transamnut

I've searched but have gotten nowhere. I have a simple question. I need to replace my stock size tires with a new set. Can I go the next size wider all around on my OEM wheels?

2010 C300 4matic sport

225-45/17 front
245-40/17 rear

Thanks in advance for any help I get..............

Rodpwnz

My girlfriend's C230 has 255 tires on her 245 wheels. They should still fit, but why not stick with 245 like you're supposed to?

dudeitsmattx

Yeah you can put next size up if you wish

AZN Optics

Those will work. It's not a big stretch from what you had. Added bonus with fatter tires is they double as curb rash protection

TheRulesLawyer

Probably. The tire manufacturer will have acceptable rim widths on their site for the specific tire you want to use.

jbt56

That's fine. I've been doing that on many cars for thirty years. In my eyes, it looks far better and unless you get really carried away, will improve handling by a very small amount.

transamnut

Thanks all for your past experiences.

To post #2..........if I should stick with what "I'm supposed to"...........why didn't you???

To post #4,...........my thoughts exactly, the stock width tires are just asking for the rims to be battered up.

edgalang

I do not know the width of a "2010 C300 4Matic Sport" wheel, however this is the process I would personally go through...

#1 Go to tirerack.com
#2 Enter in the desired tire size front/back (I assume 235/45ZR17 & 255/40ZR17)
#3 Arbitrarily select a tire, for demo purposes I chose a Y rated tire, then sorted by UTQG
(highest to lowest), then selected the first one (Michelin PILOT SPORT A/S 3).
#4 Go to Specs and look at the "RIM WIDTH RANGE" column.

According to this SPECIFIC tire...
...Your front wheels need to be between 7.5-9 inches wide where the ideal width is 8"
...Your rears need to be between 8.5-10 inches wide where the ideal width is 9"

Keep in mind if you do this, your speedometer may no longer be accurate and if you want to get technical, you can look at the revs/mile column on the different tire sizes and you can measure the differences.

Rodpwnz

Also, if you try a bit harder to read my post, it was my girlfriend's car with 255 tires on 245 wheels. And if you are able to read further, I said "why not stick with 245 like you're supposed to?".

C-Chris

When I replaced my tires I kept the stock size front tires, but switched from 245/40-17's to 255/40-17's for the rear. My reasons:


(1) The nominal diameter of the 255/40 is 25.0", which matches the diameter of the 225/45. The 245/40 is actually slightly smaller at 24.7".
(2) The rear rim is 1" wider than the front, so I think the rear tire should be at least 1" wider, too. As mentioned, the extra width of the 255 provides some curb protection. (3) The larger rear tire may not wear out as quickly compared to the front.

edgalang

Another thing to consider is whether or not the existing tire set is accurate to begin with (especially when the tire is worn down).

Example: On my wife's car (Lexus CT200h), the speedometer naturally reads FASTER than true speed (tested on multiple GPS units), so in this case upsizing the tire size is logical (assuming you are still within the tire/wheel specs).

With the C350 however, 255/35-18 tire on the rear matches the speedo & GPS units exactly (verified @ 80mph cruise).

C0d3Sp4c3

I think next size wider should be fine. Beyond will certainly balloon like my belly

OP, sorry for the minor hijack!
Wow, that's interesting about Lexus. Thought, BMW is notorious! Would you happen to know the reason why? My '10 E90 speedo behaves exactly the same as you mentioned, since new. If I hit 60mph on the CIC, you can bet multiple portable GPS will only read 55mph. I have not found legit explanation other than to avoid speeding tickets. At least that's what my dealer told me!
I went next size up from 255x35x18 to 255x40x18 and the CIC speed vs GPS matched which is great! But the trade-off is, the odometer got messed up due to bigger rolling circumference. My normal 42 miles daily commute went down to 39-ish on the CIC

jbt56

Speedos reading fast is very common, and has been for many years. I've had cars in which the speedo read up to 10% fast- including my BMWs and my 2011 Mustang GT. It's also true that going to a slightly taller tire (1/2 to 1 inch overall height) can correct the speedo reading. I was pleased to see the C250's speedo is very close to 100% accurate using GPS with stock-sized Yokohamas.

edgalang

Look at it the other way. Your odometer didn't get messed up, it finally got fixed. I didn't know BMW does this as well, but doing my research online, it would seem as though "jbt56" is correct and that this practice is very common with other manufacturers. Lexus/Toyota seems to be very conservative, vs MB seems to tell you the hard truth (which I prefer).

Example...with the MB, each tick on the gas meter represents 1 gallon. There are 16 ticks and by the time you have the needle resting on the peg you have roughly 1.4 gallons left.