Tyres | Technical matters | Back Room Forum

Mon 27 Jan 2003 15:34

Tyres - BMDUBYA

I would like to share a recent lesson learned regarding directional and non directional tyres, apologies if you all now this.

I recently had a puncture in the front near side tyre, swapped with the spare which was a non directional, however the off side front was a directional. When I was braking from 70 - 60, pulling off the motorway, I experienced quite a bad wheel judder, which wasnt there before. By chance I wondered if it was anything to do with the non directional tyre, so off came the non directional and on with a directional (correct direction) problem solved. Just to confirm my thoughts, off came both directional and on went non directional, again no judder. All tyres were uniroyals 225/60? r15 (think it was 60)

Question1. When did directional tyres become available?

Question2. Anyone else experienced this?

Question3. Can anyone offer an explanation as to why at only 60mph braking, this problem exhibited itself.

Thanks in advance.

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Mon 27 Jan 2003 17:03

Tyres - John S

BMDUBYA

This is just from memory so corrections anticipated!

The first road tyre which was sensitive to the way it operated and the way it was mounted on the wheel was, I believe, the assymetric Michelin XAS (1960's ?), but this wasn't strictly directional. The first true directional tyre was probably the Pirelli P Zero (1980's?)

Judder? I can only think it's some effect of tread distortion under braking due to the strongly directional tread pattern or maybe something to do with the way the carcass of the tyre is made to impart the 'directional' properties. However, I thought the key issue with the directionality was water dispersion charcteristics of the tread. Otherwise, one would expect hard accelleration to cause a similar problem.

Regards

John S

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