How to replace a Shimano Altus CT92 crankset?
 

Hi, I have a Trek 700 multitrack from 1997. Specs Here.
According to specs that trek sent me, it has a Shimano Altus CT92 42/34/24 riveted rings crankset. It needs replacing because of about 10 badly worn teeth on the chainwheel.

I have two questions:

1) What crankset could I replace this with so that I would not have to replace the bottom bracket (Victor VPB-33/5L)? I'd prefer one that's non-riveted in case there's teeth damage in the future.
2) What tools would I need to do the job?

I talked with a guy at my LBS, and he wanted >$100 for parts and labor because he said he'd have to replace the bottom bracket. If I keep the BB and don't pay for labor, I should be able to do it myself (with the price of tools) for less.

You'll have to find out the spindle length of your current BB (for example, by measuring it after removing the crankarms) and buy a new crankset designed for that spindle length.

thanks

The specs say that the BB shell width is 68mm. This isn't what I need? I need the spindle length? I'll try removing the crank arms (not sure how) and then I'll post back.

The 68 mm is the width of the frame's bottom bracket shell and that is standard for the very common "English" threading. The other dimension you need to match is the spindle overall length.

BTW, are you sure the teeth are "damaged"? Modern cranks, and yes that includes before 1997, have specifically shaped teeth to improve shifting and these can look damaged if you don't recognize what they are. Unless your chain is skipping on the chainwheels or there is some other problem, the crank may be fine.

dave, if you don't have experience removing crankarms, READ FIRST! It's not tough, but you will need a special tool called a crank remover, and some ways of doing it wrong will damage the crankarms; check out the parktool.com website for instructions on how to do various maintenance/repair procedures on the bike, along with a list of the needed tools (of course!). If you're not sure about something, post here (and often, uploading a photo will help us help you).

I am sure those teeth are the ones shortened to aid shifting. They are near the crank and opposite. Go look at a new crank set in the bike shop and you will see what I mean. The crank will need replacing when all the teeth have a shark fin shape. A crank removal tool costs about $15. This distance to measure, once you have the cranks off, is the overall length of the axle.

What sort of bottom-bracket is the Victor VPB-33 that came with this bicycle? ISIS? Octalink? Square-taper? This information is needed to help the OP get the right tool for the job.

For a crank extractor that can handle both major varieties:

http://www.parktool.com/products/det...=26&item=CWP-7

I think the teeth really are damaged. I think I know the special teeth that you guys are talking about. On my bike they have deeply notched teeth. But the ones on my bike are worn down and my chain skips often when I'm pedaling hard.

I just looked at a few dozen cranksets online and none had teeth that looked like mine. AndrewP, do you have a link to a photo of the type of teeth you're referring to? I tried to photograph my crankset, but my camera stinks and I couldn't get a crisp shot.

Thanks for the advice about crank pullers. After I posted yesterday, I spent some time watching crank removal videos online. I will definitely be careful and use the right tools.

I also watched some tutorials about bottom brackets. Mine has quite a bit of play to it. Does that mean it needs replacing also?

I dont have links to pictures, but the wear is only on one side of the teeth which makes them curve over like shark fins. There shouldnt be play in the bottom bracket. If the bearings are simple cup & cones, they can be adjusted, but if they are in a cartridge assembly they must be replaced ($30). The tool is another $20, but it isnt a difficult task. http://www.sheldonbrown.com/tooltips/bbadj.html http://www.sheldonbrown.com/harris/t...ombracket.html

Assuming the skipping is in front, that's sufficient evidence that the teeth are indeed damaged.

The play in your current bottom bracket. particularly if it's a cartridge type is, again, ample reason for replacing it too.

The Altus was one of Shimano's low-line cranks so it's worth changing both the crank and getting a matching bottom bracket.

Thanks for your help, everyone. The total cost of bottom bracket and crank tools is more than the cost of membership to a local bike club shop. So, rather than purchasing two tools that I'll only use once, I'm going to join the club and use their tools for the next year.

Good for you!

Update: I spent some time at a community bike shop and did a complete overhaul of my BB. The wobble is completely gone and, so far, gear changes seem smoother and the chain isn't slipping. Total cost: $0, lots of time, and lots of grease.

What type of Bottom-Bracket is the Victor VPB-33? Future reference will allow us to help other's in the future.

It's a cartridge bottom bracket. But keep in mind that I got the info about the bottom bracket from a Trek spec sheet and not from the bracket itself. That same spec sheet had other errors, because even Trek can't decide if my bike is a 1997 or 1999. Another source of info told me that my bike is a 1999 and that the BB is a Victor VPB-C55P. When I serviced it, I saw no markings indicating what it actually was.

So, if someone in the future has what might be a 1999 Trek 700 Multitrack, it might have a cartridge bottom bracket, which could be a Victor VPB-C55P. That's the best I can offer. :)