directional tyres

[SGHOM]

what would happen if you put them on the wrong way round ??

[pitslayer]

they wouldnt work and handle like a capri



edit:actually they would work, you would have to drive everywhere in reverse thow

[MPBVr4]

I think dry track Wet track

[TAR]

Directional tyres...ummm....don't like them as you cant swap them around easy.

I'm sure it would be like driving the most slippery of slippery things from planet slippy in the wet!

probably not recommended.

[SGHOM]

useful info here.

http://www.etyres.co.uk/glossary-tyr...rm=directional

& more general info here.

http://www.etyres.co.uk/tyre-tests

[WildCards]

I heard they'd pull your car in two, as both side of the car would want to drive away in different directions, you could of course adjust the tracking to compensate.

[Wodjno]

what would happen if you put them on the wrong way round ??

What size are your tyres Derek ??

[richy rich]

what would happen if you put them on the wrong way round ??

Dont tell me you didnt change them back D

[White Lightning]

Trying to get some extra life out of them for Combe I expect ...

[richy rich]

Trying to get some extra life out of them for Combe I expect ...

If this is the case just get down to you local tyre shop and get them changed round.

[SGHOM]

I'm swapping them on sunday. right to left, left to right.
I just wondered if the directional tread pattern was for water dispersment only ?? If that was the case, then I suppose they would still be ok for track use ?? [ providing the track was dry ]

It's quicker, easier & cheaper to swap the wheels rather than the tyres.

[richy rich]

I'm swapping them on sunday. right to left, left to right.
I just wondered if the directional tread pattern was for water dispersment only ?? If that was the case, then I suppose they would still be ok for track use ?? [ providing the track was dry ]

It's quicker, easier & cheaper to swap the wheels rather than the tyres.

you lardarse

[SGHOM]

you lardarse

I concur.
But I still have not got a difinitive answer ??

[bernmc]

I don't think you're even supposed to swap non-directional tyres side-to-side - only front to back.

[richy rich]

I don't think you're even supposed to swap non-directional tyres side-to-side - only front to back.

Non-directional you swap opposite corners.
Directional front to back

[SGHOM]

without having a set to hand..... & in my twilight years [ memory's going ] is there an inside & outside to directional tyres ??
If so, then they cant be changed.

[Wodjno]

without having a set to hand..... & in my twilight years [ memory's going ] is there an inside & outside to directional tyres ??
If so, then they cant be changed.

Not on GS-D3's

[richy rich]

without having a set to hand..... & in my twilight years [ memory's going ] is there an inside & outside to directional tyres ??

No.....

[zentac]

without having a set to hand..... & in my twilight years [ memory's going ] is there an inside & outside to directional tyres ??
If so, then they cant be changed.

errr sort of, kind of .....err maybe.... Depends if they are asymmetric as an asymmetric tyre has different tread patterns on its inner and outer sides. Some are both asymmetric and directional.

[TAR]

OK long and boring reply coming up.....

You have probably already guessed that tyre makers design tread patterns to pump away as much water as possible. They do this with computer models and then test those models on trial tyres.

As tyres have got fatter, it has become more difficult to pump the water away from the middle of the tread area, or "footprint" or "contact patch" . Imagine what is happening. The tyre is rolling forward and meets a wall of water. It's quite easy to divert the water away from the edges of the tread pattern, but the water in the middle of the tyre as it meets the water has to be pushed laterally to the sides, and this has to happen quite fast if it is to be cleared away before the tyre has passed over the water.

if the water is not pumped away, then the dynamics of water and rubber mean that the tyre (and hence the car) get supported on a film of water and there is no grip to speak of, You end up aquaplaning.

In the past, tyres had symmetrical tread patterns, so that it did not matter which way around the tyre was fitted, but that was when tyres rarely went above 185mm width or so. Over the last 10 years or so, fashion has meant car owners want their tyres to be low and fat. This means tyre widths have crept up, and now a 265mm tyre is not uncommon on a high performance vehicle.

The only way the tyre designers can get the water away from underneath the tread on these fat tyres is to make the pattern directional, with those sweeping grooves that start from the centre of the tread and curve out to the edges of the tyres. You see them on fancy tyres. That pattern provides a path for the water to start at the middle of the tread and accelerate laterally to the sides of the tyre before the tyre rolls onward.

The sweeping is a kind of parabolic shape, which assumes a constant forward speed and a steady acceleration from the centre to the edge. So the curves are nearly parallel to the direction of motion near the middle, where the water is moving slowly, and they curve more steeply near the edges, as the water has accelerated laterally.

By the time the water has reached the edge of the tyre, it is moving quite fast, and hence these tyres kick up a lot of spray in the direction perpendicular to the direction of motion.

If you mount those tyres the wrong way around, then first, there is no path for the water to esape from the contact patch and second, the sweeping grooves are actually pumping water *into* the centre of the contact patch.

While the precise aquaplaning speed is hard to predict (it depends critically on forward speed, water depth and tread pattern), I would guess that the onset of aquaplaning might drop by 20-30 kph, from say 90 kph to 60 kph with four directionally-reversed tyres. (that would be in quite deep standing water with new, unworn tyres). The same applies in shallow standing water (say 2mm) with worn tyres.