I was fixing/attempting to fix a friend's bike last night. He was complaining that the chain comes off of the cassette and bumps into the chain guard when shifting into 1st gear. Otherwise it shifts just fine.
I thought, simple, I'll just adjust the high gear stop screw.
However, the stop screw was already turned in the whole way and there was no more adjustment left.
The derailer is a SRAM 3.0
It seems like a longer screw would fix the problem. Are longer screws available?
The derailer and hanger looked to be in good shape and did not look bent. I'm stumped and I feel guilty about the beer I accepted as payment considering I didn't fix the problem.
Are you sure that was the high stop?
I guess you could get a longer screw but it sounds wrong. I'd be thinking the hanger was bent. How is the shifting at the other end of the range?
Is the frame and axle straight? IOW, are the cogs all parallel with the chain line? (I once had a couple of plastic spacers fail, and the cogs got askew. Wasn't obvious at first.)
You want to adjust the *low* limit screw not the high.
A longer screw is not what you want to solve your problem, in any case.
I think I got the high and low stop confused. I'm talking about the screw that keeps the derailer from going too far and kicking the chain into the spokes.
The hanger and cogs all look good and straight. The wheel turns fine so I think the axle is straight and the bike rides fine so I think the frame is OK. Shifting throughout the gears is perfect. It's a grip shifter system and when you turn the shifter to where it bottoms out on 1st gear it kicks the chain off of the cassette and into the spokes. If you shift it just right without bottoming out the shifter it shifts into 1st gear fine and stays there.
The cassette is one of those 7 speed mega range cassettes with a huge 1st gear.
I just need something to tell the derailer to stop before kicking the chain off.
Thanks for the responses.
I have to agree with the above, you want to be adjusting the screw marked "L" on the derailleur arm, if the markings have worn off, should be the upper of the 2 screws.
How much beer did you get for this adjustment? I would say 1 six pack to adjust it, 2 six packs to adjust it right.
That derailleur is designed for 8/9 spd hubs, which have a wider freehub body than 7 speed. You'll really need to pull the low limit in quite a bit. They're usually supposed to have enough adjustment to be able to do this on a 7 speed hub, but I think you may be on the right track with the longer screw.
Edit: googled the part and everything says it's a 7/8 or 7/8/9 speed derailleur, so it *should* work right out of the box... is this OEM on the bike?
This is OEM on the bike.
I 100% sure I was adjusting the correct screw.
The screw that I was adjusting would only have an effect on the derailleur when it was in the 1st gear position. I'm usually good at figuring things out mechanically, but crap at remembering what things are called.
I messed around with this thing for like an hour last night. I had the "L" screw bottomed out, the shifter cable detached and I was shifting gears by pushing the derailleur with my hand and it was still going too far and knocking the chain off. I put it all back together and took it for a ride. It was shifting properly, but the derailleur still wanted to put the chain into the spokes shifting into 1st gear. Dont worry, I rode REALLY slow to avoid spoke damage.
I have an old Shimano STX derailleur that I can put on the bike. I think I also have an Alivo collecting dust somewhere. Will either of these work with the mega range cassette? The reason I'm not sure is because this SRAM derailleur that's on the bike now has an extra arm that the shift cable wraps around. It says 1:1 pull ratio on the side of the arm.
Got one six pack for the adjustment. Consumed after working on the bike BTW.
Thanks for the help
@Heffner Sometimes but not usually. There was a lot of overlap between 7 and 8. Unless it's a particularly old freehub it's the same width as 8/9/10.
@RK No, those Shimano der's won't work with the SRAM stuff you have. They have different geometries tied into the 1:1 cable pull SRAM uses.
I thought the question was going to be, "Did I spell 'derailer' right?"
That's sheldon's spelling.
Y'know, my derailer has two different possible cable routings. If you do it one way, it works with a ten-speed shifter, and the other works with a nine-speed shifter. Just a thought.
Though it really shouldn't matter, the limit screw is supposed to be enough to keep the derailer in line.
Does this only happen when you are on the bigger chain ring? It may be an alignment issue. Forgive me if this is an obvious comment, but seven cogs with three chain rings doesn't exactly equal twenty-one gears. The lowest (biggest) cog should only be used when in the lowest (smallest) chain ring.
Sounds like you've covered all the obvious stuff. Without seeing it myself, the only thoughts I have are that the hanger is bent (you say it isn't but that's not always easy to eyeball), the derailleur body itself is bent, or the pivots are badly worn.
Yeah, I was on Sheldon's site before posting here. I figured I would take his word on the spelling.
I'll have to look at the derailleur to see if there is any alternate shift cable routing.
This happens on the small ring and middle ring. Didn't try it on the big ring.
I'll have to look at the hanger again. Maybe it was bent and I didn't notice. I'm pretty sure the pivots are in good shape. This bike hasn't been ridden much.
Given a day to mull this over in my head, I'm thinking the place where the adjustment screw meets the derailleur body got bent. It's like a 3/32" thick piece of metal. It looks kind of flimsy and is probably the weakest link in the chain of things that can go wrong.
Thanks for everyone's help.
