ive got a 2005 c55 and my tires are balding fast, i wanted to get some new tires but i dont want to get the same size. the backs are 245's i think and i wanted to go as wide as possible but i dont know where to find that information. does anyone know how i can find out what the widest size tire i can fit on my rim and still have it fit in the c55's tire well without rubbing? i have no idea where to even start looking. tirerack.com has the size my tire is now, but it doesnt say what the highest i can go for my partiuclar is. anyone know? thanks ahead of time, i appreciate it.

 

The size you have now is the widest you can go on that rim and still achieve maximum traction with the tire.

If you want a wider tire, you are going to need a wider wheel. Absolute maximum is 265/30/19 on a 19x9.5 wheel with appropriate offset.

 

I know there are many forum members running 255 width tires on the rear AMG staggered wheels.

 

Yes, u can easily fit a 255 on a rear of a 8.5" wheel. Hell u can fit a 265 on it 2 but its not recommended.

 

so for sure i can get the exact same tire sizes for the front and the exact same sizes for the back except for instead of 245's getting 255's? any negatives to doing this? i would assume it would only help traction and not hurt in any way. how about making the front tires bigger as well? is that possible/recommended? thanks for all the info guys, greatly appreciated.

 

You can go 235/40/18 front and 255/35/18 rear.

 

100% for sure?

eeeeeexcellent, thanks so much man, really, i appreciate it.

btw- any negatives to doing this? Any at all? Or only the added benefit of better traction? Thanks again.

 

Yeah, I am 100% sure they will fit. Not everyone will recommend going that size, but you should be fine. There is really not need to 235s up front. the 225s are fine. You should not rub, so no there should not be any negatives.

 

Black230coupe, thanks so much for all the info, greatly appreciated.

last question, lol, 1. why wouldnt people recommend 235's up front? 2. would it make any difference between going 225/255 or 235/255?

Again, thanks so much for everything.

 

Well, some people depending on who just might say its to wide for the width rim. But you wont have any problems with it.

 

I was debating on th esame matter for long time. But I replaced both of my rear with 255 with michelin ps2. I absolutely love those. I just can't wait to replace front with same gangs. Better traction and cornering.

 

blackc230coupe, thanks so much for all the info.

tototisha, you want to replace your front with 225's or 235's? as it is with 225/255 everything is great? no problems and only positives? do you know if changing the fronts to 235 will be better or worse? thanks for the info.

 

We should keep the overall diameter between the front tire and rear tire as close as possible.

I'll take two tires as an example:

Michelin PS2 - 225/40/18 - 25.1"
Michelin PS2 - 255/35/18 - 25.2"
Michelin PS2 - 235/40/18 - 25.4"
Michelin PS2 - 265/35/18 - 25.3"

Toyo T1-S - 225/40/18 - 25.1"
Toyo T1-S - 255/35/18 - 25.0"
Toyo T1-S - 235/40/18 - 25.4"
Toyo T1-S - 265/35/18 - 25.4"

I think 225/255 and 235/265 are better matched sizes.

 

You should get the wall as 35 to keep the diameter close to the original size.. I looked into this as well and found that bit of info.. Didnt think about how the diameter would change with brands of tires thou
thanks Harris

 

Put the largest sized tire that will fit on the front. 225/265 is not as good of a choice as the other as it may increase understeer. If you are not driving the car hard, it doesn't matter. Remember that the stock tire set up has a .26" bias towards a larger front tire and ESP is very sensitive to this when the car is pushed to its extremes. For this reason 225/265 is a bad decision. Look at the manufacturer's specs and go for the combination that offers more diameter in front.

 

ok, so based on everyone's advice, i've decided to go with Bridgestone Potenza S-03 Pole Position 225/40/18 front and 255/35/18 rear. Does this seem optimal and ok? Anyone think I should get another tire size for this particular brand or think i should get another brand completely? Thanks so much every one of you that has helped, really, id be lost without you guys. Thank you.

 

Look, I feel the point of my post was missed. You can fit a 255 on a 18x8.5 rear rim, but you will not get maximum traction. You will get roughly the same traction as the 245. The maximum allowable size for mounting a tire on an 8.5" rim safely is 255, but maximum allowable is not synonymous with maximum traction. Anyone who says differently is selling something or has some placebo effect from bigger numbers or went to grippier tire technologies in addition to going to a wider tire and is experiencing the increased grip of the tire compound rather than increased tire width.

Essentially when you put the widest tire on a wheel it angles in to fit the smaller wheel, curling up the edges ever so slightly to fit on the wheel. We are only talking about 5mm per side to make it have the same traction as a 245. On the other hand, if you put the narrowest available tire for a wheel on, then you will see the side walls bow out and will have likely even some of the side wall contacting the ground. I have definitely seen both of these things happen.

If you are looking for maximum straightline traction with a wider tire, you need a bigger wheel as I stated before with the best tire compound you can find.

When you go too wide with a tire, you don't get any more straight line traction. When you go with too narrow a tire, you lose cornering traction. Manufacturers don't want to spend anymore than they have to give a wheel maximum traction. If you think about it I am sure that you will see that a 255 Rosso tire is not much more than a 245 Rosso tire and in the face of vehicle development costs and profit margins and vehicle production numbers for the C55, it would have been cost effective for them to choose a 235 or a 255. They took the 245 and have stuck with that decision for years and years. Even my old C43 had 245 tires.

Personally, I recommend you go to 9.5" wheels in back with 265's that match the running diameter of the fronts as perfectly as possible. 235's up front would not hurt and could help, but not fix, the understeer weight balance of the vehicle.