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Cracked locknuts

Old 12-15-16, 08:12 PM
  #1  
randomgear
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Cracked locknuts

Just got done putting on the studded tires for winter, and found my rear hub had two cracked and broken locknuts. The first fell off as I removed the rear wheel and the second when I tried to adjust the locknuts.

The hub in question is a Surley new hub, fixed/free that I've built up about five years ago and haven't had any problems with until now. Thankfully, I had an old Surley hub from a deceased wheel that provided matching donor locknuts, so I didn't have to play musical LBS's this afternoon in the increasingly cold and windy arctic air.

My suspicion is that I have repeatedly over tightened the rear wheel axle nuts when replacing the rear wheel that I run as a fixed gear- in the past I have had slippage issues in the horizontal dropouts and besides making sure that the dropout and serrated washer faces are degreased, I snug the axle nuts up with a 9" breaker bar rather tightly. While they the faces look dirty, I haven't removed the rear wheel since last spring.

Anyone have other thoughts?



PS, No jokes about the Rat King, please.
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Old 12-15-16, 09:02 PM
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Well looking at the fracture faces you can see the locknuts had been cracked for a while, note the clean (fresh crack) and dirty (old) face areas. This isn't unique to a fixed gear bike but your scenario seems likely. Do you have wheel brakes on the bike? I find those fixed gear bikes that do tend to see less wheel slippage then those where hop skidding or using the legs to stop/slow you down do. Remember that fixed gear equipment these days are derived from track racing. On the track if you slow quickly or stop you loose. So the equipment capacity didn't need to tolerate sudden stops. But these days with this equipment being used on the road the forces are greater. It's not about how strong the rider is. The rider can't offer the bike the same force when accelerating as when skid stopping, and just about any one can learn to skid a fixed bike.


Simple solution is to replace the lock nuts and monitor things more often (then every 5 years). Andy
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Old 12-15-16, 09:05 PM
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Lucky you found it during maintenance and not during a ride. You might want to post this in the fixed gear forum.

I have stamped dropouts on a Bianchi Pista. They are thin relative to forged dropouts. Wabi Sub 15 wheels would slip until I installed the Wabi dropout protectors.

Rear Drop Out Protectors - Wabi Cycles

Do you curb hop or skid stop?


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Old 12-15-16, 09:09 PM
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Tim brings out a good possibility that the drop outs have become cupped or bent so that the faces that the axle and nuts bare against are no longer flat. If the cupping is inward this could easily add the lock nuts' stresses. Andy.
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Old 12-15-16, 11:19 PM
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Thanks guys. I'll check the dropouts for warping tomorrow.

The ND side was broken and fell off when I removed the wheel, suspect it was held in place firmly by compression. The other broke after trying to break it free from the axle; it would have been an unpleasant walk home if I did it on the side of the road.

I have canti brakes that I use for stopping, but I do tend to resist the pedals from time to time when slowing. I frequently curb hop, not sure if it really did much to contribute to this failure.

I do clean the hubs, wheels and tires every spring and fall when I switch from regular tires to studded and back again. To be fair I just give them a cleaning with 409, an old toothbrush, paper towels then I run a sanding block over the rims braking surfaces. I find that cleaning them with 409 will cause my brakes to squeal unless I clean whatever residue it leaves behind. Never thought of breaking out a magnifying glass to examine parts more closely.

Last edited by randomgear; 12-15-16 at 11:25 PM.
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Old 12-15-16, 11:25 PM
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And one would hope that a magnifying glass wouldn't be needed during periodic servicing...


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I agree with some cleaning solutions leaving residue behind. Andy
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Old 12-15-16, 11:39 PM
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Originally Posted by randomgear View Post

The hub in question is a Surley new hub, fixed/free that I've built up about five years ago and haven't had any problems with until now.

Anyone have other thoughts?
Buy Japanese or Taiwanese, they make the best stuff now, have been for decades actually.
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Old 12-18-16, 12:04 PM
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Not speaking as a bike expert (I know nothing about fixies) but as an engineer, since the cracks run along a diameter of the circle it seems obvious there is less support along that line. Could you place a large flat washer over the top of these lock nuts before applying the final nut to spread the load?

edit: Or a larger final locking nut with more surface area?

Last edited by jrbz; 12-18-16 at 12:11 PM.
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