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igoslo
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Discussion Starter · #1 ·
I was just about finished with a short Thanksgiving day ride when I heard a massive KAH-THUNK! I knew it was not good and feared that it was a broken frame. Upon inspection I found this:



Lucky for me it was just a broken axle and I was only 100 yards from the parking lot. The kicker was that 3 miles earlier my rear tire was rubbing and I just assumed that the drive side dropout slid forward even though it had never given me problems before. I pulled the drive side tight and continued on my way oblivious to what was really going on.

Other than the breakdown it was a fantastic ride with perfect weather.



Looks like I'm off to the shop before I ride tomorrow, oh well, Haapy Thanksgiving all!
 

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Did that twice on a Paul Hub, but have so far been able to rebuild
 

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Misfit Psycles
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a broken bolt axle hmm...i have done a QR axle but never a bolt...

you are going to have to either ease up on the pedal power or use a weaker chain.
hercules, hercules!
 

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Am I getting too bulky?
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The Pauls have three piece aluminum axlers with steel ends. Not hard to believe the axle would be a bit of a week link.
 

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Bikehigh said:
The Pauls have three piece aluminum axlers with steel ends. Not hard to believe the axle would be a bit of a week link.
SoloRider's hub is not a Paul.

My Paul WORD hubs use one piece aluminum axles with axle bolts that thread into the axle. I find it very difficult to believe the axle itself would break. I have stripped the treads in an axle, I have cracked the brass end washers. Break the axle? No.
 

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igoslo
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Discussion Starter · #8 ·
The hub is the basic Kona singlespeed disc hub that came with my Unit, my chain is a Shadow Conspiricy Interlock, I climb hard, and I weight 240. Something was bound to break, guess the axle was going to be it. I'm currently looking for a spare rear wheel for next time.
 

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two ways to break it.

SoloRider said:
The hub is the basic Kona singlespeed disc hub that came with my Unit, my chain is a Shadow Conspiricy Interlock, I climb hard, and I weight 240. Something was bound to break, guess the axle was going to be it. I'm currently looking for a spare rear wheel for next time.
Braking hard will do the same, more likely since the brake has greater leverage at that point than the cog. Check the slider bolts on the brake side.
 

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That's gonna leave a mark
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pacman said:
Braking hard will do the same, more likely since the brake has greater leverage at that point than the cog. Check the slider bolts on the brake side.
I question that theory. All things being equal, the rotor would have a mechanical advantage over the cog. But in this case, things aren't exactly equal.

The amount of force that SoloRider can generate at the rear axle when pedaling out of the saddle is much greater than the force required to lock up the rear wheel when braking on the trail.

This is due to the fact that when mashing on the pedals his weight is closer to the rear axle for the necessary traction to propel him forward. However, when he is braking, his weight will naturally shift forward, resulting in less force required to lock up the rear wheel.

Even if he was a trail-abusing-skidder, which we can assume he isn't :) , the average number of times he would execute maximum braking on loose surfaces would be much lower than the monstrous pedal strokes he subjects his rig to when hammering up the climbs. Otherwise he wouldn't get nowhere.
 

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igoslo
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Discussion Starter · #13 ·
Upchuck said:
I question that theory. All things being equal, the rotor would have a mechanical advantage over the cog. But in this case, things aren't exactly equal.

The amount of force that SoloRider can generate at the rear axle when pedaling out of the saddle is much greater than the force required to lock up the rear wheel when braking on the trail.

This is due to the fact that when mashing on the pedals his weight is closer to the rear axle for the necessary traction to propel him forward. However, when he is braking, his weight will naturally shift forward, resulting in less force required to lock up the rear wheel.

Even if he was a trail-abusing-skidder, which we can assume he isn't :) , the average number of times he would execute maximum braking on loose surfaces would be much lower than the monstrous pedal strokes he subjects his rig to when hammering up the climbs. Otherwise he wouldn't get nowhere.

Well put. Keep in mind that the axle broke on the drive side where pedaling forces are trying to put the hud forward. The rear brake may, in theroy, be able to exert the same kind of force, but when you hauling yourself down from speed the front brake is doing a lot more work than the rear ever will.
 

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give me a fulcrum and ---

SoloRider said:
Well put. Keep in mind that the axle broke on the drive side where pedaling forces are trying to put the hud forward. The rear brake may, in theroy, be able to exert the same kind of force, but when you hauling yourself down from speed the front brake is doing a lot more work than the rear ever will.
When the wheel slips the drive side moving forward and the disc side moving back look the same, you have to check both sides.

The rear brake may exert the same force (pulling back) but it has much more than ten times the leverage of the cog at the breaking point - it's sitting way out on the end of a lever arm and snapping the axle near the bearing nut. Cog lever arm = 2mm, brake lever arm > 100mm.
Scenario - grab the rear brake as you land from a rock - snap.

The Kona comes with a hollow axle, get a solid one that doesn't fold and then break when flexed. It's strong enough when supported at the ends but not strong enough when bent like a bow.
 

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That's gonna leave a mark
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pacman said:
When the wheel slips the drive side moving forward and the disc side moving back look the same, you have to check both sides.

The rear brake may exert the same force (pulling back) but it has much more than ten times the leverage of the cog at the breaking point - it's sitting way out on the end of a lever arm and snapping the axle near the bearing nut. Cog lever arm = 2mm, brake lever arm > 100mm.
Scenario - grab the rear brake as you land from a rock - snap.

The Kona comes with a hollow axle, get a solid one that doesn't fold and then break when flexed. It's strong enough when supported at the ends but not strong enough when bent like a bow.
Boy, that sounds like a lot of "if's"...
2mm vs. 100mm? What size rear cog you running these days, a 4 tooth cog? :p

Again, it isn't how much leverage is available for braking. It's the amount required to stop the rear wheel from rotating. That's a huge difference. Unless, of course, you're in the habit of grabbing the rear brake after hucking off a 3 footer. But something tells me that this 240 lb guy probably isn't doing a lot of that on his Kona Unit SS.

Look at it this way, there's probably plenty of riders out there braking hard on their Kona Unit. I doubt there's many axle failures as a result. However, there aren't that many 240 lb Unit riders mashing up the climbs. And when we find them, we best get the he11 out of the way!
 
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