Bicycle Mechanics - Bent axle

I've had this problem twice now and I'm actually not too concerned as to fixing it as I have a new (much better) wheelset on it's way right now, but I'm curious as to what did this.

My bike (was) a stock Raleigh 2.0 2006 mountain bike with pretty cheap parts all around, I'm not complaining as I got it new for $10 as part of a Dominos promotion. I noticed a problem a few months ago of the back wheel being slightly loose (like the ball bearing raceway nuts weren't close enough together) and eventually it became enough of a burden on my riding that I decided to fix it. I found upon dissasembling it that the axle had actually broken, bending the skewer with it, grinding down a spacer, and pitting a raceway.

I headed over to my LBS and got a replacement axle and raceway and bought a new skewer and reassembled it. While it may be partly due to my inexperience in reassembly, I think I did a fairly good job and the wheel was spinning properly and I installed it back on the bike.

Fast forward to my ride home tonight, where I feel my rear wheel suddenly get wobbly, I got off and checked it a few times but ended up just riding home on it. When I dissasembled it at night, the new axle (less than a week old, maybe 20-30 miles on it) was bent in a slight bow shape and the new skewer was a little off as well. The wobbling had been because one raceway was loose and backed out, but I can't help but suspect it was because of the bent axle anyways.

As I mentioned, this doesn't bother me.... it's a learning experience and I decided to upgrade my wheels and drivetrain completely only a night ago, so much better quality replacement parts are already on their way, but I am curious as to why the axle bent so quickly.

I am borderline clyde (just a tad over 200 lbs) and carry groceries/gear on my back (maybe up to 30 lbs) pretty regularly, but this is a mountain bike and I've never had problems with the tires or rims. I suspect that there may be a ball bearing missing from each side of the rear hub, which could do it I suppose, but it did not give me noise/stability problems early in the installation. I also do mostly street/light trail riding so I doubt it's due to pressure from jumping (which i don't usually do) or otherwise.

So any guess of what killed my axles?

The bent hub youre riding on.

quick release not tight enough.

a combination of both.

Your bike most like has a Free Wheel vs a Free Hub.
The way the Drive Side bearings are set up, (basically under the largest cog) is that they are located located quite far from that dropout and takes the brunt of any pot holes etc.
Look at thi link-
http://sheldonbrown.com/k7.html#advantages

Another caveat-
When tightening the skewer, the axle is actually compressed slightly which removes play from the bearings. You actually have to set them a hair loose so they have the proper clearence when the skewer is tightened. That's basically a trial & error process to learn how much looser. IF they are too tihjt, that can damage the parts also as far as cones & races.

Yeah, this old one is a freewheel and because of the problems i've had with the hub before (and because it ran some time on the broken axle) I can only assume the hub did most of the damage to the axle.


I at least think my skewers were tight enough (using locking ones tightened with a hex key).

I had the same problem with a mountain bike in the 80s. Freewheel. Must have broken that axle 3 or 4 times. With a 155 pound rider on it. It has never happened to me with a modern type hub.

You could try to find a solid axle with the same threading as your current, and nut it. That would give you a bit more strength .

Well it's good to know I probably won't have the same problem with my new hubs, got a Deore 530 freehub to replace it and a matching front hub. Nothing too fancy but definitely a step up from these 'Joytech' ones... which still managed to give me about 1500 miles.

When an axle bends the dropouts at the rear of the frame bend with it. If you change to a new axle without correcting the alignment of the dropouts the frame will not offer enough support, and may even encourage the new axle to bend. THere are two ways to check the alignment of your dropouts - the easiest is to bring it to a bike shop that has the proper tools (dropout alignment cups) and pay them $10 to chek it.

You can also get a good idea of dropout alignment at home using a pair of large screwdrivers (as long as the bottom of the handle of the screwdrivers is relatively flat)... insert a screwdriver through the dropouts on each side (pointing toward the centre of the frame) and press the flat bottom of the handle against the dropout so the shanks of the screwdrivers are exactly perpendicular to the faces of the dropouts. If the screwdriver shanks are perfectly parallel with eachother then the dropouts are aligned. If the screwdriver shanks are at some angle to eachother enough that you can see it by eye, then the dropouts are misiligned.

I thought some damage pics were in order, first off, the original axle (I knew something was wrong.....)

http://www.medpants.com/BFN/HalfAxle.jpg


Then a further sign of long-term damage in the freewheel:

http://www.medpants.com/BFN/FreewheelInside.jpg
(note the color of the grease :D)

And finally, something I've never seen before.... after removing the second axle to see what was going on in there:

http://www.medpants.com/BFN/HalfBearing.jpg
(and it's pitted!)

Over at www.cyclingforums.com (http://www.cyclingforums.com) there's a thread about a guy who found a cartridge bearing that was a nice press fit against the splined inside face of a freewheel and the axle. He claimed it increased support and lead to improved axle life.

...You can also get a good idea of dropout alignment at home using a pair of large screwdrivers (as long as the bottom of the handle of the screwdrivers is relatively flat)...

Another way is to use the two fragments of the broken axle as your measuring tool. Back the locknuts far enough off each cone that the dropout will pass between cone and locknut. Insert each axle fragment into its dropout with the broken ends pointing at each other. Adjust the cones so that the broken ends approach each other but don't quite touch. Make sure that both axle fragments are seated in the dropouts as if there was an actual wheel in there. Snug the locknuts against the dropout to lock the axle fragments in position. Now sight from above, behind and from each side to see if the axle fragments are out of alignment in any plane. If they are, one or both dropouts is bent. If they are perfect, you should be able to sight through the hole in one axle fragment and see clear out the other one.

(Don't worry about the "bent" axle giving false information. The axle wasn't actually bent into a curve. What actually happens is the axle cracks from the bending stresses and then breaks in two. If you happen to remove a cracked axle from a hub before it actually breaks, it will appear bent, but it's only bent at the crack. The two pieces on either side of the crack are still straight.)

Is that half of a ball bearing? I didn't know that was possible?,,,,BD

Somewhat surprised to learn that freewheels were still in use on a 2006 name-brand bike. Are freewheels still found on low-end Raleighs, etc.?

Is that half of a ball bearing? I didn't know that was possible?,,,,BD

It is indeed possible. One of the more pressing issues that got me into doing my own wrenching was when the LBS overtorqued a BB to the point where several bearings cracked in two. On the same bike he'd also cracked the old freehub body by trying to remove the smallest sprocket the wrong way.

That's an amazing photo. I excavated egg-shaped balls from the stoker bottom bracket on our tandem once, and it had been meticulously maintained and adjusted until it got really rough on a tour in Austria. So all you single-bike cyclists, no more of that "She's not pedalling!" stuff when we pass you, OK? :-D

Somewhat surprised to learn that freewheels were still in use on a 2006 name-brand bike. Are freewheels still found on low-end Raleighs, etc.?

1) Raleigh is not a name brand
2) Plenty of low end NEW bikes come with freewheels. Plenty.

s when the LBS overtorqued a BB to the point where several bearings cracked in two. .

I have a ridiculosly hard time believing anyone can tighten a bb enough to start cracking bearings. You'd have to be using a meter long pipe on a tool that does not slip. And even though i'm not convinced you'd crack bearings. Sounds like one of those headset overtightned leading to brinneling type bogus stories.

1) Raleigh is not a name brand
2) Plenty of low end NEW bikes come with freewheels. Plenty.

Lots of bikes at Wal-Mart and in bike shops, too, apparently.

Name Brand - a well-known brand or trademark (Webster's New World College Dictionary)

Raleigh is a name brand...

Name Brand - a well-known brand or trademark (Webster's New World College Dictionary)

Raleigh is a name brand...

Yes let's just pretend context is meaningless. Learn to read and comprehend please mr. dictionary before attempting to tell someone they are wrong.

I understand the elitist meaning... and the context.

But on the low end raleigh certainly isn't known for their quality. If you go to a 4.0-8.0, the parts actually seem pretty decent, but that wasn't an option when I basically got it for free :p

As for the bent axle, the second axle I put in (not pictured) was the bent one, and I will look closely for cracks, but it's a nice mild bow shape.



As for the BB, my hunch is that the raceway was not full enough, I put the BBs in and lubed them, careful to not knock any out, I noticed there was some extra space, probably enough for another. I later found one lying on the floor and tested the wheel, but I didn't notice any extra noise or instability so I just used it. Not having enough and having a damaged freewheel probably worked together to fracture the (already somewhat worn) BB.


Oh well, it was a hasty fix based on incomplete information when I knew less about how it all worked... and it came out with an interesting few pictures. I decided shortly after this to rebuild my drivetrain and get some new wheels, so after another tool arrives, I'll have much better components (including a deore freehub) and hopefully won't run into this again :D