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Merida Big Nine Limited Al 2020 derailleur upgrade


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Hi Folks

Being inspired by Dan's video I went with Merida Big Nine Limited bike that came with SRAM SX drive train. Good price for recreational bike but I am disappointed with the SRAM SX. It worked very well initially however after last trip circa 50 km across hilly terrain shifting deteriorated. I only have done 3 XC runs totaling circa 150 km and few smaller runs. Let's say total 200 km on the bike. No crash, never hit anything only just ride it quite hard doing a lot of uphill.

The 12 gear set worked really well and would not need anything else, however it seems now almost impossible to get the shifting right. I started from scratch not being able to understand why shifting is not right and simple index tweaking would not help. It worked like a dream out of the box though. I reset limit screws, b-gap etc. and cannot find a reason why in the middle (4-7 gear) i get bad shifting and noise (chain being lifted up by adjacent sprocket). I ordered hanger alignment tool just in case got slightly bent and causing this hell. 

Being fed up with SX a bit by now causing this issues so early now I am considering in ripping it out and putting something more reliable, i.e. GX. I am reluctant to even think about XX1 or XO1 as those cost as much as whole bike itself. I do not race, but ride hard when I go out riding at least once a week and need reliable option.

The bike has Shimano MT400-B hubs so I believe these are not Sram XD compatible as required by GX, is this right? I am also reluctant to go with NX therefore questions are:

  1. What is an alternative product that would fit on the Shimano MT400-B and give me the same performance as SRAM SX but being more robust and last a bit longer? Could it be any Shimano 12 sp? To be honest I am not too sure whether I need that many gears, the low gear though is great and lets me climb all the hills I want to be able to climb. It's my first bike so have nothing to compare with, though range of gears from SX was great, could perhaps live with one sprocket taken out from the middle giving me the top and bottom range the same.
  2. If there is no alternative, can I easily install compatible hub on my Merida Comp CC wheels? If so, can I only do it for rear wheel or all? What parts will be required?
  3. Do I need to replace whole drive train or is it possible to upgrade only the derailleur or the cassette and all other bits also need replacing? Would be great if I could put GX or XX1 derailleur on existing drive train and replace other components slowly when they wear out. What is the compatibility across different SRAM drive train parts? They are all Eagle and I can't understand whether we are dealing with one eagle or a gaggle fighting with each other.
  4. Finally, I should perhaps ask it first, can I get this SX thing to work and continue with my recreational riding? 

I must admit I have not done enough research prior to bike selection but Dan's recommendation was to me good enough considering his experience and himself riding same model. I regret though I have not went with GX train bike instead :/.

All your experienced folks help is much appreciated. I would like to get back to riding asap. Obviously on a working bike.


UPDATE 12/05/2020

Straightening the hanger with ParkTool DAG-2.2 restored good shifting on SX derailleur, I have ordered the GX derailleur to try it with existing setup hoping for enhanced performance with SX drive train (crank, cassette, shifters, etc.)

Edited by 503
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