Race suspension alignment
 

For some reason my searches seem to only bring up topics about stock suspension settings for guys wanting to run stock cars on track with a more aggressive alignment.

I am waiting to install H&R RSS coilovers and am looking for alignment specs for a track only, modified suspension car. Does anyone have that info? I'm a smooth but aggressive driver who doesn't like the rear of the car to pass the front. Looking for stability.

When I ran my 993 on track, the rule was get as much neg camber out of every corner. I'm reading here that Boxsters don't like a lot of negative camber......why?

TIA

Boxster's need and love negative camber just like any strut-based suspension! The stock set up maxes out at around -1deg camber in front but the car really needs much, much more.

A good starting point for a track-only setup is -3.0deg camber in front (where you go from there depends on driving technique, tire selection, tire temps, tire wear, etc.), maybe 0.5deg less camber in the rear, 1/16 toe (for stability, zero toe can feel "darty" but is generally faster), then add as much caster as you can get.

Of course, you'll need height adjustable coilovers, a set of GT-3 front adjustable lower control arms, adjustable front/rear drop links, and adjustable rear toe arms to reach this setup. Might as well throw in a set of sway bars while you're at it (GT-3 front, Tarett rear).

Have a race shop do the alignment and corner balance. You'll also need to keep an eye on air pressures to keep everything in balance.

This is a very good reference page: HELPFUL HINT: Porsche Boxster Suspension Setup - Stock, BSX, BSR - GSR Autosport Community

Hmm, ok thanks. Sounds like the 993 then. I don't know that i'll go all the way crazy, this is a DE car, but I am running slicks like I did on the 993, so the more camber the better :-)

Slicks for a DE car?? Whew, that's about $1600/weekend in tire expense! Yes, they will be in the sweet spot at neg 3 degrees.

Property tax is really low over there on the right coast.

Yes slicks.....I drive FAST! I also buy them slightly used so more like $300 a set a weekend :)

Yup that's why I'm here. trying to get back to Topless's neck of the woods! One day.....

Yup that's why I'm here. trying to get back to Topless's neck of the woods! One day.....[/QUOTE]

I used to live by the ocean in N.C. really cheap, in Camp Lejune. I like your rental places looks nice. :)

I used to live by the ocean in N.C. really cheap, in Camp Lejune. I like your rental places looks nice. :)[/QUOTE]

Hey thanks, appreciate that! yeah LeJeune is an hour north in Jacksonville. It's certainly cheap compared to CA ocean front living! My wife and I grew up in San Jose/Morgan Hill (NorCal) but really like SoCal and hope to be able to retire there in around 10 years.
NC has treated me pretty well so I can't complain, but we are Californians, no way out of it :-D

OP, I am running pretty close to the same set-up as Stone, which looks like good advice to me. I will add a few points that I have found:

1- Ride height, camber, and toe are all highly inter-related with this supension geometry. If you are running coilovers, then you must fix ride height & corner weights first before even thinking about camber, caster, and toe.

2- If you go too low on the rear, you will have too much negative camber, and run out of toe adjustment. This is one of the reasons that some people use rear adjustable toe links on these cars. I feel it is better not to go that low, but the after market toe links are still good to eliminate rubber bushing deflection, and be able to shim the upright attachment to adjust bump steer.

3- Optimum front to rear tire stagger is a function of what you do to optimize camber. If you don't modify camber to get near -3 deg as Stone suggested, then the optimum tire stagger will be close to "square". (something like 255 F / 265 R). However, if you crank in enough negative camber to optimize the front tire, then you will need more stagger - something like 255 F / 285 R, with the appropriately correct wheel sizes of course.

4- A GT3 front bar is the best mod you can make if you do nothing else. If you get it set at just the right roll stiffness, it will help reduce understeer by reducing the amount of positive camber in roll that all McStrut designs (911 or 986) experience. However, if you you think a little is good, then a lot is better, it will understeer like a pig.

5- If you use coilovers, go with fairly high spring rates to better control dynamic camber and toe changes. If you use a significantly higher spring rate in the rear, you may not need much or any rear bar. It is a fine balance with these cars, and sometimes a relatively small change in roll stiffness at one end can result in major oversteer or understeer. I suggest testing all new set-up changes on an auto-x course before heading to a track.

Hope to see you at a Southeast track sometime this year.

Well thank you for the write up. This is what I'm looking for. I am using coilovers (H&R) but not going crazy for just DE's.
I've not run mid engine cars before on track. My race car was a water cooled GTi. Stiff as you could rear and I always ran soft front, the car was on rails.
The 993 was similar but I cooked tires without enough camber. I'm thinking this time about adjustable camber plates for the front to dial in 3 degrees (or as close as possible).
I'll be running 8" hollow 996TT 18" wheels with Yoko slicks and thinking 35-40mm spacers with studs (questions, concerns?) to get effectively 9.5 width without all the weight of 9.5" rolling weight.

Figure I'll start there. Look forward to your responses. And I will be at VIR with Zone 2 PCA mid March. If you're there, love to meet in person. You won't miss my car :D (more to come)

Thanks

I'm not sure how well those 8" wheels will work on the rear, even if spaced out as far as possible. My guess is that the weight in the rear may overheat the rear tires after a few laps, and you may have increasing amounts of oversteer during a session. Let us know how it works out.

I've never been to VIR, but hope to some day- good luck.

Camber plates will provide about one additional degree of camber over stock which means that you'll max out at a bit over -2 deg. This will probably not be enough to keep from cooking the tires.

So how does one achieve -3 degrees?

I've got 10's and 11 hollow spokes from my 993 track days but I don't think they'll stuff under there will they? I'll try the 8's and see what happens. VIR is a low wear tire track, will probably be ok there to start learning this car.

Don't know about Stone, but I use GT3 type arms with shims for camber adjustment like these:

RSS Tarmac Series Lower Control Arms - RSS

Other advantages over camber plates are increased front track width as you add shims, and caster adjustment if you buy them with the bushing centers that rotate.

These arms are mostly for the front on our cars but are also a fairly cost effective way of eliminating all the rubber bushings in the rear when you add up all the parts and hassel of changing out the rubber bushings in OEM control arms. But, you really don't need them in the rear for camber.

If you are hooked on camber plates, I beleieve there are some tricks to get more than -2 degrees of negaitve camber out of them. These tricks seem to involve either drilling a larger center hole at the strut tower, or putting shims between the camber plate and the strut tower so that the strut center bolt has more room to move without hitting the body. If you look around on planet-9.com under the 987 competition driving section, you can find more info on how to do this. (FYI, in general there are a lot more Caymans that are tracked seriously than there are Boxsters, so you can find a lot more track info there. The 986 and 987 suspension designs are identical from what I can tell)


To use your existing wheel sizes, I would put the 8's on the front and 10's on the rear. You can forget trying to fit 11's unless you want to hack up your body work. I normally use 8.5" or 9" at front, and 10" at rear with appropriate size tires.

Good luck.

Can you explain in more detail how to shim for a reduction in bumpsteer?

If you read Carrol Smith or Fred Puhn's books, you will see there are multiple ways to do this, but they all involve moving a suspension through its' travel range, and measuring the change in toe. The change in toe is what is important, and not the absolute toe value, so home made devices work fine for this.

I use a home built laser device projecting onto my garage door like this:

http://986forum.com/forums/uploads01...1390759950.jpg


The bump steer curves on my 986S were pretty bad with significant toe-out in bump, and toe-in in droop. It takes a bit of shim work to get a good curve.

So the GT3 arms are wider or should I say longer than my stock arms? Do the gt3 arms require the steering rods etc to be changed as well? Not sure I'm understanding how one gets more camber out of arms vs camber plates. I'd love to not go the plate route since they've got a tendency to move slightly but it's what I know from my water cooled Vw days.

If you don't have any shims installed, the GT3 type arms are the same length as your stock arms. On the GT3 type arms, the inside bushing housing is a separate piece that bolts to the rest of the arm, and you add shims as needed where these two pieces bolt together to make the overall control arm length anything that you want (within reason).

The real limitation with camber plates on these cars is that the nut on top of the strut runs into the body as you slide the top in to gain negative camber. The GT3 type arms obviously don't have this issue, and you can gain caster adjustment, and eliminate or reduce the rubber bushing deflection depending on which brand you go with.

I used to be a BMW camber plate guy myself, so don't worry about making the change from being a plate guy to an arm guy.

I don't mean to seem like a complete tard, but might you have pictures of what you are talking about as it pertains to shims etc? This is all new to me. I'm a picture and diagram kind a guy :-) my car is, at the moment, a stock box I'm slowly going to transform. But these ideas are new territory. I only got to PSS9's on my 993, it was a dual purpose car. This one is track duty only but only occasionally. How can I set it up to drive 9/10ths without going crazy. That's what I'm after. I'm ok with a set if tires an event.

I went back and re read your post and looked at that site again......I get it now! So the shims force the lower arm out (how you get increased camber), while allowing for the other arms to remain the same length as stock by way of that multi holed center point (and I'm assuming that center puck rotates?). Or if not, you get a couple of different dimensioned mounting holes. Great looking product. Seems rather strongly priced for an occasional car. Looks like it almost forces on to get the adjustable toe links etc......where does it end :-D
It seems the Spec racing guys can't use these parts though per the rules, so do they just get whatever they get by lowering and squeaking out whatever is allowed by the factory parts?

Yep, if you want to run soft rubber you will need lots of neg camber in front. GT3 adjustable A arms are the way to go in a Boxster and will pay for themselves quickly in even tire wear and much longer tire life. This is the preferred method on Boxster Spec Race cars. :cheers:

I have PSS9's set as low as I can go without spacers. I had it corner balanced with my weight in the driver's seat. Then I did my own alignment (made a framework and tools specific for this car). I also do not have any rubber in the rear suspension (adjustable arms, bushings not rubber, etc.).

I set mine at -1.25 degrees front, -1.75 degrees rear. Slight toe in both front and rear. If one goes 0 toe, it gets very touchy on the highway. With this setup, the bumpsteer was huge. Using a setup with multiple dial indicators and running the front suspension through its travel, I saw major toe out when the strut was compressed. That might have been good for certain tracks but was not good for the street. I created spacers to lift the steering rack away from the crossmember. With trial and error, I found the sweet spot. Now I don't get any bumpsteer throughout the travel of the front suspension. I think that it came out to about .4" thick spacers. Many people don't think about this when lowering a car, but it can make a huge difference in drivability.

Boxster Spec allows the use of GT-3 adjustable lower control arms. This is how we reach >-3deg neg camber.

Install GT-3 lower control arms and align as discussed. This will provide the most bang for the buck and extend the life of the tires. You'll still overcook the outside portion of the tire at 9/10's but that is the tradeoff of not replacing the entire suspension.

I drove my 986 like this (all stock except for adj LCA's) for about 30 track days before I could outdrive the car and was ready for the full suspension upgrade.

Been looking around and have found some that don't use spacers. Elephant Racing has a set that is like a tie rod, it threads in/out instead of shims for adjustment. Any comments on that style either way? In theory, seems like the perfect way to go. Infinite adjustment without the need for shims or other "loose" parts.

As for the rear, simply lower the car. Camber is achieved via the concentric in the lower arm, I'll need to get new toe links, correct? Or do I have to replace all of the arms back there with adjustables?

I can't see any significant difference between shimmed or threaded types of LCA's. Shims come in varying thickness and often require more than one to achieve the desired camber. Also, the shims are somewhat expensive and can be easily lost in a tool box. It is hard to tell but I wonder if the threaded type might be vulnerable to dirt/muck getting onto the exposed portion of the thread and might be hard to adjust after a few years. Pick your poison.

Yes, lower the car and you'll need new adj rear toe links. Most folks do not use rear adj LCA's.

I agree with you about the trash getting into threads. But A) I hope not to mow the grass with the car :D B) those joints can't be any more susceptible than tie rods etc...

Could always wrap with tape to keep clean.

You've been a big help, thank so much. Now I just need to figure out who to buy from. As usual, spending waaaay more than I want to. Hate that I have the need to go fast :)

I use them on every car :) every time.. It settles down the toe gain under braking by replacing those worn out rubber bits on our donor cars :)

FYI:

Unless you perform tire temps.. on your car.. at the track.. camber settings are *only* guesses. I have drivers that heat their tires evenly with -3.6 on a shaved RA1, then I have guy's who heat the tires evenly with -3.2 on the same tire.

Camber is driver and track dependent. I don't run the same camber on the right rear at Willow Springs that I would run at CA. Speedway. The track design heats the tire differently. You see this in pressures also. You cannot run the same cold starting pressure in the left rear at WSIR as the right rear. You will burn down the left rear :(

All good info coming from group!! The toe gain explanation is one of the best I have seen online!!

Also: Raising the steering rack in the front to correct bump = we've been doing this for years in 914's and 911's. Porsche Motorsports does this on ALL the RSR's :) and I do it on Cayman's and Boxster's :)

Again, Brad I agree with what you are saying. I don't think I'm going to worry much about the track dependency. If I were arcing for $$ maybe :)
I just want to find a happy medium and go get my giggle on.

As for the raising of the steering rack, is there a benchmark to shoot for? At rest, are you trying to "level" either toe rods or some other functioning bit of suspension to know you've adjusted properly? I believe it was either my 993 or GTi back in the day, that this was an issue and I think the more level the toe rods were, the better.......same here?

This has been a great thread! Thank you all

This statement has been bothering me a bit. So, yesterday I checked my front bump steer. My set-up has aftermarket tie-rods, so I can shim the rod end at the upright rather than shimming the steering rack, but it's all the same.

My toe change was less than 0.1 degrees throughout the whole travel range with no shim adjustment. I haven't compared the tie-rods I am using to the OEM tie-rod dimensions, so it could be some difference there. The only other thing I can think of is that I am using a lot less caster than stock, so perhaps the caster change also has an effect.

I guess the moral is there is no short-cut to testing your exact configuration.

So, thought I would update the thread. I ended up getting the RSS LCA's. Really wanted the Elephant Racing threaded type but apparently they are like hens teeth and of course I had just missed the last set and new ones weren't ready from the machine shop in time for my needs. I found the RSS only 3 hours from me.

I'm going to the alignment rack tomorrow after corner balancing myself (I have mechanical scales), so we'll see what values I get.
To recap, I've installed H&R coil overs front and rear (no spring rates from H&R other than progressive). I installed the LCA's with 13mm worth of shims each side, and am running 25 1/8"- 25 1/4" ride height to fender(center of hub) all the way around. Corner weights are in the optimum range as I saw posted here recently (6xx's front just over 8xx rear). In the rear the only replaced part other than shocks are the rear toe links.

I'll report alignment values once we get off the rack. If I don't get -3 camber up front, I think I'll wait for the rest of the alignment until I can get it. Will need to order more shims. I have a couple weeks left until VIR.....
I'll check the LCA's and steering rods for "level" or other, which may be another reason to jump down off the rack early. I know if either point north while static, that's bad and so I'll have to figure out how to adjust those issues.
Thanks everyone for chiming in, been a big help :)

At that ride height, you may find that your LCA's are "over center", which you obviously know is not optimum.

Good luck.

Indeed I do know, and completely forgot to look this morning too.....had a meeting that interrupted hanging out longer with the alignment guy. But he didn't mention anything about it. I caught the need to worry about it as I was installing the LCA's, and with the spacer rings that come with them (to raise or lower the outer ball pin height), I think I got it taken care of. I can check tomorrow with the car in the trailer. Thanks for the renewed heads up.

I don't have the sheet in front of me, but I was able to manage (with 13mm worth of shims and a hint of honed out upper strut holes), just shy of -3 degrees camber. -9 degrees caster and a hint of toe front. Camber in the rear was about even with the front, and a hint of toe. I'll post actual numbers tomorrow. I didn't dial back the rear camber simply because I felt with my narrower rims and slicks, I thought it best to leave the added help keep all the rubber on the road. You're welcome to chime in :D

For your review (and comment if you must :D ) my alignment specs. Camber is maxed out all the way around with the simple mods made. Alignment guy says camber increases (to the negative) by .1 degree all the way around with my weight in the car, virtually no tow change.

LCA's all the way around are nice and level, so I'm good there. I think I'm set up to at least run 8-9 10ths :) will know in 2 weeks :cheers:

Not much to comment on except the rear looks like it has more potential to be worked on. Whether it's good or bad depends on what tyres you are running and what handling balance you want to achieve.

Maybe it's just me - but that alignment doesn't seem like much of an alignment to me. The numbers are pretty off on both sides.

Here's an old alignment sheet from my old TT. I asked for these specific numbers and as you can see - they provided them exactly as specified. The car had camber plates and adjustable rear control arms.

Maybe i'm just picky - but if I'm going to pay for an alignment - I want them to do an actual alignment to my specifications.

http://www.rastta.com/images/alignment.jpg

Well I'm not exactly sure how comparing a completely different car applies? I have been told here and by others, that the values need to be as close to -3 camber etc as I can get as a starting point to work from.
These values are maxed out as you see it. These aren't arbitrary values, they are all the car could give me for the parts I altered.

I understand where you are coming from, but some things don't look right to me either.

That right rear looks like too much negative camber and too much toe-in. I am guessing from these rear end camber vs. toe numbers that your rear end is lowered to the point that you cannot reduce the camber any more, and you are stuck with too much toe-in at the rear. You may need to raise your ride height slightly to get back into a good adjustment range.

For the front I like to run absolute zero front toe, but to each his own. It's usually not a big deal, but I think these cars naturally have a bit too much caster. If you have the adjustable bushings in the center of your GT3 arms, you can adjust out some of that caster. Sometimes this helps if you are having problems with really wide front tires rubbing on the fender liner. I also have a theory that reduced caster can help with that stupid power steering overheating issue, and seems to help bump steer.

I'd take it back, even if it meant another iteration with corner weight adjustment.

One more thing on that -3 deg negative camber thing: If you are running NT-01's, I think this is really more camber than is optimum based on tire temperatures and wear patterns I have experienced. If you are running HoHo R6's or A6's, yes you definitely want the -3 degrees. Dunlops seem to like close to -3 also. I can't say for sure on others, but generally the stiffer the sidewall, the less negative camber a given tire needs.

Good luck.

That's what I was trying to say except a little less blunt ;) I have had my geo done and it is to within 1 or 2 minutes accuracy across the axle. Some will say you won't notice it but if you are paying for it and it is relatively easy to achieve, why wouldn't you do it?

Doug, I'm running Yoko slicks on 8" rims all the way around. Everyone I talked to told me to max out negative camber. I have adjustable toe links in the rear, that right rear may be a bit much, we'll see. I can tweak it at the track if it proves ugly. As for caster I was also told these cars really like as much caster as possible, and it was the alignment guys opinion that with more right turns typically than left, this should work just fine.
It's a starting point if nothing else and will hopefully be a lot better than stock suspension and alignment and street tires :) As long as it feels safe, I'm good. It's just a DE car and I'll be using it as more of a rolling billboard for my beach vacation rentals (getting a wrap) than a full on race car so.....

Does seem weird to me that the right side of the car gets higher values than the left, wonder how that could be?