Upgrading to SRAM GX Eagle 12 Speed - When 2 Becomes 1

When the time came for Alistair Philander to replace the drivetrain on his Trek, he thought it would be the best opportunity to drop some weight and gain simplicity. After consulting with the team at The Bike Park, he decided to go for SRAM’s 12-speed GX Eagle drivetrain. With its wide range 10-50 cassette and several chainring options, it was a simple enough task to give him the range he was used to in the process.

Crankset


SRAM GX Upgrade 2.jpg

 

The GX Eagle crankset has forged aluminium crank arms that are stiff, strong and reliable. Completes its performance mission with the new X-SYNC2 direct mount chainring. With numerous Eagle X-SYNC2 direct mount chainring size options, we thought it best to discuss the rider’s needs first. A 32T was decided upon to give him the range he was used to and prefers. Coming from a 2x10 speed drivetrain with 38/24T chainrings and an 11-36 cassette the Eagle drivetrain gave him a slightly lower granny and top gear – perfect for his needs. Check the gear ratio charts at the end of the article for further details on this.

 


SRAM GX Upgrade 1.jpg

SRAM GX Upgrade 11.jpg


TRUVATIV’s crank engineers threw away the old standards and developed a new chainring geometry from the ground up. They precisely paired the different-sized chainrings and redesigned where and how the chain engages with the rings. By aligning the chainring pick-up rivets to the chain pivot pin—rather than the middle of the chain link—you get double the shift opportunities.

 

XD driver


SRAM GX Upgrade 7.jpg

 

SRAM developed the XD driver for their 1x 11 speed XX1 drivetrain to allow the use of a 10T sprocket on the cassette. Up and until that point the smallest sprocket that would fit over a freehub was an 11 tooth. On paper, it seems small, but that one fewer tooth out back has the same result in ratio jump as going two chainring sizes smaller in front. (E.g. dropping from 24T to 22T). This gave the drivetrain the extra range needed to suit the bulk of riders. That was of course before they launched the 12 speed Eagle drivetrains available today.

 


SRAM GX Upgrade 8.jpg

SRAM GX Upgrade 9.jpg


The XD compatible driver body design is an open standard available to any hub manufacturer interested in producing a driver body compatible with the XX1 10-42 11-speed or 10-50 12-speed cassettes. The cassette slides on much like the existing cassette, which interlocks with a spline system at the rear of the driver. From here, a standard Shimano-type cassette lockring tool (with a spline length of 7-8mm) is used to tighten the cassette onto the body.

 

Cassette


SRAM GX Upgrade 1-2.jpg

 

The GX Eagle cassette is made up of pressed steel cogs held together by stainless steel pins. The largest 50 tooth cog is made of aluminium. The material costs and manufacturing process are far cheaper than the XX1 and X01 cassettes that are machined out of a solid piece of steel and results in a cassette that is only 95 grams heavier. The first eleven cogs match the sizes of the familiar 11-speed cassettes (10, 12, 14, 16, 18, 21, 24, 28, 32, 36, 42) with the addition of the larger 12th 50 tooth cog for added range.

 

SRAM GX Upgrade 1-3.jpg


SRAM GX Upgrade 6.jpg

SRAM GX Upgrade 10.jpg


The open design aids in mud clearance, giving you cleaner shifting performance and longer component life. Although the manufacturing process is simpler, the cassette is not short on technology.

 

 

Chain


SRAM GX Upgrade 13.jpg

SRAM GX Upgrade 4.jpg

SRAM GX Upgrade 14.jpg

 

The GX Eagle chain features solid pin construction and smooth, efficient shifting that you can count on every time. Ultra-smooth chain inner-plates are completely devoid of square edges, resulting in a chain that engages the cassette and chainring with far less friction, for quieter performance and better wear life. The design allows a narrower overall profile that can withstand greater angles, and also allows for a flatter outer-plate, which means more consistent chain riveting and enhanced overall strength.

 

Shifter


SRAM GX Upgrade 19.jpg

 

Superior ergonomics and adjustability let you shift quickly, comfortably and intuitively with GX Eagle’s trigger shifter. It carries with it all of the enhancements and improvements that the XX1 and X01 Eagle trigger shifters received, improving trigger feel, precision, and durability in a forged aluminium body.

 

Weight savings


With the upgrade in drivetrain, the bike’s overall weight dropped from 12.29 kg down to 11.91 kg for a total saving of 380 grams.

 


SRAM GX Upgrade 3.jpg

SRAM GX Upgrade 15.jpg


The finished product


SRAM GX Upgrade 21.jpg

 

Gear range comparison


Gear Ratios 1.png
Gear Ratios 2.png




19 Comments

DirtyDan, Aug 30 2018 09:11

Beautiful!

Valuable upgrade going from the 2x10 setup.

Shebeen, Aug 30 2018 09:44

that headline is just begging for this gem from the depths music folklore treasure chest

 

Shebeen, Aug 30 2018 10:02

Beautiful!

Valuable upgrade going from the 2x10 setup.

I normally wait for the knock on effect of pricing to come down on the 2nd/3rd gen of these things. I see an eagle cassette in gold is still an insane R7k, really have to thank the rich posers for keeping the lights on at the LBS for supporting this. So I'm still on 2x10. (only moved from 3x9 XTR on mtb and 3x8 Sora on road about 2 years ago - that's now 2x9 ultegra, very behind the curve!)

 

I don't really have an issue with 2x systems, except when riding at night and when tired I can endup cross chaining. Installation cost is one thing, losing 380grams is not insignificant especially when you have items that are drivetrain wearing ones. The replacement of these items is still what scares me off for now.

 

RRP on this cassette is R2700 - https://www.cwcycles...assette-12speed

I'm guessing the closest equivalent to the 1275 is the 1070 - so that is RRP R1500 - https://www.cwcycles...assette-12speed

 

There are of course other options, but I'm not going to put that on a SRAM advertorial.

nickc, Aug 30 2018 10:38

Also went the Eagle GX route - loving it !!

Demetri, Aug 30 2018 11:21

Great insight. Allready got the eagle upgrade just waiting for the right time to install it. For now im enjoying my 1x11 Shimano setup.

slickjay007, Aug 30 2018 01:44

Really enjoy the Eagle GX setup..... smooth shifting and decent wearing.

Dirkitech, Aug 30 2018 04:25

I'm not overly familiar with newer bike weights and such, but isn't 11.91 slightly heavy, even with the new setup for a MTB?
If this exact same model bike with identical components were in 26", how much light would it be expected to be? 200g per wheel give or take, thats it?

Nick, Aug 30 2018 04:45

I'm not overly familiar with newer bike weights and such, but isn't 11.91 slightly heavy, even with the new setup for a MTB?
If this exact same model bike with identical components were in 26", how much light would it be expected to be? 200g per wheel give or take, thats it?

 

I'd say that around 12 kg is acceptable for an average specced XC bike. In fact, most of the pro bikes we looked at the Cape Epic were weighing in around the same. If it was weighed with those pedals and bombs on, then even better. I think we're just too used to seeing the top spec weights (with useless tyres and stripped down with no extras) being thrown around in marketing.

BaGearA, Aug 30 2018 04:51

Making that last cog out of alloy is A moronic move , just so they can get customers to buy more cassettes in when it wears out while the rest of the cassette is still fine 

Dirkitech, Aug 30 2018 05:03

I'd say that around 12 kg is acceptable for an average specced XC bike. In fact, most of the pro bikes we looked at the Cape Epic were weighing in around the same. If it was weighed with those pedals and bombs on, then even better. I think we're just too used to seeing the top spec weights (with useless tyres and stripped down with no extras) being thrown around in marketing.

Thanks for your input Nick :)

Furbz, Aug 30 2018 09:50

that headline is just begging for this gem from the depths music folklore treasure chest

 

 

i'm going to go ahead and feel awkward for you

 

that said, i moved from XTR di2 to sram 1x12 with twist grip and i felt it was an upgrade

riaan@uthetha.co.za, Aug 30 2018 09:58

Went from Shimano XT 2 x 10 to Sram Eagle 1x 12 on a Scott. Had gears slipping from Day 1. Returned the original derailleur to the manufactures and used a demo derailleur in the interim. Same problem. Received the brand new warranty replacement derailleur and still no joy. Bottom line is that this low end groupset is unreliable. I paid in and changed the derailleur and cassette to XO1 eagle and no problems. The problem is not with the crankset, BB or shifters. Two bike shops in Cape Town reported that they have had plenty comebacks on GX Eagle groupsets and both mentioned a bad batch (bull****). I have also chatted to a few riders on the trails and races and am yet to find a happy GX Eagle customer.

Forthelove, Aug 30 2018 11:00

Maths - a saving of only 38 grams - not 380 grams. Realy not worth the effort. Rather eat 3/4 of a banana in the morning!!

Nick, Aug 31 2018 06:40

Maths - a saving of only 38 grams - not 380 grams. Realy not worth the effort. Rather eat 3/4 of a banana in the morning!!

 

The scale is measuring in kilograms. The first decimal place represents 100 grams.

Pipsqueak, Aug 31 2018 10:19

I'm not a SRAM guy, so I've never used any of their stuff, but I'm amazed that that bearing just sits exposed on the end of the driver. Is the idea that you replace it when you replace the cassette?

bertusras, Aug 31 2018 11:28

I'm not a SRAM guy, so I've never used any of their stuff, but I'm amazed that that bearing just sits exposed on the end of the driver. Is the idea that you replace it when you replace the cassette?

 

There is an endcap that still fits on before you install the cassette

 

Dirkitech, Aug 31 2018 11:41

Went from Shimano XT 2 x 10 to Sram Eagle 1x 12 on a Scott. Had gears slipping from Day 1. Returned the original derailleur to the manufactures and used a demo derailleur in the interim. Same problem. Received the brand new warranty replacement derailleur and still no joy. Bottom line is that this low end groupset is unreliable. I paid in and changed the derailleur and cassette to XO1 eagle and no problems. The problem is not with the crankset, BB or shifters. Two bike shops in Cape Town reported that they have had plenty comebacks on GX Eagle groupsets and both mentioned a bad batch (bull****). I have also chatted to a few riders on the trails and races and am yet to find a happy GX Eagle customer.

In the entire setup, is the entry level rear derailleur the only problem? After upgrading the RD, did you retain the original shifters and cassette and can shift without hiccups?

Matturnza, Aug 31 2018 01:58

Making that last cog out of alloy is A moronic move , just so they can get customers to buy more cassettes in when it wears out while the rest of the cassette is still fine 

 

I have been running a X01 11speed cassette (the same one) since 2016. It was replaced 2016 cause it was squeaky and Sram warrantied it (i would have settled for the mechanic just putting some grease on it). It also has a aluminium 42tooth. Been ridden far, while i'm fat and lazy and never had an issue. I do replace chains every 7 or 800km.

 

Could you spend that much time in the 50t to wear it out? An expired chain will destroy any cog.

 

I think the 50t is aluminium as its cheaper to machine.

Stew rider, Nov 19 2018 10:02

I think it's really good and shifts smoothly. But I'm hoping that I won't have to replace my cassette, chain, and front chain ring any time soon