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I bought a second hand bike a few weeks ago.. sadly the rear wheel axle broke. I want to replace it, but since the bike is a little old (maybe 30 years old. it's a monark, a swedish known brand) I'm not sure if that's possible. Also, I've never done this before, so it's not very obvious what should be done.

Since I moved here a month and a half ago and don't really have any available tools.. can I get away with only a wrench and/or a cone wrench? what else is needed? I bought a new axle from a shady shop where the dude told me that if it doesn't fit he can exchange it for something else.. but I'm not very confident about this.

here are some pics: enter image description here

enter image description here

What do you think? Thanks!

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    See if the nuts from the old axle thread onto the new one OK. If not then you likely have the wrong axle, otherwise it should work fine. It's tricky installing the axle without removing the freewheel, but it can be made to work with a little planning and measurement. You have to install the cone and spacer on the spacer end and lock them together before inserting and installing the other cone. – Daniel R Hicks Apr 3 '17 at 0:40
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    (If the old nuts don't fit the new axle, take it back and get one that matches, taking the old axle and nuts with you to match. The bike is not that old/weird that you shouldn't be able to find the right axle.) – Daniel R Hicks Apr 3 '17 at 0:42
  • I'll note that there is an obvious difference between the old and new cones in the picture. The old one is larger and appears to have a larger "radius" to the curve where the bearings fit, indicating that the ball bearings are larger. If you put the new cone in there it's apt to cause the bearings to fail. But it may be the bearings have already failed -- the upper cone looks like it may be pitted or "spalled", and this could be associated with bearing failure. – Daniel R Hicks Apr 3 '17 at 12:24
  • Additionally, bearing failure is a likely cause of the axle failure. So the "cups" inside the hub must be inspected and at least cleaned. You will need to remove the freewheel. (And if the cups are gone so is the hub, and you might as well just buy a new wheel.) – Daniel R Hicks Apr 3 '17 at 12:25
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Generally speaking, you'll need to remove the cassette/freewheel/block in order to get access to both sides of the wheel.

Your photo shows no bearings - its not impossible they're still in the wheel?

Suggestion - Clean the whole wheel first. Dirty stuff makes any job harder. That rim looks pretty bad.

There's a good chance you can transfer most of the nuts and spacers over, keeping the same order as in your photo. Depending on wear of the cone's bearing surface, you might use the new or old one.

Clean out all the old grease/lube from the wheel's bearing races (the cups) Use a solvent and those paper towels to make it clean.

Then put in some grease, and use it as a "mortar" to hold the bearings in place around the raceway.

Tools You need a cone spanner and a regular spanner, to tighten the cone against the locknut and hold it in position. You will require grease for the bearings, and its always a good idea to fit new bearings while its all open. The old ones might look okay but bearings are real cheap, $3-$10 a wheel.

Endgame is to have your hub assembled like this: - yours is 99% a freehub so will look like the lower photo.

enter image description here

Your axle broke because of the loading - notice how the ball bearings (red) are not very far out-board on the freewheel compared to the freehub? This means the axle is under a continual bending stress near where it fractured. There's a chance your new axle will do the same over time, which is why freewheel designs are relegated to the cheap end nowdays and are gone from most bikes.

Still it'll be totally rideable with a new axle.

  • Don'tcha hate it when you write up a longer detailed answer then forget to submit it for 8+ hours ? – Criggie Apr 3 '17 at 6:04
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If you managed to remove the broken half of the axle from freewheel side without removing the freewheel, you should be able to insert the new axle too. Just remove everything from non-drive side, add the cone, spacer and locknut from the old axle, tighten the locknut and insert it from drive side. After that you can add the non-drive side cone and locknut and adjust the bearings.

  • I see. It seems pretty straight forward. The problem is that neither the diameter is the same nor the pitch.. I'm guessing the new cones will not fit? – arupaka Apr 2 '17 at 21:30
  • Its often possible to reuse the original cones on the new axle. (Although from the picture they may not be in great condition). – mattnz Apr 3 '17 at 0:13
  • It's not really visible in the picture, but if the thread is different the axle is no match. – ojs Apr 3 '17 at 16:14
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Doing the swap without taking the freewheel off here is a little bit of a ship-in-a-bottle type endeavor. It is technically possible but it's going to make everything about this a lot more difficult. So I would add a freewheel removal tool to your list. Also if you like working on bikes, I can't help but recommend buying a basic vernier caliper and a thread pitch gauge so you can identify the axle. They're just plain good tools to have in the arsenal. Alternatively, take the axle to a proper bike shop that can use their caliper and thread pitch gauge to let you know what axle thread it is in 10 seconds.

Beyond that you need a cone wrench for the cone size and some kind of wrench that goes on the locknuts, and that's it for required tools. You need grease for the bearings and the threads. Other useful tools are a rag, a pokey thing for pushing bearings around, and a light for making sure none are stuck floating around in the middle of the hub shell.

The actual procedure goes like this: clean everything, measure the frame spacing and your new axle, do the math to figure out how much axle is going to be protruding past the locknut surface on each side of your new axle, set up all the right side axle hardware as such and torque it down so the right side is ready to go, lay down a moderately thick bead of grease in the cups, plop the bearings in, put the right side of the axle through and very carefully keep holding it there in a manner where none of your motions can displace the left side bearings, gently thread down the left cone again making sure that when it's all closed up you know that all the bearings are in place, adjust the hub and re-install the freewheel.

The default approach is to re-use the cones if possible, although judging from the picture yours might be trashed, as cones that come along with broken axles usually are. Cones are tricky because tons and tons of different variations have been made over the years and there is no such thing as a generic replacement, despite some axle sets presenting themselves as such. If you must replace them, you're looking for the race to have the same profile and the outside diameter to be the same. Finding good replacements for random old cones is often impractical. If you google around enough you can find a legal downloadable pdf of an old edition but still pertinent Barnett's Manual chapter on the subject; it's kind of a whole subject in and of itself so it's a little much to go into here.

Getting a whole new wheel may be by far the most practical thing.

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