Bicycle Mechanics - Spokes on road bike breaks once a year

Every so often i get a spoke on my rear wheel of my road bike, breaking, for no reason
i always check my spokes before and after a ride,
usually the spoke breaks when i least expect it

what are causes of a spoke breaking?

wheel is properly trued

If they break at the head,they are too loose......if they break under the threads,they are too tight.....if the break in the middle,you need better spokes.

If they are straight pull bladed spokes,I have no idea.

wheel is properly trued

Trued wheels and properly tensioned spokes are different things.

Measure your spoke tensions. You say, you don't have a tensiometer? Shame!

Absolute tensions are important, but not as important as relative tension. Pluck spokes on one side of the wheel and see how even the tone sounds as you go around. They should all be the same tone, especially the drive side. Non-drive side will be a lower tone, and usually more variable.

Are you breaking drive-side spokes or non-drive-side?

Measure your spoke tensions. You say, you don't have a tensiometer? Shame!

You say you can't tension a wheel without a tensiometer, and you want every cyclist with spoke probs to buy one? Shame!

1. If they break at the heads/elbows:

- MAJOR = The wheels has been slightly or considerably under-tensioned from the start.
- MINOR = The lacing has machine lacing, outside pulling one side, inside pulling on the other side. Spokes move more also pulling rim to one side cyclically changing the head/elbow angle.

2. If they are breaking at the rim hole along with nipple barrel and head separation:

- Spokes are too short.

3. If they are breaking at the nipple insertion point and threads:

- These are 1.8 / 15g spokes - it does happen. Thread valleys are themselves a stress riser - the smaller the diameter - the greater the impact.
- More pressure was applied than needed between the dies of spoke thread rolling machine - prematurely introducing fatigue in the spoke.
- The angle at which the spoke enters the nipple is too great - turning the nipple edge into a stress riser.

4. If they are breaking mid-span:

- Cheap stainless steel was used - rust set in where impurities in the stainless steel existed.
- Physical damage led to it - i.e., dropped chain.
- Bicycle left in very corrosive environment, pool service room, beach front patio, etc. Much more than the wheel would be affected though...
- Previous builder experienced wind-up - and didn't use a "twist-resist" tool to counter it.

If several spokes have already broken over the past year - consider a rebuild with new spokes via a wheel builder who properly tensions and stress relieves the wheel.

=8-)

In my experience, (which is considerable) the most significant causes of spoke breakage are, failure to properly set or relieve the bend at the elbow, combined with a poor fit at the flange, and the use of plain gauge vs. butted spokes. There are other factors as well, but these IME are the most consistent.

There's lots of voodoo in wheelbuilding practice, so, especially regarding tension, too loose? too tight? too uneven?, maybe some of each or none of the above. The fact is that most halfway decent wheelbuilders address the relieving at the elbow, when they build, and so end up with decent wheels who's spokes don't fatigue as quickly. They also get the rest right so they can credit anything they want and be right.

Elbow breakage is caused by metal fatigue, so whatever is done to address that will build a more durable wheel.

Note, that spoke breakage is sort of like making popcorn. there are variations in spokes, so first one will break, then later another, then thre time between shortens until you come to a period where breakage is almost an everyday thing. OTOH, after a while the process slows, as the last holdouts (if you have the patience to take it this far) may outlast some of the replacements.

My rule is the 1st broken spoke is a fluke. the second a warning of things to come, and the third, or 4th time to rebuild depencing on if I see the shortening of the interval.

If you're breaking one a year, and it's still only one a year, it's a tossup whether to replace and true, or rebuild.

1. If they break at the heads/elbows:

- MAJOR = The wheels has been slightly or considerably under-tensioned from the start.
- MINOR = The lacing has machine lacing, outside pulling one side, inside pulling on the other side. Spokes move more also pulling rim to one side cyclically changing the head/elbow angle.


More likely is that no one stress relieved the spokes, parts of the elbow had high residual stress in areas that were not taken past its elastic limit, and that radically reduced the number of fatigue cycles they can survive.

More likely is that no one stress relieved the spokes, parts of the elbow had high residual stress in areas that were not taken past its elastic limit, and that radically reduced the number of fatigue cycles they can survive.

...didn't leave it out. Read the last part of my post...

=8-)

Not enough info. How many spokes and what size are they? How much do you and the bike weigh?

I was breaking a $7 bladed spoke monthly on brand new Shimano RS10s (20 spoke wheels, 200lb rider). After the third, I called it quits and got some Mavic Open Pros. No spokes broken, years later.