Kevin56

I've been having an issue with the cassette on my Trek skipping or suddenly spinning freely while riding recently. Took the wheel off and found that there's some play in it...and then there's not. Bike does okay for a day or so and then it starts skipping again. I've never taken the cassette off and don't have the tools to do so...but have repacked the bearings with grease. My question is what could cause this to happen? The mileage on the bike is between four and five thousand miles. Thanks.

Bill Kapaun

It sounds like the pawls in the free hub may be hanging up.
Possibly the grease is getting stiff in cooler temperatures?

Kevin56

Thanks for the info Bill. I guess I'll buy the tools and have a look at it.

pressed001

Are you sure it is the freewheel and not the chain/cassette? I used a really worn cassette a few weeks ago and it would so-to-say "skip" under a specific amount of load. Have you changed your chain and cassette regularly?

Kevin56

Haven't changed the chain or cassette yet but might do so over the winter. It seems to skip while in higher gears and the other night after coasting down a hill I started to pedal the upgrade and there was nothing...it just spun when I pedaled. I stopped and worked the pedal in both directions and it was okay again....at least long enough to make it home. I sure don't need that to happen in the middle of a busy intersection after the 'walk' light turns red.

cale

If it spun without engaging any pawls, this is serious and the maintenance shouldn't be neglected. That's no joke.

There's three pawls in a typical hub, if memory serves me, so you're shooting blanks on occasion. Missing on all cylinders, as it were.

Depending on the wheel, your freehub may be serviceable but not likely by a home wrench. (The hub and cassette carrier are typically joined with a great deal of torque.) Another option is a new wheelset.

Kimmo

Get the axle out of the hub, and spray WD40 into the gap between the bearing cup and the shell of the cassette body (you'll need to remove the dustcap).

Keep pumping it in there while spinning the shell; eventually it should come good. Spin it some more to help drain out the WD40, and chase it with some thick oil.

Jeff Wills

It hasn't been that cold in Massachusetts lately. I'm going to guess that the freehubs' ratcheting mechanism (aka cassette body) is damaged. I had one do as you describe on a summer tour in Canada. Once it started doing that, total failure happened within about 50 miles.

Replacing the cassette body is fairly advanced bicycle mechanicing. I've done it a few times, but your LBS might not have. It may be cheaper to simply buy a complete replacement wheel.

pressed001

When it is "spinning" and you're not going anywhere, does the chain and cassette spin too? Or does the chain just skip over the cassette teeth whilst the cassette is fixed?

I think @Jeff Wills is most likely correct here and that your cassette body is shot. I would do as he suggested and just go buy a new or used good condition rear wheel as replacement.

Tim_Iowa

If the freehub or freewheel pawls are broken/inoperable, the OP can replace the freehub or freewheel instead of the entire wheel.

Freehubs (cassette body) and freewheels are easy to replace and only require two tools: chain whip (can be made at home from spare chain) and the proper freehub/freewheel removal tool (there are many, but they're usually <$20). It's also a quick and easy job for a shop to do, and they'll have the correct tools.

nfmisso

IF it is a Shimano hub, the freehub is easy to replace, and readily available. If it is not Shimano - all bets are off.

For Shimano, after you have removed the cassette and axle, you only need a 10mm hex key and a LOT of torque. Replacement Shimano Freehubs start in the $20- range and go up - most, but NOT all are interchangeable.

Now if you have a FREEWHEEL, things are even easier; just replace the FREEWHEEL.

See Sheldon Brown's website for the difference between a cassette and a freewheel.

Always replace the chain when ever you replace the cassette or freewheel.

Matt Gaunt

Ish. If you look after your drivetrain, there is absolutely no need to replace the cassette every time you change chain. Of course, if you let the chain wear beyond, say 1.25% or 1.5% then sure, you probably will have issues. But if you're replacing at the sort of 0.75% mark every time, you'll get at least a couple or three chains out of a cassette.

Buy a chain wear checker and be surprised at how long your cassette will last.

nfmisso

Matt; please re-read what I wrote: replace the CHAIN whenever you replace the cassette or freewheel. I did NOT say replace the cassette whenever you replace the chain. I see no reason to waste money on a chain wear checker with any ruler or tape measure plus a tiny bit of math does the job.

Matt Gaunt

Yep. I mis-read that. Apologies, nfmisso. Agreed that you should start a new cassette of with a new chain.

Retro Grouch 

This is "quick and dirty" but it sometimes works:

1. Take your rear wheel off of your bike. Lay it over a waste basket or something similar, cog side up.
2. Spin the cogs with your fingers. Notice what spins and what stays still.
3. Spray some WD-40 or something similar at the crack separating the spinning and non-spinning parts. Spin the cogs for a few minutes with your fingers.

If it frees up the pawls you're golden. If it doesn't work, you haven't lost much.

pressed001

Yeah, it would be more cost effective to just replace the freehub body. I think I bought my last shimano freehub body for 50 bones and install took an hour or so. So we're looking at about 80 bucks cheapest for a bike shop to do it.

nfmisso

Bikerdave222

If its the free hub then> https://www.youtube.com/watch?v=f19BGYc5ysA

If its the cassette then> https://www.youtube.com/watch?v=W4tQcAc9Lo0

nfmisso

Amazon.com: shimano freehub body - Outdoor Recreation: Sports & Outdoors

A LOT less from Amazon.

Kevin56

Thanks for all the replies everyone. I decided to buy the tools and take a look. Not to save money but to learn. Removed the cassette and freehub and cleaned the freehub and put new oil into those tiny bearings. Used bar chain oil and since I only had a 10mm allen wrench where an 11 or 12 was needed, I slid a tiny allen wrench in along side the 10mm and it worked like a charm. 8o miles riding in cold weather since with no issues so far. Knock on pavement.

Tim_Iowa

Bar & chain oil should work fine on the freewheel pawls. It's a great lube for chains, too (obviously, it's in the name), but it attracts dirt quickly and gives you that filthy black chain like you had as a careless youth. On the freewheel pawls, it should stay clean and work well. Phil Wood's tenacious oil is even better, but it can't beat generic bar & chain oil for the price.

Kevin56

Thank you for answering the question I forgot to ask....whether or not the bar and chain oil would be okay for the pawls too. Didn't have time to go look for the Phil oil and had the bar and chain oil here already.

pressed001

I wonder how that oil does on the bearings though. It is cool that you fixed it yourself. Something I would have done too. But I just hope you reached the correct torque spec by re-install. A freehub working itself loose during use could cause disaster.
@nfmisso : indeed, a lot cheaper! however, I was mistaken. it was a 2001 bontrager freehub-body body that I replaced. It could very well be the same part, it sure looks the same.