I picked up a 2021 coupe a few weeks ago. Had catless downpipes and Wiestec tune done. Car simply couldn't handle power before tune and now both 1st and 2nd gear I have to feather them to try and keep traction.

Ive seen it mentioned that a 305/30/20 will fit on the car but that isn't gonna be enough either.

Has anybody rolled a rear fender, flared a fender, or added some sort of rear widebody fender to accommodate a 345/30/20 or something of substantial size over stock?

Link to thread if anyone is familiar with a thread that discusses the possibility....Thank You for any assistance

 

******What brand and size tire is on your car now? Stickier tires in 305/30/20, usually a Michelin PS4S seem to work for most guys with significantly more done to their cars than a tune and catless pipes. Tough to get much more meat under the car than a 305 size, and that would require wider wheels to optimize width and profile of the fatter tires. It can be done by flaring the fenders (cutting and welding the flare and then repaint..) and with a properly backspaced wheel. A tire that wide (345's) introduce other stresses and tracking issues related to alignment depending on what your goals are. If all you care about is straight line performance like a quarter mile car then yea it can be done but you don't get something for nothing and the overall handling balance of the car will be very negatively affected especially on turns unless the front wheels/tires are also addressed to somewhat reduce the great disparity in size of the tires footprint and ratio between front/back. AMG and Benz spent a lot of time optimizing the C63s for very decent handling over a wide variety of courses versus just a straight line type vehicle.

There are a couple of guys in my area that have done the 305/30/20 or thereabouts on stock height suspension (C63s) and it rubs a bit toward the inside on hard turns - nothing major and a small spacer helped to reduce that a lot with just enough room to not have to roll the fenders though it is tight in there for sure. An extra passenger or two in the back and it rubs.

Anyway, a decent body shop can easily do the flares, and plenty of aftermarket wheels are available or you can have the stock wheels widened with proper backspacing and width to accommodate the wider tires and keep a stock wheel look. I've done both on other platforms along with doing mini-tubs on live axle cars and it came out great. Not cheap.

Good luck

 

Good info. I’m running rear PS4 305’s on stock rims and suspension. I’ve had zero rubbing issues, but then again I haven’t had any rear passengers yet. What size spacers would you recommend going with to eliminate any possible rubbing should I ever have rear passengers? And would you also recommend front spacers if I install rear spacers?

 

The difference in width between a 295/30/20 is about 2 3/8".

I would certainly change the rims. For me, I'm more of a straight-line guy with cars. Motorcycles, I'm a track guy, so cornering is where the fun is. But I likely wont track my car so I would rather be safe.

currently its running pilot sport cup 2, 295/30/20....First gear breaks lose at about half the boost. All my 0-60 trys are around 5 seconds so far. Its a fun 5 seconds but would be nice to hook up a little better.

Im not really interested in widening the front tires.

Ill need to do a fair amount of research before I decide to pull the trigger.

Thanks for the reply

 

***** You might be able to get by with no spacers on a stock ride height car, assuming the rear suspension is still in decent shape. Unfortunately you can't completely eliminate the rubbing issue with such a wide tire if you load the car up with people, but having about 5-7.5mm of space between the inside edge of the tire and the wheel well will greatly reduce the chance of rubbing on turns if the car is loaded down - look inside that area of your car and see if there are scuff marks on the inner edge of the well or you see scuffing on the inner upper edges of the tire. The edge can be trimmed a bit or sometimes folded back to make a bit more room, but it is definitely easier to use a smallish 5-7.5mm or so spacer depending upon the car (some cars are not square and have a bit less room on one side). That way you can revert the car back to stock with no mutilation or rolling the wells, etc..

If there is no evidence of rubbing, honestly don't mess with spacers unless you want a more aggressive look or stance, etc.. Depending upon where you drive, you might end up with a few more rock chips from flung debris on such a wide tire with stock wheelwells.

Good luck and mebbe others can better give advice on how wide a spacer works on stock wheels with stock ride height, but on my ride it doesn't seem to rub even though I only have 295's at the moment. There seems to be enough room for 305's, and the guys in my area with that setup ARE running spacers but they have lowered cars with less room to play with.

 

Thanks for all the input. Yeah the stock rear suspension is still darn near new, with only 4.1k miles on it so far. I’ll check the wheel wells / inner edges of tires for any rubbing. I’ll go with a 5-7mm spacer as you suggested if I do see any evidence of rubbing, but I’ve put on 4k miles on my beast on these 305’s and haven’t heard or felt any rubbing as of yet, so hopefully I can leave it alone as is. I definitely don’t want to mess with rolling fenders. I did go up in tire size mostly for a more aggressive stance / look so I’d welcome an even more aggressive stance if I do end up going with rear spacers. Our Houston roads aren’t the best in some areas with respect to potholes but they’re relatively rock and debris free, at least in the areas I drive in the most.

Here’s a couple of pics of my diamond white coupe on 305’s. I had to enhance the contrast so the tires would be more visible.