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H: Hubs, Wheels and Tyres Tyre Tread Pattern and Rotation Direction Arrows

Nulli Secundus

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An article from 2009 that is still relevant today can be read at: Avon tyre direction arrows
It mentions tread splice direction and the water displacement mentioned by Robert. As I said in an earlier post, some tyres are universal and can be fitted either way.
Not sure if I am being a bit slow on the uptake here, but when I read that article it mentions water dispersal as copied here:

There are many different tread patterns but there is one main reason to have any tread and that is to disperse water. (dust, dirt)

A tread pattern can be designed to disperse more water by making it rotate in only one direction. Thus, the need for directional arrows.


So how come when I look at the V pattern grooves in my AM26 Roadrider tyres on my 19" diameter Vincent and Commando wheels, plus the 21" & 19" combination on my Rudge race bike, all the tread patterns on the front tyres point in an opposite direction to those on all the rears?

My 19" tyres can be used on the front, or rear, wheels, but the 21" is a front tyre only. All the direction arrows are correct for the application.

This does not seem to be in line with the second sentence in blue above.

Can others confirm if the pattern on their tyres point in opposite directons when the direction arrows are correct on each wheel?
 

ClassicBiker

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I have AM26s fitted to three different bikes. I can confirm what you are writing. I have a 21" front on my Shadow and a 19" rear. The 21" is a front only and the 19" has arrows pointing in opposite directions dependent on front or rear fitting. The tread patterns there for are pointing in opposite directions.
On the two Triumphs I have fitted with AM26s, 19" front and 18" rear the same is true as well, opposite tread patterns.
I suspect it has something to do either with being driven versus driving or when braking the weight transfer forward unto the front wheel. Those are the only to reasons that spring to my mind.
Steven
 

Nulli Secundus

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VOC Forum Moderator
Thanks Steven for confirming what I have found concerning tread pattern direction.

Assuming that the pattern direction is optimun for water dispersal on the front wheel then perhaps there is an assumption that the rear will have less water to disperse at speed.
 

Robert Watson

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I think Steven is correct. Load on the rear is driving and will push the water out along the groove. Load on the front is greatest for braking so instinct (not engineering or even testing) tells me that is why it is opposite.

As an aside I have always thought that a good set of front brakes could put more horsepower (even tho negative) on the front tire that the stock engine could on the back one and if so then why does the rear have a 10 bolt hub (Shadow) and the front only ever a 5 bolt hub. Maybe just because the max hp is applied to the rear far more often than the front. That should give a couple of you a few sleepless nights?
 

bmetcalf

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I remember seeing photos in one of the US magazines of the wear patterns on the tires on Kenny Roberts' TZ750 or GP bike. They were opposite orientation per Robert's comments above.
 

Nulli Secundus

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VOC Forum Moderator
Thanks to all for their replies. I can now sleep tonight now I know the groove direction is correct, apart from though worrying about the number of bolts holding my Shadow rear drums onto my Rapide rear hub............
 

passenger0_0

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VOC Member
I'm no tyre expert however I understand that it is the manufacturing process that also determines tyre rotation direction. To explain this, before the tyre is placed in the mould, the outer elastomeric material that becomes the tread is wrapped over the inner tyre structure. This outer strip material is overlapped at the joint. Tyre rotation direction is specified to prevent the lap joint from opening up. If you look closely at a used rear tyre on a high powered bike you sometimes see what looks like a straight knife cut running the width of the tread. This is the lap joint coming apart due to the high driving torque pulling the joint apart.
That's my take but someone might know better.
 

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