Avon storm's - grooves wrong way?

[SIII]

Just had a pair of Avon Storm II's fitted. Thought the tyre guy had fitted the front one on back to front and had to check the direction arrows. According to them it is the right way.


Can some learned folk on here please explain why the V's go the opposite way to the rear and every car tyre I have ever bought. Always thought the groove's pushed the water forward and out of the way?

[dizzyblonde]

yes they're right dunnae worry!

Go by the direction arrows. I know the theory with car tyres is that the apex of the "V" faces rearwards - if it faced forward the water would be 'squeezed' toward the centre of the tread, causing a film of water to collect in the centre, promoting aquaplaning.
If you look at bike tyres, there isn't a symmetrical "V" pattern. I think that's because the centre patch area is a lot smaller on bike tyres.
One of my mates at work was convinced that the tread pattern was the wrong way around and insisted to the tyre fitter that he fit them the other way. After discussions with various bikers at work he started doubting his logic and emailed the tyre manufacturer. They told him to follow the direction arrow, so he ended up having t go back and have them refitted.
I don't recall if the response had much technical info as to why they are designed that way, but I remember they said they were tested as pairs (front and rear) and the interaction between them was optimised. If I remember I'll see if he still has that response.

[keith_d]

According to the man from Dunlop who did a presentation on tyres, the front tyres have the major grooves placed along the direction of the load on the tyre. The reason being that this reduces wear along the edges of the blocks.

That means near the center of the tyre where the load is along the axis of the tyre the grooves run more front to back. But as lean angle increases, the sideways load increases and the angle of the grooves changes to match. The edges of the tyre don't see wet tarmac because the grip runs out before the bike leans that far. So they don't need grooves to shift water and can be slick.

I took a quick look on Google and tyres like Pilot CT2, Diablo Rosso and D211 certainly fit this description.

For the back tyre things are different because a major component of the load is that noisy bit under the seat. So they need to be optimised for traction, cornering and braking loads. Which means compromises between tread wear and performance.

Then, when the engineers have done all this work the marketing people come along and say, "But we want it to look like last year's design". Aaaaaghhhh!!

Hope this makes some sense,

Keith.

My mates tyre was a Pirelli Metzler. This is the response that he got...

Subject: RE: Marathon ME880 tire
Hello
This is a common misconception about the ME880 and motorcycle tires in general. People tend to confuse FLAT car tires with round m/c tires and how they act in the rain. The idea of front motorcycle tires is they channel approx 85% or more of the water away and to the rear. This means the front tire cuts and splits the water to allow the rear to run on a dryer area of the road so to speak. Rest assured the tires are correct .

[TamSV]

Some offroad Landy drivers fit their front tyres with the V the wrong way round. I think this is mainly to help reversing but also means that, if you're sliding down a muddy hill, the grooves don't channel muck into the centre of the tyre and you retain some control over braking and cornering.

Thinking along the same lines, maybe the rear Avon is maximised for traction whereas the front is maximised for braking? The size and shape of the contact patch on the front possibly means aqua-planing isn't much of an issue until you apply the brakes.