Hey all,
I have a 1997 Marin Pine Mountain. The middle (front) chain ring has a broken tooth. I believe it is a 32 tooth Deore. I have found a couple on eBay. Which one do I need? Is there any difference? I found a M490 and a M590. Or are these not compatible at all? I would prefer to do just the center ring so I don't have to replace the BB. Any help?

It should work, I believe the only difference between the models is the gearing, but the chain rings should all be interchangeable.

You have a 4 or 5 bolt crank spider ?

The bolt circle diameter is the important data you need to know.

If it is a rather common 110 5 bolt circle

anything smaller than 34t is smaller than the bolts to mount it.. so 32t middle must be something else.

Well, I checked. It is certainly a 32 tooth 4 bolt pattern ring. In the part description, it states that it is for a 9 speed. My bike is 8 in the rear. I dont see how this could change anything. Stupid question, but does it even matter?

With that info, the bike you have is pretty irrelevant, more relevant is the model number of crank (the 1997 Marin Pine Mountain had a Sugino (White Industries branded) crank as stock which was a compact drive 5 bolt).

Find the model number of the crank (it will be marked on the back of the arms) and use that as a starting point for getting a replacement ring (would look at the other rings, as if you have more than one which needs replacement soon a complete crank could be cheaper in the long run)

Are you sure that it's broken?

Check 180 degrees from the tooth in question. If you see another tooth that looks the same, you are looking at features that are designed to improve shifting.

It's broken. The tooth is sheared off.

I'll check it out. Pretty positive it's a Deore. But I'll look. The rest of the gears are actually good. A tooth is sheared off.

My point was that giving the model of the bike (especially an old MTB) is meaningless when parts have been changed out.

You need to know what is on the bike as at today, rather than when it was sold 18/19 years ago.

For example, I have a 1995 Marin Pine Mountain, the only original parts are the rear hub, frame and crank arms. In the last 21 years everything else has either broken,been upgraded, worn out or just replaced with other parts.

If the bolt circle patterns and diameters match up, it does not matter if it's for an "8 speed" or "9 speed."

Golly, how'd that happen?

I wish I could say that it was from the extreme muscle power of my legs but sadly, nope. I bought the bike from a guy and thought I would fix it up. I discovered it while tearing the bike down.