new tires or wheels

[Alpine 318is]

so i was looking at my tires and this is def a noob question. the numbers on my front tires are 215/45R17 and the rear is 235/4ZR17. what do these numbers mean please help

[maverickuk]

See if I can get this right for you

The 235 part is how wide the tyres are. So looking from behind 235 look quite wide. (You can tell looking at yours as there is a fair difference between your front and back ones (mine are both 225 front and back))

The 45 part is the height of the tyre from the alloy to the top of the tyre. So the lower the number the thinned the look from the side (mine are 50s front and back)

The 17 relates to the size of the alloys they go on, ie in your case 17 inch.

The letter relates to the speed rating of your tyre
H = upto 130 mph
V = upto 149 mph
ZWY = Over 149 mph (probaly most common ones)

Generally I think people say you should have same speed ratings all round, so not to have Vs at front and Ys at back etc.

Regarding the R. This could mean the tyres are remoulds. I hope not but someone could confirm this.

R on speed rating would only be upto 106 mph if it is that.

Cheers

[CobaltFire]

On a radial tire, they wouldn't be remoulds. I can't remember why, but most tires have a R on them now, I hope Jim weighs in on that one. As for the other numbers, here is an example: 235/45-17 That is the stock tire size on my 530i Sport. Here's a decode of that: 235 is tire width in mm, 45 is % of 235 that the sidewall is on each side (45% of 235mm = 105.75mm), and 17 is the wheel size the tire is designed for. Hope that helps.

[Alpine 318is]

so in inches how wide are my tires, and how wide could i go without rub, mods, front and rears? thanks

[CobaltFire]

Don't think in inches, get used to mm, as tires stopped being measured in inches years ago. A 3 series guy will have to let you know on what your car will fit, and what offset of wheels you'd need to fit it.

[guinness325i]

Don't think in inches, get used to mm, as tires stopped being measured in inches years ago. A 3 series guy will have to let you know on what your car will fit, and what offset of wheels you'd need to fit it.

The funny part is the width is in millimeters (mm) but the diamater is in inches (i.e. 245/35/18) .
As for how big you can go? check this forum because that question is asked a lot and it depends on rim size, offset and your suspension/ride height..

[Renaud]

235mm * (1in / 25.4 mm) = 9.25"