Bicycle Mechanics - Grip shift problems
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09-04-11, 02:09 PM
I have tried to replace a derailleur cable on a bike with a grip shift (Some kind of SRAM) and it shifts up fine, but it will only shift down once from the top gear. It's not the tension, it seems like something is blocking the downshift. I have checked some of the SRAM manuals, but I can't tell what I'm doing wrong. Any ideas?
09-04-11, 02:56 PM
I'm not understanding the exact problem. You can somehow get it to the lowest gear, then it shifts normally all the way to the highest gear (one click, one gear), but when you try to downshift from the highest gear, you can only make the thing click once and downshift one gear? And then, you can't rotate the shifter any more? Or what?
09-04-11, 03:29 PM
OK, so I originally replaced the cable in 1st gear (which as it turns out is the wrong gear to start with). Anyway, with the grip shifter I had to partially take it apart to put in the new cable. So I put it back together, try it out and it shifts up fine from 1 to 8. But when I wanted to go down, I went from gear 8 to 7 and could no longer move the grip shifter. I thought the problem may have been putting it together in gear 1, so I tried again in gear 8, as the manual says. Well the same thing happened on the down shift. I went from gear 8 to gear 7 no problem, then the shifter got stuck. It's not a tension problem, because even if I take all the tension out, the shifter still won't budge.
09-04-11, 04:21 PM
It would be lack of tension if you can't downshift. Could be a cable routing within the shifter problem. Those things can be tricky to get back together properly. Try it again in gear 8. Make sure you have all the slack out of the cable. Try running through the gears without the cable attached to the derailer while gently pulling on the cable. See if the cable pull seems normal.
You can usually replace cable on Sram MRX and some other Gripshifts without disassembly, by the way.
09-04-11, 04:57 PM
Could be a cable routing within the shifter problem.
Yeah, did you make sure to thread the cable through the little slot on the bottom of the rear of the derailleur? Also, do you have finials on all the cable housing ends, and are they seated right in the cable stops? And that the cable is correctly wound inside the shifter barrel?
Hope you get it working, grips can be a real PITA to service.
09-04-11, 06:39 PM
Update: I feel like a jackass about this one. After trying again with very little tension, I realized that the shifter just gets stuck on the way down from 7 to 6. I needed to twist with a ton of force to get it to shift. After that, it downshifts fine. I still have to work out the right tension on the cable, but I solved the hard part. Thanks for the input!
09-16-11, 07:47 AM
The SRAM GripShift 'comp' comes with the cable already installed so it is a good choice if cost is not a problem. One thing though, the MRX version is only for SHIMANO derailleurs; it is the version WITHOUT 'MRX' that is for SRAM derailleurs. I had a similar problem threading a cable into one of these and frankly there was just no way to do it. Eventually I had to move to position 7, the highest gear on mine, then ease off the parts, the grip then the rotating wheel.
Those who have a working GripShift should seriously consider studying the internal cable run by opening the shifter BEFORE attempting to run a new cable. Do not just pull out the old cable without studying the matter in detail. The SRAM procedure cannot be trusted.
The internal mating part of the grip section fits above the spring when you are putting it back, and remember to put back the wheel on the high position. (As I see it, position 1 is an absolute mix up). Anyway, feed the cable through the outer grip then across the wheel and through the small hole in the wheel, then down the side channel to go through the barrel adjuster. It helps if you bend about half a centimeter at the end of the cable, to help it through the barrel adjuster. Then reassemble and check that it lengthens and shortens the cable correctly before reconnecting the derailleur.
The SRAM version of how to install a new cable in a GripShift is absolutely impossible to follow, and I suspect many just buy a new shifter with cable installed for that reason. The straight 1:1 versions are getting a bit harder to find though, so it would be good if somebody with a camera made some photos of it and produced an instruction set for all of those who will some day need to thread a cable themselves.
Regards, and good luck, Honestron, London
09-16-11, 07:14 PM
I must be really lucky because I replaced 6 grip shift cables on a bunch of kids' dept. store bikes not long ago. My main issue was finding the varied position on different grip shift models where the cable head actually threaded through. Some were tucked under some rubber flap of the twist mechanism. Some on an inside edge of the shifter facing the brake lever clamp. But in all cases, I was able to thread the cables back in no problem. I think the reason was that prior to running this repair workshop, I got a cheap soldering iron and just melted a little soldered one the cable the tips of a few new derailleur cables and then pinched the tips to make them sort of pointed but no overly so. This really let me push around inside the cable routing path and not worry about causing the end to bend a strand off the cable.
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