rmfnla

If you look at the 2nd photo that axle is way off center, leading me to think either bent axle or missing bearing balls.

Or is that just the camera angle..?

habilis

.

A bent axle is easy to diagnose, without even disassembling anything. Raise the rear wheel and spin it, looking directly down at the freewheel. If the freewheel wobbles rhythmically, the axle is bent. Recently saw this on a garage-sale bike.

CliffordK

Most freewheels will have a bit of a hop when coasting. Even some cassettes. It doesn't really mean anything.

A bent axle will be fixed in one location when bolted, or attached with the QR, and wouldn't give such a hop.

Did the garage sale wheel also wobble? How could the freewheel wobble without the wheel unless it is part of the freewheel, and not the hub?

On occasion, I've straightened bent axles on used MTBs.

FBinNY 

Sorry to blow your theory, but that's an incorrect diagnostic approach.

When either part of a bearing is misaligned it will manifest ONLY when the bad part is turning. A wheel will spin true on a bent axle (since the axle is static), whereas a bent axle will show wobble if/when it's the moving part.

Conversely, it you have an untrue wheel, or bent hub flange it'll manifest when the wheel spins, regardless of the condition of the axle. But if the axle is OK in a wobbly wheel, it's still spin true in your fingers.

The above statements become obvious if you just give yourself a moment to think about them.

BTW freewheel wobble is something entirely, and is normal. it's the result of threads not being perfectly concentric and axial on bith the hub and freewheel, which makes the freewheel's bearings not aligned with those of the hub, creating a wobble when the wheel spins. Note that despite the misalignment, the freewheel will spin true when the wheel is static.

habilis

Damn, Clifford and FBinNY, you have indeed torpedoed my theory clear out of the water. Upon reflection, since the axle (if bolted properly in the dropouts) doesn't turn, it won't impart a wobbling motion to anything. The garage sale bike was a low-end MTB that my son was thinking of buying. I spun the rear wheel looking for an out-of-true rim, but instead I noticed the dramatically wobbling freewheel and looked no further.

Not sure how it could be a normal condition, however. I've gone out to the garage and checked both of my geared bikes - no noticeable FW wobble when I spin the rear wheel backwards. I would have been dismayed if there had been. I guess a wobble might not affect power transmission or shifting, but it seems like a real quality control issue to me.

FBinNY 

You wouldn't see the freewheel wobble when the wheel spins backward because the freewheels motion hides it. However pick up the rear wheel and spin it forward at decent clip (coasting) and you'll see the characteristic freewheel dance.

CliffordK

Did your bikes have freewheels or freehubs/cassettes?

I think I've seen the "dance" with cassettes, but it is much less noticeable.

As FBinNY mentions, it is usually noticed when coasting. Spin the wheel forward, then stop pedalling.

In the case of the OP, if the axle is broken, it will just fall apart.

If it is bent, it may be difficult to diagnose because the bearings are so loose, so it would still need to be disassembled, then inspected. I like to just roll the axles on a flat surface like a thick piece of glass. If the axle is tight, one can often see the spindle wobble when turning.

habilis

Went back to the garage and tried the fast forward wheel spin, but couldn't make the FW spin unless I also rotated the pedals forward. When I did that, I really couldn't see a wobble on either bike (my Premio and my wife's Centurion). I then tried it on my son's Trek 800 mtb - same result. Am I doing something wrong?

FBinNY 

Yes,

from the prior post
......However pick up the rear wheel and spin it forward at decent clip (coasting).....

Look for wobble while COASTING

habilis

Okay, it's obvious that I'm misinterpreting something. I raised the bikes by their seat posts with my left hand. I spun the wheels fast with my right hand in a forward direction, simulating coasting. The FW didn't spin. Then, I repeated the forward spin by raising the bike with one hand and pedaling with the other hand. The FW spun, of course, but no apparent wobble. What am I missing? During actual on-the-bike coasting, the FW would also be stationary with respect to the ground, not rotating.

[Edit: The garage sale bike, a Diamondback, exhibited a pronounced FW wobble when the rear wheel was spun backwards.)

habilis

I got it! The FW doesn't ROTATE when the wheel is spun forward as in coasting, but I should expect it to wobble with respect to the wheel. In the case of my 3 bikes, I don't see the wobble, but 3 bikes do not a universe make.

FBinNY 

It can be subtle. what you're looking for. Watch the freewheel against a stationary frame of reference

hopwheels

Haha, you just described many of my weekend! LOL

habilis

Thanks for posting. The garage sale bike had a wobble that made me seasick. I guess it was just a pretty low-end bike.

PilgrimUK

That is what I am aiming for now. The price changed once he saw it...

Thanks. Highly likely to need it! I have already measured things and ordered a new axle, because...

When I looked at it properly, they were not rotating at the same angle. Although I have not stripped it yet, it must surely be the answer, very bent at least...

I did a test on it for about 100m coasting downhill as it is. When I pedaled and then let it coast, it did so with a lot of back end noise and looking down I could see the rear wheel turning left and right, stopped only by the frame...
If I lift the back end and rotate the wheel backwards, it basically grinds to a stop almost immediately (not a brake problem).
Should I order new bearing as well to save waiting to see if they are gone? (Cannot strip the bike for a few days).
Thanks again all.

habilis

Two things to consider:
1. It may be unwise to buy parts before disassembling and seeing exactly what's what.
2. Consider buying a whole wheel or even a wheelset on sale. Some months ago, I bought a new Weinmann wheelset on sale for $99. More recently, I bought another new Weinmann rear wheel on Ebay for $50. There are Ebay dealers who buy wholesale from manufacturers and sell the wheels without doing any of the truing and bearing adjustment that retailers normally do. You would still be getting a new item; you would just be doing the "setup" work.

fasdriah

They're finishing a major expansion and looking for a tag slogan for Facebook and such.

CliffordK

Have the bike shop remove the freewheel (if they haven't done it already). Or, buy the freewheel tool and a cone wrench (15mm???)

You probably will need new cones and bearings, and maybe an axle (often an axle will come with the cones as a set).

And some bicycle grease (although you may be able to just use regular shop grease).

However, you should take it apart and see what it looks like inside before buying a bunch of stuff. You may decide that it is so badly torn up that you don't wish to rebuild. Or, you may be surprised and find the overall condition is better than you expected.

But, I'm guessing you will need a bunch of 1/4" bearings (18 of them???) Get a whole set, and don't just replace some of the balls.

I think FBinNY suggested making a seal... I like to use stuff like lids from margarine containers, or various plastic can lids. Cut it to size to fit under the freewheel, with a hole just bigger than the cones.

PilgrimUK

Okay, I finally managed to strip everything down and get the back axle out. The wheel was a 9 1/4" bearings system. There were no bearings on one side at all, the other had the 9.
The tiny ball bearings from the freewheel cassette (had to take it off to help getting the axle off) were also only on one side (the side nearest the wheel), there were none on the other side. Apparently these tiny ones (not the 9 1/4") are supposed to be on both sides? Are there freewheel cassettes that only have these tiny ones on one side?
I have attached a few more photos...

Homebrew01

Spinning the wheel backwards is not good for much. If you are even moderately cross chained, you'll have the chain trying to derail to a center cog. Always spin the wheel forward.

habilis

Based on the photos, it's safe to say that you need, at the very least, a new rear hub. The inner bearing race visible in the first photo is damaged, as well as the threaded portion that receives the freewheel. If you bought just a suitable hub for your wheel, you could lace your rim and spokes onto it. I was in your position recently and faced the same decision: rebuild the wheel with a new hub or buy a new wheel. I priced the new hub and matching freewheel, and they came to about $40. I searched Ebay and found a new replacement wheel of decent quality, including freewheel, tire and tube, for $50, including shipping! Unless you really want the learning experience of building a wheel, I'd look for a complete replacement.

If you get a replacement wheel - either new or second hand - research how to grease and adjust the bearings and you can avoid future damage.