semicycler

Question regarding two-piece GT3 style front LCA's and the shims to adjust negative camber. After the LCA's are installed and the car properly aligned, can I add or delete shims without affecting toe? Caster might change a little but that shouldn't be a problem. Not sure about toe though.

Ideally I want to tweak my front camber adding or subtracting a few shims until I'm happy with the handling, without having to pay for a proper alignment after each shim change. Is this possible?

AWay

I don't believe so. Why not settle on your alignment specs beforehand and do it once and done? What are your reasons/need for the camber and I'm sure we can steer you in the right direction.

mdrums

Nope....

Do you track a lot?
What tires?
Have you taken tire temps?

Need to know this before you settle on alignment specs. Your driving on the track and tire temps and wear will tell you more about where you set alignment specs.

semicycler

Current setup is -1.1 F/ -1.5 R with the stock C2S one piece LCA's. Front 2-piece GT3 LCA's will be installed in the next week or two. Without any shims the GT3 LCA is pretty close to the fixed C2S length. I plan to install wihtout shims myself and drive it to my indy for a proper alignment.

I'm not sure what final camber values I want just yet. GT3 specs are -1.5 F/ -1.5 R, this is my minimum. A more likely setup will be -2.0 F/ -1.5 R. Maximum I'd go is -2.5 F/ -2.0 R. If toe is not affected by adding shims, I could make camber adjustments until I'm happy then go in for an alignment once. But if toe changes in the wrong direction when adding camber shims, the tires would get chewed up.

How about you track folks? Do any of you adjust camber while at the track without an onsite alignment, playing with the number of shims only? How do you manage it?

semicycler

Anywhere from 2-6 track visits a year on MPSS tires. I'm looking for an aggressive street/mild track camber setup with a more neutral setup. I don't have enough track experience to fine tune it just yet.

mdrums

Ok you're still on street tires at the track....the absolute most I'd go is

-2 camber front per side
zero toe
8.5 degree caster

-1.7 camber rear per side
1.5mm toe in per side

This spec is really probably about too much for PSS street tires run at street pressure so you could back camber down to around -1.5 for front and rear.

mdrums

Add the shims but adjust camber by moving the top of the coilover. You don't take out shims and add shims all the time to adjust camber for the alignment. You also don't do this between track events either. Yes your toe will be changing as you change camber.

semicycler

Thanks Mike, this is exactly the answer I was looking for and points me in the right direction for a solid one time alignment setup. You rock!

semicycler

Hey Mike, one more question:

You are recommending rear toe in at 1.5mm. I'm used to seeing this in degrees/minutes. Follow my math for a second to convert to deg/min and compare to 997 GT3 toe in specs.

My wheels are 19" or 482.6mm. Using this calculator http://www.furybusa.org.uk/camber.php and the 1.5mm toe in recommendation gives 0.18 deg. Converting deg to min we get 10.8". 997 GT3 toe in spec is 13" +/- 2". So the spec ranges from 11" to 15".

Your recommendation is to go towards the lower side of the GT3 rear toe in spec range at 11" or 1.54mm. Is this correct?

mdrums

Correct go to the lower side of the GT3 spec...for your street tired and that you only track a few times a year.
You will get much better wear on the street this way since that is where you drive this car the most.

Hella-Buggin'

I just did this to my C2S. I switched to AD08-R tires because I felt I was reaching the limits of the MPSS and wanted something with more grip. Here's the alignment my shop gave me. I seem to have more rear camber than most mention on the forum but the car has been transformed in the corners.

Front:
Camber -2.0 (7mm shimms)
Caster 5.0
Toe -.02

Rear:
Camber -2.5
Toe +2.0

mdrums

Mark those AD08R tires are really good. Street tire but leans more towards track performance. I use this tire too for street and I won an auto cross on them too.

Anyway you should really re-evaluate your rear camber specs. Even with r-comp tires track tires we don't run -2.5 in the rear. You will get better traction and braking by decreasing the rear camber at least to -1.7 by putting more tire on the pavement. You would need to be running a true race tire slick at low pressure on the track at full G grip load in a corner to benefit from -2.5 camber in the rear.

Now having positive toe in the rear...toe outwards is absolutely wrong and extremely dangerous in these rear engine cars. Please fix toe to at least .16/18 degrees and/or 1.5mm toe INWARD
I hope this helps!

Hella-Buggin'

Thanks Mike, a few people have told me that but at the same time the tires are showing wear marks all the way to the indicators. I'm running the rears up to about 42 PSI (track hot). The next time I take it in I'll discuss reducing it and see why he set it up this way. My guy does many cars for our PCA group and lots of Spec 911's so I wonder if that's influencing his decision. This is my first aggressive alignment beyond stock and it's amazing what a difference it makes. It's just so glued in the corners. I'm not running Damptronis so my car even in the PASM Firm mode has some lean to it.

I'm digging the AD08-R's a lot. quite a step up from the Pilot Super Sports on the track. They're still very steerable but they deal with the pressure and heat changes better than the MPSS's on the track.

semicycler

Now I'm confused. Online 997 alignment specs keep showing positive rear toe numbers. I thought positive toe numbers meant toe-IN?

If correct than Hella-Buggin's rear toe of 2.0 (assumming mm) is 14.4', within the 11' to 15' factory spec, although on the higher side. His front toe of -.02 is extremely close to zero (doesn't matter mm or deg here, still close to zero) and also within spec for 2010+ of 0'+/-2'

kisik

That is correct. Positive number on rear means toe in. That is what we want. On the front it is zero or tiny bit toe out.
Here is what I run. I put weights on a driver seat.
Front: -2.5deg, 7.3deg, -0.4mm
Rear: 2.0deg, 2mm
I am running NT01 (235/305 combo)

My confusion is that if you go to different shop the alignment rack will show a different numbers to start with.

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05' 997.1 C2S