Mountain Biking - Drivetrain guru's! Please advise. Where did I go wrong in my drivetrain build? Grind!
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05-20-09, 09:16 AM
So, I have pretty good components, but I think I messed up in the way I built my drivetrain over time. It wasn't smooth in all gears and its still a little rough is some spots... very annoying.
Here is how my drivetrain progressed:
- Stock Giant Trance
- (5 months later) Upgraded cassette to new XTR
- (1 month after cassette) Upgraded to X.9 rear deraileur
- (4 months after cassette) installed used M960 XTR crankset
[discovered a grind/rough noise throughout drivetrain]
- (1 month after installing used crankset) installed new middleburn rings to replace old, worn XTR rings on crankset
- Same time as installing new crank rings, I installed new KMC chain.
By replacing old XTR crank rings with middleburn rings, the grind reduced significantly. But, it is still not as smooth as I'd like.
I think the parts had different degrees of wear so it was completely out of unison and created rough movement.
Since the crank rings are relatively new (no signs of wear-- only few months old with little riding), and the chain is relatively new, should I replace the cassette with a new XTR cassette (and chain?) to resolve all drivetrain issues? It is either this aforementioned 'solution', or I am going to just get a new XTR crankset, XTR cassette, and XTR chain, and call it a day.
Thanks for the input in advance!
If I may...if you have the expendable cash to throw around willy-nilly at XTR cassettes, why didn't you just upgrade the entire drivetrain to new stuff all at once?
05-20-09, 10:26 AM
Hi there. Have you ascertained exactly what is grinding on this thing? You said "throughout the drivetrain", but i suspect that a few components in particular are responsible for the cacaphony. Put the thing on a stand, or flip it over if you don't have a stand. turn the cranks. what's rubbing, if anything? What's the chain doing across the cogs and rings? jumping? skipping? not setting into the teeth? Remove gthe chain. Turn the crank. Crunchy? That's your BB. With the chain still off, spin the rear wheel. Rough and noisy? Rebuild the hubs.
Being that you noticed the most problem after installing the crank, I suspect that the q-factor and, consequently, the chainline were effected. I'm not trying to offend, but i reckon you tossed the crank on without adjusting the front derailer. If this is so, it'd make things grind and bump as if you're cross-chaining even in combos that aren't crossed.
Speaking of which, you're not running this thing crosschained alot, are ya?
The above are all shots in the dark. The brand/line of the componenents is only part of the equation when diagnosing these problems on a forum; the details of the set-up play a massive factor, too.
05-20-09, 12:56 PM
chelboed- my methodology was not 'willy nilly' (defined as random), it was simply in the interest of finding the desirable parts at a reduced cost. The XTR cassette I purchased for $90 new at a local shop. So, I had a list of parts I wanted, and I started to search for them online. I did not consider uniformity or compatibility (with regards to wear patterns). I slapped all the parts on and thought it would spin like a new drivetrain. I guess we live and learn.... If I had known this from the beginning, I would have bought a new drivetrain.
surreal- Thanks for the thoughtful response. I appreciate it! Great points that I have not thought of.
I noticed a grinding feeling through the pedals (when I was riding) after installing my used XTR crank. Prior to the crank install, I had a stock crank, X.9 rear der., XTR cassette, and stock chain. That led me to believe the crank rings were the culprit. I then installed the middleburn XTR replacement rings, and it helped. But didnt completely cure it.
As far as diagnosing things, this is what I have noticed: the chain doesnt skip or jump across the cogs/rings. The BB is smooth (luckily). The hubs are smooth. What I dont know is why I still get a rough feel through the pedals. Could it be that the old chain wore with the XTR cassette, and when I threw a new chain on, they didnt 'agree' with eachother?
I get help with installing these components from my local shop. I installed an XT front der. when I installed the used crank. I can see why an improperly adjusted front der. would pull on the chain and cause adverse grinding.
I dont run by small ring with a cog past 3rd/4th gear. I switch to my middle crank ring at that point-- and usually stay there. I do, however, run my middle front ring with my lowest (largest?) cog (i.e. 2x1). I hope thats not bad....
Again, thanks for the input. If you have the time, I'd like to hear your thoughts on the above.
Wow...$90 for a new XTR cassette is a steal.
I had some odd grinding in mine too yet all my stuff was brand new. (odd) I'm running PG990 cassette, Raceface 32t ring, and a SRAM 971 chain.
Mine seems to have gotten smooth now after a couple of rides.
Could it be that the old chain wore with the XTR cassette, and when I threw a new chain on, they didnt 'agree' with eachother?
Could be the culprit.
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