What adjustment can I make to fix this problem ?
 

What adjustment can I make to fix this problem ?

I developed a new problem on my Trek 7300 Hybrid today. The right hand (rear) deraileur control seems to slip into higher gears with the most minimal touch. The gear changer is a twist grip. If I make the smallest movement it shifts into a higher gear. This began rather suddenly. The only thing different is that I washed and greased the bike just before the ride prior to this.

Can anyone tell me if there is an adjustment I can make to correct this ?

I have Attached photos of the derailleur & control.

Thanks.

Babel

Slightly off topic: Your username is also a film. Have you seen it? Great movie!

Slipping
 

You might want to adjust the rear barrel adjuster just a bit. It sounds like the cable is a bit loose and it wants to jump up into the next gear at a moment's notice. That would cause this type of reaction. If not, make sure there is no bind anywere in the cable. If the cable is bound somewhere and is putting too much pressure on the cable and it could jump. You will need to make sure there is a straight line from the cable housing at all locations. Make sure the cable is lubed also.

Higher gear meaning, smaller cog or bigger cog?

Put the chain on the small chainring up front and the big one in back and take up the slack. Screw the barrel adjuster in all the way and then turn it counter clockwise about 3 turns. Then tighten the cable, that should do it. You'll have enough to fine tune it with the barrel adjuster when done.

Operator: higher gear meaning smaller cog.

Donegal: I did not find anything obvious putting pressure on the cable. I've never lubed the cables; perhaps I should. Excuse my inexperience, but where is the rear barrel adjuster ? Is it a screw ? Could you direct me to a diagram that shows it or point it out on the pictures I uploaded ?

George: This rear barrel adjuster - after I put the chain on the small chainring up front and the large one in the rear, how do I take up the slack ? Sorry, I really don't know much about these things. After I locate the barrel adjuster and screw it in then out, how do I tighten the cable ?

Thank you everyone.

Babel.

Loosen the bolt that holds the cable, then with pliers pull the slack out and retighten the bolt.

That looks like a SRAM rear derailleur to me.

I suspect that your rear shift cable needs a little more cable tension. That's common on relatively new bikes after they've been ridden for a while. Shift into your smallest rear cog. The shift cable should still feel taut. If it doesn't, there is a barrel adjuster where the cable exits your shifter. Turn that barrel counterclockwise about 1/2 turn and go for a ride to check the shifting. Repeat if necessary.

Sorry about that, Retro Grouch, is right, it is the small cog in back.:o

Do you mean that the shifter moves to freely? You might have a broken or collapsed ratchet spring. You can replace the spring but the shifters are pretty cheap.
On the other hand if it easily shifts/drops just one gear and requires over shifting to get it to go to an easier gear you need more cable tension

+1
This sounds like the best answer to me. It may be that the cable has slipped where it is attached to the rear derailleur.

This is not a cable adjustment, since it isnt a question of the chain getting into the right position on the sprocket. It looks like there isnt enough friction to hold the shifter in its detents. I think Rev Chuck has it on the broken spring. The SRAM website doesnt show any friction adjustment so your best solution is to go back to the shop where you bought the bike.

Here's what I just did: I loosened the Allen bolt and tightened the rear derailleur cable as much as I could, which was about a quarter of an inch [I've never been brave enough to adjust a deraileur before, so thanks for talking me through it, guys]. That made me unable to get into the largest rear cog and put the numbers on the twistgrip wrong, telling me that the cable tension was correct in the first place. In addition, the spring on the rear derailler appears to be seated normally and to have a normal tension.

Rev.Chuck: are you referring to this derailleur spring or a spring in the handlebar grip shifter ? I now feel the handlebar rear twistgrip shifter is the problem, as there is too much "play" in it.

I guess I will have to bring it into the shop I bought it from. Unfortunately the shop is far and I can only get there on a weekend. Since the mechanic is there weekdays only I have to leave it & pick it up later. Since tomorrow is a half day in most places I can't drop it off or I won't be able to pick it up to ride on New Year's Day. Well, it is still very ridable, I just have to be careful to not let the rear shifter slip into a higher gear unexpectedly.

I'm off to ride. Will drop the bike off at the shop January 6, giving them a whole week to work on it.

I am talking about the spring in the shifter. It is a hairpin spring with a bump in the middle of one of the pins that gives you the detents. Since the bike is new a trip to the shop is in order because I am pretty sure they are going to just replace the shifter.

Thanks, Rev.Chuck.

A broken or disconnected spring in the handlebar twist-grip sounds right.
The bike is actually about three-and-a-half years old.
It is likely, as you said, they will replace the shifter. Not sure what that would cost but it certainly sounds necessary.
I will bring the bike in as soon as I can get there with enough time for them to work before the next weekend, so probably not until afternoon of January 6.

Babel .

I was able to get away from work early enough yesterday to get the Trek to the bike shop three towns away . I spoke to them today and the mechanic confirmed it is the shifter that needs to be replaced. I will pick up the bike, ride it this weekend, then drop it back off on Sunday. The mechanic will order the shifter and work on it next week. Hopefully all will be well.

You hit the nail on the head guys. Thanks !

I'll let you know after all is done if the problem is solved.

Still waiting for shifter part to arrive at bike shop. Twice I've brought it home Friday to ride over the weekend and returned it Sunday afternoon. This time I'll just wait for them to call me that they've received the part.

They decided to take the shifter off a stock bike and put it one mine. Just picked it up. Seems to have solved the problem. Will take it out this weekend and see for sure. Wonder why they had so much difficulty obtaining the rear derailleur shifter?

Sometimes the suppliers are out of stock. We need some 20" and 24" unicycles but ALL of our suppliers are out. A while back we had trouble getting SRAM shifters in singled and had to get them as sets. When they finally got them back in stock we grabbed a bunch(Which might be why your guys had a hard time finding some :) )

Could be Rev.Chuck, could be indeed.

Well I hope my guy can get one SRAM shifter, or a pair, before he needs to sell that other bike he took it off of.
And it was a pleasure indeed riding today without having to devote attention to staying in gear on the rear deraileur. A pleasure indeed.

Thanks, everyone, for the advice.

Babel.