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luddite
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212 Posts
Discussion Starter · #1 ·
I finished my Dos build three rides ago. I will attempt to post a pic at the end of this message, but for now... I have shredded two derailleur hangers in three rides. I am open to suggestions about what to do -- and going SS has crossed my mind. But I'm not there yet. I am faced with a perplexing troubleshooting exercise.

Summary:
Twice in the last six days I have wrapped my rear derailleur around my cassette. The first time I was standing a climb and the RD started to mishift and then - bammo. A three mile walk home. Bought a new hanger, mounted the (same) RD, adjusted so it shifted perfectly on the stand, rode up and down the street to fine tune the indexing, went on my ride. 10 miles into the ride, after a couple of standing climbs and some easy spinning the chain starts to sound like it's going dry, you know, a slight grinding/creaking. It's dusty here so those noises are fairly common. Then, while spinning a mild incline - bammo. This time it was a 6 mile walk home. First time I was in 32x28 (or something just lower than middle) and today I was in 32x34.

Setup:
Medium Dos Niner frame (17.9" chainstay)
68x113 bottom bracket, no spacers on either side
SRAM PC-99 chain (correct length out of the box = 114 links, big/big + 2 links)
Cassette: First time = SRAM PG-990, 11x32, Second time (today) = Shimano XTR 12x34
RaceFace Turbine LP 44/32/22 crankset
DT Swiss FR rear hub
SRAM X9 rear der
New XTR cables
Both times the chains were new from the box, de-waxed with SimpleGreen and lubed with ProLink Gold.

My initial idea was that it might be a chainline issue but that doesn't hold up to scrutiny. Circumstantially, with EXACTLY the same drivetrain (I swapped it over) that was on my 26er I have never had an issue. The real reason is that the geometry doesn't work out; for the same dropout spacing, BB width and cassette width (identical for both bikes) the longer chainstay on the 29er dictates a straighter chainline (my 26er had a 16.7" chainstay length). The only thing that changed is my rear hub and the length of the chain itself. I don't imagine this is a chain length issue because there is still plenty of travel left in the der cage (I'm only in 32 up front!).

Things I can imagine might be wrong are:
1. Bent frame. This would be evil.
2. A misaligned (brand new) hanger from the shop. Not unheard of. I haven't tested the alignment yet -- that's my next step.
3. A mucked up derailleur. I don't know that I have ever heard of such a thing but it's possible.

Anyone? Bueller?
 

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Complete Bastard
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Don't dewax their chains, especially not with a caustic cleaner like simple green. The sram product manager is probably tearing his hair out reading this. Just run them with the crap that comes on them or use something else but don't take that stuff off the chain. These aren't shimano chains. Also have your der hanger alignment checked. They can be off when new, and your frame may be tweaked after the first one. I spent a lot of time on the phone with edwin at sram trying to figure out some chain issues and he got me straightened out, no drivetrain issues whatsoever, but you gotta take his advice.
 

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You say the EXACT same drivetrain from your old bike? It sounds like maybe you are having new chain+old drivetrain issues. Can we get a pic of the cassettes and the front chainrings? The gear combo you said that you were in are some of the first to get worn out on, how old are the cassettes and chainrings? If it had been a while since you had put a new chain on the old set up the new chain on this bike could be catching on the cassette or middle ring up front. Check your front rings for wear and if the cassette is older take it to a shop and have them put a Rohloff cassette checker on it to rule out wear.

And I'll second the NO dewaxing of the SRAM chains or any chain with simple green!

Hope you get your issue solved. I have loved my Dos! I haven't had any issues other than a broken wrist, but that wasn't the bikes fault :)
 

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798 Posts
Check your upper jockey pulley

Nice bike :) Sorry to hear about your woes.

I've had some trouble with my X9 rear derailleur jockey pulleys. My upper jockey pulley froze up after two rides in the dusty Nevada trails. Since the upper jockey froze up and held the chain in pretty much a fixed position, back pedalling actually pulls the derailleur cage forward. So much so that it damaged my derailleur and hanger.

I've since replaced it with a new rear derailleur and my issues are gone. I would have just replaced the upper jockey wheel, but the derailleur was damaged too.

Jason
Salsa Crew
 

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luddite
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212 Posts
Discussion Starter · #5 ·
Both cassettes were brand new.

heenan-

heenan said:
You say the EXACT same drivetrain from your old bike? It sounds like maybe you are having new chain+old drivetrain issues. Can we get a pic of the cassettes and the front chainrings?
Ah... that would be a good guess, but what I did not mention in the first post is that both cassettes were brand new (to go with their chains!), a critical omission for troubleshooting purposes. I put the SRAM on my wife's bike (and probably won't go back to it because I like the 34 with the big wheels). Here is a pic of the XTR cassette and chainrings.

Jason-

Both jockey wheels are smoooooth. I, too, have had that issue some years back (on my old full rigid Barracuda).


Thanks, guys. Keep it coming! And lesson learned about the SRAM chains. I have one more that I will not be de-gunking.
 

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Not really that big!
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Run with the gunk??

"And I'll second the NO dewaxing of the SRAM chains or any chain with simple green!"


Why are you not supposed to take this stuff off? It seems to collect all of the trail grit when I leave it on. First time I have heard this. Was it in the owners manual with the chain? (Yeah, yeah, I know I'm supposed to read those)
 

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luddite
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212 Posts
Discussion Starter · #7 ·
Follow up - mode of failure identified

This one goes out to Jason @ Salsa.

My upper jockey wheel runs smooth most of the time, though occasionally the bearing will lock up and the jockey wheel will barely move. So when I checked the jockey wheel movement I could spin the wheel relatively smoothly for, say, maybe 30 sec or more and then it would sieze completely. After yanking on it with some pliers I could unstick the bearings and it would move freely again. So not all the time is the wheel siezed but it only takes once.

BTW, LBS said the dropouts and new hanger were dead nuts straight. Straighter than any stock bike they have seen. Or so they said.

I solved the problem by buying a new X.O rear der. No problems (yet).

Thanks, all.
 

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luddite
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212 Posts
Discussion Starter · #10 ·
My dewaxing techinique is less severe

mward said:
There's a lot of stuff about sram chains that isn't in the manual. Yeah though I think it says don't dewax them. If you don't like the gunk on your chain, try road biking. ;)
Hmm. This is all very interesting. I will give a good faith effort to not simple-green my chain and see what happens.

I don't disregard the SRAM advice, it's just that 1) I don't read the directions that come in the chain box, 2) I have never heard of this before and 3) I don't have a history of chronic chain failure. I end up replacing my chains due to stretch/wear after about 5 months anyway, so no chain is ever are long for this world once it hits my bike. Come to think of it I don't recall that I've ever broken a chain that hadn't gone bone-dry from all the damn dust around here. And even then it's the link that pulls off the pin, not a tensile failure. Maybe it won't stretch as much? 'Save me $50 a year! Right on!

For the record, I will now explain my dewaxing technique, and you can all shake your collective heads in disbelief at my naievity. I put a brand new chain in an plastic jug (~1.5 L volume, mine is a square-ish shape with a really wide mouth screw top, I think it had crumbled feta cheese from Costco in it) with 50/50 water/SG and shake for a couple of seconds, let soak for 5 min, shake again, then dump on my driveway, hose the whole mess off, put the chain back in the jug with straight water, shake, hose, pat dry. Then I put it in a ziplok bag with about 5 mL of Prolink gold, slosh until coated, wipe off the excess, done. Normal chain lube procedure is to spin the crank slowly and douse every link of the chain, let sit for a few, then wipe the excess. SOP for chain/bike cleaning is to spray 50/50 mix all over everything, wipe off the crud with brush/rag and then rinse and relube chain and all pivot points of the hardware.

'Never had any problems until the stuck jockey wheel. But then again, I hear that's what drunk drivers say.
 

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Complete Bastard
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2,282 Posts
It's amazing your drivetrain lasts any time at all. "Slosh until coated" doesn't do anything for the part of the chain that really needs the lubricant, the rollers. Edwin at sram talked me into trying what is his favorite chain lube, mobil1 synthetic 0w30. I drop it on each roller so I know they've got lube, then wipe everything down till the sideplates are dry. It's really not any messier than white lightning and it runs very smooth.
 

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Map Maker
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1,244 Posts
MadCowRider said:
I finished my Dos build three rides ago. I will attempt to post a pic at the end of this message, but for now... I have shredded two derailleur hangers in three rides. I am open to suggestions about what to do -- and going SS has crossed my mind. But I'm not there yet. I am faced with a perplexing troubleshooting exercise.

Summary:
Twice in the last six days I have wrapped my rear derailleur around my cassette. The first time I was standing a climb and the RD started to mishift and then - bammo. A three mile walk home. Bought a new hanger, mounted the (same) RD, adjusted so it shifted perfectly on the stand, rode up and down the street to fine tune the indexing, went on my ride. 10 miles into the ride, after a couple of standing climbs and some easy spinning the chain starts to sound like it's going dry, you know, a slight grinding/creaking. It's dusty here so those noises are fairly common. Then, while spinning a mild incline - bammo. This time it was a 6 mile walk home. First time I was in 32x28 (or something just lower than middle) and today I was in 32x34.

Setup:
Medium Dos Niner frame (17.9" chainstay)
68x113 bottom bracket, no spacers on either side
SRAM PC-99 chain (correct length out of the box = 114 links, big/big + 2 links)
Cassette: First time = SRAM PG-990, 11x32, Second time (today) = Shimano XTR 12x34
RaceFace Turbine LP 44/32/22 crankset
DT Swiss FR rear hub
SRAM X9 rear der
New XTR cables
Both times the chains were new from the box, de-waxed with SimpleGreen and lubed with ProLink Gold.

My initial idea was that it might be a chainline issue but that doesn't hold up to scrutiny. Circumstantially, with EXACTLY the same drivetrain (I swapped it over) that was on my 26er I have never had an issue. The real reason is that the geometry doesn't work out; for the same dropout spacing, BB width and cassette width (identical for both bikes) the longer chainstay on the 29er dictates a straighter chainline (my 26er had a 16.7" chainstay length). The only thing that changed is my rear hub and the length of the chain itself. I don't imagine this is a chain length issue because there is still plenty of travel left in the der cage (I'm only in 32 up front!).

Things I can imagine might be wrong are:
1. Bent frame. This would be evil.
2. A misaligned (brand new) hanger from the shop. Not unheard of. I haven't tested the alignment yet -- that's my next step.
3. A mucked up derailleur. I don't know that I have ever heard of such a thing but it's possible.

Anyone? Bueller?
I had this same problem - I know other have suggested you have a sticky jockey wheel but you also have not accounted for chain growth.
the chain length should be big + big + two links + the suspension fully compressed.

It made a two link change in length for me on a single pivot bike.
I lost three rear deraillers until I figured my chain was too short. DOH!

Simple Green is fine as long as you don't Soak in UNDILLUTED solution for a long peroid of time. Just use at LEAST a 50/50 cut with water and only keep it in the sollution a little while. Most of the problems have come from days long soaks in Strait simple Green.
Good luck!
 

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Complete Bastard
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cbchess said:
Simple Green is fine as long as you don't Soak in UNDILLUTED solution for a long peroid of time. Just use at LEAST a 50/50 cut with water and only keep it in the sollution a little while. Most of the problems have come from days long soaks in Strait simple Green.
The people who make the chains disagree with you.
 

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Map Maker
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1,244 Posts
mward said:
The people who make the chains disagree with you.
Good Point -there are probably much better alternatives to simple green that don't have any danger of hurting the chain.

But I get about a year out of my chains before chain wear becomes too great and I must chuck the chain.
 
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