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Select Low Gear to nurse damaged wheel?

Discussion in 'Bicycle Mechanics and Repairs' started by torrens, 13 Sep 2007.

  1. torrens

    torrens New Member

    Riding with my cycling buddies a few days ago, one of us had the misfortune to experience a rear wheel spoke breakage. We trued the wheel as best we could and were able to continue. Someone advised that the machine should be kept in a low gear for the rest of the trip to "prevent the damaged wheel from being strained more than necessary".

    Is this correct? Surely selecting a gear as high as possible would minimize the "strain" on the rear wheel? When I suggested this though my idea was met with hoots of derision.

    "Imagine the strain involved in setting off in top gear, you'd have to stand on the pedals etc, etc" they said. So I kept my counsel to myself from then on! I find myself doing this quite often; there seems to be quite a lot of "lore" in cycling IMHO!

    Anyone got any thoughts on this?
     
  2. The strain on the rear wheel will depend on the weight of the rider and the loads transferred from the hub to the spokes. The gear ratio has no bearing whatsoever. Accelerate up to 10mph in 30 seconds in top gear or accelerate up to 10mph in 30 seconds in low gear, the loading on the wheel is the same. One might deduce that accelerating up to speed in a high gear will take longer for physiological reasons and therefore conclude that those accelerative forces, spread over a longer time period, must be reduced at the hub.

    You are right. They are wrong.
     
  3. Smokin Joe

    Smokin Joe Legendary Member

    Don't agree. In a lower gear, the load on the wheel is lighter.
     
  4. Think of it this way then; can you pop a wheelie in top gear? Nope because you cant get enough torque to the back wheel in top gear. Its perfectly possible to wheelie in bottom gear tho right? Low gears are capable of delivering more torque to the hub.
     
  5. asterix

    asterix Comrade Member

    Location:
    Limoges or York

    That would apply only as the low gear enables you to accelerate very slowly and carefully and limit your speed so less braking is needed.

    Otherwise the force on the wheel must surely be the same as the torque of the hub, regardless of the gear.
     
  6. Pete

    Pete Guest

    It depends on your cadence. If you can achieve a good steady cadence without ever having to 'honk', and without uneven surges of pressure, you're in the best gear for a weakened wheel. In an emergency you'd need to avoid the steeper hills, I'd say. Of course, with a lower gear, the same amount of pedal pressure results in more torque, hence more strain, on the wheel so that's not the simple answer.

    I once had to ride a fair distance (~50 miles) on three broken spokes, rear wheel, and I got home OK. :ohmy: I walked up most of the hills, though. :smile::blush:
     
  7. Smokin Joe

    Smokin Joe Legendary Member

    In a higher gear the load on the drivetrain is greater. The same as in a car, when driving in too high a gear causes premature wear on the main bearings, con rods and big-ends.
     
  8. On the drivetrain yes but the thing we are concerned about here is the load twixt hub and spokes, this isnt part of the drivetrain its the wheel. Driving in too high a gear in a car will have no detrimental effect on its wheels.

    Its easier to apply a high torque load to the spokes using a lower gear than with a high gear.
     
  9. skwerl

    skwerl New Member

    Location:
    London
    this man's right. your cycling mates clearly don't know squat about mechanics. I guess they figure that if you have to pedal hard then the force on the wheel must be hard
     
  10. Smokin Joe

    Smokin Joe Legendary Member

    Spoked wheels are different to the solid wheels on a car. The drive is concentrated through a small number of spokes at any given time, and they effectively form part of the drive train to the rim.
     
  11. I refer the right honourable member to the answer I gave a few days ago.