Different tyre sizes on rears.

[supra-ireland]

I've just noticed that my two rear tyres are different sizes.

Passenger side is 235/45/R17 and driver side is 235/40/R17.

 

I'm thinking this isn't exactly ideal but how big a deal is this?

 

-Cheers

[ellis]

Both wrong!! Stock tyres on 17s should be 255/40s on the rear!

[Dnk]

Tyres should be the same on both sides of the axle, on what car are these fitted to as you've posted in non supra tech

 

If the tyres you posted were brand new then there would be a 3.5% differance in diameter

or 23 mm from one side to the other

Edited July 1, 2010 by Dnk (see edit history)

[supra-ireland]

Both wrong!! Stock tyres on 17s should be 255/40s on the rear!

 

 

They're not stock wheels, they're Sparcos.

 

Tyres should be the same on both sides of the axle, on what car are these fitted to as you've posted in non supra tech

 

If the tyres you posted were brand new then there would be a 3.5% differance in diameter

or 23 mm from one side to the other

 

The car's a TT Supra, I posted in here as it's a non-Supra specific question.

I know they should be the same size I was just wondering how bad it is to have it like that.

[James]

I wouldn't want to have wheels that narrow (presuming it's not stretched tyres) on the rear anyway.

 

Get the tyres changed to match though. Don't want to be running mismatched. It's ok when front and rear are different to one another, not on the same axle though.

[tbourner]

They're too narrow, so it'll be dangerous with TT power going through them.

The sidewall is slightly too small on both, so your speedo will be wrong (unless it's measured some other way?).

More importantly, having different diameters will mean one is turning more than the other all the time, which is bound to wear them unevenly.

[Dnk]

Seems fairly supra specific to me but not to worry, what width are the wheels ?

[supra-ireland]

I wouldn't want to have wheels that narrow (presuming it's not stretched tyres) on the rear anyway.

 

Ok, never realised 235s were a bit narrow, maybe that's why I can never get my speedo accurately calibrated.

I should be able to get a set of 245s on instead.

There's a useful tool here.

 

What about the aspect ratio?

How low is it safe to come down from 45?

 

Seems fairly supra specific to me but not to worry

 

Well tyres are tyres, but I was rather torn between which forum to use

[tbourner]

What about the aspect ratio?

How low is it safe to come down from 45?

 

The 45 is a percentage of the width, so 45% of 235 is a smaller sidewall than a 255/45 for example.

[Dnk]

how wide are you wheels, this needs to be answered before you start fitting differant size tyres, no good fitting o/e size (255's) if their only 8" wide !!

 

Heres a guide as to what size tyres should be fitted to several widths of wheel

 

Rim width---Min tyre width---Ideal tyre width----Max tyre width

 

7.0 inches-----195 mm--------205 or 215 mm-----------225 mm

 

7.5 inches-----205 mm--------215 or 225 mm-----------235 mm

 

8.0 inches-----215 mm--------225 or 235 mm-----------245 mm

 

8.5 inches-----225 mm--------235 or 245 mm-----------255 mm

 

9,0 inches-----235 mm--------245 or 255 mm-----------265 mm

 

9.5 inches-----245 mm--------255 or 265 mm-----------275 mm

 

10.0 inches----255 mm--------265 or 275 mm-----------285 mm

 

10.5 inches----265 mm--------275 or 285 mm-----------295 mm

 

11.0 inches----275 mm--------285 or 295 mm-----------305 mm

 

11.5 inches----285 mm--------295 or 305 mm-----------315 mm

 

12.0 inches----295 mm--------305 or 315 mm-----------325 mm

 

12.5 inches----305 mm--------315 or 325 mm-----------335 mm

Edited July 1, 2010 by Dnk (see edit history)

[supra-ireland]

what width are the wheels ?

 

Oops, I went out to measure and I noticed I read the size wrong earlier.

3 of the wheels are 235/45/R17, the mismatched one is 255/40/R17.

 

So I guess that gives sidewall size of 105.75 and 102.

The alloy itself is about 8.5" measured on the inside of the wheel, prob about 9" on the outside.

 

The 45 is a percentage of the width, so 45% of 235 is a smaller sidewall than a 255/45 for example.

 

I know but how narrow is it safe to have the sidewall?

[tbourner]

I know but how narrow is it safe to have the sidewall?

 

I just meant it depends on the width, it's no use saying you can go down a 30 sidewall if we don't specify the width as well.

 

Basically you need to keep the rolling circumference as close to stock as possible, so your calculation that the mismatched tyre is 3.75mm different in diameter gives you that.

I'd suggest getting 2 new 255/40 R17s on the back, assuming both rear wheels are the same then they should fit safely if one has one fitted already.

[supra-ireland]

I just meant it depends on the width, it's no use saying you can go down a 30 sidewall if we don't specify the width as well.

 

Basically you need to keep the rolling circumference as close to stock as possible, so your calculation that the mismatched tyre is 3.75mm different in diameter gives you that.

I'd suggest getting 2 new 255/40 R17s on the back, assuming both rear wheels are the same then they should fit safely if one has one fitted already.

 

Ok, cheers, 255s sound like the best option.

I like the low profile look but I'll stick with a 40 ratio if you reckon going lower is a bad idea.

[Dnk]

i suggest you go get the tyres popped off and measure the wheels properly then start from there

[tbourner]

If you want that look it means new wheels I'm afraid. You could get some 285/30 R18s then.

[supra-ireland]

If you want that look it means new wheels I'm afraid. You could get some 285/30 R18s then.

 

No, I'll stick with what I have, I think they really suit the car.

I must get them reconditioned though, there's a fella nearby who does a good job for 50euro per wheel.

 

 

i suggest you go get the tyres popped off and measure the wheels properly then start from there

 

It is kinda hard to get an accurate measurement with them in situ.

Although going by the chart you posted, 255s should be fine with 8.5" - 9".

[tbourner]

It should say the size of the wheel on the inside rim or inside one of the spokes. Take one off and have a look for 8.5J or 9J.

[supra-ireland]

It should say the size of the wheel on the inside rim or inside one of the spokes. Take one off and have a look for 8.5J or 9J.

 

Can't see any size marking, just Crimson.INC and Racing Sparco?

[add heywood]

It's a MOT fail to have different sized tyres on the same axle IIRC, although I don't know if that applies to Ireland.