I recently changed out my worn chain and rear cassette on my year 2000 Trek 7000 mountain bike. I am find that I still have drive train issues, my 32 tooth (center) chain ring needs replacement also, as I am getting chain skipping only on this chain ring. I am looking around for replacements and having a bit of trouble identifying exactly what I have. An online Trek manual for the bike identifies the cranks/chain rings as Icon Onyx, 4 arm 44/32/22. My chain ring appears to be 104mm BCD.

My question is this. I can find lots of chain rings, but some of them have the following statement or something similar -
•ChainRings: from Shimano HollowtechII & Octalink MTB cranksets have different length tabs & are not interchangable
My crank set is neither, but I don't know which of these my Onyx cranks are compatible with. Can someone provide some insight on this? I tried searching the shimamo website but could not ever pull up any documents, and they are not accepting email.

I pulled the chain rings off today, and the middle one is marked with Shimano M9 N-32, then opposite this marking is "EB". The large chain ring is similarly marked Shimano M9 N-44, and not too far away is "AE". The smallest chain ring is marked with just "22". The crank is marked with AOB21L 175

I know I have previously replaced at least the outside and middle chain ring previously. The inner one looks pretty clean, so I suspect it is a replacement also.

Despite no picture, I suspect that your crank arms have supporting shoulders for the middle ring. That means the mounting tab has to be machined in a circle to fit. Many rings are made to fit arms that don't have locating shoulders and therefore won't fit.

Tab with machined circle

wrong tabs

Hollow tech desire I'm supposing is a whole crankset BB replacement

stick to flat chainrings , when in doubt visit a Bike sdhop where they can see what your kit is

Shimano Chainring guide

octalink has been superseded by the external bearing .. tube fixed into the right crank arm

https://www.google.com/search?q=Shim...ml%3B615%3B461
there are aftermarket suppliers of the 4 bolt chainring ( I'm not recommend any on line sellers, thats up to you)

"EB" and "AE" are likely the date codes. EB=Feb 2006, AE=May 2012.

Here are a couple of pictures



Based on these and the advice from FB I think I am looking for a chain ring as he posted with tabs with machined circle.

thank you all for the feedback.

Matt

the tab is so the shift pins & ramps of all 3 are in the right places , relative to the power stroke..

you align them up.. ..

If you cannot find the right rings at a reasonable price, you can buy standard ones and file enough off the tabs to clear the shoulders. You'll lose the benefits of the shoulders, which help keep rings concentric and prevent the bolts from working loose, but many cranks these days don't have the shoulders and they work reasonably OK.

Looking at this for the middle:



and this for the outer 44t

How did it work out? I have the same problem; I have a 2000 trek 7000 but can't find spares advice anywhere.


Which chain ring did you find to replace the worn original that came on the icon onyx crank?

It could have been better. The middle chainring worked fine, it was a Shimano Deore M532 32t 104mm 9-Speed Chainring

The outer chainring was a Shimano Deore LX M580 44t 104mm 9-Speed Outer Chainring
I had to dremmel a few places to get it to fit onto the crank properly. Not the end of the world, but I basically wasted the hour or so doing research trying to find one I would not have to modify. The actual work took maybe 10 minutes.

I could not provide advice to you as to how to pick the right outer one without having to modify it. But if you have the tools (file would work, dremel type tool is much easier IMO) it is not a big deal.