Brian S

So the dealer was able to get only 1.5 degrees of camber out of the front of my car. After looking for myself the car already had 8mm of shims in the arms that they apparently don't know about, I've added another 6mm of shims to each side so I believe I have something in the 2.3-4 range now but it looks fairly drastic. Unfortunately the shop that I usually have align my car isn't available until after this weekend but I figure if they had both set to 1.5 and I install the same shims on both sides everything should be even.

Any idea how the lower arm affects toe?

NJ-GT

it does affect toe drastically, the more shims, the more toe-in, way excessive toe-in.

With 8mm shims (probably a 7mm shims plus a 1mm shim) and the struts not rotated fully inboard, the car should get -2.5 easily. If all they could get was -1.5, their alignment equipment is wrong.

GT3 Chuck

+1^ that doesn't sound right at all...you should get close to 2 deg without rotating the struts and without any shims...if you want more than 2deg neg camber the best solution is to rotate the struts to keep castor in spec and then add shims for camber, while you're at it get it corner balanced too

Brian S

1.5 sounded low to me as well but my wife took the car in and they claimed that was the best they could do when I specifically wrote down the part #'s and even the page number in the manual that someone listed here a while back, and they didn't know about rotating the top because my usual service manager is out on sick leave. I have 14mm of shims right now, I will have to look at the top, and may take some out before the track this weekend.

I was thinking about the toe, I think you would get toe-out right? if you lengthen the arm, but not the steering linkage it would make the linkage shorter in relation to the pivot point. I just don't know how much 6mm per side did, I guess somewhere near 6mm of toe rod length short.

fc-racer

A quick question regarding shims vs. strut rotation: Is it better to use shims, rather than rotating the strut, because the shims widen the front track which should increase grip more?

997gt3north

- Most gt3s were able to get about -1.7 camber without shims - some have report getting to -2.1 so maybe -1.5 is also with the variance range.
- In my own previous path down the route that you are taking, my very rough math is that 1mm of shim is .1 degree (this is very rough math)

- So, here are some of the possibilities:
1) their machine is not working and you are at -2.9 front camber (-1.5 + -1.4with 14mm of shims) - car will be fine on the track
2) the original owner used the shims to get to the -2.5 range but then left them in and returned the top strut adjustment fully outboard to reduce the camber back as much as possible, your shop didn't see this and just added more shims (maybe you are at -1.5)
3) something about your gt3 is unique (possible not very likely)
4) could they have put the shims in the wrong spot?????

I would still go to the track and just monitor things but for sure go get it "fixed" after the event

Brian S

Real quick note for anybody thinking about trying this at home.. DON'T go too far.. I started with a claimed 1.5 degrees of camber and 8mm of shims, I installed 6mm more shims and the car was completely undrivable on city streets and exhibited dramatic darty toe-out characteristics. I think my next alignment will be on brand new hoosiers instead of the worn Corsa's I took it in on for accuracy.

I am back to 7+3, so 2mm more than they had and the car is drivable but I am closer to the 2 degree range and will play with the top strut tonight. I have a crude way of measuring camber based off what the dealership claimed to be fact so I can get where I want to be but it needs to be in the top of the strut and not in the arm because of the toe. I like however much the toe moved this time though, it is an improvement on the turn in from before (since front toe affects turn in, and camber affects the car more when it is actually loaded harder)

I am the 2nd owner of the car, the original owner was a bling bling type who put 800 miles on it (traded it for a f430) and would not have had the car re-aligned in my opinion. so that begs the question, do all 08 gt3's come with 8mm of shims in them to begin with because the only place that has aligned my car claims to have no idea that they even exist plus the bolts holding the arms together were consistently dirty with the rest of the arm and did not have tool marks on them.


Note on the bottom arm length, yes it does widen the front track width which would make the car push and sort of feel like the car has more grip for an unknown reason to me but I know it for a fact from racing RC cars (at a national level, these cars are extremely complicated and configurable and I have tested countless geometry changes)

Caster is also important and I believe affected by the lower arm the way it mounts on the GT3, less caster will make the car turn in harder and more caster will make the car more stable in higher speed corners. Again I don't know the physics behind it though.