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  1. #1
    Member babo's Avatar
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    Chevron direction to lower rolling resistance

    I'm preparing my winter bicycle for riding and for the first time in ten years I am second guessing how I am mounting the winter tires I have. I can see no markings on the tires that might aid me (Nokia Mount & Ground "W"). Which way should the chevron be to lower the rolling resistance? If I am astride the bike and I look at the front tire, should the chevron be:

    (a) <<<<<

    or

    (b) >>>>>

    I have always mounted it (b).
    I'll stop when you do.

  2. #2
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    If you try it both ways and can't tell the difference, it's a matter of aesthetics. Maybe someone knows that for safety reasons the chevrons always have a specific direction.

  3. #3
    Senior Member Eclectus's Avatar
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    It's always point to the front on top and to the back on the ground IIRC. It seems opposite to logical to me, in terms of grip, but I presume people have studied it and found it best. Point first on top would maybe be more aerodynamic at high speeds, but you see it on tractors and other slow vehicles, IIRC.

  4. #4
    Senior Member JasonC's Avatar
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    Quote Originally Posted by Eclectus View Post
    It's always point to the front on top and to the back on the ground IIRC.
    This is correct. Although, I also don't know exactly why.

    Just in thinking about it for a few minutes... one possibility is that in loose terrain the tread is trying to push the loose stuff out of the way and make contact with something solid. I imagine if a single point of tread makes contact with the ground first, and then spreads out from there, it makes it easier to push the loose stuff to the side and in between the tread. Kind of similar to the actions of a breaststroke.

    -Jason

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    My Nokian W106's have a Rotation arrow on the sidewall that have the chevrons rolling as you indicated in B) >>>>>. Front and rear are the same rotation direction.
    You go where you look

  6. #6
    Senior Member Eclectus's Avatar
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    It seems to make sense that as the rear of the tire leaves the ground, if the point of the chevron is up dirt will drop off and slide off laterally more readily from the spaces between the chevrons . If the point was down, there would be more of a "scooping" effect maybe?

  7. #7
    Senior Member canopus's Avatar
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    On car tires it is because the chevron, when pointing to the rear on the top of the tire, points forward when on the ground... This forces water from the middle of the tire to the outer edges in the direction of usual travel (i.e. going forward) to keep you from hydroplanning.
    However, at the low speeds and small contact area of bike tires it doesn't really matter so put them on however you like them.

  8. #8
    Single-serving poster electrik's Avatar
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    Quote Originally Posted by canopus View Post
    On car tires it is because the chevron, when pointing to the rear on the top of the tire, points forward when on the ground... This forces water from the middle of the tire to the outer edges in the direction of usual travel (i.e. going forward) to keep you from hydroplanning.
    However, at the low speeds and small contact area of bike tires it doesn't really matter so put them on however you like them.
    I agree, the only way you can lower rolling resistance is to get rid of squirmy tires/knobs... that means super-hard slicks, but that is a no-no in the winter!

    I can think of one reason to follow the tire F/R rules is in case of knobs on your off-road tire being "ramped". Anyways, most people mount them chevron pointed forward.

    http://yarchive.net/bike/tire_directional_tread.html
    Last edited by electrik; 10-12-09 at 12:01 PM.

  9. #9
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    Quote Originally Posted by babo View Post
    I'm preparing my winter bicycle for riding and for the first time in ten years I am second guessing how I am mounting the winter tires I have. I can see no markings on the tires that might aid me (Nokia Mount & Ground "W"). Which way should the chevron be to lower the rolling resistance? If I am astride the bike and I look at the front tire, should the chevron be:

    (a) <<<<<

    or

    (b) >>>>>

    I have always mounted it (b).
    I'm inclined to think that option A would have slightly less rolling resistance but option B might have slightly better traction. This is based on the idea that as the tire and tread pattern deforms and the wider side of the V deforms it can do so easier at the open end since at the closed end the treads are reinforcing each other. But at the closed end of the V pattern the tread can trap mud and loose things like snow easier.

    However, this is only a theory and I doubt that the difference would be large. It might be best to experiment. And inflation pressure would probably have a greater impact on rolling resistance than the tread direction.
    Last edited by Hezz; 10-12-09 at 12:20 PM.

  10. #10
    Single-serving poster electrik's Avatar
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    From above link....
    > I think the general rule of thumb for mountain bike tread patterns is
    > that the "V" should point in the direction of rotation for the front
    > tire, but opposite the direction of rotation for the rear tire (as
    > evidenced by treads on tractors). Rear tires, however, typically have a
    > "ladder" tread rather than a "V" tread.

    Tractor treads are intended to dig but cleanse themselves by pushing
    soil to the side as they 'spin' in soft terrain. This occurs only if
    the chevrons of the tread slide pointed end first. Therefore, I think
    you have the directional notation reversed. However, all this does
    not effect bicycles because they do not dig in wheel slip mode as a
    tractor. This analogy is as out of place as the acceleration of
    rotating mass in wheels, because on a bicycle there is no net long
    term acceleration. Likewise there is no long term wheel slip as on a
    farm tractor. Bicycles don't sit in place and dig.

  11. #11
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    As already mentioned by Eclectus, it should be A in the front and B in the rear. In each case, the choice is dictated by the intention to minimize slipping.

    Take a wheel that is coasting, which is always the case for the front. The rotation of the wheel, relative to the bike, is produced by the friction force between the ground and the wheel. If the wheel were slipping, say in consequence of braking, its rotation would have been slower than required for rolling without slipping. For the ground to grab the wheel and bring it back to the non-slip angular speed, it is better to have A.

    Now, with the rear, the possibility of slipping additionally occurs when you try to accelerate. You are then trying to rotate the rear wheel faster than for rolling without slipping. To prevent the slip in this situation, it is better to have the B pattern. Of course, you may say that you care more about braking for both wheels. Then you should go with A for both. However, a general recommendation is to use primarily front for braking and with this, and otherwise, A in the front and B in the rear represents a sensible compromise.

  12. #12
    Member babo's Avatar
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    Thanks for all the replies.

    I've tried the tires in multiple chevron direction combinations and empirically, when the chevron is <<<<< and I'm riding on asphalt or concrete, the tire rolls "lighter", but feels squirmier. The snow didn't stick around. It'll be back. I agree with the comments that <<<<< will force snow into the centre of the tire, but at the slow speeds and low weight, it might not make much difference. >>>>> will, in theory, keep the tire clear of snow.
    Last edited by babo; 10-26-09 at 07:18 AM. Reason: typo
    I'll stop when you do.

  13. #13
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    I just noticed an actual recommendation for opposite directions for the front and rear on a Continental tire:

    CTT2000.jpg

  14. #14
    Senior Member Medic Zero's Avatar
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    Quote Originally Posted by 2_i View Post
    As already mentioned by Eclectus, it should be A in the front and B in the rear. In each case, the choice is dictated by the intention to minimize slipping.

    Take a wheel that is coasting, which is always the case for the front. The rotation of the wheel, relative to the bike, is produced by the friction force between the ground and the wheel. If the wheel were slipping, say in consequence of braking, its rotation would have been slower than required for rolling without slipping. For the ground to grab the wheel and bring it back to the non-slip angular speed, it is better to have A.

    Now, with the rear, the possibility of slipping additionally occurs when you try to accelerate. You are then trying to rotate the rear wheel faster than for rolling without slipping. To prevent the slip in this situation, it is better to have the B pattern. Of course, you may say that you care more about braking for both wheels. Then you should go with A for both. However, a general recommendation is to use primarily front for braking and with this, and otherwise, A in the front and B in the rear represents a sensible compromise.
    Thanks for this excellent explanation!

    Just getting around to doing some mountain biking again after a several year hiatus and was scratching my head while mounting some of the mish-mash of old knobby tires I have kicking around onto my and my girlfriends' bikes. You'd think there'd be more about this out on the web, maybe my google-fu was just week today, but I wasn't finding anything illuminating until a search on the forum turned up this thread.

    Thanks again!
    ISO: 22" GT Rebound frame, year 2000 model

  15. #15
    Born Again Pagan irclean's Avatar
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    Gettin' my Fred on.

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