Went for a bike ride this morning. My wife has an older mtn bike. A few times during the ride, my wife's pedals would spin and the chain wasn't driving the wheel. A friend thought the chain was not tight down on the sprocket. I couldn't detect this. Is is possible that the ratcheting (?) mechanism that allows the sprockets to freewheel when coasting would fail to engage when she started pedaling? The problem occurred when she was transitioning from coasting to pedaling. When I spin the pedals backwards on her bike, the mechanism does not seem as smooth as on mine. I've never had a hub apart far enough to understand how that freewheeling mechanism works and whether it can fail, keeping the sprockets from connecting to the hub.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The freewheel mechanism uses pawls and a ratchet face. If you get enough dirt inside, the pawls can stick. It's not common, but I have seen it before.

Dismantling a freewheel mechanism is not for the feint-of-heart. In addition to the pawls, there are about a hundred tiny steel bearing balls. You also need special tools to do the job. You might not need special tools to remove the freewheel mechanism from the hub, depending on the brand and age - some use a special socket, others use a large hex key.

If you've never worked with one before, it might be a good idea to take it to a shop and have them install a new freewheel. Depending on the design, you might use your old sprockets.

What kind of hub is on the bike?

I would imagine that the freewheel mechanism is either gunked up or literally broken inside. It could also have rusted. If you're not good with bikes, just take it to a shop (if it is worth the money...maybe think about just buying a new bike), some of the older specialty tools are tough to come by. Immediately I am thinking of the freewheel tool on my '75 Viscount...normal Shimano freewheel from the pre-85 era, but the damn tool was almost impossible to find since they haven't used them in a while.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Did that Viscount have the cast aluminum fork?

Don't know what kind of hub it is. Bike is probably from the mid-80's. In playing with the freewheel in my hand, I think I can feel one place where it moves double the distance before catching. Not sure if this is the same place on every rotation or whether it just happens once in a while.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

It is unlikely to be broken teeth on the ratchet face. Much more likely that it is contaminated with dirt. Many freewheels aren't sealed very well.

It is either a freehub design, or not. This page http://www.sheldonbrown.com/k7.html shows images of both. Note the distinct bulge in the center section, where the freehub bolt threads into the hub. Freehubs are sealed better than the other design, but dirt can still get in. They're also a lot easier to replace, but you do have to service the wheel bearings at the same time.

I can't tell which it is. Not sure if the bike is worth repairing or not. It's a Ross Hi Tech 4130.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I'm not familiar with that model. If it only needs a freewheel mechanism, that won't cost a whole lot at a shop. If the bike has been neglected and needs maintenance, that of course subtracts from its current value.

If you take the bike to a shop, they will likely be able to easily identify what's there.

In playing around with it, I just realized that in addition to this slipping problem, the crank bearing is bad. So, it's not worth fixing I think. What kind of used mountain bike should I look for?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Perhaps it is a lost case, because the rest of the bearings are almost certainly due for service.

I have no clue about the market for used bikes these days. I haven't worked in a bike shop in quite a few years; that was a college and graduate school thing.

The problem when buying used is that you can only look at a small subset of bicycles for sale - those in your size. Brands don't matter very much, really. It might be a good idea to get a bit familiar with the various lines of parts grouppos, which tends to be a good indication of the quality of the machine. Unless it has nice parts, but is very heavy. I've seen good parts put on very cheap frames to make the things look better than they are.

What kind of riding does she do?

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You don't need a weatherman to know which way the wind blows - Robert A. Zimmerman

All good advice. But all very fixable. The rear hub can probably be replaced and the crank bearing are likely very serviceable. Cost to repair should be under $125. About an hour labor.

If looking for a newer bike consider one with a sealed crank bearing assembly (aka bottom bracket). These will be more inline with modern components.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Mostly bike trails around town with an occasional easy dirt trail. We rode to the dinosaur tracks in the Purgatoire River valley--about 7 miles of dirt/sand. Nothing really hard. But she definitely needs something other than an around-town bike.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

From what I can gather on the net, the bike is only worth about $25-$50 so it's not worth putting much into it.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Bike shops don't charge by the hour, but rather by the job.

Indeed, any bicycle can be saved if the frame is not damaged. But it probably should have a full overhaul service done. That will cost another hundred or so, but will also greatly extend the life of the bike.

It is probably not a bad idea to take it to a shop and ask for an estimate. Problems in the bottom bracket usually mean that its parts must be replaced anyway, and the shop would be happy to sell you a sealed unit instead of using the original parts - if one is available in the correct dimensions.