Tyre rotational direction. Does it matter?

extra grip, handling in the wet there will be other reasons and yes its a MOT fail

Tim Downie ( snipped-for-privacy@obvious.yahoo.co.uk) gurgled happily, sounding much like they were saying :

Yes, it most certainly does. If the tyre's directional, using the tyre in the other direction will increase wear and decrease grip.

Same with assymetric tyres fitted the wrong way round.

Your handling & grip will be vastly improved when reversing (well, if your others matched) :-)

Aren't spares supposed to be bi-directional ? What's the point of directional spares unless you have 2 of them!!

in the real, average driver world you are very unlikely to notice a difference, but they should be fitted the right way round, using a wrong way spare as a get you home/to a tyre place is fine but if you intend to continue to use it then get it reversed and re balanced. Over the years I have seen dozens of wrong way tyres, you would not know by driving, but most mot testers will spot it.

mrcheerful

On my Supra I had two directional spares. The alloys were right or left sided too.

Carried one in the car just in case and changed it when I got home if it was the wrong one.

In message , Tim Downie writes

I would have said yes, however it looks as if it might not:

They found no effect on wet braking and cornering:

"The two most important wet weather characteristics, namely wet braking and wet handling, were completely unaffected by running one tire in the reverse direction."

They found that resistance to aquaplaning was reduced but that it was still within the bounds of other tyres on the market:

"There were measurable differences in aquaplaning performance noted in most of the tests. In all cases it was shown that the decrease in aquaplaning performance of a tire mounted in the wrong direction was less than the dispersion of aquaplaning performance encountered between different tire brands or different tread patterns within the same brand. In no case was the decrease of aquaplaning seen as a safety concern. The differences are small in relation to the overall spread of aquaplaning performance seen in the marketplace."

They concluded that it should still not be recommended:

"The tire industry concludes that using a directional tire in the wrong direction is not unsafe. Nevertheless, it should be discouraged, and drivers who are obliged to mount a directional tire in the wrong way should do so as a temporary measure only. Continued use of a directional tire rotating in the opposite direction can lead to customer satisfaction issues such as uneven tire wear, and/or the generation of increased noise and vibration levels."

You will when you hit standing water. The difference between normal tyres and directional tyres is pretty massive, and I imagine backwards directional tyres would be fooking shocking at getting water out from under the tyre.

So by implication, it's a bad idea to have a directional tyre on the spare.

I suspect that most owners with steel rims rotate the spare in at some point. So directional tyres are a disavantage to them. Those with alloys only use the spare as a get-you-home as it's usually steel. At least with "spacesaver" spares the argument doesn't arise!

Doki ( snipped-for-privacy@gmail.com) gurgled happily, sounding much like they were saying :

And you will in the wear, too.

The insurance company would probably dispute any accident claim, even if relevant.

Yup.

Thanks for all the replies folk. I'll get is swapped over when I replace the tyre.

Tim

Mates SL had directionals - even worse his fronts and rears were different sizes too.

I bought a car that was like that once ;-)

I mentioned it to the seller when I noticed it (after changing them).

He said he thought it was OK since the axle sets were the same.

The spare was yet another different size.