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Old 03-10-2020, 05:48 PM
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TheBandit TheBandit is offline
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Join Date: Jan 2006
Location: Ventura County CA
Posts: 4,654
I'm gearing up for my next autocross in April and I've made a punch list of items to address. Since the last autocross all I've really changed on the car are the front brakes (now C6 Corvette variety) and the driver seating position. I have a couple of priorities to address before my next run through the cones. First I need to fix the tire clearance issues I have up front; the tires are still rubbing at the back of the fenders. It seems like it got worse when I swapped the brakes, even though I was expecting it to get better. The new brake setup should have reduced the track width by 0.240in per side and I can't figure out how that would lead to the tire shifting more rearward in the fender. Yet somehow it seems to have done exactly that because I'm getting rub in normal driving scenarios that I didn't get before. I did check to make sure the subframe hasn't shifted and it's still in good alignment. I can't think of what else would have changed.

Before I start modifying my inner fender to gain tire clearance, I want to start by seeing how the alignment impacts clearance. Based on my research and looking closely at photos from my last autocross, I think the car could benefit from more camber. At the same time I'm wondering if taking out some caster would improve the tire clearance. So I broke out my old angle cube angle finder and bought myself some toe plates and decided to try a DIY alignment at home.

For my car, I can easily check camber by placing my angle cube on the end of the hub. Caster can also be measured this way, but requires a bit more work to sweep the tires through a suitable steering angle. After doing the research, I came up with a method and explain it in the following YouTube video. I'd love to get feedback on whether this method is correct and if there's anything I might need to do differently.



I decided the easiest way to check toe was to get a set of toe plates. I bought some Longacre Racing ones and they seem to work very well. I may also string the car later so I can check toe side-to-side.

As of now the alignment is as follows:
Camber: ~1.1deg both sides
Caster: ~6deg/6.5deg driver/passenger
Toe: 0in

I'm wondering what effect there may be on the rear tire clearance if I reduce the caster a bit. The way caster is adjusted on my car is by shimming the upper control arm to move the spindle upper ball joint forward or backwards. If I move the upper balljoint forward, that should result in a small forward shift of the tire as well as a caster reduction. Reducing the caster is not desirable but if I can gain a little tire clearance this way it might be worth making a quick change. I'm thinking about going down a degree to see what happens. I also want to see what increasing negative camber will do, both for the performance aspects as well as tire clearance. Now that I have the tools, I just need time to play in the garage and try it out.
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Last edited by TheBandit; 03-10-2020 at 05:51 PM.
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