C5 widebody 12/13 offset question
 

So, I'm trying to think this out, based upon my car. I have a set of custom cut et53's all around, 18x11 with 11.1" of contact patch. They poke approx 1" (measured at the rims edge, not the shoulder of the tire..shoulder of tire probably 1/2", then when compressed with camber gain...no issue), but no rub at all, even under compression, due to the shoulder of the Michelin rolling slightly inward, etc. I have JUST enough inner clearance to steer lock to lock, and I JUST clear the inner fender liner while steering. So, from my setup, everything has to go outward, another half inch or 12.5mm inner would like start hitting things, so if I were to go 12" rim, that's what I'd do. So theoretically, if I wanted a 12" wheel to fit the same as mine, with same inner clearance, I'd need that back half inch to move outward in offset. So, my 53 would have to go 12.5 in offset to move that half inch of rim outward...putting me at basically 41. Looking at your pic with 36mm offset, while it may look like a lot, I'd be curious what the actual contact patch width of the 335's you're proposing, actually is, which will determine what the shoulder of the tire is going to do. With 2-3 degrees of camber up front, I think it starts to work at 41 depending on the tire.

In my opinion, fitting it straight is one thing, but fitting it under compression while turning is another. My 18x11 et53 is maxed out in all ways clearance wise. If I did an 18x12 with my exact offset, it'd go out and in exactly 12.5mm, but I'd start having contact with the backside of the bumper where it transitions into the wheel well and the upper inner wheel well area. In my mind, that'd be the number to get them to work with a street camber and non square shoulder tire but I suspect I'd be touching SOMETHING in the wheel well during certain turning angles.

With my left front tire, if I turn right, the tire JUST clears the liner, it'll even sometimes squeak as the rubber squeaks the plastic. Any further outward, and it'd be hitting it. On the very inside upper portion of the wheel well, I have rubs marks but nothing more than touches. I suspect you're in the range with 45 as the happy medium to get your inner clearance, and your outer fitment but...I have a feeling you'll be dealing with inner liner issues and need a certain camber to make it all happen and look right.

So, in summary...I'd concur you're likely on the right numbers but...it's gonna be a dice roll...lol. You just have to pick and take a shot. The 18x11's at 38 seem like the best thing you have shown that won't start contacting everything, I'd personally probably consider doing a slightly narrower wheel and tire if it were me. With that much offset, you must certainly be eligible for "super deeps" from forgestar, as to where I could only squeak out the "deeps" at 53.

Sounds like you are going to track the car (autocross...road race?), in which case I would give some consideration to scrub radius. If you run a wide wheel with shallow offset, you will increase the scrub radius significantly, and that can have adverse effect on turn-in.

Pappy

I run a 12 inch front wheel and for my configuration (ZR1 hubs on an aftermarket spindle - not a C5), I ended up with an 8.5 inch backspace (63.5 mm offset) to get 1/2 inch of scrub radius. I built a plywood mock-up wheel and added the tire/rim profile to the front and back to check my clearances. I had to do a lot of modifying to the inside of the fender well to get clearance, especially under compression with the tire turned. With a lot of caster, the tire really moves around a lot in the wheel well when it is turned back and forth, so you need to do some dynamic checks. Good luck.

Pappy

https://cimg9.ibsrv.net/gimg/www.cor...2ad958df73.jpg

I moved the fender wells - LOL Again, not a C5. The biggest clearance issues were the inside of the wheel drum and the tie rods and the lower control arm legs.

Pappy

Pappyhttps://cimg2.ibsrv.net/gimg/www.cor...c417b121eb.jpg
https://cimg2.ibsrv.net/gimg/www.cor...eac4e337da.jpg

here is my C5
I have mounted 10.5x18 ET37 and 12.5x18 ET52

Cölestin

http://www.bilder-upload.eu/thumb/c51e93-1533556999.jpg

Let me clarify, I have no first hand experience with this wheel size on a C5. However I do have access to a stock '02 and I have read lots of wheel setups on here and recorded the measurements. In planning for a wider wheel/tire setup for the '02 I have found the most you can go is about 8.5-8.75" of backspacing before rubbing on the inside, and you won't be able to turn full lock. That puts you in the 50-55mm range for offset on a 12" wide wheel. It will stick out a bit, but remember you gain camber on compression so rubbing the fender should be minimal (although very dependant on spring rates, sway bars, aero, etc).

I have no knowledge of those flares. You really have to mock it up and then set the car at the correct ride height all around to get an idea. I wouldn't hurt to jack the car up on stands at that point and compress each wheel to full travel to get an idea of possible interference.

Pappy, I just rented a shop space in Boulder City sight unseen and am uprooting my sh*t from Atlanta next week and heading out there. What you have going on, anything interesting? I'm looking to meet up with some people, get in the game with some folks. I have full setup capability, TIG/MIG fab, tuning, etc. Not opening to the public anymore, pursuing some composite fabrication, etc but...would like to meet some people that know the lay of the land.

Did I mess up big time, movin to the foot hills...lol?

What did you find out after installing fenders? I'm looking at a set of 18x12s with 51mm offset, and using them with a CC front flare as well.