SRAM GX shifts fine up but not down. Do I need a new shifter?

PB Forum :: Mechanics' Lounge
SRAM GX shifts fine up but not down. Do I need a new shifter?
  • Previous Page
  • Next Page
Author Message
flag ShaolinWood
O+
Posted: Sep 1, 2022 at 0:49 Quote
Hi all. I'm trying to fix the shifting on my bike, here's the setup:
11 spd SRAM GX rear derailleur
SRAM GX eagle shifter
No front derailleur
(Not sure when last bike has been serviced. Bought it second hand)

So far I've set the limit screws and they seem perfect.
The tention on the cable feels right when you start from the highest (hardest) gear, shifts one at a time perfectly all the way to first gear (biggest cog)
BUT
From the largest cog when you shift down it doesn't go to the next one... it does if you shift 2... but then it starts getting all crappy through the middle. If you shift 2 or 3 at a time and then go to gear 2 it sits fine... and the all the way to gear 11 (smallest cog)
Also the click on the shifter dropping from that big gear feels very hard. You really have to press hard with the thumb, unlike all the others...

So I don't know if my chain might be stretched, don't have the tool. Can't see any stiff links
I don't know how to check the derailleur hight... I'm just eyeballing it... can this be an issue?
I have a few chipped teeth on my front chainring. I need to replace it but surely that won't influence things?

My logic tells me that since the ratios of the shifts upwards goes perfectly one gear at a time but down doesn't follow the same spacing... maybe the shifter is faulty? (Sorry down meaning to the smaller cog)
Or could this be something stupid like the cable housing needs to be replaced Razz

As you might have guessed I'm trying to avoid running to the bike shop for each little thing... also want to learn how to do this myself... so any help is greatly appreciated.
flag TimMog
Posted: Sep 1, 2022 at 3:42 Quote
If it's not shifting down properly, you probably have too much cable tension. Try a quarter turn at a time until it shifts up and down ok.
A bent mech hanger would usually shift fine at one end of the cassette, but not the other. Unlikely to be that, so try the cable tension first.
flag M0rd4c4i
Posted: Sep 1, 2022 at 4:39 Quote
A good clean of the derailiuer and reducing the cable tension should sort it.
flag ShaolinWood
O+
Posted: Sep 1, 2022 at 4:54 Quote
Hey thanks for that. That was the thing I tried first... but if I reduce the tention then it doesn't shift up right. The up shifting (small cog to big cog) works like butter... but once it gets to the biggest cog it doesn't come down on that first click... then if you drop it 3 then 2 back up it goes back to working well...

I've been tweaking cable tention for the last 2 days and keep getting into this situation... that's why I'm wondering if it might be the shifter...
flag ShaolinWood
O+
Posted: Sep 1, 2022 at 4:56 Quote
M0rd4c4i wrote:
A good clean of the derailiuer and reducing the cable tension should sort it.
Maybe I should try that. Not sure how I'll clean it though, but could be that it's gunky... maybe that's why it's not releasing once it's that tight. Mmmmmm
flag lyzyrdskydr
Posted: Sep 1, 2022 at 8:44 Quote
Sounds like you might need a new shifter cable and housing. When they get old/corroded/gunked up it creates friction between the cable and housing, causing issues shifting down to smaller gears as the cable tension is not released fully/evenly when you shift. Also sounds like the shifter could be gunked up if you are having to push hard on it in certain spots.

To diagnose you could disconnect the cable at the derr, and slide the cable housing down from the shifter. You can drip a few drops of chain lube down the cable into the housing and cycle the cable back and forth. Also perhaps try spraying some solvent/cleaner into the shifter to clear it out. This is not a long term fix but if the shifting improves from lubing the cable it confirms you need new cables and housing.
flag johnovey
O+
Posted: Sep 1, 2022 at 8:54 Quote
Check hanger alignment, b-tension adjustment & check for any resistance in the cable & housing.
Unlikely the shifter, but possible.
flag aegiz
Posted: Sep 1, 2022 at 11:22 Quote
Hold up... 11s RD with an eagle (12s) shifter?

*edit* I should have said, 11s rd & cassette?

Number of cogs on the cassette should match the shifter.
flag lyzyrdskydr
Posted: Sep 1, 2022 at 11:28 Quote
aegiz wrote:
Hold up... 11s RD with an eagle (12s) shifter?

Works fine if you set the limits right. Sram 11/12s mtn have the same cable pull rate
flag aegiz
Posted: Sep 1, 2022 at 12:13 Quote
lyzyrdskydr wrote:
aegiz wrote:
Hold up... 11s RD with an eagle (12s) shifter?

Works fine if you set the limits right. Sram 11/12s mtn have the same cable pull rate

11 and 12s SRAM shifters have the same pull ratio, but do not pull the same length of cable.

11s shifter on an eagle derailleur, paired with an 11s cassette will work.

I'm sure some people have gotten OP's setup to "work", but it's likely that the indexing and shift consistency is brutal.
flag brianl
Posted: Sep 1, 2022 at 12:35 Quote
could be cable/housing like was said. If you unhook the cable from the rear mech, pull on that end and run the shifter up and down to see if the cable moved freely or hangs up. Also check that the mech pivots and moves back and forth freely.
flag M0rd4c4i
Posted: Sep 2, 2022 at 4:07 Quote
ShaolinWood wrote:
M0rd4c4i wrote:
A good clean of the derailiuer and reducing the cable tension should sort it.
Maybe I should try that. Not sure how I'll clean it though, but could be that it's gunky... maybe that's why it's not releasing once it's that tight. Mmmmmm

Use a brush and some degreaser, and don't forget to lubricate it afterwards to make sure it moves freely and efficiently.
  • Previous Page
  • Next Page

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv65 0.010510
Mobile Version of Website