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[ktdw]

I have 255/35R18 on right now...just wondering what the difference is, and whether it would fit.

Thanks.

[former]

Best guess, it would probably be too tall.

Below is an excerpt from:
http://www.autotropolis.com/wiki/ind...izes_Explained

P215/70R16 100S
The ... number trailing the slash (/) indicates the height of the tire in a percentage of the section width. In our example, the number is 70, which means the tire height is 70% of the section width, which is 215 millimeters. The height of this tire would be 150.5 millimeters. The lower the number is, the lower the profile of the tire.

[SV Concepts III]

The 45 profile tire will be 10mm taller than the 35 profile you have now and would be too tall for your car.

[Berduderunner]

Originally Posted by Nick@Jlevi SW

The 45 profile tire will be 10mm taller than the 35 profile you have now and would be too tall for your car.

my understanding is that the middle number (45) is the percent of the width of the tire.

245 x .35 = 85.75

255 x .45 = 114.75

the difference is 29mm, not 10mm if im correct in my thinking.
if not please tell me

[arrutled]

^Correctamundo, at least to what ive read.

[vmcllc]

Originally Posted by Berduderunner

my understanding is that the middle number (45) is the percent of the width of the tire.

245 x .35 = 85.75

255 x .45 = 114.75

the difference is 29mm, not 10mm if im correct in my thinking.
if not please tell me

Your close...but his section width is the same for both tires in question.... But you are correct...the profile is a percentage of the stated section width of the tire...and this only gives the sidewall height...so for his question with regards to whether or not it will fit...

OD of 255/35-18 is ((255*.35)/25.4)*2+18=25.03"

OD of 255/45-18 is ((255*.45)/25.4)*2+18=27.03"

That is a full 2" taller tire...quite a bit difference...now I can't comment on whether or not it will fit...but you should also consider that your speedometer will now read incorrectly...so for the two tires in question based on 255/35-18 as stock and traveling at 60mph...putting on 255/45-18 while your speedometer may indicate you going 60mph...you will now actually be going 64.8mph...which is just about an 8% increase in error... Just some food for thought...

[N54tt]

i have 255-40-18 on my car and i have rubbing!!! a 255-45 will not fit on the car.. you would have massive rubbing issues..

[BMW F22]

Originally Posted by Berduderunner

my understanding is that the middle number (45) is the percent of the width of the tire.

245 x .35 = 85.75

255 x .45 = 114.75

the difference is 29mm, not 10mm if im correct in my thinking.
if not please tell me

Right but you're talking about overall measurement. The difference between a 35mm and a 45mm is 10mm and is actually too high for 18" wheels. I would recommend running 35 profile or 40 at the most.

[lambammm]

listen to n54tt.

[vmcllc]

Originally Posted by Kenny@JleviSW

Right but you're talking about overall measurement. The difference between a 35mm and a 45mm is 10mm and is actually too high for 18" wheels. I would recommend running 35 profile or 40 at the most.

Where are you getting 35mm and 45mm???

Is this where you are getting it??? 255/35-18 and 255/45-18

35 and 45 above do not in any way reference a measured dimension. They are percentages of the section width(which is the first three digits), in this case 255. This percentage of section width, dictates the sidewall height for the tire...

255*35%=89.3mm
255*40%=102mm
255*45%=114.8mm

That is an increase in sidewall height by about 25mm which is quite a bit different than 10mm wouldn't you say? This only represent one sidewall height which is an increase in the tires radius of about 25mm for the same diameter rim...

The only time your thinking would be true is if we were comparing these two tires...

100/35-18 and 100/45-18

100*35%=35mm
100*45%=45mm

But in this case we would be riding motorcycles...not driving a car..


But if N54tt has rubbing with 40 Series tires...then more than likely you will too with 40 series and almost certain you will with 45 series...especially if you have lowered your car..but you would want to be sure you're comparing apples to apples...because if N54tt has put wider rims with a shallow offset and is running spacers on a lowered car, not saying you are...that would be helpful info...as all of that pushes the tire out and closer to the wheel lip...

[jeremyc74]

Here's a good link someone posted here earlier that will help clear some of this up:

http://www.rims-n-tires.com/rt_specs.jsp?postId=906

You can plug in different tire sizes side by side and get the measurements.


And just to save you some trouble, here's the front and rear already configured:

Front (stock on the left):

http://www.rims-n-tires.com/rt_specs.jsp?item=Wheel-Tire%20size%20comparer&showRim1=1&showTire1=1&sw1= 215&ar1=40&bd1=18&rd1=18&rw1=7.5&et1=49&showRim2=1 &showTire2=1&sw2=235&ar2=40&bd2=18&rd2=18&rw2=7.5& et2=49&text1=135i-Stock%20Front&text2=

Rear:

http://www.rims-n-tires.com/rt_specs...k%20Rear&text2=

[vmcllc]

Good post jeremyc74....that give a nice picture so people can understand it more clearly...

[N54tt]

Originally Posted by vmcllc

Where are you getting 35mm and 45mm???

Is this where you are getting it??? 255/35-18 and 255/45-18

35 and 45 above do not in any way reference a measured dimension. They are percentages of the section width(which is the first three digits), in this case 255. This percentage of section width, dictates the sidewall height for the tire...

255*35%=89.3mm
255*40%=102mm
255*45%=114.8mm

That is an increase in sidewall height by about 25mm which is quite a bit different than 10mm wouldn't you say? This only represent one sidewall height which is an increase in the tires radius of about 25mm for the same diameter rim...

The only time your thinking would be true is if we were comparing these two tires...

100/35-18 and 100/45-18

100*35%=35mm
100*45%=45mm

But in this case we would be riding motorcycles...not driving a car..


But if N54tt has rubbing with 40 Series tires...then more than likely you will too with 40 series and almost certain you will with 45 series...especially if you have lowered your car..but you would want to be sure you're comparing apples to apples...because if N54tt has put wider rims with a shallow offset and is running spacers on a lowered car, not saying you are...that would be helpful info...as all of that pushes the tire out and closer to the wheel lip...

good point!!! my car is stock ride height and my rims are 18x9.5 in the rear w/a +45 offset.

[crzy4135i]

just to put it in perspective.. I was at the dealership and saw a M6 convertible on the showroom floor. That car had 285/35-19 on the rear! The sidewalls looked about twice as tall as on our cars.

If you're trying to fit larger tires the best bet is to go to the "spec" tab on tirerack and look up the exact specs of the brand and size of tire you're considering. Different brands of tires have slightly different overall dimensions (such as overall width) which is why some tires will rub while others the same size won't.

[TheFastestOne35]

Originally Posted by ktdw

I have 255/35R18 on right now...just wondering what the difference is, and whether it would fit.

Thanks.

What kind of rims do you have on your 135, i have the m sport rims which take 245/35/18's but got some 255/35/18's for free and want to put them on but i'm not sure if they will work?? Do you have the stock m sport rims too and have done the switch to a little wider??

[e85sbm]

From what I can tell, a tire sized 255/35 R18 will make a small difference in overall diameter, but the width is 10mm wider.

Essentially, by switching the rears to this new tire size, your speedo will be 1.1% slower (essentially the tire has a slightly larger diameter).

Check out the following link to compare overall size differences.

http://www.miata.net/garage/tirecalc.html