darguy

Hey Gang,

I picked up a mixed set of 18x10 C5Z rears 2 Alcoa's, 2 Speedlines locally for a pretty good price - now I'm trying to figure out what setup to run. The car is a 99 FRC and I've recently installed a set of Alcoa C5Z rims and NT05 tires with rev-2 TPM's, which I'm daily driving and doing track days with. I'm pretty happy with them, but when the deal on the 18x10's came up I had to grab them.

It rains a lot here, 3 of my 4 track days have been in the rain - so the NT05's have been pretty good for the most part. But, I'd like to get some R-Comps set up on the second set for when the weather is better. I know some folks like to run all 18x10's and use the same size tire on all corners, but I'm wondering about allignment settings and swapping between the two sizes. The car is my DD, and I don't want to be doing wholesale allignment changes at the track if it dries out and I want to put on the stickies.

So, I'm thinking of trading/selling the 18x10 Speedlines for a set of 17x9 Alcoas to make an R-Comp track setup that I can swap over from my street tires without any allignment changes.

Is this crazy? Thoughts / suggestions?

davidfarmer

I wish you were closer, I'd love to have more 18x10.5 speedlines. they are a great wheel to use ALL AROUND. I've run everything from 275-315's on them, and they are light and strong

GettReal

I agree with David, running 18x10.5 on all four corners is what people are acutally looking to do and its what I do as well. Your alignment should be fine switching between different sets of wheels (track and street) unless you have huge neg. camber set for r-compounds like hoosiers or pure slicks, maybe David can confirm that.

I would keep them all the same personally.

C5ZEE06

If i understand the OPs dilema, hes asking about switching between the 17s he uses for DD, and the 18s he wants to run up front at the track - and the effect on his alignment - I think.

jaa1992

I'm running 275 on all four of mine!
I like the squre set up on the 92, just need more camber on the front

OBTW - I use 275 on 17 in wheels for dailiy driving.

Use the right sizes and you don't have any issues. Bot the street and track tires are 25.5" in diameter.
Pretty cool.

davidfarmer

alignment is a fixed entity, tire/wheel size doesn't effect it at all. I'd personally keep the 18's for track regardless of street tires. 18's are readily available, new and used, and if you aren't a super-aggressive driver then you can even run same tires all around and rotate.

ssdeuce

darguy

Thanks for the feedback, Guys!

I was under the impression that a tire diameter & width change would produce some changes in how the car 'hangs' off the suspension in terms of the angles that an allignment rack would report. This would be more pronounced with a big negative camber, as you've said. But, I would think that ride hight could at least be an issue depending on how much difference there was in the race tire sizes (18") and the street tires (17"). I'm not certain how dramatic that would be, but it would be one of those things to consider when picking allignment / ride hight settings - and another point of compromise between an ideal road-race setup, and something that doesn't chew street tires and scrape speed bumps much worse than the car does now.

These are interesting points on running 18's all around, particularly for brake clearance. I'm running stock rotors and calipers now, but can imagine upgrading to a bigger brake system down the road a year or two. I may transition the car into a dedicated race vehicle in the future, and am trying not to make too many upgrade decisions now that will have to be undone later. The recent auto-**** thread on the killer AP calipers mentioned at one point that the stock C5Z rims cleared them - so those at least would be an option (not a cheap one to jump into, but super sexy).

Do people run mixed sets of 18's, or try to go with straight Alcoas or Speedlines?

Any other comments/thoughts on the wheel/tire size and allignment issues? Another thing I didn't mention is, that the class I'm currently in does not allow much in the way of suspension changes (other than adj) - so using one of the aftermarket allignment kits that would facilitate a quick change may not be an option - although it would probably address this issue.

drivinhard

they are fairly much the same wheel. the alcoa are forged, and slightly heavier (probably stronger). The speedline are spun cast and have fatter spokes and are lighter. I don't think I've ever seen/heard of the C5Z wheels coming apart/breaking, although I suppose they eventually could with enough track abuse.

I have seen a pic of a broken wagon wheel at a DE event and have seen a C6 wheel break.

also the alcoa allow a slight amount more spoke/caliper clearance with the thinner spokes.

IMHO the Alcoa look better, sharper edge spokes, and darker paint

darguy

I would agree with that - and why I decided to go with Alcoas for the DD set. Didn't know about the larger clearance though. From what I remember the weight difference wasn't much - but once you start spinning it...



Edit: I just checked, and a set of 315/30ZR18 Hoosier R6's are the same diamiter as my Nitto NT05 275/40ZR17 front tires. So, that pretty much makes the ride height question irrelevant...