are directional tyres ok wrong way round ?

[wiliferus]

Noger said:

McSam said:

Nobody's yet mentioned that directional tyres fitted the wrong way round are not roadworthy and would fail an MOT immediately.

This, I should say, also means your insurance isn't valid.

You are wrong on both counts.

MOT wise he's right -

Reasons for failure of a tyre -

f. a tyre not fitted in compliance with the manufacturers sidewall instruction, e.g. an asymmetric with a sidewall marked ‘outer’ fitted with the marking to the inner side of the wheel.

Note: Direction of rotation may be indicated by an arrow and/or words, but an arrow by itself should not be taken to indicate direction of rotation.

Insurance wise, invalidate? No. Cause you problems if you have a smash and your insurance company inspect the vehicle and decide it was a contributary factor? Probably!

[McSam]

Steameh said:

McSam said:

Nobody's yet mentioned that directional tyres fitted the wrong way round are not roadworthy and would fail an MOT immediately.

This, I should say, also means your insurance isn't valid.

I doubt MOT is much of an issue in this case.

No, it's not really - but I figured it was worth mentioning for anyone else reading it and thinking they might as well do the same on their summer tyres on their road car.

Wouldn't knowingly doing something that would cause the car to fail its MOT, particularly in a safety-critical aspect such as the tyres, be grounds to invalidate your cover?

[Noger]

McSam said:

I've got a fail sheet saying exactly this, so clearly it is a test criterion?

And if the manufacturer says they should be that way as linked above ?

Can't say I have problems with MOT and tyre direction. Maybe for more "normal" cars and tyres ?

[Paul_M3]

I've also just remembered that this is still in my inbox from when I e-mailed Kumho for clarification on this:

"There’s absolutely no reason why you can’t run the V70A the “wrong way round” (against the direction of rotation) in the dry. A lot of people do this to even up the wear.

Best regards,

Mark.
Mark Hamnett.
Technical Manager.
Kumho Motorsport UK"

[wiliferus]

Noger said:

And if the manufacturer says they should be that way as linked above ?

Can't say I have problems with MOT and tyre direction. Maybe for more "normal" cars and tyres ?

That's probably because you use a MOT tester who is human and sensible. A rare beast nowerdays, being replaced by the jobsworth variety!

[Noger]

wiliferus said:

MOT wise he's right -

Reasons for failure of a tyre -

f. a tyre not fitted in compliance with the manufacturers sidewall instruction, e.g. an asymmetric with a sidewall marked ‘outer’ fitted with the marking to the inner side of the wheel.

Note: Direction of rotation may be indicated by an arrow and/or words, but an arrow by itself should not be taken to indicate direction of rotation.

They dont usually say "inner" and "outer" in the tyres we are talking about. And as above, manufacturers instructions. Toyo say much the same thing.

Obviously if you really need Inners and Outers, and get them wrong, then that isn't good.

[Noger]

wiliferus said:

That's probably because you use a MOT tester who is human and sensible. A rare beast nowerdays, being replaced by the jobsworth variety!

True

The whole "can you undo your 6 point harness with one hand" thing can get overlooked too.

Anyway, fair point. Don't put your tyres on backwards unless you are sure you know you that is ok.

[blank]

The only correct answer is to ask the manufacturer.


I have been told some stories about moving tyres around to even up wear when doing high speed testing on banked circuits.

With one particular tyre there were actually a number of situations where the performance was better when fitted 'backwards'.

[Andyjc86]

I was going to metion the MOT rule, it's now a fail, so technically not legal. However for use only in the dry I can see no problem, I would like to see what happens in the wet though.

[mrmr96]

wiliferus said:

Sorry, I may be being a dimlow - but that looks to me like the n/s/f & o/s/r are set to rotate 'forwards' (in the specified direction) and the o/s/f and n/s/r to run backwards as it were, which from a physics balance POV i can see the logic.

I may of course be reading the diagram completely wrong...

ETA - My reading of the diagram is based on the fact that normally the spec number of the tyre would be on the outside tyre wall, and is thus visible.

Edited by wiliferus on Thursday 29th March 22:46

You're wrong.

The reason is that there's two common types of tyre pattern:
- Asymetric (where the inner and outer are different but the direction of rotation doens't matter)
- Directional (where the inner and outer are the same, but the direction of rotation DOES matter)

You'll find that Asymetric tyres have one face labelled as "outer" (which you're incorrectly interpreted as the 'x' on the diagram).
Whereas the directional tyres (in the diagram) will have a rotation arrow on each face, of course one will be clockwise as you look at it, and the other anti clockwise. To distinguish between these two sides the tyre ALSO evidently has a spec written on one of them, as denoted by the 'x' on the diagram. Hence why the picture shows the rear two going one way and the front two going the opposite way to the back ones.

HTH