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Old 08-13-13, 09:47 PM   #1
dilkes
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Stress on rear wheel - spokes

I have an Aerostream GT Cruiser bike with a kit I installed from e-bikekit.com. It's a front geared 350watt motor and I drive it with a 10ah 48V LiFePO4 pack mounted on the rear rack. The bike also has internal 3-speed gears in the rear hub. The 700C wheels on the bike have 14 gauge stainless steel spokes on the rear, and the replaced front wheel with the motor came from e-bikekit.com with beefier 12 gauge spokes.

I'm finding I'm breaking spokes on the rear wheel more often than I would like. Could be because of: more weight on rear wheel (battery); generally driving faster and braking more; other? I myself am no lightweight at 240 as well.

Trying to figure out likely cause and possible solutions:
  • just replace spokes as they break?
  • re-lace whole wheel with thicker gauge spokes like are on front wheel (not sure how practical this is)?
  • re-lace whole wheel with butted 14 gauge spokes?
Any experience or ideas? (other than go an a diet!!)
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Old 08-14-13, 05:50 AM   #2
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Originally Posted by dilkes View Post
I have an Aerostream GT Cruiser bike with a kit I installed from e-bikekit.com. It's a front geared 350watt motor and I drive it with a 10ah 48V LiFePO4 pack mounted on the rear rack. The bike also has internal 3-speed gears in the rear hub. The 700C wheels on the bike have 14 gauge stainless steel spokes on the rear, and the replaced front wheel with the motor came from e-bikekit.com with beefier 12 gauge spokes.

I'm finding I'm breaking spokes on the rear wheel more often than I would like. Could be because of: more weight on rear wheel (battery); generally driving faster and braking more; other? I myself am no lightweight at 240 as well.

Trying to figure out likely cause and possible solutions:
  • just replace spokes as they break?
  • re-lace whole wheel with thicker gauge spokes like are on front wheel (not sure how practical this is)?
  • re-lace whole wheel with butted 14 gauge spokes?
Any experience or ideas? (other than go an a diet!!)
After installing new wheel tighten spokes/true wheel after 50 miles or so. Dont hit curbs hard or go off them hard,
I broke spokes twice first 500 miles, then after making sure i tightened them @ proper interval havent broken any in 4200 miles.
Spend a hour watching youtube videos on truing wheels, I replaced the spokes myself & trued them if I can do it anyone can. After they are re-tightened & trued up rim the bike finds it's groove. I rarely even check mine now I'm over 200 lbs & my bike uses thin gauge spokes..The re-tightening after inital 50 { some people go 100 ** miles is the important step, like re torquing heads just milled & installed on an engine , has to be done.
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Old 08-14-13, 06:07 AM   #3
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I'm 6' @ 220# and have always been rough on rear spokes, so I carry zip-ties to hold broken spokes inplace and a nipple wrench to true the plot just to get home.
(after a second spoke breaks... I'd respoke the wheel... just me, YMMV)

Having built many sets of wheels over the years for self use only and having just bought a powerful ebike this rear spoke issue is on the brain.

For spokes, consider Sapim Strong. They are 2.3mm at the head. The hub holes might have to be opened up just a tad.
Shop well as prices vary... wheelbuilder offers single spoke in DT & Sapim.

If your rear wheel has alot of dish, consider a rim with O/C holes. DT and Velocity offer such.
Or consider a rim that can take high spoke tension. The Velocity Synergy O/C seems to not be strong enough for high tension.

Good luck Chubby!
I was 270# with 42" waist 4 years ago.
Fact: Fat people do not age well, by this time next year my goal is 195#.
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Old 08-14-13, 08:48 AM   #4
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Yes, Re-tighten all the spokes after 50 - 100 miles... I also over tighten mine "just a little bit" and that seems to have stopped my spoke breakage for almost 1,000 miles now...
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Old 08-14-13, 10:55 AM   #5
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Spokes and hubs can take a lot of tension, it is the rim hole that will bend & crack.
Search for rim issues with your type of rim OP.

I've tensioned good double butted spokes to cracking a light Mavic rim.
Then I loosened all the front spokes 1.5 turn and ran that front on a pedal only bike.
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Old 08-15-13, 07:56 PM   #6
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Lightbulb

I got tired of spokes breaking, so I went "whole hog" on a solution.
I felt the spoke flange was too thin.
Which stressed the elbow.
First I added 12g spokes. (redrilled flange with 1/8" bit)
Flange still appeared too thin.
So, I added #4 sae washers that pulled the elbows tight to the flange.




With the spoke "enarmored" as best as I could devise, I felt the wheel might not measure up.
So I drilled wheel at 3/16" wrapped it with a couple layers of duct tape and reinforced with #10 sae washers.



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Old 08-15-13, 08:56 PM   #7
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Originally Posted by DrkAngel View Post
I got tired of spokes breaking, so I went "whole hog" on a solution.
I felt the spoke flange was too thin.
Which stressed the elbow.
First I added 12g spokes. (redrilled flange with 1/8" bit)
Flange still appeared too thin.
So, I added #4 sae washers that pulled the elbows tight to the flange.

With the spoke "enarmored" as best as I could devise, I felt the wheel might not measure up.
So I drilled wheel at 3/16" wrapped it with a couple layers of duct tape and reinforced with #10 sae washers.
Thanks for that and for the clear pictures. I have those 12 gauge spokes on my front wheel which has the hub motor and they are brutes. I am going to try and replace the two broken ones on the rear with the stock 14 gauge, check frequently for tension, and hope that works. If it doesn't, I may do something like you have done as well.

Thanks again!
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Old 08-15-13, 09:21 PM   #8
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Lightbulb

Stainless steel washers recommended.

12ga spokes do not flex.
After bending while trying to "lace" them.
I found it best to pre-position all spokes before inserting into rim, I laced and positioned using scotch tape at every crossing.

Pre-laced and taped 14g model.


Better picture showing washer advantage.



See original article - eZip Broken Spoke - Solution


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Last edited by DrkAngel; 08-16-13 at 06:29 AM.
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Old 08-16-13, 07:24 AM   #9
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Interesting solution.

Keep in mind that those spokes are always in tension, never in compression. So, I don’t see any advantage to the work you did on the wheel. Did you have problems on that side of the spoke? You don’t have them pull through do you?

Dilkes – you didn’t say how your spokes broke? Mine usually break at the elbows at the hub, as a result of abuse or improper maintenance. How many spokes do you have on your wheel? If the spokes are kept properly tensioned, they shouldn’t flex that much at the elbow. 36 strong spokes is a good way to go though.

Once you have 2-3 spokes break, the odds are that the wear is on all of them and relacing is a good option. However if your wheel doesn’t get too out of true with a broken spoke, you can just replace them one by one if you want. That works better if you have 36 spokes vs 24 spokes (where breaking one spoke is going to but a major warp in the wheel.
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Old 08-16-13, 12:25 PM   #10
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Spokes break at elbow.
No support near the elbow places a leveraged stress at the elbow.
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Old 08-16-13, 01:10 PM   #11
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Dilkes – you didn’t say how your spokes broke? Mine usually break at the elbows at the hub, as a result of abuse or improper maintenance. How many spokes do you have on your wheel? If the spokes are kept properly tensioned, they shouldn’t flex that much at the elbow. 36 strong spokes is a good way to go though.
I have 36 spokes and they break at the elbow. I am going to replace the current 2 broken and then check tension more frequently going forward. If I still have problems, then I will look at re-lacing, perhaps with butted spokes or thicker gauge. Thanks for all the guidance. Comforting? (or something like that) to know I'm not alone with this type of problem.
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Old 08-16-13, 01:42 PM   #12
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Spokes break at elbow.
No support near the elbow places a leveraged stress at the elbow.
Yep, that is why I find your solution so intriguing....
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Old 08-16-13, 01:44 PM   #13
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Yeah, if you have several that have broken, it sounds to me that they are all probably pretty worn due to age, wear, load, maintenance, etc.

With 36 spokes, you can probably ride fine with one missing. Its fairly easy to do one at a time (as long as there are not a lot of torque arms and stuff in the way), its just the ones behind the cog/freewheel that can be more of a pain.


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I have 36 spokes and they break at the elbow. I am going to replace the current 2 broken and then check tension more frequently going forward. If I still have problems, then I will look at re-lacing, perhaps with butted spokes or thicker gauge. Thanks for all the guidance. Comforting? (or something like that) to know I'm not alone with this type of problem.
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Old 08-17-13, 06:39 PM   #14
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Quote:
Originally Posted by chas58 View Post
Interesting solution.

Keep in mind that those spokes are always in tension, never in compression. So, I don’t see any advantage to the work you did on the wheel. Did you have problems on that side of the spoke? You don’t have them pull through do you?
If I was going to overbuild I was going to go whole hog.

Like when I built my own studded tires ... "go big or go home".

The HedgeHog


See - Making Your Own Studded Tyres


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Old 08-19-13, 08:32 AM   #15
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That is too cool.
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Old 09-03-13, 07:36 AM   #16
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All my spokes broke @ the nipple, so that tells me many variables for each case including wheel design, weight of rider, materials etc...

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