Slightly different tyre and ABS

[smillion]

Hi all

I am having new winter tyres fitted next week. The fronts are same size as the current Pirelli summer tyres, however the rears will not be 285 but 275 (275 30 19). My tyre fitter has suggested that the move to 275 from 285 may effect the ABS...... Has anyone any experience of this ?

Cheers

Marc

 

[renault12ts]

The front and rear tyres must have as near as possible the same diameter...if they don't the ABS will kick off at higher speeds. What size are your fronts?

 

[smillion]

Fronts are 255 35 19
Summer rears 285 30 19

Winter rears proposed 275 30 19

Same diameter .... Just very slightly narrower

 

[Dieselman]

Same diameter .... Just very slightly narrower

Not so, slightly smaller diameter.

It won't affect ABS but might affect cruise control.

 

[Will]

Could you fit a slightly narrower front tyre to compensate - ie 245/35?

The height of the sidewall is based on the width and profile. Eg 255mm x 35% (0.35)

So the 275/30 will be a smaller diameter as well as being narrower. Hence the CC and ABS might think that the rear wheels are turning quicker than they should be.

 

[Alps]

one size diameter either way is normally fine, i use 265 35 18 on my winters and 275 30 19 on my summers with no issues.

 

[renault12ts]

As Will says they are a different diameter. The side side wall is 30% of 285 as opposed to 30% of 275. So, they are actually 3mm smaller on the radius. It is very small...and probably wouldn't upset the cruise.

 

[Will]

^^I agree, but the only thing I noticed is that with the standard sizes (255/35 and 285/30), the rears are already on the smaller side compared to the fronts - 245/35 and 285/30 would have been a better match originally?

 

[smillion]

^^I agree, but the only thing I noticed is that with the standard sizes (255/35 and 285/30), the rears are already on the smaller side compared to the fronts - 245/35 and 285/30 would have been a better match originally?

These are the tyres from new,, with front wheel 8.5" and rear 9.5"

Thanks for the quick and helpful responses guys ...

Marc

 

[renault12ts]

Correct. So, in this case the further reduction to 275 probably will be the last straw.

OP...you should have 245/35 and 285/30...they have exactly the same radius.

 

[Will]

These are the tyres from new,, with front wheel 8.5" and rear 9.5"

Thanks for the quick and helpful responses guys ...

Marc

Sure

Was only pointing out, that with the standard setup (staggered sizes) the rears are on the smaller side diameter-wise, so if you have a choice I'd be tempted to opt the other way if making any further changes. Ie - reduce the fronts or slightly increase the rears.

A 245 section front tyre would be fine on an 8.5 rim - with winter tyres I think you're better going slightly narrower anyway

Just a thought

 

[bing]

Difference in diameter between the two , 285 30 19 v 275 30 19 is -0.92% or -6mm.! Quite negligable IMO , so you're fine!

Here try this "tyre calculator" : Tyre Size Calculator - Changing Tyres - Etyres

 

[renault12ts]

Difference in diameter between the two , 285 30 19 v 275 30 19 is -0.92% or -6mm.! Quite negligable IMO , so you're fine!

Here try this "tyre calculator" : Tyre Size Calculator - Changing Tyres - Etyres

Except you haven't taken account of the size of the front tyres...and IMO the difference is too much.

 

[smillion]

Correct. So, in this case the further reduction to 275 probably will be the last straw.

OP...you should have 245/35 and 285/30...they have exactly the same radius.

Thanks for the advice here guys. Ordered the set up suggested by Renault12ts, even though it meant having to wait for the 245/35's to come from Germany (next week). Dunlop Winter Sport 3D all round @ £840 including delivery. Result

Let me know if you want details of the supplier.

Marc