Maizeandbrew

Just bought new wheels, 198x5 ET 40 and 19x10 ET52 Forgestar fitment for W204 C63, curious about tire size.

What is the widest we can run in front back whilst still maintaining OEM tire height and not messing up speedometer or odometer reading?

I have 235/35/19 front and 255/30/19 Rear currently ... can we fit a 255/30/19 in the front? Just wondering as I have Michelin P4S mileage warranty on the current tires and will be using that towards new set (less than 10k miles on one set of rears!, and I have a light-ish foot...), and would love to be able to go to a square or staggered w/ wider rear fitment

Sorry for the noob question, but would love some advice!

Thanks,

ertimark

I would suggest you to put maximum 245/35 for the front (to follow MB standards) - the ideal would be 235/35.
About the rear, 265/30 could be the maximum with the mentioned offset to avoid rubbing.

Anyone please correct me if I am wrong..

Bonesxxx

Lot's of threads on this issue. I've been taking notes on them since I am not in a rush (my stock sized Conti DWs are brand new and I am quite happy with them).

But what I have written down is 255 max up front and 275 max on rear -- may require 12mm spacers on either or both so I figure I'd have them available when I make the swap just to be safe.

Appreciate anyone correcting me if I got something wrong.

toosteeley

OP will not need spacers with that setup; spacers DECREASE the offset (ie, 12mm spacers would = 19x8.5 ET 28 and 19x10 ET40 which would rub like a ****).

IMO, 245 front and 275 rear would be ideal. Maybe slight rubbing over large dips with 275, but it will be minimal at most.

Yes, 255 would likely fit in the front, but the rolling diameter of a 255/35 will be more than a 275/30. 245/35 and 275/30 is almost identical.

Bonesxxx

Can you translate those sizes for 18" wheels please? I think the ratio changes slightly, no?

toosteeley

Just go to Tirerack and play around with different sizes looking at Overall Diameter. Below example for PS4S in the sizes I mentioned:

Ludedude

As a rule, 245/40 and 275/35 would be the equivalent in 18" rim fitment assuming stock or nearly stock height and stock offsets. Those are the sizes I'm running in 18" with PS4S.

Maizeandbrew

So the 255/30/19 would not fit up front? Is 35 the correct profile regardless of width up front in a 19?

Sorry - I know this has been answered loads of times -- but having trouble parsing through all the relevant info.

Really want to make sure that I maintain correct tire size, and do not mess w/ Odometer or Speedo readings?

Sounds like that requires a 35 series up front and a 30 series in the rear?

Thanks,

m a x i m u s

Just calculate it. The 35 or 40 number is the aspect ratio. The height of the sidewall is a % of the width. So for example to calc the sidewall height, multiply 275 x .35, or whatever the case may be.

Ludedude

To minimize apparently speedometer changes, you need to stick as closely as possible to the OEM tire diameter. Getting there is dependent on width and sidewall height and how those work to change the diameter of the tire. Go wider and you need a shorter aspect ratio to maintain the same diameter. Go skinnier and a taller tire is needed. All within reason of course, and also determined by physical dimensions of the hole available to stuff a tire into. The tables on Tire Rack are a great way to compare all of that.