Different tyre profiles ??

[Tattooboy]

Noticed today whilst checking the air pressures on the GTS, that the fronts are 245/35/20 but the tears are 275/30/20 ???

Why would this be? I could understand it on different sized wheels etc but why different profiles on the same size wheels?

I'll be needing a full set of boots shortly, should I stick to the same or change to 35 profile on the rear?

[Magic919]

Different width. It's an attempt to keep sidewall height similar.

[jameshsv]

Tattooboy said:

Noticed today whilst checking the air pressures on the GTS, that the fronts are 245/35/20 but the tears are 275/30/20 ???

Why would this be? I could understand it on different sized wheels etc but why different profiles on the same size wheels?

I'll be needing a full set of boots shortly, should I stick to the same or change to 35 profile on the rear?

But there not the same size

[Granby]

Aren't rears 9.5" wide while the fronts 8" like the VXR8

[Tattooboy]

Arh yes, senior moment, keep forgetting the width will affect the profile height !!

Thanks chaps

[jameshsv]

Tattooboy said:

Noticed today whilst checking the air pressures on the GTS, that the fronts are 245/35/20 but the tears are 275/30/20 ???

Why would this be? I could understand it on different sized wheels etc but why different profiles on the same size wheels?

I'll be needing a full set of boots shortly, should I stick to the same or change to 35 profile on the rear?

But there not the same size

[moif]

Tattooboy said:

Noticed today whilst checking the air pressures on the GTS, that the fronts are 245/35/20 but the tears are 275/30/20 ???

Why would this be? I could understand it on different sized wheels etc but why different profiles on the same size wheels?

I'll be needing a full set of boots shortly, should I stick to the same or change to 35 profile on the rear?

The 19's on the vxr8 are 40 sidewall front and 35 wall rear, the reduction on the sidewalls when your on 20's is to keep the overall diameter of the tyre similar to the 19's so it doesnt mess with gearing, speedo,blah blah blah

Edited by moif on Sunday 15th March 15:55

[ARAF]

The 'height' size is an aspect ratio (a percentage of the width), not a pure measurement.

245 x 25% = 61.25mm

285 x 20% = 57mm

285 x 25% = 71.25mm

305 x 20% = 61mm

So, the sidewall height of the rears is 4.25mm shorter than the front. If you used a 25 profile tyre, it would be 10mm taller.

If you can get a 305 on the rims, it would be the closest.

[mik_ok]

Araf's post is correct, but would have been even better with the right numbers.

245 x 35% = 85.75mm
275 x 30% = 82.5mm

[S800VXR]

mik_ok said:

Araf's post is correct, but would have been even better with the right numbers.

245 x 35% = 85.75mm
275 x 30% = 82.5mm

Arafs always short....

[ARAF]

Sorry.

[DRC72]

The Gen F runs on 275/35/20's on the rear and 255/35/20's on the front.

[007 VXR]

I run
245 35 19
285 35 19

[Tattooboy]

007 VXR said:

I run
245 35 19
285 35 19

Then surely you should be running a 30 on back?

What the side wall difference like? As I was thinking of going 275/35's on the back of mine.

[007 VXR]

Tattooboy said:

Then surely you should be running a 30 on back?

What the side wall difference like? As I was thinking of going 275/35's on the back of mine.

should be 30.
buy 35 feel better and look abit more purposeful on the rear imho

[Tattooboy]

007 VXR said:

Tattooboy said:

Then surely you should be running a 30 on back?

What the side wall difference like? As I was thinking of going 275/35's on the back of mine.

should be 30.
buy 35 feel better and look abit more purposeful on the rear imho

Will do some research and see what the wall difference is in 30 & 35

[R8VXF]

DRC72 said:

The Gen F runs on 275/30/20's on the rear and 255/35/20's on the front.

EFA

EDIT: EFA again!

Edited by R8VXF on Monday 16th March 12:47

[pah250]

R8VXF said:

DRC72 said:

The Gen F runs on 275/30/20's on the rear and 245/35/20's on the front.

EFA

DRC was quite correct in that the fronts on the Gen-F are 255's, according to HSV's web site anyway.

What do you have fitted on the front of your Gen-F?

[R8VXF]

pah250 said:

R8VXF said:

DRC72 said:

The Gen F runs on 275/30/20's on the rear and 245/35/20's on the front.

EFA

DRC was quite correct in that the fronts on the Gen-F are 255's

Good point, just checked my pictures, I really should double check these things

[MyM8V8]

Tattooboy said:

Arh yes, senior moment, keep forgetting the width will affect the profile height !!

Thanks chaps

"Aspect Ratio"