View Full Version : Would 255/40/18 on an RS6 18x8.5 fit ?

12-09-2007, 12:13 PM
I am fitting 255/40/18 dunlop winter sport M3 tires already on a RS6 18x8.5 ET30 on a B5. Right now, I have 235/45/17 on Konig wheels 17x8 ET35. The thing is the current wheels clear the fenders by a lot. I actually wonder why some of you guys need them rolled. The problem would seem to be the control arms, especially the rear ones. They are only half an inch away from the tires I have right now (17 in). Upgrading to 18 in with wider tires seems like an unworkable situation. Ironically, based on my setup, any rim over 17 and the tires should rub against the rear arms, so I don't know how you guys do it.
Someone needs to go to their car, check the clearance between their back tire and their control arms and reassure me. Especially the 18 and 19 in rim havers.

Quattr0, the noise

12-09-2007, 12:24 PM
because your et is 30. Most people are running et 35 pushing the tire closer to the control arm. It also depends on the rubber some people use. I know for sure I could not fir 235 ona 8.5 in et 35 rim

12-09-2007, 12:30 PM

12-09-2007, 12:50 PM
Speedy, those tires are 235's mine will be 255, that's almost an inch wider. I am affraid I am going to rub the control arms. That's the issue. 30 mm as opposed to 35 is just 5mm, that's not half an inch even.
and yet the new tires will be an inch wider than the old ones.

Quattr0, the noise

Lazer Viking
12-09-2007, 09:07 PM
why do you want 255's on an 8.5" ... i think thats going to look pretty stupid
most people that want a meatier look on 8.5's just run 235's

12-09-2007, 09:14 PM
255's are wide for an 8.5" wheel especially for a winter tire.

12-09-2007, 09:54 PM
The 2004 RS6 came standard with 255/40/18. That's what I am mounting. I am just doing it on a A4 b5.
The thing is I am running 235/45/17's right now, and I just think the 18's are going to rub. Not the fenders, but the arms. For the fenders, you could probably still fit a dog in there. I don't understand why most people have to roll. Right now, the arm are just an inch away from the 17's so I don't even know how most people run 19's. I guess I am lazy, I don't want to get new tires on that RS6 wheel, which is what I should probably do. The M3 cost 400 per tire, and it would be a hassle to buy a new set then sell the 255. I just wish I could mount them. The other thing is, I am getting them Wednesday, so we ll see if they rub or not, but they should, and in fact anything over 17 inches should normally rub, unless my car is special. 99 sports suspension by the way. The arms are just too close to the 17's and should be for any b5. So 18 or 19 should be inconceivable, unless audi made mine different from the rest.
Could you guys check your rear arms and tell me how close they are from your tires?

Quattr0, the noise

12-09-2007, 10:01 PM
The 255/40-18 is too tall for the B5 A4. 255/35-18 is still a little taller than stock. I run 245/40-17 on 17x8 et35 and have pictures of the front and rear inner arm clearance. Search for winter fatties and you'll find them. You'll need rolled fenders and maybe some spacers to get it perfectly centered.

12-09-2007, 10:35 PM
I think my fenders are fine. I put my arm in, and they go deep in. It's the arms, that I think will be the problem. Technically you have 17's so I am sure you cleared the arms. But I think a lot people on here are rubbing without knowing. Because at least based on my setup, they should. In fact with only half an inch between my tire and the arm right now, with 17s. I know I rubbed occasionally when transporting three people at the back, but I never noticed while driving. So I am sure lots of people over 17 rub without knowing. The thing is it's pretty dangerous. Also i noticed the inside of my tires were pretty worn out, I thought it was a 4wd thing like the skyline GTR that also wears out on the inside, but that wear is right were the arms are, so I think I know what it is. This is actually why I am changing tires, (Too worn on the inside, the rest is fine)

12-09-2007, 10:50 PM
Technically? You sure I don't just have them figuratively? The wheel size changes nothing. You're looking for sidewall clearance. I am absolutely positive that I have no rubbing anywhere. 245/35-18 is numerically the same size as a 255/35-18. That does depend on the tire manufacturers keeping tight to their dimensions which they just don't do. In the end the only way to know is to mount the tires in question and then bounce the car at full lock both ways. Things that hurt clearance include lowering the car, leaving the fender lips stock, and not spacing the wheel very carefully.

Are you saying you have wear on the inner sidewalls or on the edges of the tread? There is a very big difference between the two. Generally, if you have excessive wear on the inner edges you have excessive camber coupled with toe in or toe out.

For what it's worth, I had less clearance with 225/50-16 on stock wheels than 245/40-17 on 17x8 et35 wheels. Larger wheels means shorter sidewalls which usually don't bulge as much as taller ones. That yields more clearance for the control arms. Pics of the 16" wheel's inner clearance is also in that thread.

12-09-2007, 11:17 PM
I am actually talking about the rear tires. If you look at your set up you will see the arm right above them, coming from the fender, passing over the tire, and going towards the hub. Between the inner tire sidewall and the arm, there is only half an inch. So technically, a wider or taller tire should touch it.
The arm is just an inch above the top of the tire, and half an inch from it's inner side walls. That's why since this is for the 17's I have right now, I am assuming that anything (tire) taller or wider should touch. And I am sure lots of people touch but don't know. the arm is metal and solid, so you would not hear anything, in that event. I ll try to get pictures, it's tight in there, but I ll get pictures, so you ll see what I mean.

12-09-2007, 11:51 PM

FIRST of all, thanks for helping me, onemoremille, some others are just ignoring.
Ok, now you see the arm above the tire. That's only 1 inch above it.
those are 17's if I run 18, I rub for sure. It's pure logic.
between the inner tire wall and the arm there is only a .5 in clearance as the picture states. if I run a wider tire, I rub from sure. right now I am running 235's so 245 shouldn't even be doable. see the fender gap? I don't need to roll anything, even with 20 in weels. it's the arm my problem. Based on this setup, which is a 99 sport suspension setup, a lot of people are rubbing without knowing. and it's pretty dangerous. You see the side where the arm goes down? that's where the tires are quite worn. There is only .5 in of clearance there. Now what do you think, is yours and anybody's different, or did Audi make my car specially different. B5 A4

Quattr0, the noise

.Mad Hatter.
12-10-2007, 04:07 AM
other people may have an offset that allows more clearance, or they run spacers

12-10-2007, 05:52 AM
I can assure you that my 225/40/18's do not rub at all, they are on an 8.5" wheel, lowered approximately 2.5" with a 24.5" ground to fender gap up front and about a 1/4-1/2" higher in the rear. I still do not understand why you want to go with a wider than necessary tire when you are concerned about rubbing. Also why are you bringing up the fact that a RS6 runs the tire you want to, this has no relevance to your situation since they are two completely different cars.

12-10-2007, 07:11 AM
Your new tires are out of spec. They are wider than stock which affects fitment and scrub radius but isn't a big deal as long as they fit. They are also taller than stock which affects final gearing and how your speedometer reads. If you're cruising along at 75 don't be surprised when you get a ticket for 82.

If you want to get this perfect you can follow my plan. Replace the lug bolts with long hardened studs and open ended nuts. Get some spacers of varying width like 3,6,10 mm and play with the combinations until fitment is dead on perfect.

12-10-2007, 07:24 AM
I guess spacers would be the way to go. I am getting the wheels tomorrow. I will put them on and see.
Does anybody need 4 "Dunlop Winter Sport M3 MO 95V " 255/40/18 tires ? Cause if they don't fit,
I will get different size tires, and have to let them go.

Quattr0, the noise

12-10-2007, 09:04 AM
One of the issues you'll face is that different manufacturers will size their tires differently. A 225/50-16 Sumitomo is nearly as wide as a 245/40-17 Yoko Guardex snow tire. The Sumi is on a 7" wide wheel whereas the Yoko is 8" You can see the difference in sidewall shape.

Here is the rear left inner clearance in the 245/40-17. Your 255/40-18 is the equivalent of a 255/45-17 which would never work back there. If you add a half inch of height (radius) to the tire it would hit the arm. Add 1/5 of an inch width (half of the additional 10mm) to it wouldn't even bolt to the hub. You can also see that due to the curvature of the arm, the sidewall is never an issue. The corner of the tread will be the first to contact.

12-10-2007, 09:55 AM
That's awesome input there onemoremile. Your sidewall clearance is wider than mine. Like you said some manufacturers sometimes slightly deviate from the norm. I remember when upgrading from stock with the same spec tires, the new ones seemed smaller than the old ones. Just skinnier, but the written specs were the same. So I just have to hope that's the case with the 255, but if I have clearance issues, I ll just buy new tires, have them mounted, then balanced, which is what I didn't want to do because I have a race coming up soon, and I don't have time to fiddle with my daily driver. I usually run gravel tires in winter, it's quicker, less safe, but when you know what you are doing it's not a problem. That being said, snow is not my favorite surface.

12-10-2007, 10:26 AM
My wife's Outback has tires which are an inch taller than those on my Avant. Yours will be another 1/4 taller still. I put her new tires and wheels up next to my car on stock sport suspension and there is no way they would have cleared the fenders while turning. Hers might have at 225 width but not at 255.

I'm working on a way to get 255 or 265 tires under my car for track work. It can be done but it isn't easy.

12-10-2007, 10:37 AM
Yes wider tires, better traction. I drove a dtm bmw for a hill climb last year. While we are sweating trying to fit 255's, this thing had 335 for rear tires on a 3 series based body. 18 in wheels. Fenders were obviously remodeled.


Quattr0, the noise

12-10-2007, 11:17 AM
http://www.audizine.com/gallery/data/500/thumbs/1174IMG_2023_small.jpg (http://www.audizine.com/gallery/showphoto.php?photo=12289)
I'm familiar with wide tires. Their benefit in the snow is dubious. Summer is a different story. I am running a 245 width snow tire this year and it is great other than through puddles, deep snow, or slush.