (or oversteer):
https://nasaspeed.news/columns/driv...using-the-handling-problem-and-how-to-fix-it/
 
#30 ·
I believe the stock Cayman is inherently unbalanced with too much understeer. I installed both front and rear adjustable sway bars to allow me to dial in the correct balance. I run 245/275/18 tire setup with normal tire pressures. I did install Front LCA to increase front camber. I run .5 degrees greater camber in front than in the rear. My car feels very balanced now and rotates into turns easily.
 
#31 ·
What is the final setup of your alignment (camber & toe). Is there a reason why you chose to go with LCA instead of camber plate? I know that LCA will push the lower out instead of pull the top in so the track will be a bit wider but the camber plates replace the compliant rubber ring with spherical bearing so there are pros on both front. I think camber plates is a little cheaper but doesn't provide as much adjustment.
 
#35 · (Edited)
Thank you for your respond, looking forward to knowing your toe specs.

Camber plates will provide an additional 1.1 deg of adjustment based on vendor claim. Currently my front setting is maxed out at -1.75 deg, so in theory with camber plates I should be able to get to -2.85. If I add camber plates my competition class point increases by +20, this still keep me in the same class so I am thinking about it. Before I jump off the cliff I want to make sure the adjustment provided by camber plates is sufficient to bring the front camber into the "ideal" range. Otherwise I have to consider LCA or both.

991/981 Clubsport Camber Plates-Rennline, Inc.

Product Auto part Wheel Metal Steel
 
#36 ·
Nobody has mentioned X73. Haven't been able to push my new GTS that hard, but feels incredibly capable right from the factory at 0.9Gs. Wife didn't allow me to drive it any harder due to dizziness. It wasn't even breaking a sweat at that level, and felt neutral to me other than tight bends, where all cars will understeer to some degree. My car also has PTV (LSD) and SC. Don't know how much difference those make, but there're a lot of suspension/option combinations that will affect handling. The main one IMO is X7's more aggressive suspension tuning/alignment, and its lower stance. Porsche did a lot of R&D on that, so unless somebody wants a dedicated track car, can't get much better than X73 IMO. And it's not that expensive to retrofit, for what I've read.
 
#38 ·
My alignment numbers:

Front Camber -2.5 Toe (0.03-0.06)

Rear Camber -2.0 Toe (0.10-0.14)
 
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#39 ·
So you got zero toe front. I am debating whether to go zero toe front or slightly toe out for better turn in. I do like the -2.5 up front and -2.0 rear; however, at a later date I may increase the rear a touch if it's tail happy.

I ordered my camber plates on May 11 and they're still in production :(
 
#40 ·
Yep, I went with the more conservative zero toe front. Correct, slight toe out will give you better turn in.

Yep, I like the more agressive front camber to improve turn in.

Sorry to hear about your camber plate delay. That sucks.
 
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