[coffeebeans]

Hey everyone,

This is somewhat of a noob question, but we all gotta start somewhere, right?

I was riding through a trail and hit an unexpected turn, I went off the trail and hit a rotting log with my first chain ring. I bent a few teeth and it's unusable with a few gears. (I've dealt with it as I normally don't use the first chain ring). So along with that the whole thing wobbles from hard riding. I'm looking to replace it, and I've heard that when you replace your chain rings you should also replace the chain so the stretched out chain doesn't ruin your rings. Is this a good thing to do?

Any help appreciated. :biggrin:

 

[Wumpus]

1) Chains don't stretch. :biggrin:

2) It depends how old the chain and rings are. If they are relatively new, it wouldn't hurt to replace the chain since they are relatively cheap. If the drivetrain has a lot of miles, you might end up replacing all the rings, cassette and chain.

3) If you bent the big ring, just replace it with a bash guard then next time you ride off the trail you won't bend anything.

 

[coffeebeans]

Thanks for the help.

It was the smallest ring of the three. The cassette I was told is in relatively good condition by the mechanic who tuned it last, and that wasn't but maybe a month ago. I'll look into replacing the rings and chain as well.

 

[Wumpus]

The cassette I was told is in relatively good condition by the mechanic who tuned it last, and that wasn't but maybe a month ago.

I would just get a ring to replace the bent one and a new chain. I replace the chain about every six months.


If you get a new granny, look for a steel one like the Blackspire Chuck ring.

Measuring Chain Wear
The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:


If the rivet is less than 1/16" past the mark, all is well.

If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.

If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.

If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.

 

[coffeebeans]

That last quote that you posted, the mechanic did mention that I wore out the 8th sprocket and he had to replace that on the cassette. Along with that he either didn't check the chain for wear or it was alright because he didn't mention anything about it.

I'm going to replace the entire crank set with something better instead of just changing that one ring. The damn thing creaks all the time if I don't put some WD-40 on it and the bolts that hold the arm onto the crank (I don't know the technical term, it's inside the frame, that part) doesn't really hold all too well as it is constantly in need of tightening. Thanks Suntour!

 

[MtnbikeMike]

What kind of cassette is it? It's very rare to replace an individual cog. Usually you'd swap out thw whole thing.

 

[coffeebeans]

Shimano, I'm not quite sure what particular model. It's an 8 speed. The man was British, he obviously knew a lot about what he was doing. The people at that shop say he's the best.

 

[MtnbikeMike]

That's odd. I believe Shimano cassettes were all riveted together(all of mine are in one way or another). You sure he didn't replace the entire cassette?

 

[HAB]

Most of Shimano's cassettes LX level and below are bolted together. Look at the back side. There's a little bolt back there that threads into the third smallest cog (the smallest one that's attached to the others) after threading through a hole in each of the larger cogs. The XT is riveted on to the carrier. Some versions of the XTR were in fact bolted to the carrier. I don't recall exactly which ones.