hieu

My wife 2011 E350 sedan has 245-40-18 and 265-35-18 on front and back, respectively. I would like to have both F&R on the same size tire. Is this possible? Thx.

Diesel #2

The majority of E 350 sedans have 245/40/18 all around. So yes you can.

berti_00

i have the identical as you... but i plan on going 19's and vogtland springs so not sure what i should run after that

cetialpha5

The RWD cars got the staggered wheels like you have now. 4matic cars had the same 4 tires like the 245/40/18 or the 245/45/17 all around.

aquinob

I have a 2010 and it has the 18" staggered setup since it was the Sport model. The Luxury version came with 17"s all the same size. I imagine you could fit the 240's all around and it should handle fine.

hieu

Mechanic @ costco told me that no can do since front dia. is 8.5" and rear is 9". They said in their opinion, it's properly the rear can fit in 245-40 but by policy they won't do it. What do you guys think?

cetialpha5

Well you'd have to get the 8.5 rims. The 245/40/18's might only be meant for 8.5s.

belarus27

i think to run 245s in the rear you might wanna buy 2 more 8.5" wheels to replace rear ones which are 9" i think.
otherwise tire might be too stretched and not look right and wont perform well. my thought. this is optimal.
unless you fit 245s on 9" rear wheels and take pics to show us.

C280 Sport

If you have 4Matic the tires and wheel sizes should all be the same. Also, I would not be going to Costco for tires.

cetialpha5

Sounds like he just has a RWD setup, not 4matic. RWD you can't rotate the tires so they wear out quicker. Costco sells the same tires as everyone else, you can get Michelin's there for a pretty good price. They have insurance requirements so they probably won't put a tire that's meant for a 8.5 rim on a 9 rim. A small mom & pop place might do it if you sign a waiver. The big box stores don't even bother.

C280 Sport

I was more worried about who would be doing to work. Not so much where the tires are coming from. I personally like to use a good independent shop but thats me.

cetialpha5

Costco actually has a pretty good rep of paying their workers well and being a well run company. Now if you were talking about tire installers at Walmart, I might understand what you're saying.

hieu

According to this site, http://www.tyresizecalculator.com/ty...ize-calculator, 245-40-18 tire could fit from 8"-9.5" rim width which is in the range of the rear wheel. Costco guy thought it could fit too but won't take the order. I may have to call other stores then order tires from tirerack.

Diesel #2

Why not just run 255/40/18 all around ? The 255 will fit the 9.5" wheels much better. And you can still have a square setup. The diameter of the tire will go from 25.7" to 26.0" which is fine. I currently have 26.4" in the front and 26.3" in the rear with no issues.

hieu

That is a very good suggestion. Thx.

cetialpha5

I wouldn't do it. The speedometer will be off a little bit and then you're going to rotate the 9.5 to the front?

Plus while a wider tire would be better in the dry, it's worse in the wet and snow. There's always trade offs. Just pick up two used rims on eBay and have the same size rims on all 4.

davidjohnbamber

A square rim, and tire setup would allow you to rotate the tires.

hieu

Why with this square setup, the speedometer will be off? It's more to do with the width, a fraction of an inch which certainly happen just on uneven air pressure, than diameter. Still learning so i can make a right decision.

cetialpha5

The 40 is an aspect ratio so the wider the tire, the taller the tire with the same aspect ratio. Basically the 40 refers to 40% of the width of the tire.

Also I'm not sold on the rotational aspect of having bigger rims on the front than the rear. Something just doesn't seem right about it. But maybe it's not enough to really matter. Not something that's commonly done so that's why I don't trust it and I wouldn't do it.

blegthbloo

The overall diameter of the wheel is what causes the speedometer to be off... it's calibrated for a wheel with a diameter of 26.7" (on the 4Matics), so a wheel with a diameter smaller than that will complete one revolution slightly quicker and the speedo will read some% too fast, while it'll be the opposite for a wheel that is slightly bigger. In the end it changes about 1-3mph difference, so it's up to you if you think that's a worthy trade-off. But for the 4Matics that's a bigger deal than for the RWD models... I think usually the speed sensor is on the front wheel, so the rear wheels might be able to be bigger in diameter without causing any issues if you have RWD.

Diesel #2

He can just rotate the tires.

That might be a typo, all W212 [RWD and 4Matic] have 25.7" diameter tires.

blegthbloo

All the measurements I found on various sites were 26.7" ... but it could be wrong... I haven't actually measured it myself. In either case, the concept still stands... the tolerance is "supposed" to be within 0.1" or you start messing with the calibration. It could be recalibrated, but that's extra work when all I want is my car to look good on its new shoes lol