Bike repair question: replacing rear cassette?

In My Humble Opinion
1

Ah, spring. The trees are blooming, the birds are singing, and although I love the beater I’ve been riding through winter, I need to get my everyday bike back on the road. You people have been very helpful in the past in getting her up and running again, so I thought I’d come back and ask again.

Problem: I do not have the terminology to effectively describe the problem so please dumb down your answers. Last time you put me in touch with Sheldon Brown’s bike repair sites but there aren’t enough pictures, and I can’t figure out what I need to know from there.

Resources at my disposal: I have a place where I can go use whatever tools I want, and have the support of experienced mechanics. I just need to know what to know (and to buy) before I go in.

Now, here’s the situation: what I believe is called the cassette (the thing on the rear wheel with all the gears on it, number 23 on here) spins freely, not only backwards but also forwards. Suffice it to say this makes forward progress on the bike nearly impossible unless I’m going downhill. I’m told that this will need to be replaced as it’s probably filled with grit and salt and all the crap it picked up riding through three winters. (How the heck do you clean in there, anyway?)

I understand that, since it’s very old, I should also replace the chain along with it.

So, the questions:

What else would I need to replace? Do I need to replace everything at once or can I go in stages? The rest of the bike is getting old and crusty as well, but still works. The derailleur, for instance, nearly died last year but I restored it to workable condition.

How would I replace the cassette (I need specialized tools, right)?

To complicate things, I wouldn’t mind buying new wheels, mine are rusty and steel and I’d like some aluminum ones. Should I just do it all at once - buy new wheels and chain and whatever else I need? Is that substantially less work than buying a new cassette, fixing it to my old wheel, then later removing it and fixing it to a new one?

Also, it’s a road bike. Can I put (thin) racing wheels on it so I can go faster?

Anything else I need to know?

Thanks so much for your help.

2

Well, unless the teeth on the gears (cassette) are broken or severely warn down, you probably won’t benefit much from replacing it.

It’s possible that depending on the miles and the abuse of a dirty and sandy chain has done significan damage but that can only be seen with a trained eye or when compared to a brand new cassett of the same type.

What is most likely the cause of your problem is a dirty and warn out hub. The thing that the cassette is attached to, the doodad that all the spokes lead to at the center of the wheel.

Some hubs are accessbile and cleanable (bearings can be cleaned and repacked) and some are not. There is also a bit of experience that is necessary to properly pack, seat and tighten the bearings after cleaning.

If you go to a local bike shop, they will probably do a good job and it won’t cost much at all. Buyint the tools necessary to do the repair yourself may cost you more. But if you’re in it for the experience and fun of learning and doing then they will recommend the exact tools you need and some advice on how to perform the repair.

Or you can go with new wheels.

3

If your cassette is able to spin forward, you’ve got something crazy going on in there.

Your bike has a freewheel. It’s either in the hub (axle) , or in the cassette (the sprockets).

For starters, let’s determine what a “freewheel” is.

This is what a freewheel looks like. (not a bicycle one, but same thing). It basically has little cogs and cams that don’t let it spin freely in one direction. They “catch” when you spin forward, and slide by when you spin backwards. It’s a ratchet.

Now, let’s look at Sheldon Brown for a second.

You either have a “fixed hub” (on the left in that picture) and the freewheel is part of the cassette. Or, you have a cassette that is just teeth on a ring, and the freewheel is built into the hub of the bicycle wheel. He calls that a freehub.

Wherever your freewheel is (cassette or hub), it’s friggin’ SHOT.

SO. . .if you have the freewheel as part of the cassette, you can get by with replacing just the cassette and keeping your wheels. However, you’ll need a cassette with a built in freewheel, and I don’t even know if they make those anymore. They probably do, but I don’t know.

If you have a freehub as part of your wheel, and it really is shot. At a minimum, someone could probably get into the hub and fix the freewheel. Or, you’ll have to replace just the hub. If you do that, you’ll probably have to buy a hub, and spokes, and then pay someone to build it. And you’re better off just getting a whole new wheel at this point.

This puzzles me. If it’s a road bike, I’d think it already has thin wheels on it.

But, if your bike now has fat wheels. . .probably the brakes, fork, and frame are designed around that and you can’t just put thin ones in there. It’s not going to make much of a difference in speed, anyway.

4

Ok, if the cassette is spinning freely in both directions, the problem isn’t with the cassette but with the freehub body. This is the black cylinder that the cassette fits on. They can be replaced and while it is fairly easy for an experienced mechanic to do, I’d say it’s moderate to hard for a novice, depending on mechanical aptitude.

Steel? Really? Steel wheels are usually a sign of a cheap bike, and by cheap I mean disposable. But that doesn’t seem right, since this is your regular bike and not your beater. Is there a model name on the rim and hub? That might give us an idea if it’s worth fixing or not.

5

Bike Nashbar has them. Scroll down and they havefreehub bodies (if it’s a cassette hub), and 6 or 7 speed freewheels if it’s a freewheel hub.

6

I understand the cassette to be the ratchet mechanism between the cogs and the hub. The cassette with the cogs attached is the freewheel.

If it doesn’t ratchet correctly, maybe there’s dirt inside keeping it from working properly. You might be able to get away with having it cleaned. You could also have the cassette changed out for a new one.

Safe money is have the freewheel and chain replaced in one shot, because of wear. Unless you have a big honking vise or a big honking wrench plus a freewheel puller, it’s a job for a bike shop.

While they have it off, have them inspect and replace the bad spokes on that side of the wheel.

You could also get thinner tires if you like. If you want speed, go for it. However, the beefier the tires and rims, the more forgiving the bike is to road hazards; a consideration if you commute or tour.

7

Nowadays, people tend to refer to the whole set of cogs as a cassette. As in “I have a 9 speed cassette with gears 11-23”.

If you tell a bike shop guy you need a new cassette, he’s probably going to get you a set of cogs that has no ratchet mechanism at all.

The ratchet mechanism on new bikes is built into the hub, and the “cassette” (in modern usage) just slides onto a splined hub. See the sheldon brown link I posted.

8

I freely admit to being in the old school of bicycle technology…

9

Yes they do, Nashbar lists several. Although I only see 6 and 7 speed freewheels - anything else may be difficult to find. But there’s always eBay.

And I believe a “cassette with a freewheel” is an oxymoron; it’s either a “freewheel” (freewheel mechanism with gears attached to it) or a “cassette” (just the gears stuck together, mounts onto a “freehub”).

Anyway, whether you have a freewheel or a cassette, you’ll need some special tools to remove it. I’d suggest taking the wheel to a local bike shop and either buying the appropriate tool, or having them fix it.

10

Wow! Thanks for all the advice, folks. Are you as itching to get on your bike as I am?

The story of my bike: I got it several years ago, basically out of the back of a van. It was likely someone’s beloved beater that was nicked. I don’t buy bikes this way any more, which is why I want to fix mine up into something nice instead of dropping thousands on a new one that I will constantly worry about getting stolen. I commute to work every day in a city with a major bike theft problem, so I want something ugly but functional, which is what I’ve got (well, I will once it’s functional again).

Yes, yes I do.

I will have to have a closer look and figure out what exactly is going on in there. But something definitely needs removing and replacing, and it’s not something I can do with my Allan wrenches.

Yes, it is cheap/disposable (see above). But I really like the frame, and I’ve sort of made it a personal project to fix her up into something reliable and fast yet not particularly stealable. I will check for the model name (on the rim, right?)

I definitely could use some new rims, these are rusty and probably a bit warped, I would bet the cost of a new set that they are not worth fixing.

I don’t, but I have access to a workshop where they do. I’d like to figure out how to do it myself, if only because I’m sick of giving money to bike shops. There is a co-op that I quite like but it’s not exactly nearby and it’s hard to carry a non-functioning bike across the city.

So it sounds like I need a new freewheel, chain, and rims. I will haul my old wheel to the nice co-op, let them sell me what I need, and take the whole shebang to the workshop.

Do I need to replace the front chain rings too if I get a new chain?

11

Only if they’re worn. With bad ASCI graphics, a good tooth will tool like /, and a worn one looks like /(