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So I'm fairly new to cycling. I have a gravel bike and the rear wheel spokes keep breaking. I wanna get something more reliable. The wheelset I have now is 700c. Would I be able to use 29er mtb wheels on this type of bike(I would think they would be stronger)? I think I can put up to a 700x 40 tire in the space. Thanks I appreciate it. Finding a wheelset is overwhelming to me.

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    What kind of brakes do you have? If you have rim brakes it's impractical to change rim diameter. (And if spokes are breaking it may be you just need stronger spokes.) Apr 23, 2021 at 1:45
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    For once, I think the Juhist solution of higher spoke count would help here. How much do you weigh and how many spokes do you have?
    – MaplePanda
    Apr 23, 2021 at 4:14
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    700c and 29er are both names for same 622mm diameter.
    – ojs
    Apr 23, 2021 at 11:49

2 Answers 2

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There may be no need to replace your wheels - wheels are expensive.

Before dropping money on the problem, start off by checking the spoke tension. Spokes can break because they're too tight or too loose, and loose is far more common than too tight.

If you tap the spokes lightly with a hard plastic or a metal item, you get a sound. Very approximately you want a sound that is lower than a guitar-string TING and higher than a dull thud

Another gauging method is to squeeze two crossing spokes together with your hands. They should deflect with some effort, not be floppy while not being bow-taut.
You can calibrate your fingers approximately by checking the spoke tension on a bunch of other bikes.


Yes, you could put 29" MTB wheels in place assuming the OLD of the axle is the same, and the brakes match (likely disk brakes on both) and they were affordable.

Both use "622mm" tyres, when using the ETRTO measurement system. However the rim's internal width will suit a range of tyre sizes.

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    If it keeps breaking spokes, the chances are many of the original spokes have been stressed and may still break soon even if the wheel is retensioned. That's not to say don't try it, but that it might not be enough
    – Chris H
    Apr 23, 2021 at 8:19
  • Also, the OP should note that many current MTB wheels are built to Boost spacing with 148mm rears. Older MTB wheels are going to be 142mm rears, so that's likely fine. They will use a different rotor standard (6 bolt, whereas drop bar bikes will use center lock).
    – Weiwen Ng
    Apr 23, 2021 at 12:16
  • @WeiwenNg why would drop bar bikes require centerlock brake rotors? Also I did briefly mention OLD but that probably warrants an additional answer on that one point.
    – Criggie
    Apr 23, 2021 at 12:31
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    Drop bar bikes absolutely do not require center lock, it’s just that that’s become the de facto standard on drop bar bikes. The MTB world is still on 6 bolt. So, just to be clear, the OP could use any wheel with a 6 bolt rotor if they want, but they’d have to get 6 bolt rotors going forward.
    – Weiwen Ng
    Apr 23, 2021 at 12:57
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    I've recently been seeing more Centerlock on MTB wheels again (but I tend to be looking at 26ers).
    – Armand
    Apr 23, 2021 at 15:03
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I have a gravel bike and the rear wheel spokes keep breaking.

There can be a number of reasons why wheel spokes are breaking:

  • You have a high weight. The more the weight on the wheel, the greater the likelihood of spokes breaking
  • The spokes are all from the same set and have a manufacturing defect or are of poor quality
  • The spokes are straight gauge instead of being butted (ideally triple butted)
  • There are too few spokes -- 36 should be preferable for 622mm (28") wheels, 32 might be acceptable on 559mm (26") wheels especially if the wheels have low pressure tires
  • The spokes have not been stress relieved during building the wheel
  • The spoke tensions are not equal and high
  • The hub has a particularly high asymmetry -- most likely today on 130mm OLD 11-speed road bike rear hubs

First, assess the situation. Fixing an existing wheel (by stress relieving all spokes, replacing the ones that broke, and tightening them to a high and equal tension and truing the wheel) takes about 2 hours. If your time is valuable, you might want to use it effectively and build a high quality wheel from the scratch (takes about 3-4 hours) rather than trying to fix a low quality wheel such as one having poor spokes or too few spokes. But most existing wheels with enough many spokes can be fixed to reduce the rate of spoke breakages.

If you want to build a new high quality wheel, my advice is 36 triple butted stainless steel spokes, a rim having double eyelets and a hub having cup and cone bearings. You should tension the spokes to an equal and high tension, stress relieve them, and take into account spoke windup when turning the nipples with the spoke key.

If you want to fix the existing wheel, the way to go is to grasp four spokes all going in the same direction and squeeze tightly with your hands -- so tightly that it's practically impossible to do this properly without thick gloves or else your hands will hurt. Some spokes may break during this and if they break they need to be replaced. After all quadruplets (4 spokes each) have been stress relieved, you may begin to increase spoke tension to an acceptable level, equalize the spoke tensions and true and center the wheel. Each increase of spoke tension should be followed by a new round of stress relieving. If an otherwise true rim becomes slightly untrue after stress relieving, or if every event of truing the rim causes the rim to become untrue in some other location, it's a sign that the spoke tensions are too high. Back off the tension of all spokes and try again with a slightly lower spoke tension. A spoke tensiometer helps to achieve the correct tension: most rims have a specification of 1200 Newtons (about 120 kilograms of force).

The reason stress relieving works is that spokes are formed from a wire bent to a coil plastically (elastically bending it would be a major hazard as it could explosively unravel). The wire needs to be straightened to a straight line by bending it back plastically, and then the hook at the end of the spoke must be bent. Those bendings cause parts of the material to reach yield stress. A component with oscillating load at the yield stress doesn't last a long time; instead, it will fatigue. By grasping the spokes, the stress is increased above that of yield stress, relieving the stress and thus the spoke no longer operates at the yield stress. For a new wheel, the spokes won't break but for a wheel with history of spoke breakages, it's likely some existing spokes will break during this stress relieving. The ones that didn't break will be strengthened by stress relieving and will subsequently last a long time.

For more information, you can read the book The Bicycle Wheel written by Jobst Brandt. Unfortunately, Jobst Brandt is no longer among the living, but his book can still be purchased.

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