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resolvedI was happily putting on faster tyres for the summer, had completed the rear tyre when I noticed the front tyre had a "Rotation this way" marker, and "Yes" the rear tyre was the wrong way round.
(They are Specialised All Condition Armadillo which I had supposed were below such sophistication. How wrong.)
So, all put right, but I'm left wondering what would have been the difference if I hadn't bothered.
Explosions.
I somehow contrive to do this almost 50% of the time I change tyres...
Given the treads on the tyres tend to be at a diagonal to direction of travel, I presume they're designed to provide more grip in one particular direction?
Just to confuse the issue, some tyres have different arrows pointing in opposite directions. It depends whether it's on the front, or the back. Schwalbe Snow Studs a case in point.
I've previously seen the theory that it's to do with surface water skimming. The Specialised markings could do this albeit in an erratic way, but not the markings on my Continentals.
Quite like the explosion theory, particularly given the almost impossibility of seeing the instruction in the first place. Our streets should be more exciting.
Due to the carbon atoms in the tyres, and also Lenses law, when spun the wrong way round the tyre produces a magnetic force which acts to counter the rotation of the wheel. So you'll slow down faster than you would have done if the tyre was on the right way round. Theoretically when put on the rightway round the induced magnetic force will act to increase the wheel turning and you don't need to pedal to work. You can just cruise once up to speed. Of course the friction of the rubber on the surface you're riding on means this remains theory and you eventually slow down, so need to keep pedalling.... and you thought it was just about the water displacement eh?? ;0)
I believe it is so that the water is dispersed away through the tread. If they are on the wrong way round, the water will not be pushed away, instead the water will be retained, meaning it is more likely to aquaplane.
Lenz's law, DaveC?
Nope Lenz was on about metal. Lense was talking about rubber ;0)
"... meaning it is more likely to aquaplane."
I'm sure I read somewhere that the width of tyre on a bike it would have to travel at something like 1000mph to aquaplane....
*off to have a look*
Still going with explosions. Don't do it folks. You know all the massive potholes you occassionally come across? That's all that remains of cyclists who didn't scrutinise their tyres in sufficient detail.
That chart is disappointingly missing the pressure needed to achieve aquaplaning at 88mph, I'd like to think it was 12.1 bar...
I can't find anything about Lenses law. Can you point me in the direction of a resource please, DaveC? I'm interested to learn, y'see.
Another suggestion re: direction and thus to potential explain crowriver's point about some tyres going on different directions for front and back, is that the front wheel does most of the braking and the back wheel does most of the power transfer. Therefore, the tread on the tyre is important so that it can either stop (front) or go (back). This doesn't seem to explain a tyre with only one direction marker, though.
The short answer is that all tread is cosmetic unless the tyre rubber is harder than the surface you're riding on.
Some offroad tyres are designed with knobs that don't work well in one direction (hence they have two arrows for front/rear wheel), while most work OK in either direction - one arrow. I have some of both.
The most directional one has knobs that have one vertical face and one smooth sloping one, so they wouldn't be much good put on the wrong way around I suspect.
I imagine that a tyre fitted in the "correct" direction might be a bit better at throwing water out sideyways rather than in your face, if it does indeed follow those little channels in the surface.
+1 to the spray/hydraplaning, although I didn't know you had to be going that quick, so it's really just the spray.
Like many a lazy indecisive flipflop single/fixie pilot I've ridden around for weeks at a time with a backwards Marathon tyre on the back wheel, and couldn't tell any difference in dry performance, although I think there might have been more gubbins coming up on wet days.
With full mudguards even that issue is pretty trivial.
With an almost treadless tyre like the Armadillo I think you'd need to be Dave in a particularly obsessive mood, armed with a slowmotion camera and a set of rollers submerged in a puddle-simulating tank to measure any difference.
Ah thats why Dave wants a garage near the WoL!!
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