My last post about my tyre blow-out experience prompts me to confess it was only recently this year I figured out the difference between an asymmetric tyre and a directional tyre. I have heard of non-directional and directional tyres but the term asymmetric tyres only recently came to my attention and for a while I thought directional and asymmetric were the same thing in the tyre world.

It turns out they aren’t.

There are non-directional tyres that can be installed any way around on the wheel – they can rotate in any direction - and the big benefit of these is they can be swapped around the vehicle if required. Any wheel/tyre assembly can be put at any corner of the car. The downside is they are a compromise in performance.

Then there are directional tyres which must be fitted to the wheel rim in relation to the direction of rotation – the tyre must only rotate one specific way. There is no inside or outside to the tyre but they must only rotate in one given direction. The upside is greater performance can be gained from design tuning. The downside is that any wheel/tyre assembly can only be swapped front to back and vice versa from the same side of the car – you can’t just sling it on the other side of the car unless you de-mount the tyre and refit it to the rim to keep its rotation correct.

Then to confuse everyone (me included) they brought out asymmetric tyres. They are non-directional and can be moved around the car to any corner without de-mounting and re-mounting the tyre as with the first type. The real important thing is for the guy fitting them on the wheel rim must get the inside and outside correct – the outside face must be on the outside and the inside face must be on the inside - you can’t have the faces set incorrectly.

Looking at the three types I think the asymmetric is a very good compromise. It gets many benefits by allowing some design tuning of the tyre but allows freer wheel/tyre assembly swapping. I look forward to having all my tyres as asymmetric.

Regards

Phil