bebbetufs

I'm heading for the track next week. It will probably be my only chance this season, so I would like to get my baselines setup as close as possible.

Right now I'm installing GT3 control arms on the rear corners. I'm considering setting the fork in the front offset hole in the puck to increase the wheelbase slightly. Would you advise against this?

Nickshu

Mine are in the offset hole (not center) in both front and rear. This is to correct caster (or position of the wheel in the wheel arch for rear) depending on how much camber you are running. In general, if you are running lower camber then use the center hole. Higher camber use the offset hole. Camber widens the track, the control arm hole just corrects the wheel position resulting from the thrust arm driving the wheel forward as you add camber. You have more control over the track width in the front by running the strut top all the way out, then shimming the control arm to get the track width, of course there are limits to symmetry here as each chassis is not perfectly even left to right. Beyond that, spacers would be a good way to widen the track further once your alignment is where you want it. All of which has to still tuck up under the fenders depending on your ride height.

bebbetufs

Thanks for your quick response. I ran -3.5 front and -1.5 rear last time (2016).
I have done the same, but I'm worried that the front offset is not enough for -3.5. I'm running CUP LCAs in the front and the solid caster puck.

I'm using the central hole, which i guesstimate has about as much offset as the max offset of the rubber bushed GT3 LCAs. Would you recommend just going for max offset in the front?

Side note: Are you running spacers on your wheels to fill the arches as much as you are? With the GT3 CUP arms and 16mm shims my tires are not even close to the arches. I'm running 225 fronts though.

Nickshu

Those GT3 Cup LCAs pictured above have solid caster pucks. The allen bolt allows you to rotate them to get the desired caster (or wheel centering in the rear). So you would want to set the car upon an alignment rack and then adjust them as needed to get the desired setup.

In SPB class here in the USA we are only allowed to run the ones on the bottom photo w/ 2 positions and rubber inserts. So options and adjustment are more limited.

For sure at -3.5 in the front you would not want to use the center hole. Your caster would be way off and the tire will likely rub a lot at the front of the wheel arch liner.
On the rear at only -1.5 the center hole is probably where you want to be.

I run spacers front and rear, within the limits of what SPB rules allow, which is about 5mm front and rear. I have run Hoosier R7's in the rear with 15mm spacers w/o a problem (at -3.5 camber), that is legal in NASA here in the USA, but not in SPB.

bebbetufs

Thanks for your advice. You have posted a lot of useful information which helps a great deal.

Will I run into drive shaft issues at some point in the rear, or is there enough play in the CV-joints to accommodate for reasonable camber angles for track use?

Just to clarify, With the arms you are allowed to run, you will use the offset hole in the front?
What shim thickness would correspond to -3.5 camber up front? Do you get any rubbing with that setting and -3.5 camber?
Roughly what castor angle will you get with this setup?

Due to differences in length of various inner uniball housings comparisons of shim stacks will be off. The CUP uniballs housings (short version) are 3-4mm. longer than the RENNLINE housings I have. Still, it would be useful for me to gain more information on this.

Nickshu

I have run up to 3.5 in the rear w/o driveshaft issues. Tarret sells spacers that go on the inner CV with longer bolts to make up for this, but I am unsure at what degree of camber those become necessary. Maybe someone else can chime in on that as I have wondered about that myself as well.

Yes on the arms we are allowed to run I am on the offset hole both front and rear. I have run a camber range of 2.5-3.5 with the offset hole w/ no issues w/ caster (front) or wheel position (rear).

At around 3 or 3.5 of camber up front my caster measures about 5.5. That is not adjustable on my setup, but with your solid adjustable caster pucks you would be able to adjust this within reason. Caster of 4-6 I would think is acceptable.

I would have to look but I think my shims are 7-10mm per side. However the CUP arms are not the same length as the street GT3 arms, so those measurements won't apply to you up front. If you are running the rubber GT3 LCAs then they would. Again every chassis is a bit different so it won't correspond exactly. I think you were trying to point this out above so it appears you are aware.

I'd recommend you get a digital camber gauge, they are not that expensive and will make this much easier if you don't have one.

bebbetufs

Great info. Thanks!

I have an alignment machine which i'll use this time. In the future I'll go to DIY strings and setup wheels.

Would you increase rear camber?
I'm running seven year old Federal 595 RS RRs. They've had one track day but they may have gone hard.

Nickshu

I would use tire temps at the track to decide on camber, or look at your tire wear. But I would say 3.5 front and 1.5 rear is bigger spread front to rear than I generally see used, across any car really.

And get some new tires. At least in our PCA region for DE the limit for tech is 6 years old. Not sure in Norway on clubs/rules.

bebbetufs

I'll increase rear camber and see how I go.
I agree that ideally I should tune the setup. Unfortunately, there is no way I can dial things in at the track, other than pressures. This will be a one shot deal and I need to get it as close as possible. The track is an eight-hour drive each way and I have no equipment or time to change the alignment at the track. It is also likely this will be the only track day this year, so I'll buy a set of fresh tires next year instead. I'm thinking of entering the cup then. Hopefully, I'll be able to do some testing before then.

Thanks for all your help so far.

Lemming

I run -4 all around with no issues.

bebbetufs

That's good to know. What tires are you running?

Lemming

Spec tires for SPB are Toyo RR's dry, Toyo RA1s for wet.

bebbetufs

Thanks for the info and sorry for the delay. I've been working full days in order to get the car ready or the track today. Unfortunately, I did not make it.
Thankfully, there is a new opportunity this weekend. The forecast is sun for Saturday and rain Sunday. Will be interesting...