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Old 06-20-08, 05:54 PM   #1
commute
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What 7 speed cassette and crankset?

So I replace my derailleur and the chain, and the bike works great indoors on the trainer. But the chain skips cog teeth under load up hills. Ugh!

At first I figured the chain was too loose, but sure enough, the cassette has some "shark fin" teeth now. (photos attached)

How do I find a compatible cassette and crankset? The shifters are GripShift 7 speed. Bike is a 95 Cannondale M400. Can I choose any 7 speed cassette? And any 3 ring crankset?

Any suggestions for something affordable yet good for commuting?
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File Type: jpg sharkfins.jpg (97.1 KB, 72 views)

Last edited by commute; 06-20-08 at 05:59 PM.
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Old 06-20-08, 06:21 PM   #2
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You ought to be fine with any 7-speed cassette from Performance or Nashbar. Their Shimano-compatible house brands are cheap-ish, and will work okay with your drivetrain. As for the chainrings, leave 'em alone, and replace just the cassette... Then take a ride. If the bike shifts okay and doesn't skip under load, you've taken care of the big problem.

Shimano Hyperglide chainrings have weird shaped teeth among the normal looking ones. Look carefully for hook-shaped ones... They're telltales that the chainring is worn out... But still, you'll get many years out of the chainrings... I've got two bikes with better than 65K miles on them. One's chainrings are just starting to wear down, the other's look new.

I bet your's are okay.

Just FYI, I have a 7-speed roadbike, an ooooold Trek. I get about 2,500 miles from a chain before I'd better replace it... Get into the habit of replacing the chain promptly, and you can get 20K, 30K from your cassette.
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Old 06-20-08, 06:23 PM   #3
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If it was my bike I'd get a new SRAM or Shimano cassette and see if that fixes it. My bet is that'll do it.

I was going to mention that you could replace just the chainrings on your existing crankset, but you can probably replace the whole crankset for about the same or maybe even for less money.
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Old 06-20-08, 07:00 PM   #4
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From the appearance of the cassette in your pictures, I would change the chain, chainrings, and cassette. Looks like chain stretch/wear took it's toll on the drivetrain. Have the LBS check it out though, you might get lucky with just needing a cassette and chain replacement.
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Old 06-20-08, 08:20 PM   #5
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The only thing here that needs to be 7 speed is the cassette. If you have recently replaced the chain, you might be able to keep it. But if you have been using it a while, you would be better off replacing it (in case it has worn to the worn out parts).

As far as a crank goes, if the ring sizes suit, a Sugino XD would be ideal. Otherwise, I would try and find a Shimano Sora triple crank and use that.
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Old 06-21-08, 05:32 PM   #6
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Your chainrings are worn out.
Look at the teeth on the right side. I see 2 that are half size.

This crankset should work:
http://www.jensonusa.com/store/produ...Cranksets.aspx

Use this link for the Price match.
http://aebike.com/page.cfm?PageID=30...id=1098&type=T

Buy a square taper bottom bracket. Your current one is worn out, too.
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Old 06-22-08, 01:19 PM   #7
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The chain is a brand new Shimano IG70, only ridden about 1/4 mile.

Quote:
Originally Posted by Barabaika View Post
Your chainrings are worn out.
Look at the teeth on the right side. I see 2 that are half size.

This crankset should work:
http://www.jensonusa.com/store/produ...Cranksets.aspx

Use this link for the Price match.
http://aebike.com/page.cfm?PageID=30...id=1098&type=T

Buy a square taper bottom bracket. Your current one is worn out, too.
Thanks!

Doh! Those teeth have been half size for the last year or so (since I checked last), so I just assumed that half height teeth were the correct size.

I guess the Sugino crankset is better than Alivio M410?
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Old 06-22-08, 03:08 PM   #8
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Quote:
Originally Posted by commute View Post
So I replace my derailleur and the chain, and the bike works great indoors on the trainer. But the chain skips cog teeth under load up hills. Ugh!
Most likely it's a worn-out chain. Measure the distance between 12-links (24-pins) and see what the distance is.

Worn chainrings won't skip. Due to the number of teeth, it'll grip the chain and hold just fine even when the tips of the teeth are so worn out, they don't even stick up above the chain. But worn rear-cogs or chain will definitely cause skipping.

So replace in the following order:

1. chain, if still skips, then
2. rear cassette cogs, if still skips, then
3. front chainrings

Last edited by DannoXYZ; 06-22-08 at 03:12 PM.
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Old 06-22-08, 04:52 PM   #9
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Quote:
Originally Posted by commute View Post
Doh! Those teeth have been half size for the last year or so (since I checked last), so I just assumed that half height teeth were the correct size.

I guess the Sugino crankset is better than Alivio M410?
I think that the broken chain ring teeth can quickly destroy your chain.

Sugino XD300 is a very good crankset. It has the steel chain rings that are more reliable than aluminum ones.

Shimano Alivio has a different interface: Octalink.
You have to buy a compatible bottom bracket.

If you have to change both the cassette and crankset, first calculate the gears for your current setup http://www.sheldonbrown.com/gears/
Find out what gear ratios are your favorite and then compare with available cassette/crankset combinations.

It seems that all your components are worn out.
I would consider changing the following:
1. cassette
2. crankset with bottom bracket
3. cables and housing
4. brake pads

It's just cheaper to buy all components at once if you want to order online.

Last edited by Barabaika; 06-22-08 at 04:56 PM.
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Old 06-22-08, 08:33 PM   #10
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Quote:
Originally Posted by Barabaika View Post
If you have to change both the cassette and crankset, first calculate the gears for your current setup http://www.sheldonbrown.com/gears/
Find out what gear ratios are your favorite and then compare with available cassette/crankset combinations.
Wow. Gearing! I should have thought of that myself. Sheldon's site is great.

It turns out that I'm using 180mm cranks. Even if I move down to 170mm (or 175mm with the Alivio), I'm going to have to think about the gearing some. I'm not sure I could get used to 170mm cranks (long legs).

I'm actually temped to go with the Alivio and replace the bottom bracket too (there's no play in it, but it creaks under load). Everything seems to have worn out except the frame!
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Old 06-30-08, 10:44 PM   #11
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BTW: I wimped out and got an ac 11T cassette from LBS instead of ordering online. It's a direct replacement. (There might have been cheaper stuff at jensonusa, but the descriptions were so vague that I didn't know what I'd be getting!)

Anyway, with the new cassette there is no skipping, but the crankset and BB still need replacing. On to that next.
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