GT-3 Alignment and sway bar settings

[dave murray]

I just bought at 2005 GT-3, and would like some advise for alignment and sway bar settings. I will use the car 80% track and 20% street, michelin sport cups, std sizes. Car is nervous in high speed sweepers and is headed for alignment as soon as I have feedback. As an instructor for Ozark Lakes Region, I have lots of seat time in 993-996 and 996tt and am looking to avoid brain damage of set up. Thanks Dave

[mds]

I just bought at 2005 GT-3, and would like some advise for alignment and sway bar settings. I will use the car 80% track and 20% street, michelin sport cups, std sizes. Car is nervous in high speed sweepers and is headed for alignment as soon as I have feedback. As an instructor for Ozark Lakes Region, I have lots of seat time in 993-996 and 996tt and am looking to avoid brain damage of set up. Thanks Dave

Congrats on the car. I run my car setup like this:

Front: ride height 115mm, camber -2.5°, toe 0.05° in per side, sway bar 1 softer than full stiff, pressure 33psi hot

Rear: ride height 128mm, camber -2.4°, toe 0.30° in per side, sway bar 2 softer than full stiff, pressure 36psi hot

To get -2.5° front camber, you will need to shim the front arms with about 8 to 10mm of factory shims per side. Alternatively, you can rotate the strut tops to the alternate set of mounting holes, but you won't be able to get much less than about -2.7°.

New cars are often shipped with front ride height 10mm too high, so you may need to lower the front. Rear height is usually pretty close to 128mm.

The softer rear bar helps getting on the power early. However you will suffer from more understeer in slower corners. A bit of trailbraking helps get some rotation. For autocross, a softer front or harder rear helps.

[clord]

Congrats on the car. I run my car setup like this:

Front: ride height 115mm, camber -2.5°, toe 0.05° in per side, sway bar 1 softer than full stiff, pressure 33psi hot

Rear: ride height 128mm, camber -2.4°, toe 0.30° in per side, sway bar 2 softer than full stiff, pressure 36psi hot

To get -2.5° front camber, you will need to shim the front arms with about 8 to 10mm of factory shims per side. Alternatively, you can rotate the strut tops to the alternate set of mounting holes, but you won't be able to get much less than about -2.7°.

New cars are often shipped with front ride height 10mm too high, so you may need to lower the front. Rear height is usually pretty close to 128mm.

The softer rear bar helps getting on the power early. However you will suffer from more understeer in slower corners. A bit of trailbraking helps get some rotation. For autocross, a softer front or harder rear helps.

Dave.... after two years of fiddling, I support Mike's recommendations completely. You say you will use the GT3 80% on the track. While that alignment will work on the street, it won't be the best for steering stability and tire wear. I can get 3+ alignments done for the price of one rear tire....so, I realign for track and back for the street. I run my car on major road trips too and difference is worth the time and trouble of realigning. BTW, I had a local machinist make some aluminum shims for the front lower arms in 3/8" stock. He patterned them after the factory shims....and, they work just fine.

[dave murray]

Congrats on the car. I run my car setup like this:

Front: ride height 115mm, camber -2.5°, toe 0.05° in per side, sway bar 1 softer than full stiff, pressure 33psi hot

Rear: ride height 128mm, camber -2.4°, toe 0.30° in per side, sway bar 2 softer than full stiff, pressure 36psi hot

To get -2.5° front camber, you will need to shim the front arms with about 8 to 10mm of factory shims per side. Alternatively, you can rotate the strut tops to the alternate set of mounting holes, but you won't be able to get much less than about -2.7°.

New cars are often shipped with front ride height 10mm too high, so you may need to lower the front. Rear height is usually pretty close to 128mm.

The softer rear bar helps getting on the power early. However you will suffer from more understeer in slower corners. A bit of trailbraking helps get some rotation. For autocross, a softer front or harder rear helps.

Dave.... after two years of fiddling, I support Mike's recommendations completely. You say you will use the GT3 80% on the track. While that alignment will work on the street, it won't be the best for steering stability and tire wear. I can get 3+ alignments done for the price of one rear tire....so, I realign for track and back for the street. I run my car on major road trips too and difference is worth the time and trouble of realigning. BTW, I had a local machinist make some aluminum shims for the front lower arms in 3/8" stock. He patterned them after the factory shims....and, they work just fine.

[dave murray]

Mike and Craig, Thanks for your reply to my questions. I am set to get the car aligned in new couple weeks. I was given tip to set front bar full stiff, rear 2-3 from soft as a starting place, do you agree? Thanks Dave

[clord]

Mike and Craig, Thanks for your reply to my questions. I am set to get the car aligned in new couple weeks. I was given tip to set front bar full stiff, rear 2-3 from soft as a starting place, do you agree? Thanks Dave

HI Dave....I started with the factory settings of 1 off of full hard on both ends (also reputed to be Roland Kussmaul's recommended settings). I find it a good balance for short, lumpy tracks we have in Colorado. As I gained confidence in me and the car, I decided that a bit more rear grip on bumpy exits would be a good thing, so I softened the rear one more notch (to two off of full hard). For my tastes, this is a good setup. I suspect that the advice you received stems from the line of thought that one unfamiliar with the handling of a 911 is safest starting out with a setup that minimizes the chance of oversteer. If you start there, you will likely feel understeer on turn-in as you get faster. Be ready to experiment and let us know what works for you.

[mds]

Dave,

On the rear 2 or 3 from soft is the same as 1 off full hard or full hard, assuming you did mean to say soft and not hard. If you did mean soft, then your suggestion is roughly either an overall harder version of what Craig and I am using, or an overall harder version of the factory setup. If you did mean hard, then I agree with Craig, that would likely be too much understeer.

When I decided I wanted more rear grip than the factory setting, I decided to soften the rear rather than harden the front because I figured going harder might make the car more tricky to drive if weight transfered faster. It is also easier to change the rear than the front, access is better. But this alternative is worth a try.

Once the tires are up to temp it is very easy to feel the difference between settings. So it won't be difficult for you to dial in what feels best.

When changing the bars, be sure to use blue loctite on the nuts otherwise they will tend to loosen up. Also a slimline 17mm open end wrench is helpful, such as this one. Torque the nuts to 35 flbs.

-Mike

[dave murray]

Mike, Craig, thanks again, sorry if my communication was not the best, a racer gave me the suggestion of full stiff or hard on front, 2 from full soft rear. After tinkering a little over the weekend, I can't imagine needing full stiff/hard on front, currently in 1st hole from full stiff. Rear is in 2nd hole from full soft. After aligned, and 1st track day, (end of march) I will have an idea how close I am to right.

I also have 996tt, with X-73 suspension, this car is fantastic, but I have to admit it is heavy, but the X-73 transformed the car from severe understeer to a real hoot to drive. Bought the GT-3 because of desire to go back in time to my old cars but have all the 996 features I have come to enjoy in new generation cars. For sure the 996tt has made me lazy in my driving and I need to step it up a bit with the new car.

Tire pressures? on michelin sport cups, on turbo I started at 29 front 31 rear, hot went to 35-36 hot, assume GT-3 I will start lower due to weight difference in the cars. Once again thanks!

Dave

[mds]

I try to keep the tires always at 33 front/36 rear hot. It is easy to feel a 1 or 2psi change and these pressures seems to work best for maximizing front and rear grip, IMO. For street driving I set them at 30 front/31 rear cold as usually the front tires warm up about 3lbs and the rears 5lbs on the street. For track driving, I start with 26 front/27 rear cold, and then adjust them to make sure they are always 33 front/36 rear hot after every session. When cold the first lap they will feel very bad, too soft and no grip, the second lap they are much better, and from the third lap on they are nearly fully up to temp. For autocross, where you really can't get any heat on a single lap, I start the day at 33 front/36 rear cold and adjust them downward as necessary after every lap.

Mike, Craig, thanks again, sorry if my communication was not the best, a racer gave me the suggestion of full stiff or hard on front, 2 from full soft rear. After tinkering a little over the weekend, I can't imagine needing full stiff/hard on front, currently in 1st hole from full stiff. Rear is in 2nd hole from full soft. After aligned, and 1st track day, (end of march) I will have an idea how close I am to right.

I also have 996tt, with X-73 suspension, this car is fantastic, but I have to admit it is heavy, but the X-73 transformed the car from severe understeer to a real hoot to drive. Bought the GT-3 because of desire to go back in time to my old cars but have all the 996 features I have come to enjoy in new generation cars. For sure the 996tt has made me lazy in my driving and I need to step it up a bit with the new car.

Tire pressures? on michelin sport cups, on turbo I started at 29 front 31 rear, hot went to 35-36 hot, assume GT-3 I will start lower due to weight difference in the cars. Once again thanks!

Dave

[dave murray]

Mike, thanks, kind of what I was expecting on pressures, similar to what I have determined with hot pressures on 996tt. I assume you are using michelin sport cups?

[mds]

Mike, thanks, kind of what I was expecting on pressures, similar to what I have determined with hot pressures on 996tt. I assume you are using michelin sport cups?

Yes. I've played with the stock tires a little bit, they seem to work well at roughly 4psi more all around than the Cups.

[clord]

I try to keep the tires always at 33 front/36 rear hot. It is easy to feel a 1 or 2psi change and these pressures seems to work best for maximizing front and rear grip, IMO. For street driving I set them at 30 front/31 rear cold as usually the front tires warm up about 3lbs and the rears 5lbs on the street. For track driving, I start with 26 front/27 rear cold, and then adjust them to make sure they are always 33 front/36 rear hot after every session. When cold the first lap they will feel very bad, too soft and no grip, the second lap they are much better, and from the third lap on they are nearly fully up to temp. For autocross, where you really can't get any heat on a single lap, I start the day at 33 front/36 rear cold and adjust them downward as necessary after every lap.

Again, I agree completely with Mike. (We must be similar drivers with similar driving preferences). I start Pilot Sport Cups with 26/27 front/rear...and have the same comments about how they feel and how they warm up. Do pressure test them hot after each session....warming afternoons may have you bleeding off more air. AND BE SURE to air them back up to street pressures for the ride home. You won't get track type heat in them driving home and too-low pressures on the street will risk sidewall failure (read: Catastrophic Failure) on a long ride home.

[dave murray]

Thanks again, really appreciate your advice, exactly what I hoped for!

Dave

[dave murray]

I try to keep the tires always at 33 front/36 rear hot. It is easy to feel a 1 or 2psi change and these pressures seems to work best for maximizing front and rear grip, IMO. For street driving I set them at 30 front/31 rear cold as usually the front tires warm up about 3lbs and the rears 5lbs on the street. For track driving, I start with 26 front/27 rear cold, and then adjust them to make sure they are always 33 front/36 rear hot after every session. When cold the first lap they will feel very bad, too soft and no grip, the second lap they are much better, and from the third lap on they are nearly fully up to temp. For autocross, where you really can't get any heat on a single lap, I start the day at 33 front/36 rear cold and adjust them downward as necessary after every lap.

Again, I agree completely with Mike. (We must be similar drivers with similar driving preferences). I start Pilot Sport Cups with 26/27 front/rear...and have the same comments about how they feel and how they warm up. Do pressure test them hot after each session....warming afternoons may have you bleeding off more air. AND BE SURE to air them back up to street pressures for the ride home. You won't get track type heat in them driving home and too-low pressures on the street will risk sidewall failure (read: Catastrophic Failure) on a long ride home.

[gormanfly1]

I just bought a 2004 GT3 on Friday. I am having Michelin Pilot Sport Cups put on this week. I have these same tires on my Boxster S as well.

Labor Day weekend, I was driving my Boxster S at a PCA DE event at Road America in Wisconsin and met with a Michelin tire engineer who was there. He told me optimal hot pressures on the PSC were 32 psi front and back.

I see a number of you recommend higher hot tire pressures for your GT3s with MPSCs. Perhaps the engineer's recommendation was specific to my Boxster S, but I suspect not. Can anyone elaborate as to why you like the higher pressures?

[pgwilliams]

Perhaps it has to do with the differences in weight distribution between the Boxster (about 50/50 ?) and the 911 (about 60/40?)

Edited October 3, 2006 by pgwilliams

[clord]

Perhaps it has to do with the differences in weight distribution between the Boxster (about 50/50 ?) and the 911 (about 60/40?)

I agree. 32-33 hot is good general advice, but, with the weight distribution on the GT3, I find 35-36 hot best. In talking with a respected Cup Car racer last weekend at Miller, he concurred on that number for the rear, and commented that for a turbo 911 (GT2, even heavier in the rear) he would recommend a pound or two more, hot.

[Feds]

Are there any recommended technical manuals one can purchase that show how to make these typeof changes to the alignment and sway bar?

Thanks in advance...