Derailleur compatibility.

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Salty seadog

Space Cadet...(3rd Class...)
Morning,

I may be replacing my rear mech, at present I have a Sram via GT groupset on my 2014 Whyte Montpellier.

https://www.sram.com/sram/urban/products/via-gt#sm.0000y095ehuzdfi10p12i61j5mvuh

https://www.avonvalleycyclery.co.uk/850152/products/whyte-2014-montpellier-carbon-hybrid-bike.aspx

I have never needed to change a rear mech before and would like some advice as to weather this one would be compatible and which cage length for an 11-32 cassette, long, medium, I suppose short is out.

http://www.wiggle.co.uk/sram-gx-2x10-speed-rear-derailleur-type-21/

all advice welcome thanks.
 

greenmark

Guru
Location
Geneva
Should be OK

This might be better: http://www.wiggle.com/sram-x5-10-speed-rear-derailleur/


Get long cage if you have a triple up front. Medium cage if you have a double. Short cage if you are running only single ring up front.


Key things you need to look out for in rear derailleurs:

  • Actuation: by how much the rear derailleur moves sideways for each millimetre of cable pull. These should match your shifters. Both the GX and the GT use “Exact actuation” (that’s 1:1 actuation). If you were to get an rear derailleur with a different actuation than your shifters then each click would not accurately move the RD accurately between cogs at the back.
  • Max Tooth: The GX has max tooth of 36 teeth, which is more than the largest cog in your your 11-32
  • Capacity: Most derailleurs have a rated max capacity, say, 46Teeth. The longer the cage then the larger the capacity. The capacity represents the total of the difference between the largest and smallest chainring up front and the largest and smallest sprocket at the back. So if you have say 48/32 up front and 11-36 at back, you would need a derailleur with at least 48 – 32 + 36 – 11 = 41 tooth capacity.
    SRAM doesn't quote the capacity of the GX derailleur but their compatibility map says if you have 11-32 then use long with triple, medium with double, short with one chainring.

The main difference between the GX and GT is that the GX is a clutch derailleur. This means it has movement restricted so that it’s more likely to keep the chain at tension when you’re going over bumps – which is nice if you’re doing big jumps on your bike. However, the clutch is a bit more fiddley to keep correctly trimmed and means you need to push an additional lever to allow it to get out of the way when you remove the wheel. You will need to familiarize yourself to the new system. If you want a simpler, easier system then look for non-clutch type medium-cage derailleurs from SRAM X9, X7 or X5 ranges, which is why I suggest the X5.


SRAM Compatibility map is here:

https://sram-cdn-pull-zone-gsdesign...v_c_compatibility_map_2016_mtb_components.pdf
 
OP
OP
Salty seadog

Salty seadog

Space Cadet...(3rd Class...)
@greenmark blimey, that's a great full answer thanks for the time. my setup would be 48-32 up front with the 11-32 cassette. It is on a flat bar fast hybrid not actually a mtb. I'm familiar with the clutch system as I have it on my 901 mtb. Would you say as bike for road use then you would go for the x5. I note the comment about about the GX clutch system being a bit more fiddly to keep trimmed, I'm not sure what you mean by this. Does it need more adjusting to keep it shifting smoothly?
 
Last edited:

greenmark

Guru
Location
Geneva
Some people have found clutch needs more frequent adjustments of the barrel adjuster to keep it shifting smoothly. It isn't a massive difference, truth be told.

Your choice of using clutch/non-clutch is up to you. If you have lots of bash marks on your chainstay from your GT then go for clutch. If you're constantly fixing punctures and need to take your wheel on and off a lot, go for non-clutch.
 
OP
OP
Salty seadog

Salty seadog

Space Cadet...(3rd Class...)
Some people have found clutch needs more frequent adjustments of the barrel adjuster to keep it shifting smoothly. It isn't a massive difference, truth be told.

Your choice of using clutch/non-clutch is up to you. If you have lots of bash marks on your chainstay from your GT then go for clutch. If you're constantly fixing punctures and need to take your wheel on and off a lot, go for non-clutch.

The review on the GX are somewhat mixed but are mostly from mountain bikers, I'm putting it on a flat bar road hybrid so will lean towards the X5. As a premium option there is this....

http://www.chainreactioncycles.com/mobile/sram-force-wifli-10-speed-rear-mech/rp-prod108149.

A road mech with a medium cage capable of taking the 11-32 cassette.

Pricy but with good reviews.
 
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