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SRAM MRX Plus Grip Shift lost its detents?
#1
Thank you for letting me join your group. My Giant Sedona 21-speed has a SRAM MRX Plus grip shift for the rear derailleur. It suddenly wants to stay in the 7th gear position. I can shift gears down to the first gear position, but the shifter does not click through each gear, it just goes smoothly through the gears against what feels like spring pressure or tension that wants it to return to the 7th gear. If you want it to stay in one of the lower gears, you have to hold the shifter in that position, as there are no longer any detents or stops to keep it in gear.

I am a complete newbie and don't know what the inside of the shifter looks like, but it feels as if it were constructed with a ring of 7 ratchet-like teeth and that ring is no longer there. Hope that makes sense.

I watched the "How to Adjust your Rear Derailluer" video, but I didn't think that was my best first step, because I cannot put the bike in the low gear (or anything but high) unless someone is holding the shifter.

Any help or advice is appreciated before I take it to the local bike repair shop. Thanks.
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#2
(01-15-2011, 08:53 PM)IamMatt Wrote:  Thank you for letting me join your group. My Giant Sedona 21-speed has a SRAM MRX Plus grip shift for the rear derailleur. It suddenly wants to stay in the 7th gear position. I can shift gears down to the first gear position, but the shifter does not click through each gear, it just goes smoothly through the gears against what feels like spring pressure or tension that wants it to return to the 7th gear. If you want it to stay in one of the lower gears, you have to hold the shifter in that position, as there are no longer any detents or stops to keep it in gear.

I am a complete newbie and don't know what the inside of the shifter looks like, but it feels as if it were constructed with a ring of 7 ratchet-like teeth and that ring is no longer there. Hope that makes sense.

I watched the "How to Adjust your Rear Derailluer" video, but I didn't think that was my best first step, because I cannot put the bike in the low gear (or anything but high) unless someone is holding the shifter.

Any help or advice is appreciated before I take it to the local bike repair shop. Thanks.

It sounds as if the shifter may be stripped, best repair is putting on a new shifter. You may be able to find a bike that uses a similar shifter that will work at a yard sale or auction or something like that, but I would guess a new shifter is in order.
Adjusting the deraileur will not help, but I think you already figured that out.
A new shifter like that should run about 10-15.00 plus whatever the shop charges for the repair. They are not difficult to change and they usually comes with the cables installed so, then after you install it you will probably need to adjust your deraileur at least a little, but maybe not too much.

I can get the shifter for you through my shop at http://www.thebikeshopinbooksandmore.com or you can get them through ebay or amazon.
Join me to discuss anything cycling at http://www.blogtalkradio.com/the-bicycle-nut
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#3
Most grip shifters have a c shaped spring clip that locks into each detent. It's possible it slipped out of place or broke. It fairly easy to open these up and take a look (although pay attention to the cable routing as you take it apart.
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#4
(01-15-2011, 08:53 PM)IamMatt Wrote:  Thank you for letting me join your group. My Giant Sedona 21-speed has a SRAM MRX Plus grip shift for the rear derailleur. It suddenly...

I recently had the same problem with old (~15 years) 7-speed SRAM gripshift. Opened it up and found that detent spring had broken in half. Knowing that I was looking at replacing both shifters as chances of finding replacement spring near zero, and being a bit crazy, I fabricated spring from piece of springy steel. Working great now. If you're crazy enough, and model is similar construction, cut strip of springy steel to same thickness as original spring with tin snips, bend bump in center to fit detents, then use needle nose plier to curl both ends gradually until spring fits fairly snugly in position end-to-end with detent bump nearly touching housing.
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#5
Get a new one, and take your old one apart to figure out how they work.

http://www.amazon.com/SRAM-Bicycle-Twist-Shifter-7-Speed/dp/B000C15HS2/
Nigel
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#6
+2 Get a new one
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#7
+3 for a new one. They aren't that expensive.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Giant
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