When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
This might get technical and I’m open to opinions.
Front 1 inch flared fender on a c5 with an 18x12.
Full disclosure;
Fenders aren’t installed yet
Penske shocks aren’t installed yet. (Old pfadt coilovers in the car)
The car sits on a tsw 10.5 with 65mm offset. No rubbing no issues on a Pirelli 305. Also speedline 10.5s with 58mm and nitto 315s with a 3mm spacer have some poke with no rub.
Magic question what offset with an 18x12 and a 335 tire. If you don’t want to disclose offsets don’t reply!
I can tell you I have 8 forgestars in my shop and the wheels forgestar says will work, I’m confident won’t work.
36mm 18x12 isn’t going to fly. Imo. It has 10mm more inner clearance than the tsw and there are no issues with the tsw. But it’s OUt THERE
18/12 57mm (5mm spacer) 52mm compressed. Wheel is inset a couple mm more than tsw and the poke is significantly less and if it doesn’t clear flares will be a slight poke.
18/11 38mm wheel has plenty of inner clearance and shouldn’t be an issue with fenders
Tsw 10.5 65mm
This leaves me to my target area of 45-50mm for an 18/12. Forgestar is willing to make right and cut what I need. Thoughts?
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.
Last edited by KnightDriveTV; 08-04-2018 at 02:08 PM.
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.
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.
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.
One of the pieces of your puzzle is “Whose fenders are you running”? I had the Lewis L5 fenders on and ran the 12” CCW’s with 8 1/2” backspacing but with a 315. Even with relieveing the inside edge of the fender, I would end up with a slight cut in the tread of my Hoosier A7’s Other factors are going to be ride height, how much negative camber and spring rate. If you are running one of Kerry Hit’s wide body packages, I can tell you the fronts easily accommodate a 335 in the front.
CC front flared fenders. 1 in flare. Correct I think a lot of factors will be had here. I’m going to do some testing on my own after the flares are installed.
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).
CC front flared fenders. 1 in flare. Correct I think a lot of factors will be had here. I’m going to do some testing on my own after the flares are installed.
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.
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
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?
It looks like that 335 is quite wide for that 12”. My goal was a 315 on an 11.5” on stock fenders, it sounds like that is likely not viable based on how much your tires poked out.
Would you agree that an 11” rim is the max on a stock fender if you want to preserve full suspension travel?
08-04-2018, 10:03 AM
C5 widebody 12/13 offset question
