[Alex Prikhodko]

Hi folks,

Today I picked up a year old 2013 Specialized RockHopper. After going over the bike with a fine toothcomb, adjusting, lubricating, and cleaning, I took the 29er on its maiden voyage. As I was going uphill, I tried to upshift from the crankset middle cog to the smallest cog and the chain got stuck between the chainstay and the crankset.

After doing some research on the possible causes, it seems that a bent or damaged tooth on one of the crankset cogs is the likely culprit. After examining the crankset I found a tooth that seems to have been damaged and is not as pointed as the other teeth. I am attaching a picture for reference purposes.

Do you think this damaged tooth is the source of my chain suck problem? Should I take this as an opportunity to replace my crappy SR Suntour PFF crankset with something nicer? What about the bottom bracket, should I replace that too while I am in there?

Thanks in advance!

P.S.
Some of the troubleshooting steps I have taken are as follows:
- Cleaned the chain and made sure there were no stuck links
- Adjusted front derailleur per Shimano instructions

:madman:

 

[jeff]

File the tooth straight and try again.

 

[RumbleOn]

It looks like your smallest chain ring is brand new. The chain has stretched to match the wear in your older chain rings It is getting wedged on the small chain ring and riding up instead of releasing cleanly. You could replace the chain and likely fix the small ring issue, but you would get skipping on the other rings then. At this point to avoid frustration; replace the chain, the middle and big rings, and the cassette. - this is my recommendation based on this 1 picture and is caused by not checking chain stretch regularly.

 

[jeff]

He could be right but do yourself a favor and try the tooth trick first before you dump $$ into it.

 

[Tha Dawg Catcher]

As I was going uphill, I tried to upshift from the crankset middle cog to the smallest cog and the chain got stuck between the chainstay and the crankset.

Always thought this was called a downshift, secondly probably more important so, would be shifting while climbing especially hard on the rear but killer on the front I would try to avoid doing that. If not check the low limit on the front derailleur this can cause chain problems especially if trying to really jam the shift while putting power on the pedals.

 

[Cotharyus]

Get a chain wear gauge. They're cheap, and can help you avoid a lot of problems like this. I think the tooth you're looking at is that way by design, to aid in shifting, and the likely cause is as indicated above that the chain has stretched and didn't mate up with the small chain ring right when you shifted. Plus, replacing chains in a timely way rather than waiting for problems to start will make the rest of your drive line last longer.

 

[Epic_Dude]

Your middle and top chain rings are definitely worn, you will need to replace them and the chain. Don't know the condition of the rear cassette so I would not be able to say for sure if that needs to be replaced. Also check your jockey wheels, if you need a rear cassette then it's likely those are also worn out.

Like others have already said, a worn out chain causes other parts to wear out faster. Get a chain wear measurement tool when you purchase the new chain and rings.

You can get a new Suntour Triple MTB crankset for about $40 online (about the same price as two rings and you have a new crank), a new KMC chain for $16, and a chain measurement tool for $10 and get some chain lube and a chain cleaner while you are at it. Total out of pocket is about $70 for the parts.

If you want to upgrade your crank, check eBay for a good deal on a Triple ring MTB crankset.

 

[RumbleOn]

I am guessing that since the OP did not mention chain skipping, his cassette is in the same condition as the middle and big rings and will cause problems once the chain is replaced.

 

[Fleas]

Trying to shift to the granny gear under heavy load is pretty hard on any drivetrain. Try to take a couple hard cranks in the middle ring right before you downshift, then lighten up on your pedaling while you downshift, then put the power back on full after the chain engages the granny gear. Or, just drop into the granny before you even start climbing.

IMO, a worn chain might shift worse, but I don't believe it will cause the problem you are having, esp. if it works OK in every other gear (even if they are all worn). I'd look at your front derailleur position.

And yeah, that small tooth is by design. There are probably at least 2 of them, symmetrical on the chainring.

-F

 

[Mr. Doom]

Most middle chainrings have a few shorter release teeth and your middle ring is not total shark teeth yet so maybe the chain/cassette have some life left. On cheaper cranks sometimes the ring is soft and bent so the chain gets wedged between the rings, replace the cheap cranks with some Alivio-Deores if filing the (burr) is not solving the problem.

 

[J.B. Weld]

Your middle and top chain rings are definitely worn, you will need to replace them and the chain.

You can tell that the big ring is shot from a blurry pic. showing only half of one tooth? What's your secret?

 

[Skedasticity]

I have some experience with this issue as I got the same 2013 Rockhopper 29er brand new. The exact same chain suck would occur right after I got it fresh from the shop, so I think it may just be due to the weak parts spec on the entry level model. I basically never try to shift into my small chainring when I'm applying any sort of power to the pedals, which means I have to make sure I switch prior to climbing. I also am careful to apply some power prior to shifting and watch for the chain getting hung up so I can do a quick half reverse pedal stroke to free it up. I definitely am looking forward to my next bike where it isn't so finicky with this issue.

 

[Alex Prikhodko]

Hi folks,

Sorry for radio silence, I have been in furious troubleshooting and research mode. Here is a list of fixes I have tried to no avail:

1. Took the crank apart and carefully examined all the teeth to make sure there is no damage or burrs. Nada, the crank is almost new, so new in fact that much of the original paint is still on the teeth.
2. Used a dremel and 240 grit sanding disks to carefully remove paint and polish the tops of the crank teeth. This was done in an effort to reduce friction between the crank teeth and the chain.
3. Cleaned the chain for the nth time and re-greased with a light-weight lubricant.
4. Adjusted the FD for the nth time.

At this point I am tired of fiddling with this thing, and it seems that many RockHoppers are suffering from the same issue. So I decided to upgrade all components in question.

Please reference a follow-up thread, where my component related discussion is documented.

http://forums.mtbr.com/29er-components/crank-upgrade-2013-rockhopper-906691.html#post11108245

I will continue updating this thread regarding my success or lack of there of.

Thanks again!