SRAM GX rear derailleur

[HermanMathee]

Need some help!!!

 

Trolled the net to death, but not able to figure out the differences between the 1x11 and 2x11 SRAM GX rear derailleurs?

 

Yes you get two versions, never expected it:

https://www.sram.com/sram/mountain/family/gx

http://www.chainreactioncycles.com/za/en/sram-gx-1x11-speed-rear-mech/rp-prod135897

http://www.chainreactioncycles.com/za/en/sram-gx-2x11-speed-rear-mech/rp-prod135898

 

After looking at the SRAM tech docs, it seems that the 1x11 is only avail in a long cage version that makes sense, but apart from that, what is the real world differences, will a 1x11 unit work on a 2x11 setup. As I see it , it is as easy as the rear derailleur should just be able to shift 11 gears.

 

Shimano only has one 11sp Xt derailleur, why does Sram need 2?

 

Looking at GX 2x11 crank + 104bcd single chain ring, 2x11 front derailleur, XT 11-42 cassette (due to XD driver), xt chain, SRAM GX shifters, but the rear derailleur is the Q?

 

The above will enable me to experiment with a 1x11 setup and still be able to change over to a 2x11 setup for the days that you start at the back and need to work your way thru the walkers on the hills, or help to get to the end of the TransBaviaans.

[Captain Fastbastard Mayhem]

It's a different parallelogram. Moves very differently through the range of motion. You'll see that the pivots on the 1x RD are more vertical, which means it moves more sideways rather than across and down, which is what the 2x RD does. 

 

It apparently is optimized for 1x and helps with the chain retention and shifting on a 1x system. 

 

With its “horizontal parallelogram” design and pulley offset, X-HORIZON™ keeps the chain gap constant across all 11 gears, providing fast, precise shifts. By limiting all movement to the horizontal axis, this design is faster, reduces shift force and eliminates ghost shifting. ROLLER BEARING CLUTCH™ technology reduces bounce and chain slap. CAGE LOCK™ technology makes wheel removal and installation easier than ever before. Paired with the XX1 shifter, the X-HORIZON™ RD forms the backbone of X-ACTUATION™ technology for unbelievably smooth shifting action.

• This XX1 rear derailleur is an integral part of the SRAM 1x™ drivetrain system. NO COMPROMISES.
• X-HORIZON™ design reduces shift force, ghost shifting and chain slap
• 12-tooth X-SYNC™ pulley wheels
• Large upper pulley offset automatically adjusts chain gap
• Ceramic bearings
• Carbon cage

[HermanMathee]

Makes sense that the movement on the 1x11 would help wit chain retention as more of the chain will stay in contact on the front chain ring.

 

The question now, will this 1x11 derailleur be a bad thing when used with a 2x11 setup or the other way?

[Captain Fastbastard Mayhem]

Makes sense that the movement on the 1x11 would help wit chain retention as more of the chain will stay in contact on the front chain ring.

 

The question now, will this 1x11 derailleur be a bad thing when used with a 2x11 setup or the other way?

2x11 can def be used on a 1x setup, but I'm not sure of the other way. A cursory search didn't bring anything up with regard to compatability, but I wouldn't do it. Criminal, I say.

[HermanMathee]

I'm also thinking the best compromise would be the 2x11 unit, especially seeing that I want to cater for two different types of scenarios.

 

Who's prices on SRAM components is the best in our country?

[Christian van Zyl]

I'm also thinking the best compromise would be the 2x11 unit, especially seeing that I want to cater for two different types of scenarios.

 

Who's prices on SRAM components is the best in our country?

Check out https://www.buycycle.co.za they also have a live chat where you can ask an agent about stock and pricing. Also ask if they can do a good deal for you. 

 

They have 3 stores, but is also tapped into the distributor's stock sheets

[droo]

You can't use a 1x RD on a 2x setup - the X-Horizon parallelogram with its offset pulley is designed to work on 1x setups - the offset pulley maintains the gap between the pulley wheel and the sprocket using chain length.

[HermanMathee]

Thanks for all the input, you are spot on.

 

Here is CRC response:

The 2x11 rear mech is designed to cope with the extra slack chain you will have between chainrings of a double crankset. The 2x11 will still work with a single drive train.  

There is medium and long cage versions of the 2x11 mech.

Long - Needed for suspension bikes, due to chain growth.  

Medium - Hardtail's only.

You cannot use the 1x11 rear mech on a double crankset. You will need to change the chain length between the two set-ups. 2 chains and a link removal tool will help.

[Skylark]

You can't use a 1x RD on a 2x setup - the X-Horizon parallelogram with its offset pulley is designed to work on 1x setups - the offset pulley maintains the gap between the pulley wheel and the sprocket using chain length.

 

Meaning if you change the chain length(from the perspective of the RD) by shifting from say the small blade to the big blade it will make the 1x RD spaz out?

For interest sake what happens if you do that?

[Hilton.]

Meaning if you change the chain length(from the perspective of the RD) by shifting from say the small blade to the big blade it will make the 1x RD spaz out?

For interest sake what happens if you do that?

 

Here's the pic from the SRAM site, showing their 1x tech:

 

See how the upper jockey wheel is offset quite a bit from the bright red knuckle pivot point? See how It is locked into a fixed position / angle relative to the knuckle pivot point and the lower jockey wheel?

 

That is done so that as you go up the cassette to a larger rear sprocket (easier gear), the cage (arm) is extended forward, which also now brings the upper jockey wheel downwards, thereby keeping a constant distance between it and the sprockets (i.e. constant chain gap). The angle and offset of the upper jockey wheel is precisely calculated so that the chain gap is constant all the way up / down the cassette, based upon how the rear cassette sprockets are sized (10-42).

 

If you now use this in 2 x 11 speed, it wont react very well when you change the front chainring. The cage will have to extend forward going to the bigger chainring to accomodate the extra length required, but this will also bring the upper jockey wheel down, away from the cassette sprocket which hasn't changed. This means the chain gap would change dramatically when moving between front chainrings.

[Captain Fastbastard Mayhem]

Meaning if you change the chain length(from the perspective of the RD) by shifting from say the small blade to the big blade it will make the 1x RD spaz out?

For interest sake what happens if you do that?

Yes. As explained perfectly by Hilton

[Spoke101]

Meaning if you change the chain length(from the perspective of the RD) by shifting from say the small blade to the big blade it will make the 1x RD spaz out?

For interest sake what happens if you do that?

 

You rip your DR apart or if you lucky the hanger will go first.

[HermanMathee]

At the end of the day I went for a 1x setup, just used the GX 1400 crank, this way I can swop spiders and convert to 2x if needed without changing cranks.

 

But as I see it I'll just gear it by swapping chainrings, for a long event like the TransBaviaans a 30 or even a 28 will work a treat, no need to paddle like crazy on the downhills at night.