Monday, August 14, 2017

Sram GX 1x11 MTB drivetrain 1000 mile review

This spring, I finally caught up with the rest of the world and got rid of the front derailleur on my mountain bike. Now I've got some good miles and a few races on it and thought I'd write some more words. I see way too many reviews of stuff that consists of "hey check out these new parts, looks cool, right?" Well, try it out for an extended period of time and get back to me. So that's what I've done, and the conclusion is that it's pretty good.





I used the following parts:

Sram GX 11-speed shifter
Sram GX rear derailleur
Shimano XT 11-42 cassette
Shimano HG-601 chain
One-up 32t sram direct mount chainring
Total cost was around $260.

GX is one of Sram's cheaper 1x offererings, sitting above NX, and below X1, X01, and XX1. There is also now a 12-speed eagle version of GX which is very well priced. I went with these parts because I was on a budget, and GX is the least expensive level that offers "zero-loss" shifting. This means there is no free play in the levers before cable moves. I tried the NX shifter, which does not have that feature, and could notice the extra movement in the lever before it shifts. The GX part feels good and shifts are crisp and instant. Coming from my di2 road bike I actually don't even notice much difference, although sometimes I find myself holding down the upshift paddle, expecting it to keep going. An NX rear derailleur would have saved a bit of money with probably no change in function, but the GX part was barely more expensive (about $30) so I thought I'd have it match. Making the jump to X1, the next level, however, would have cost way more; MSRP on an X1 shifter and RD is an extra $155 but as far as I can tell it's functionally the same, and the listed weight saving of the two parts is only 10g. So no thanks. X01 and XX1 are even more and I just can't justify that kind of $ per gram of savings.

And yes, I mixed shimano and sram, for two reasons. The XT cassette is way less expensive than a Sram equivalent (only $65 online, sorry MBW), and it works on my freehub. When I toasted one awhile back I tried to find a Sram XD driver but Easton doesn't make one for my wheels, since they were made all the way back in 2012. But still, I wanted to use a sram shifter and derailleur because I like them, it matches the rest of the stuff on the bike, and the brake lever and shifter go on the same clamp which is nice and clean looking.



I moved the the fork lockout, which is built into the clamp, to the other side so that I wouldn't have three things coming off the right side and just a brake on the other. I'm considering going to a non-remote lockout compression damper to clean things up even more. And when sram comes out with e-tap for mtb and cx bikes that will be really nice.

My cranks (sram X9), use a removable spider to attach the rings, so I was able to just remove that whole thing and put a ring straight on. Way less stuff, way lighter. The single ring compared to the spider, ring, bolts, shifter, derailleur, cable, saves 430g. That's like a whole pound off the bike.


So, I simplified, and added lightness. There is only one downside, and that is the narrower gearing range. Before, I had 26/39 x 11-36. To get the equivalent range with a 1x I would have needed sram's new 12-speed eagle; a 36t and 10-50 cassette works out nearly the same. This loses out on both ends, with 32x42 being equivalent to 28x36. (so it's like if I had a double with an 11-36 cassette but 28/32 rings. Not much of a gap there). My previous gearing was already fairly tall, and this takes it a step further, but it works on a light XC bike. 32x11 on the other end seems to be plenty for trail riding and racing, but runs out at about 25mph, which you do encounter going downhill on roads..

There are a few ways to get more range out of 11s. Firstly, the sram XD freehub with a 10t little cog. 30x10 is taller than 32x11, so I could have used a smaller chainring without losing out on the top end. But no such luck with my wheelset. Another option would be Shimano's 11-46 cassette, but I was worried about the big jump to that cog, since the next smallest gear is the same size, 37t, on both. I find myself going up onto the 42 under load pretty frequently and even that takes slightly longer to catch compared to shifts in the middle of the cassette.

The lack of range, however, is more than made up for by how well it works, and the ability to ditch the front derailleur. With the old setup, I would experience chain suck, shifting problems, occasional dropped chains, and noise from the chain hitting the chainstay. The narrow wide chainring and clutched derailleur hold the chain in place much better, so the drivetrain is silent and the chain always stays in place. And despite GX being the budget group, shifting performance is excellent. I would challenge anyone to say XX1 feels or works any better.

If you still have a front shifter on your mountain bike, I'd strongly suggest getting rid of it. This is old news I suppose, but I only just got around to it and still see plenty of them around. I accept that there are still some cases where a front derailleur is useful, like bikepacking/touring, but now that we have 12-speed 10-50 cassettes I'm not even sure about that. The only caveat is that you need to do a little gear-chart math and be realistic when choosing a chainring size. If I was riding a heavier, full-suspension, more trail oriented bike, I would definitely want easier gearing.




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