Tyres Question - Reverse Rotation - is it an issue?

[Marcellus]

Not the best subject I know so sorry, but;

I've had to put my spare tyre on and they're "Directional Tyres" (ie have the rotation arrow on)... but the spare was mounted onto a wheel for the other side of the car so now it's going backwards (if that makes sense).

I'm overseas, about 1500miles from home and won't be back until the weekend so I'm wondering if it's an issue and whether I should go to a tyre centre and get them to change it round so it goes the correct way.


BTW: For those who question the spare and suggest I should get it sorted it's ok but slightly too worn so I'm going to sort it out when I get back as tyres are soo expensive in France and when I do this tyre will go back to being a spare.

[XG332]

It will be dreadful in the wet as the grooves are working backwards and drawing water to the center of ther tyre.
Not what you want.
If it is dry I would go for it. But stop every so often to check on it.

[andy-xr]

I'd drive it. I wouldn't want to do it for an extended period of time but getting home, even that distance, just throw it on

[mnkiboy]

As above it's a huge aquaplaning risk if you hit a puddle. The water is basically being channeled to the centre of the tyre, rather than towards the edge. I don't know how much effect it will have, but i'd be very nervous driving 1500 miles on it in winter.

[y2blade]

I'd drive on it, Just keep an eye on it and bear it in mind if it is wet.

[jagnet]

As others have said, just drive home on it. Any difference in grip levels wet to dry will be too small to detect, and it's only aquaplaning that will be affected to any degree, although not by a lot. Just take it a bit easier if you find a lot of standing water on the way back.

The directional tyre will not "channel" water into the centre.

[hman]

It's a big "if" but would this not affect your insurance if you aquaplaned and crashed the car?

Personally I'd be getting the tyre turned around on the rim by a garage it would cost less than 20 euros to do.

[Marcellus]

Cheers guys... at the moment the biggest issue for me is snow not water!!

[hman]

Until you get to a gritted road where there will be plenty of standing water...

[Marcellus]

hman said:

Until you get to a gritted road where there will be plenty of standing water...

lol... more like an inch of hardpacked snow and ice, where the tread doesn't make much difference as they're not winter tyres!!

[kambites]

As above, just be a bit careful in the wet - don't go plowing through flooded roads and expect it to stuck as well as the others. A new tyre on backwards will probably be no worse than having a tyre that's the right way 'round but approaching the legal limit.

[XG332]

Marcellus said:

Cheers guys... at the moment the biggest issue for me is snow not water!!

Go steady if you pass a garage wave 20 euros at him to swap it over. It's a 2
Minute job.

[ED209]

I the wet it will be deadly, trust me, after i had the discs/pads done on a mx5 the mechanic put the directional tyres on the wrong way round, the first sign of damp and it span, how i didnt hit anything i will never know.

[jagnet]

ED209 said:

I the wet it will be deadly, trust me, after i had the discs/pads done on a mx5 the mechanic put the directional tyres on the wrong way round, the first sign of damp and it span, how i didnt hit anything i will never know.

Interesting. What tyres were they?

[cptsideways]

Dry it will make no difference at all, the only thing you might notice is in torrential rain/puddles. 99% of the time you wont know the difference.

[mrmr96]

If a tyre is directional then the tread pattern will be designed to throw water from the centre to the edges of the tyre to clear a contact patch with the road. When run in the opposite direction the effect is reversed, with the channels guiding water from all across the face of the tyre towards the centre. This will make a significant difference to the risk of aquaplaning.

Note, that this effect only occurs when there a significant amount of water ABOVE the surface of the tarmac. Hence there's no problem in the dry, and do problem in the damp. There might even be no problem in the rain. However the two circumstances where I do see a problem will be i) hitting a patch of standing water (aka puddle), or ii) driving hard rain, where the speed of the rainfall is causing sheeting across the road. In these two circumstances I would seriously consider pulling over and waiting for conditions to improve.

PS - next time you have a spare tyre fitted to your rim, make sure it's not directional.

HTH

[jagnet]

mrmr96 said:

If a tyre is directional then the tread pattern will be designed to throw water from the centre to the edges of the tyre to clear a contact patch with the road. When run in the opposite direction the effect is reversed, with the channels guiding water from all across the face of the tyre towards the centre. This will make a significant difference to the risk of aquaplaning.

But that would require that the tyre will act as such an effective pump that rather than the water taking the path of least resistance out to the sides it'll be forced into the centre where there's nowhere for it to go aside from physically lifting the car up to allow it to escape?



In the picture above of the contact patch at 8mm tread depth from Nokian, you can see that despite being a directional tyre, there are multiple grooves and channel exits in contact with the ground at any one time. If you dropped the tyre vertically onto the ground the water wouldn't really care which way the tyre was facing.

If you imagine the tyre rotating, then if reversed the channel exits would contact the ground first, dispelling water as more of the channel rotates. As I see it, the worst of the problem comes when the tyre continues to rotate and the channel exits lift off the ground, forcing the water to exit in front of the tyre into the path of the building wall of water which you're trying to disperse. Presumably the more aggressive the directional pattern the bigger a problem this becomes.

When you consider how many performance tyres don't even have much in the way of cross tyre channels such as the Nokian Z G2 below, yet manage to disperse water and grip in the wet better than budget tyres with a heavy directional tread, then I don't see how a reversed directional tyre is going to be massively compromised.



NB I'm not a tyre designer, so I could be talking rubbish

[y2blade]

Marcellus said:

hman said:

Until you get to a gritted road where there will be plenty of standing water...

lol... more like an inch of hardpacked snow and ice, where the tread doesn't make much difference as they're not winter tyres!!

this^^^

just go steady

[Captain Muppet]

ED209 said:

I the wet it will be deadly, trust me, after i had the discs/pads done on a mx5 the mechanic put the directional tyres on the wrong way round, the first sign of damp and it span, how i didnt hit anything i will never know.

You asking us to trust that the thing that didn't kill you is deadly.

I've run loads of directional tyres the wrong way round* on the back of my MX5 Turbo and like you I am not dead. Unlike you I didn't find that it had noticably reduced grip in the wet. Makes bog all difference in snow too.

OP - just drive it, slow down for standing water like normal people do and it won't be a problem.

* I had a reason, but it isn't in any way relevant to this thread. Also it's quite dull.

[mnkiboy]

Would an insurance company be interested if you had an accident that could be blamed on the wrongly fitted tyre? For example you could aquaplane in to a school full of promising footballers, by mistake.

You could of course quite genuinely claim you didn't know about it.