jdowdy411

This derailleur has me completely stumped. It's a Shimano Altus running with SRAM X-3 7-speed trigger shifter on an old Bianchi Nyala. Today, I was cleaning up my cassette and replacing the chain (replaced a too-long Wal-Mart chain that was a quick fix with a KMC-Z72). The problem I'm about to describe has been happening since I upgraded the cheaper SRAM twist shifters to the triggers and it gradually got worse.

Okay so problem:

The limits are set and so is the b-screw(except I removed the b-screw as an experiment and the der was still in the right position? weird?)
and the cable tension is relatively low (I know, you'll say just tension it, but read on). Okay, the chain is on the smallest cog (7) and the large chainring. When I shift once, it's fine; clean shift from 7 to 6, matching the index.
The next shift is when it gets bad. Shifting to next cog, going from 6 to 5, the chain skips 5 and goes right to 4. Now, the index is off by one gear. And sometimes on this shift the chain sits on 5 for an quick instant and then skips to 4. Now the chain is on 4 and the index says 5.
The next shift is worse. Supposed to be from 5 to 4 (index). But it's already on 4, this shift skips the chain to 2 (skips 2 gears). Now the index says 4 and the chain is on 2.
Kind of a cascading effect: with each shift it gets more off.

Now I've tried changing the cable tension and it has no effect on the problem until I get it so tight that it skips on the first shift instead of the second, making an even worse cascade effect.
I've also laid the der on a flat surface and the cage isn't bent.
As to the possibility of it being a bent der hanger, I didn't have this problem with grip shifters on the bike. And if it is bent, it happened at the time or very shortly after the change to trigger shifters. Also, the bend is small enough for me to not really notice anything significant looking at the der from the rear. Also, I can't do a flat surface test with the hanger because it's the type that is built in to the frame (derailleur hanger gauge is unfortunately not in the budget right now).

I also have this other issue that I've never seen before that may be related:
As the tension arm on the stretches further, the chain doesn't engage the tension pulley right away. Instead the first few teeth of the pulley hit the top edge of the chain on the side closest to the wheel and then engages a couple teeth later. This causes a very annoying click and a quick up/down bounce down the chain.

Nothing I try seems to fix all of this. And, I could be mistaken, but I'm fairly sure all the components are compatible (Shimano Altus der, SRAM X-3 7-speed trigger shifter, and a KMC Z72 chain. Suggestions please?

FBinNY 

Someone may correct me, but if I remember correctly all Sram controllers with numbers, such as X-3 or whatever, were only for Sram deraileurs, which have a different pull ratio than Shimano. Sram contollers made for Shimano derailleurs had names like Comp, Mtx, or Rocket.

So unless I'm wrong (someone will correct or confirm in short order), your first (and maybe only) problem is a lever/derailleur mismatch.

Do nothing for a little while until the next post.

jdowdy411

Gotcha. I was told by a guy at an LBS that ALL Shimano/SRAM components were compatible, from cassettes to derailleurs to shifters. Could've had a bad source...I stopped using that bike shop a couple years ago when I found a better one anyways.

FBinNY 

Sram and Shimano cassette splines and spacing are the same, so you could use Shimano derailleur system with Sram cassettes, or vice versa, but derailleurs and the levers must speak the same language.

jdowdy411

Yeah, did some more research. Found the derailleur these shifters were made for. Says it'll work with the Shimano cassette I have with the bike already.

Amazon.com: SRAM X.3 Long Cage Rear Derailleur (Black): Sports & Outdoors



Now that I know a solution, buy compatible shifters or a compatible derailleur? Haha

lopek77

Good reason to learn and become a member of growing DIY community. Yearly member dues are only 2 broke spokes and 1 stiff link.

dweenk

I just checked a one of my bikes with SRAM twist grip and Shimano cog. The model is an MRX. As I recall the SRAM X was for SRAM clusters only.

Bill Kapaun

The SRAM & Shimano cassettes are interchangeable so it doesn't matter which brand "shift system" you use.
Not all SRAM shifters are interchangeable with Shimano DERs or vice versa