Mrow

Hey all, obviously haven't posted a lot but I lurk these forums for all the wonderful info y'all have. So I have a question.

I like my 17in wheels, but id like to see if I could get bigger tires, as the ones I have now (225/45 and 245/40) seem to give me a stiff ride. I'm wondering if bigger tires would give me a smoother ride? If so, could I get slighter bigger tires without having to change my wheels?

I searched for answers already but couldn't seem to find anything. Thanks!

Sportstick

If 17" are giving you too stiff a ride for your liking, you could try changing same size tires to ones specifically designed for ride comfort, such as Michelin Primacy MXV4 (be careful with Michelin nomenclature...similar sounding tires are actually quite different performers). Larger tires such as 18"-20", which will result in increasingly narrower sidewalls, will cause the ride to become even more stiff as the compliance of the tire will be reduced.

Do you know if you have a Sport or Luxury model? It seems you might be a Luxury model buyer, which has a smoother and softer ride.

Mrow

I have the sport, and i love it. it's just the goin over bumps and things on the road that show me how stiff the car is. before this i was driving a 1999 528i and it took everything on the road real well. i guess i was just hoping i could throw some fatter or taller tires to ease the car off bumps and humps and all.

Mrow

also, i would want a larger sidewall, hence the getting bigger tires idea. i'd like to keep the 17in wheels and just slap on tires with a larger sidewall. I was told in order to do that i'd need smaller rims, and i don't know if i believe that...so here i am!

thanks for the reply btw!

dcjwlee

What would happen if the OP just changed the tire to one with a taller sidewall without changing the stock rim.

Mrow

basically what i was wondering, i just dont know much about tires and wanted to see what yall would say. 'cause i was told it's not as easy as that.

also would anyone have any ideas as to how big i could go without rubbing in the wheel well, if that's possible?

thanks again!

dfordham

While I'm no automotive expert, surely the car is designed with a specific wheel circumference in mind. That's why when you go, for instance, from 17" wheels to 18", the sidewall height must decrease to maintain the same circumference.

Such things as gear ratios and speedometer calibration must depend on the specified wheel circumference.

Regards,
Don

Mrow

so then, could i stick with the stock rims and just get tires with a taller sidewall? i feel like that would be a similar change, no?

or am i missing something

dfordham

No, that would increase the circumference.

Regards,
Don

Sportstick

That move will also invite the same problems. You could either try the more compliant tires, such as the ones I mentioned above, or see if 16" wheels fit, as they are used on C Class in some markets, but need to be compatible with the size of the brake assemblies installed on your car. If ok, then the appropriate tire will have the taller sidewall for a more compliant ride, and again, seek the best ride tires you can find. Check tirerack.com owner surveys and test results for ride quality.

Mrow

all right. thank you very much all!

Samieee

I think the best way is to do what Sportstick suggested - get tires geared towards comfort. Using tires with larger sidewalls will result in slight odometer discrepancies. I believe your odometer will read slightly higher than true mileage. There are online calculators for this. My dad wanted to do that with his car so I ordered slightly larger tires for him from tirerack.com. They called me a day later to tell me about the odometer issue (great customer service) so I went back to OEM sizing.

Sportstick

The speedometer problem will make the car seem to go slower than actual. I used the calculator on 1010tire.com and compared the 225/45-17 to a hypothetical 225/55-17 for a taller sidewall. With this change, if the car was indicating 60mph, it would actually be travelling 65mph, with the tire doing 55 fewer revolutions per mile.

kevink2

1st, what speed (and load) rating are your current tires? A V rated tire has much stiffer sidewalls , vs the 91H rating of the OEM's for both lux and sport C300's. With V's, the ride will be much stiffer, esp if the tread has worn down. Make sure they are the MB specified 91H.

Also, bump test the shocks at ea corner. Make sure none has locked up. If bad, replace with Lux model shocks.

Changes (if needed) For Smoother Ride (low$ to high)

1) Try removing front and rear sway-bar end-links on one side. Drive on local roads, not highway. (DIY or use local shop)

a) If you feel the ride is smoother, replace front and rear bars with softer lux model bars (used if possible) with new end links (rockauto.com). Note trade may be worked out on this site.

b) If no smoothness improvement, replace end-links.

2) Buy another pair of front rims for rear, so both are 225/45/17 tires. The oem 40 series 17" rear tires have even stiffer sidewalls for same speed rating front 45 series.

3) go with step 2) rims, run 50 series front & rear. Find spacesaver spare with same oem specs, except .92" larger dia.

4) Go with a set of proven 16"x7" rims, with 205/55/16-91H tires. These have been oem for various C230 and C220 models in other countries. But they have smaller front calipers, so all 16" wheels will not clear the calipers for the 11.6" front disc on C300's. Check out link below, and pic of 16" rim that fit with some attention to balance weight outer location.

C300-W204, 16-wheels that fit, with 205-55 91H tires



.

Mrow

Could I recalibrate the speedometer?

Mrow

I honestly don't mind, especially if there are online calculators for that kind of thing.

Mrow

I have the contiprocontact tires currently. I see according to tirerack that they are 91h. I'm researching for the rest of what you're saying haha

kevink2

Best to verify speed rating on tire, must have it in raised print, usually after the size marking.

Yes, step 3) will make the speedo'r and odom'r read about 3.5% lower than actual. And, you will have 3.5$ less torque at the wheels for any rpm ... may feel that a bit. But no other control issues, as I recall.