[feeshta]

Hello everyone. I realize that there are some threads out there somewhere that might have some info on this subject, and I have skimmed through things a bit on that front, but I wanted to gather some knowledgeable opinions for my personal setup and usage situation.

So, I just ordered Ohlins R&T coilovers for my 07 Cayman S. I will be doing the install myself, and then taking it to a pro for a performance alignment. The one change I would like to do myself to avoid the labor costs is the installation of control arm spacers. My car currently has GT3 control arms installed, but set to the factory camber spec for a Cayman S due to a misunderstanding between myself and the installer. I believe it was something under -0.1° if I remember correctly, which seemed extremely low. I would like to get more grip and response out of the front end, and the car has been chewing up the outer edges of my front tires, so I plan to go significantly more aggressive on the front camber. My question would be what you fine folks think might be an appropriate number, so that I might determine which spacers to order for the control arms.

The car will never be track driven, at least not for the foreseeable future, as I can't afford to become addicted to such a drug. It will be aggressively driven on deserted Pennsylvania back roads, which are quite bumpy. Think paved rally stage and you are not far off. It also needs to be at least acceptable in highway driving, as I frequently travel a @200 mile round trip to visit family and friends.

In the past, I have only ever run higher than normal negative camber on one previous car. That car was a 2012 BMW 135i. I initially installed M3 front control arms as a performance upgrade, which added about -0.75° to the front camber, bringing it up to around -1.5° when coupled with pushing the mounts out as far as they would go. This was a massive boost in performance. Maybe the single most transformative mod I have ever done on the aspect it affects. I didn't even know it was possible to get that much of an effect, or I would have done it years ago!

I was quite happy with the results, but eventually needed to make a change in order to accommodate wider front wheels and tires. The 135i came hamstrung with 215 width front tires, and not much space for anything bigger. The addition of Dinan camber plates brought the total camber up to -2.5° and allowed me to tuck 245s inside the front fenders with no rub by pulling the top of the tire in slightly. Honestly I didn't feel that the added camber produced much more of an impact on front end behavior on that car though. There was of course an improvement due to the wider rubber and switch away from run-flats, but not much beyond this that I could appreciate with the way I drive. Even with that much negative camber, the car didn't eat the front tires though, going 7K miles with no noticeable uneven wear.

Taking all that into account, my initial instinct is to go with around -1.5°, as that produced the increased grip and turn in, but might help mitigate long term wear issues. The thing is, I don't know the behavior of this car as well as my BMW with respect to changing camber. Maybe these actually like higher camber numbers? Maybe you don't even need as much? So, what do you setup gurus out there think would be the way to go? Any suggestions on toe settings to complement the camber and avoid wear issues? Anything else I may be missing?

 

[Blessed]

I'm not sure if setting the TOE to offset Camber will be a valid option as they are two different angles.

It is like that car meme: More negative camber wear than a fat chick in UGG boots.

It will wear out your tires if out of spec. This is just fact. Your tires will suffer the wear and your handling will benefit. Completely up To you and your pocket book.

 

[feeshta]

Here is the logic behind changing the toe settings. Manufacturers typically set their cars up with a little bit of toe in from the factory in order to provide more highway stability. When the camber settings are relatively close to vertical, the scrubbing action this produces due to the wheels not being perfectly aligned with each other when going straight is spread across the tread width. This will accelerate tire wear slightly, but it is spread evenly across the tread width and typically calculated conservatively enough that it doesn't heat the contact patch enough to increase tire wear to a large degree.

When additional camber is added, the scrubbing action from the toe in is focused on the inner edge of the tires, and heats the smaller amount of rubber to a greater degree, resulting in a significant increase in tire wear. The remedy is to run something closer to zero toe and try to eliminate the scrubbing action from the equation. You need to account for the limited amount of flex in the suspension to set things up properly though. Basically, when sitting static you would have a little tow in. When the car is run at highway speeds though, the drag pulls the wheels back slightly, decreasing tow in. Ideally you want the car set up so that this action produces zero effective toe at highway speeds, but the starting point depends on the car in question and how resistance to flexion the suspension is.

So I need a little advice on how to get as close to zero toe at highway speed with this car.

 

[Blessed]

The positive toe will help at highway speeds true. We set cars up similar when I managed mechanical shops.

I was in reference to Camber wear.

Your needs and set desire up will need to be addressed by a Porsche Tech and or someone far wiser than me.

I know for me I try to keep at zero and or as closet spec zero range as possible for daily driving.

Beautiful car BTW..!

 

[cajundaddy]

For a 100% spirited street driven Cayman, this is where I would start for improved front grip while preserving tire wear:
F -1.5 degree camber, zero toe, max castor
R -1.0 degree camber, 1/16th total toe in.

This might vary somewhat based on exact tires you plan to run but it should get you close to your goals. A pro corner balance is also recommended with your alignment and I suspect they will add a bit of forward rake which will also move grip forward. My usual recommendation to alignment specs is to find a local Porsche performance shop, give them clear goals for the car, and get out of the way and let them handle the setup details. There are a lot of interacting settings and measurements and the guy with tons of experience understands how it all works together. Trying to micromanage your setup shop by calling out exact settings you want usually ends badly.

 

[feeshta]

Thank you so much for the input, Sir. I was not aware that the castor was adjustable on these cars, so that is certainly something to consider. Do you happen to know what size shim I should go with to make the -1.5° front setting middle of the road on the factory adjustment? I've heard -1° is about max on the factory adjustment, but my car is at practically zero front camber.

One thought I would add to your closing statement. I think this is probably a good plan, IF you speak directly to the person who will be doing the work. Last time I spoke to the desk man at my local specialist. My basic words were, "I would like to add more negative camber. I will trust your judgement on how to set it up to get me some extra grip without shredding my front tires faster than the rears". End result was tires nearly vertical because the tech thought he meant I was afraid of camber due to tire wear.

I know better than to just talk to the desk man now.

 

[cajundaddy]

I don't do setups so I don't know the shim count on your car. If a pro shop is handling the alignment and corner balance, just have them shim it as needed. As to communicating your goals, simply write it down on the work order. I never talk to the actual setup guy in advance but make sure they are very clear on my goals.
Something like this:

100% street car but looking for a performance alignment and corner balance with more neg camber and grip up front without sacrificing too much to tire wear. Maybe F -1.5 degrees? I trust your judgement. Modest front lowering and adding some rake is ok during corner balance but not so low that it will scrape at every gas station entrance. 20mm? (Street car)

This give the tech a target to shoot for but also the latitude to work his setup voodoo... And it is voodoo.

 

[feeshta]

I have a rather unique issue that might make a little rake a problem. My car only clears by about an inch going into my garage at the moment. There is a recessed drain right in front of my garage, which sits in about an 3 inch depression. Unfortunately I live in a condo, so I don't have the latitude to modify this, or I already would have. If I go through there at more than a couple miles an hour, it already scrapes. The thing is, my shocks are currently toast, so I'm not sure how much that affects the issue. Bottom line though, I don't think I want to go much lower than the Ohlins (20MM lower than stock) recommended stance, or I might not be able to get the car into the garage when I get home. Might have to take the car home and try to get some measurements at the baseline Ohlins ride height before I take it to the specialist. Maybe the Ohlins ride height in front and closer to stock in rear would work. Of course, it's also possible Ohlins baseline setup adds a little rake to the car to begin with. I think I better take some before and after measurements when I do the swap.

 

[cajundaddy]

Absolutely. If you are already scraping you should get some measurements and share this with the setup shop. I have a steep driveway and depending on the angle my Cayman might scrape the nose lightly. I am ok with that. When my 986 Boxster was setup for Time Trials they initially lowered it quite a bit in front and I couldn't get the car up the driveway and in my garage. D'oh! Back to the shop for a do-over after I got some clearance measurements.

Driving a street car that is too low is a royal PITA.

 

[Apex1]

Dave, I too have Ohlins Road and Track on order, but unlike feeshta, Cantrell Motor Sports in Kirkland, Wa. will be doing the install along with adjustable Tarett Sway Bars, Tarett Links, machine slots for front top camber adjustment, corner balance, competition alignment and wheel spacers. We are targeting -2.4 camber front and -2.0 rear. We maynot get that with the slots, but close to -2.0 F and -1.6 R will do. Caster and toe is up to them. I have asked them to set up the car for back road fast driving, using the full suspension travel, even with a lowering of 25 mm. This is unique to Ohlins Road and Track set up, which does not interfere with preload as on other coilover shocks. I guess I will figure out if this is the way to go if I need to install skid plates. Cantrell is excited about this project and have been talking with Ohlins USA about my car and one other Cayman that is on their install books. Ohlins, Swedan sent 5 sets to the USA in their inital batch, one of which is going to feeshta, so we will have some discussions about best practices of adjustments on the shock. Mine for daily drive 95% and autocross the other 5%. Cantrell is going to give me a crash course of how to change sway bar and Ohlin settings in their shop when I pick up the car and offer some after install assistance if I get into some issues. Thanks

 

[sjfehr]

Loose is not fast, you really need more in the rear than the front for a car that's stable at the limit. It's hard to get too much camber with our cars, even with camber plates and LCA: my advice is to dial in as much camber as you can and then adjust your swaybar(s) to suit.

FWIW, I'm running maxed out camber front and rear within OEM adjustability (About -0.8F and -1.9R) on my 987.2S with slight toe-in front and rear, and it's handling fantastic for autocross with an OEM rear bar and a front tarret GT on the 2nd loosest hole. It's extremely stable in transitions and corner entry, but still rotates when I want it to. Tire wear from street miles is very light compared to track/autocross wear; the outside corners wear down long before the insides.

I actually have a good demonstration video from a few weeks ago if you want to see the difference; the alignment rig on my left rear slipped and I ended up getting different alignments on left and right rear: the right side was what I wanted, about -0.8F/-1.9R. Left side was about -0.8F/-1.1R. Consequently, my car was incredibly stable in left-hand turns, letting me trail-brake and carry a lot of speed into corners, and slow as hell in right-hand turns and sweepers because the rear end peaked out at such lower lateral gs and couldn't handle as much weight transfer during trail-braking. You can see pretty clearly in this video how nearly every right-hand turn/transition taken anywhere close to the speed I'm taking the left-handers ends in having to catch a slide due to the poor left-rear camber. That's a significant loss of cornering force and lower lateral gs through those sections.

 

[Apex1]

sjfehr, I will be taking my car to a performance shop next week for the installation of Ohlins Road and Track and Tarett Sway bars. I have told them to include machining adjustable camber slots into the top of the front shock towers, which is approved in PCA GT class autocross, adjustable lower control arms and upper ajustable control plates are not approved. So, from your set up, if I could get -2.0 F and -1.9 in back camber and with the adjustable sway bars, I should be able to dial in the stable transitions, corner entry and rotation you mention. I also am asking for a 25 mm drop in suspension from the Ohlins, which according to Cantrell Motor Sports, this allows for more internal negative camber. Maybe the back could be more negative camber with the drop. Not sure, but I want a car that is not twitchy at 130 with this autocross setup. Maybe a little caster to add some feel back into the steering from the drop in suspension. Thanks,

 

[Brian C in Az]

Here is the logic behind changing the toe settings. Manufacturers typically set their cars up with a little bit of toe in from the factory in order to provide more highway stability.

You need to account for the limited amount of flex in the suspension to set things up properly though. Basically, when sitting static you would have a little tow in. When the car is run at highway speeds though, the drag pulls the wheels back slightly, decreasing tow in. Ideally you want the car set up so that this action produces zero effective toe at highway speeds, but the starting point depends on the car in question and how resistance to flexion the suspension is.

So I need a little advice on how to get as close to zero toe at highway speed with this car.

Are you asking about front toe or rear toe? The rear should be toe'd in to provide better tracking and stability. Front toe can be set in (positive) or out (negative) depending upon the requirements of the driver. Toe in for the front does not equate to stability; nor does front toe out equate to instability. Many factories spec the front toe to be negative (toe out). I prefer toe out in the front of my Cayman because the car handles better, turns better on track when set that way. Having the front toe set negative on my car does not make it unstable at triple digits on the track. Rear toe out would definitely make the car twitchy though.

Much of your question and explanation of your question is based upon incorrect assumptions and lack of experience in car preparation.

As far as tire wear issues due to more camber and toe, simply rotate your front tires (and rear also) as needed. Dismount them off the wheel, then flip them and remount. Now install them on the opposite side of the car. If you can't follow that verbally, then mark them with chalk and you will see the direction of rotation does not change and the outer edges are now the inner edges and you will maximize your tread life.

 

[feeshta]

Are you asking about front toe or rear toe? The rear should be toe'd in to provide better tracking and stability. Front toe can be set in (positive) or out (negative) depending upon the requirements of the driver. Toe in for the front does not equate to stability; nor does front toe out equate to instability. Many factories spec the front toe to be negative (toe out). I prefer toe out in the front of my Cayman because the car handles better, turns better on track when set that way. Having the front toe set negative on my car does not make it unstable at triple digits on the track. Rear toe out would definitely make the car twitchy though.

Much of your question and explanation of your question is based upon incorrect assumptions and lack of experience in car preparation.

As far as tire wear issues due to more camber and toe, simply rotate your front tires (and rear also) as needed. Dismount them off the wheel, then flip them and remount. Now install them on the opposite side of the car. If you can't follow that verbally, then mark them with chalk and you will see the direction of rotation does not change and the outer edges are now the inner edges and you will maximize your tread life.

Well, that runs counter to advice from a friend who is a BMW Master tech and several dozen BMW track-day nuts, as well as my own personal experience. The car was definitely more of a handful when I went to 0 front toe than when set up at the factory spec, which was a bit of tow in in the front. Rear toe was left alone as recommended, and was slightly toed in. "Stability" may not be the completely correct word for it, but the car had a much more pronounced tendency to be pulled off course by road surface irregularities after the front toe settings were changed. Some people call this tram-lining. What you got in return was much better initial turn in, witht he car feeling much more willing to turn in general. That was a worthwhile trade in my opinion, especially when tire wear is improved. Some might not like it though.

Speaking of tire wear, my own experience with the BMW, backed up by several dozen other board members, was that zero front toe eliminated the uneven wear issues on the front tires with a 135i. Several people reported getting 40+K out of a set of Pilot Super Sports with @-2.5° front camber and zero toe. Those that stuck with factory toe settings were getting only around 25K.

Here is a picture of one of the front tires from the BMW when I was selling them with about 7K miles on the clock at -2.5° front camber and 0 front toe. Wear was pretty much completely even.

Here is one of the rear tires of the same set, with the same mileage at the factory toe spec, which was slight toe in and @-2° camber. There was slightly more wear on the inner edge of the tires than outer edge, which would be the right side of the image.

It's entirely possible that things work a bit differently with the Porsches, that's why I was asking the question after all, but I would like to hear from more folks to confirm. Also, your advice about rotating the tires does not work for some tires. Michellin Pilot Super Sports for example have a directional tread pattern with an inner and outer edge that would make this impossible.

 

[Apex1]

I have Michlin Pilot Super Sport tires, so changing the tread pattern to the other side is not advisable, but having the correct mix of camber and toe is where I am going with my project, at 95% road and 5% autocross. Not exactly sure why I am spending a ton on this project for Ohlins, adjustable sway bars, corner balance and performance alignment. The end result is that I am expecting this investment to last a while. It will also give me the satisfaction of slightly better autocross times as I gain seat time and experience of changing the set up to match the track and my driving style.
I will be surprised if I get -2 degree camber in front (more like -1.8) even with machining of camber slots in the car body for the base of the shock tower. No camber plates or adjustable LCA's permitted by PCA autocross rules. So, maybe about -1.8 camber F and -1.5 R camber. 0 toe front and -1/16 total toe in back, will be asking about a small caster adjustment in front to compensate for the 25-27 mm drop from the Ohlin coilovers. At least this is the current plan. Tarett front sway is second hole from soft and rear last hole for soft. Even at soft, the bar is stiffer than stock. As Cajundaddy points out, not to go into too much detail, but knowing some initial settings will help me understand the conversation as we make the final blueprint for the performance alignment and sway bar set up. Thanks

 

[Brian C in Az]

Well, that runs counter to advice from a friend who is a BMW Master tech ...

I'm sorry, I thought that we were on a Porsche forum, not discussing a front engine BMW....

There are MANY differences between a mid engined car and a front engine car when it comes to suspension set up and track alignment. What works for a 987 won't work for a Beemer. Whatever a BMW tech says is correct for his BMW, I really don't care (no disrespect to him or his experience) because it is not applicable in any way to a 987.

The cars aren't even driven the same way through a corner on track. Braking, turn in, trail braking, and power out will all be totally different between the two cars; even the apex is different.

 

[feeshta]

I'm sorry, I thought that we were on a Porsche forum, not discussing a front engine BMW....

There are MANY differences between a mid engined car and a front engine car when it comes to suspension set up and track alignment. What works for a 987 won't work for a Beemer. Whatever a BMW tech says is correct for his BMW, I really don't care (no disrespect to him or his experience) because it is not applicable in any way to a 987.

The cars aren't even driven the same way through a corner on track. Braking, turn in, trail braking, and power out will all be totally different between the two cars; even the apex is different.

You obviously didn't read the whole post there.

That said, I still don't see how this could be all that different in street driving, which is what I was discussing. I just can't see how 4 wheels interacting with pavement can change all that much when you are going in a straight line down the highway. No offense, but I would need it on more than just your authority.

 

[sjfehr]

I have Michlin Pilot Super Sport tires, so changing the tread pattern to the other side is not advisable, but having the correct mix of camber and toe is where I am going with my project, at 95% road and 5% autocross. Not exactly sure why I am spending a ton on this project for Ohlins, adjustable sway bars, corner balance and performance alignment. The end result is that I am expecting this investment to last a while. It will also give me the satisfaction of slightly better autocross times as I gain seat time and experience of changing the set up to match the track and my driving style.
I will be surprised if I get -2 degree camber in front (more like -1.8) even with machining of camber slots in the car body for the base of the shock tower. No camber plates or adjustable LCA's permitted by PCA autocross rules. So, maybe about -1.8 camber F and -1.5 R camber. 0 toe front and -1/16 total toe in back, will be asking about a small caster adjustment in front to compensate for the 25-27 mm drop from the Ohlin coilovers. At least this is the current plan. Tarett front sway is second hole from soft and rear last hole for soft. Even at soft, the bar is stiffer than stock. As Cajundaddy points out, not to go into too much detail, but knowing some initial settings will help me understand the conversation as we make the final blueprint for the performance alignment and sway bar set up. Thanks

I'm running neutral toe for the exact same reason. Front toe out helps turn-in, but is annoying on the highway and destroys the inside corner of your tires. It's just a bad idea in general to run front toe-out in a street driven car. Front toe in fixes all that, but hurts turn-in. Thus the compromise of zero toe.

I'm running about 1/16 rear toe in but have been thinking about dialing in another 1/8". Play in the bushings can give dynamic toe-out which is dangerous in the rear, and I think this is happening to me. There's really no harm in running modest toe-in in the rear (no wear or highway issues) and it helps stability in oversteer.

If this is for autocross, you'll really want to get some RE-71R to replace those MPSS. Sadly, they're backordered in most of our sizes.

Double-adjustable Ohlins? More buttons to tweak! I still think you need more rear camber than you're plannning.

 

[Apex1]

Car finally going into the shop tonight for the new parts and alignment. I wil ask to get at least same camber front and rear. With the machine front camber slots, shooting for -2.0 in front and rear. After autocrossing this past weekend, I see what you mean with the outside of front tire really getting hammered, even with 38 lbs of air. Negative camber will help that. This event also showed me I need a temp gauge for monitoring the tire tread. Hopefully, I can get through the summer with my MPSS, then switch to RE-71R's. Looking to increase interior wheel size to 9 inch in front and 10.5 in the rear, so I can handle a little more rubber footprint. Thanks,

 

[cajundaddy]

Car finally going into the shop tonight for the new parts and alignment. I wil ask to get at least same camber front and rear. With the machine front camber slots, shooting for -2.0 in front and rear. After autocrossing this past weekend, I see what you mean with the outside of front tire really getting hammered, even with 38 lbs of air. Negative camber will help that. This event also showed me I need a temp gauge for monitoring the tire tread. Hopefully, I can get through the summer with my MPSS, then switch to RE-71R's. Looking to increase interior wheel size to 9 inch in front and 10.5 in the rear, so I can handle a little more rubber footprint. Thanks,

Sounds good. Maybe shop for a good used takeoff set of 18" wheels and get some RE-71r mounted right away for AX. It will immediately knock off 2 seconds from your time sheet compared with MPSS. Save your MPSS tires for regular daily street use as they are excellent for that. Also for AX you want to get heat in the tires quickly for best grip. Running much wider tires works against you here. I currently run 225/255/18s to good effect. I recommend near stock sizes and then just monitor tire wear for setup indications rather than attempting to read and apply tire temp data. Tires never get fully heated up with single lap AX events and tire temps can sometimes be misleading.