Tyre tread direction for grass, loose surfaces

[Chuck Glider]

So, I think the only thorny issue here is about the orientation of the rear tyre tread. I'm fully aware of that some manufacturers have rotation arrows on sidewalls and some info on that in brochures. I say there's no issue with the front tyre, because every elite MTB or cyclocross bike I've seen has had the front tyre oriented so that looking from above, the chevron/arrow in the tread points forwards and this has always been consistent with the manufacturers recommendations.

As to the rear tyre, I've just looked at hundreds of photos of elite riders' MTB and Cyclocross bikes on t'net. This includes a number of ex world champions and national champions (eg Stybar, Wyman, Nys). I found the following:

Out of 15 bikes of elite riders, only one had the rear tyre oriented so that the chevron/arrow points backwards when viewed from the above. The one exception was Tim Johnson's MTB bike (he's more known for CX) on which had the rear tyre (a Schwalbe Rocket Ron) the other way, with arrow pointing back when viewed from above. The majority bikes include some fitted with Michelin Mud2s, which I know have arrows on them indicating that the rear and front point in opposite directions. In other words, the rider is ignoring the manufacturer's arrows! From this I conclude that elite MTB and elite cyclocross riders nearly always have their tyres oriented like this:

>>>>>>rear wheel>>>>>>>---------===+BB+===------------>>>>>>>front wheel>>>>>>>>

and will go against the manufacturer's arrows on the side walls when they do that. Sometimes they put the rear tyre the other way round, but this appears to be rare.

Well that solves this long standing puzzle for me. I will simply do what they do!! And take support from the fact that this is also the orientation for tractor tyres.

Any thoughts?

[meic]

I reckon that front tyres are set to maximise grip when braking and rear tyres maximise for when being driven by the pedals.

I think the one exception was probably a mistake, after a couple of pints possibly.

Sorry, I didnt follow it properly, the one expert was doing that, the others were maximising grip for braking on both wheels.

[Brian73]

Schwalbe has some info here

It has directional arrows on its tyres for front and rear usage.

http://www.schwalbetires.com/tech_info/tire_tread

Most SCHWALBE tire sidewalls are marked with a "Drive" arrow, which indicates the recommended rolling direction. When in use, the tire should run in the direction of the arrow.

Many MTB tires are marked with a "Front" and a "Rear" arrow. The "Front" arrow indicates the recommended rolling direction for the front wheel and respectively the "Rear" arrow is the direction for the rear wheel.

[Brucey]

With Chuck's observed orientation: the rear is thus set 'tractor style'. The theory here is that the tyre will dig, displace mud sideways, and find grip.

At the front you can't afford to slip, especially when leaning over during cornering. This means ( I think) that the tyre has to be the way round that you see it; if it was on the other way round you would wash out the front every time you touch the brakes when leaning even slightly.

I have no idea why the manufacturers might make a different recommendation to this, unless they think that you won't displace mud to find grip with the rear wheel...?

cheers

[Chuck Glider]

Meic and Brian73, I've just edited the OP, just to clarify the background and what I meant.

I would rate the empirical evidence and practices of world and national CX and MTB champions higher than Schwalbe's note or indeed, the email exchanges that our CJ had with Continental tech folks some years ago (you can read about that in the CTC Technical Q&A section).

I run Michelin Mud2 on my CX bike, and currently I follow the manufacturer's recommendation from the arrows on the sidewall. Which means the manufacturer says:

<<<<rear<<<<<=========BB=========>>>>>front>>>>>

Whereas elite riders (including some using Mud2s) do this:

>>>>>rear>>>>>==========BB========>>>>>front>>>>>

I will probably do some qualitative testing of my own one day, to see if I can notice the difference off road.

[Landy Mann]

The tractor style is meant to be self cleaning, however some lots of ag trailers have there tires fitted the other way round, but I can't remember why.