sram shifting problems

[coolatt]

Does this sound familiar

RE Sram PG-950 cassette

I had to replace the OEM chain, so I put on a Sram chain (it's a Sram cassette, so it'd seem logical, right?) only to have all sorts of shifting problems and ridiculous amounts of noise. I did some investigating and finally found Sram's dealer technical publications, which listed chain compatibility as being only Shimano for this cassette (it used to be on Sram's website, but the link now leads to the 2005 technical publications). So, I put a Shimano HG-93 chain on it, and it's been great ever since. According to the 2005 technical publications, the compatibility is now Sram, but if you find a 2004 version, beware of that.

I have a 2005 Devinci magma with an x7 rear der. PG950 cassette and a sram PC950 chain as well as 7.0 gripshift. I can't get this thing to shift smooth. Is it really a chain-cassette combatibility issue?

The chain has problems shifting from the smaller cogs to the larger ones sometimes. The chain kind of rides around the cassette on top of the teeth then falls in to place all at once. It's not every shift, it's more like every third shift if I just go from 1st to 2nd over and over.

I've never had a problem with this before on other bikes and I've built my own bikes a few times so I'm familiar with setting up a der. but I've never used Sram before and this is pissing me off.

[JSinclair]

Generally you would replace cassette and chain at the same time. The chain and cassette wear together over time and develop the same amount of play and wear.

When you buy a new chain, the wear between the cassette and the chain are different and this may cause skipping and shifting issues.

Sounds like you might also have a bent deraileur hanger or a bent deraileur.

Generally with a SRAM kit (Because of the 1:1 shifting ratio) once the set screws have been set and you are in the high gear (Small cog) you should be able to hand tighten the shifter cable into the derailleur and it should shift.

If your shifter cable is old, sometimes it will affect the shifting as well.

Any decent bike mechanic should be able to solve your issues.

[coolatt]

Thanks but it's not wear, the bike is brand new.




My last bike had a XT der., XT cassette, sram chain and Attack gripshifters and never had this problem. I could set up the shifting in 10 minutes. I've been working on this one for hours.

[Oldfart]

Probably over 90% of shifting woes can be traced to a dirty stuck cable and housing. One really muddy day at the park can foul a cable and housing. There is a little overshift built into shifters. You push the paddle, twist the grip or push the lever down against a spring in the derailleur, the derailleur actually goes slightly too far and when you release pressure on the shift mechanism, the derailleur settles in line. (assuming it is properly adjusted) Introduce dirt and you need to push harder and the derailleur does not go far enough so you adjust the cable tension a bit, so it shifts in one direction but then not so well in the other so you adjust some more, get frustrated then post on some website that your SRAM?Shimano? Whatever is crap. Or you get the folks who have old beat crappy stuff, buy new stuff and claim that thier new SRAM?Shimano?whatever is the bees knees and way better than what they had before, until that stuff wears out from a lack of maintainance or old age and the cycle repeats. Anyway I'm blathering.

Jay: Generally speaking I believe one should change the chain before things get too worn for a new chain to mesh OK with the cassette and rings. That way if you mangle a chain, you can probably get away with simply installing a new chain. Plus if you run the entire drivetrain until it's trully dead, you'll have non-optimum shifting for the later part of the drivetrains life. I like to keep it fresh. Leads to better rides.

Anyway coolat, I'd recommend new cable and housing first. I've never heard of any cross compatibility issues between SRAM/Shimano cassettes and chains other than 7 v 8 v 9 speed issues.

[coolatt]

Originally Posted by Oldfart

Anyway coolat, I'd recommend new cable and housing first. I've never heard of any cross compatibility issues between SRAM/Shimano cassettes and chains other than 7 v 8 v 9 speed issues.

Yikes, chill out. Like I said the bike is brand new. I'm not slamming anybody. Iv'e never heard of combatibility issues either but I might buy a different chain just to see what happens.

It definitely looks like at a certain point in the shifting the chain doesn't align with the teeth on the cassette.

[JSinclair]

Can you take two more pictures? One from right behind the bike that includes the hanger and deraileur and one from the side that does the same thing ?

I don;t think Oldfart was bagging on you BTW. No need for the "chill out" comment.

If the chain is shifting gears in the highs side (Small cogs) and doing that when you get to low gears (Big Cogs)...I am willing to bet you have a bent hanger or bent deraileur.

When you set up your shifting did you make sure yoru barrel adjuster was in the middle of it's adjustment at the shifter end?

if so wind it towards the shifter (in) and the chain should drop onto the the cog. The barrel adjuster is the fine tuning of the shifting.

When you wind it in, it slackens your cable and shifts the chain towards the smaller cogs (Non rapid rise). If you find your gears are climbing up from smaller to bigger (ie from 2nd to 1st) this adjustment will fix the problem.

If your gears are not shifting all the way up (ie your in 2nd, you shift and the chain goes between 2nd and 1st but won;t make the change completely, you woudl screw the adjuster barrel out (increasing cable tension).

If you know all of this and have done the fine tuning, then you have a bent hanger or deraileur.

[Oldfart]

no offence taken. My ranting was not directed at anyone in particular I just took the oportunity to vent a bit. Still waiting for my shock to be repaired correctly. I coughed up all its oil 3 weeks ago, got sent east of here for a warrantee repair as it's only 4 months old and came back leaking oil still. grrrr.

The photos look like the cable tension OR low limit screw is off. But you said it was all shifts to lower gears ( larger sized ones) so I'd be tightening the cable, turn out the barrel adjuster until the chain goes into place. For a bent hanger to cause shifting woes, it would be easily visible. It's possible to adjust most derailleurs to work fine on a slightly bent hanger. Especially Shimano ones with the floating top pulley. Maybe SRAM's less so.
But I still put my (your) money on fouled cable and housing. You said the bike is new. How new. How many hours on it and what kind of conditions. Like I said, one muddy ride can screw up the cables enough to mess up shifting. Can be even worse if you keep the bike in a cold damp place where it can't dry out. Cables and other metal parts can go bad fast under those conditions.

[Testy]

Like to see a photo from behind showing the hanger. A bent one would cause that miss alignment.

[Futurelooks Guy]

I found that after years of working on Shimano, the SRAM stuff is very senstitive to bent derailler hangers and B-Tension adjustment. The picture you show looks like a combination of a bent hanger and a B-Tension adjustment, however, as the others mentioned, it is tough to diagnose without a rear shot of the derailleur.

[coolatt]

Originally Posted by Futurelooks Guy

I found that after years of working on Shimano, the SRAM stuff is very senstitive to bent derailler hangers and B-Tension adjustment.

That seems to make sense. The hanger might be twisted a little bit but if thats the case it must of been freak thing that happened and it's barely noticible. I coudn't say for sure unless I compared to another one on the same bike.I've only ridden 2X. I've noticeably bent hangers with shimano der. and managed to get it setup ok. I don't have a picture right now but maybe tomorrow I'll get one.