Advertise on Bikeforums.net



User Tag List

Results 1 to 10 of 10
  1. #1
    Member
    Join Date
    May 2007
    Location
    california
    My Bikes
    1936 Phillips City Model, 1965 Raleigh Sports (x2 - red & black), 1973 Phillps, 1973 Raleigh LTD-3, 2007 Raleigh One-Way
    Posts
    28
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Does tire size help with broken spokes?

    Reading Rivendell's catalogue, it seems that a heavier load (in the rider or loaded touring) needs a bigger tire. Could a larger tire (larger than 700cx23!) help with periodic broken spokes?

    My friend is about 250lbs, very strong legs, and keeps breaking spokes on his Rush Hour. I've suggested larger tires (don't know how big that bike will accept). Or does he need to get better spokes and/or rims?

  2. #2
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
    Join Date
    Mar 2006
    Location
    South Florida
    My Bikes
    Techna Wheelchair and a Sun EZ 3 Recumbent Trike
    Posts
    16,014
    Mentioned
    10 Post(s)
    Tagged
    4 Thread(s)
    Larger tires at a lower inflation do provide a more compliant cushion. That said, it depends on whether they're breaking from the impact or from torque sheer. Clyde's can put a lot of foot pounds of torque out.
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

  3. #3
    Tossed some weight Redrom's Avatar
    Join Date
    Sep 2005
    Location
    Northampton, MA
    My Bikes
    '96 Specialized Rockhopper, '70's Fixed Fuji, '02 Organic Engines Troika Tandem Trike
    Posts
    465
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    As an ex-Clyde, I'd say the rim would taco before the spokes should break. At least that's what happened to me. 250 lbs should be within tolerance of most bikes. I finally had my first spoke break a couple of weeks ago, and I don't think it's because of my weight. I switched them all out to 14 ga. double butted spokes, and hope to have no more trouble. There's no shocks on the bike and high psi in the tires, on a bumpy trail, so I think that's what caused the broken spoke.

  4. #4
    Senior Member
    Join Date
    Feb 2007
    Posts
    298
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Spoke tension will be reduced slightly by an inflated tire as it is compressing the rim to some degree so it should hold that a narrower high pressure tire will reduce your spoke tension more than a wider lower pressure tire.
    Here is a short article on spoke tension:
    http://www.cyclingnews.com/tech/fix/?id=tm_1

    I am unaware if this reduction in spoke tension is significant enough to contribute to broken spokes in a properly built wheel.

  5. #5
    SNARKY MEMBER CardiacKid's Avatar
    Join Date
    Jul 2005
    Location
    South Austin
    Posts
    2,829
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I am not a physicist, but I don't think bigger tires would help except when you hit a bump. There is going to be the same amount of weight on the wheels, regardless of the size of the tires. In fact, there is going to be more weight on the wheels with bigger tires, because the tires weigh more. Additionally, the contact patch is going to be shorter and wider, with the wider tires. I would think this would focus the weight onto a smaller cross-section of the wheel. As Tom pointed out, tire size will have no effect on torque.
    This seems to be intuitively wrong, but intuition and physics don't ever seem to get you to the same place.

  6. #6
    Senior Member
    Join Date
    Feb 2007
    Posts
    298
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I have never read the Bicycle Wheel, nor do I intend to, but I did find this claim in a much earlier post:

    I have been reading Jobst Brandt's "The Bicycle Wheel." Amazingly, the effect of twisting the rear hub under acceleration -- even in a sprint -- makes a pretty small impact on the spokes. Brandt indicates that a fully-inflated tire produces a greater affect on the spokes than the cyclist's pedaling forces!

    I have always been suspect of claims that the torque a rider puts out presents a problem with spokes. I think a hard application of a disc brake probably results in more stress on the hub/spokes than pedaling could.

  7. #7
    Member
    Join Date
    May 2007
    Location
    california
    My Bikes
    1936 Phillips City Model, 1965 Raleigh Sports (x2 - red & black), 1973 Phillps, 1973 Raleigh LTD-3, 2007 Raleigh One-Way
    Posts
    28
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    so what would that mean regarding my original question?

  8. #8
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
    Join Date
    Mar 2006
    Location
    South Florida
    My Bikes
    Techna Wheelchair and a Sun EZ 3 Recumbent Trike
    Posts
    16,014
    Mentioned
    10 Post(s)
    Tagged
    4 Thread(s)
    Your original question:

    Larger tire volume at lower pressure will likely reduce spoke breakage by some factor. I can't quantify the exact reduction in probability, but the softer ride is less stressful on the bend where they enter the hub.
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

  9. #9
    Senior Member john bono's Avatar
    Join Date
    Apr 2006
    Posts
    733
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by CardiacKid View Post
    I am not a physicist, but I don't think bigger tires would help except when you hit a bump. There is going to be the same amount of weight on the wheels, regardless of the size of the tires. In fact, there is going to be more weight on the wheels with bigger tires, because the tires weigh more. Additionally, the contact patch is going to be shorter and wider, with the wider tires. I would think this would focus the weight onto a smaller cross-section of the wheel. As Tom pointed out, tire size will have no effect on torque.
    This seems to be intuitively wrong, but intuition and physics don't ever seem to get you to the same place.
    Bumps, potholes, etc are the major source of stress on a wheel. If us clydes only rode on perfect tarmac, we wouldn't need very strong wheels at all. When we nail a pothole, the stress on the wheel is far higher than that sustained by just our body weight. If I could ride on perfect pavement, I'd be able to get away with 18 spoke weight weenie wheels, instead of 36 spoke 3X Deep Vs.
    Ride a bike. It makes your legs stringy, and less tasty to our Kanamit friends.[SIGPIC][/SIGPIC]

  10. #10
    Senior Member
    Join Date
    Feb 2007
    Posts
    298
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It would mean that the stress cycle of the spokes is increased by a higher pressure tire but I would doubt that it actually makes that much difference.

    The bike you referenced (Rush Hour) appears to use an Alex DC19 rim. If that is the case then it is a pretty narrow rim and unlikely to take a very wide tire in the first place (rims have max tire widths, you could research it on Sheldon Browns site) so it is probably a moot point to suggest a bigger tire.
    The rim itself is described as an economy rim, which does not necessarily mean it is weak but there are no doubt stronger ones out there. It is also listed as 32 spoke, all other things being equal a 36 spoke would be stronger but that would mean replacing the hub and rim as well.

    If I am looking at the right bike it is a single speed with a 48/15 or 48/16 gear ratio so torque is certainly not going to be an issue as a teenager in the granny gear combo on his mountain bike will generate way more torque at the rear wheel.

    If I were having the same issues I would take the wheel into a shop and have them relace it with new spokes. My favourite shop charges 35.00 for this.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •