Shimano GRX & 105 12-speed mechanical groups

shimano GRX 12-speed mechanical gravel bike being ridden on smooth dirt road

Shimano has delivered two premium mechanical 12-speed groups, giving riders who shun battery-powered drivetrains more options for road and gravel. Here’s all the new tech and features, starting with GRX, then 105.

Shimano GRX RX820 gravel group

shimano GRX 12-speed mechanical gravel bike drivetrain group

TL;DR Overview
The new GRX 12-speed adds a cog and dramatically increases gear range, especially for the 1x groups thanks to much larger cassettes. It remains an Ultegra-level equivalent, making it the highest-end mechanical shifting 12-speed group on the market.

A modular 1x rear derailleur lets you swap cages if you want to switch cassette sizes. Brakes get more pad clearance, and the hoods have improved ergonomic shapes, but all levers and performance stay the same. Crankset carries over with a new finish, and chainrings have the same sizes but are now optimized for 12-speed chains.

Wider-range gearing options

The original GRX was 11-speed and maxed out with 11-34 cassettes for 2x, and 11-42 cassettes for 1x. The new GRX 12-speed goes much bigger:

GRX 2x Gearing
The 2x drivetrain keeps the 48/31 chainring combo but borrows the larger 11-36 cassette from the new 105 12-speed groups. You can also pair them with 11-34 Ultegra and Dura-Ace cassettes for a lighter, narrower-range option.

GRX 1x Gearing
The 1x drivetrains keep the 40- and 42-tooth chainrings, but now work with the larger 10-45 and 10-51 mountain bike cassettes. XT is the official pairing, but it you can use Deore, SLX, XT or XTR cassettes.

Here’s what that means for your gear range:

Put into percentages of total range, each option gives you:

  • 1x 10-45 = 450%
  • 1x 10-51 = 510%
  • 2x 11-36 = 506%

That’s a massive amount of range on all options, and also means that the only reason to choose a 2x group is if you prioritize closer gear steps and optimum cadence over simplicity and weight savings.

Why not drop down to a 10-tooth cog on the cassette?
Because larger cogs are more efficient, creating less bend between chain links, and Shimano is all about efficiency. Except for the wide-range gravel gearing, where total range takes a slight edge over total efficiency. Also, being able to use existing road and MTB cassettes means fewer SKUs for them, and more price-point options for us.

Modular rear derailleur

shimano GRX 12-speed mechanical gravel bike rear derailleur and cassette closeup

The 2x group has their rear derailleur (RD-RX820), but the 1x groups get two derailleurs that share the same body – the only difference is the pulley cage:

shimano GRX 12-speed rear derailleur hanger comparison for different cassette sizes

The smaller 10-45 cassette gets a shorter cage (RD-RX822 GS), and the larger 10-51 cassette gets the longer cage (RD-RX822 SGS).

If you want to switch between cassettes, just swap the cage. You’ll probably need two chains, too, as the chain length will be at least 2-4 links longer for the big cassette.

internal view of shimano GRX shadow RD+ derailleur clutch mechanism
This is what Shimano’s derailleur clutch looks like. Did you know you can adjust the tension to customize how it feels?

Swapping them isn’t as easy as popping off the cage on the new SRAM Transmission derailleurs, but it’s not too hard. And you can check the cleanliness of their Shadow RD+ clutch while you’re at it.

shimano GRX 12-speed mechanical gravel bike rear derailleur and cassette closeup

B-Tension and High/Low limit screws are there, too.

Cassettes, freehubs & lighter gravel wheels

shimano GRX 12-speed mechanical gravel bike rear derailleur and cassette closeup

Because the 1x groups use Shimano’s latest 12-speed mountain bike derailleurs, they mount to the wheel with their Micro Spline freehub body standard.

Since the 2x cassettes come from the new 12-speed road groups, they mount with the new HG L2 freehub standard. This means they’re also backward compatible with standard HG freehub bodies, too, but this lets Shimano make…

Shimano GRX RX880 carbon gravel bike wheels
Photo courtesy of Shimano.

The new RX880 carbon gravel wheels are not technically “GRX”, but launch alongside the group using the same wide carbon rim from the RX870 wheels they launched in May 2022.

Shimano GRX RX880 gravel wheel hubs with micro spline versus HG L2 freehub bodies

The big difference is the new hubs, which are Shimano’s first hub with interchangeable freehub bodies.

These hubs dropped ~65g off the RX870 wheelset weight largely thanks to new aluminum freehub bodies, which is made possible by using the more numerous splines on the Micro Spline and HG L2 design.

If you’ve ever had your cassette dig into a lightweight 3rd party alloy freehub body, then you know why Shimano never made a lightweight alloy HG body. With MS/HG L2, the increase splines provide enough (double!!) surface area to support steel cogs on an alloy body, so now their wheels can be lighter.

RX880 “GRX” wheel specs are:

  • 25mm internal width
  • 30mm external width
  • 32mm depth
  • 24 bladed spokes
  • Direct Engagement silent drive mech
  • Cup & Cone bearings
  • HG L2 or Micro Spline freehubs
  • 1394-1397g claimed weights
  • $1,549 MSRP ($699 front / $849 rear)

Improved Ergonomics & Braking

shimano GRX 12-speed mechanical gravel bike shifter brake levers

The GRX brake levers keep their flat-faced shape and are optimized to match 16º flare gravel handlebars, which is a very common angle for most bars. The hoods have the same ribbed texture, and the levers have the same anti-slip coating borrowed from Shimano’s fishing products.

shimano GRX 12-speed mechanical gravel bike brake lever hoods

What’s new?
The top surface of the hoods has been flattened out to spread out the pressure on your palms, reducing hot spots.

comparison of hood shapes on shimano GRX brake levers
Red = original GRX 11sp lever, Blue = new GRX 12sp lever

The angle of the levers stays the same, but the tops are reoriented to be more comfortable.

shimano GRX 12-speed mechanical gravel bike brake lever hoods
All photos except graphics or as noted are ©The Lunch Ride

Internally, they have the same master cylinder with Servo-Wave braking (meaning, braking comes on in signature Shimano style – quick, but with a linear increase in power once they contact the rotors).

The calipers look the same but now have 10% more pad clearance for reduced brake rub. Shimano recommends pairing with the RT-CL800 Ice Tech Freeza rotors, which debuted with the latest Dura-Ace group.

GRX 12-speed pricing & weights

When does Shimano GRX 12 speed come out? Right now. All parts are available and shipping at launch!

PARTMSRPWEIGHT
Shifter/Brake Levers w/ Brake Caliper
• Right side/rear shifter$444.99 *
• Left side/dropper remote$414.99 1009.5g
• Left side/brake only$384.99 943.2g
• Left side/front shifter$441.99 1009.5g
1x Crankset w/ chainring$249.99 655g
2x Crankset w/ chainrings$249.99 721g
Rear Derailleur$126.99 270-290g
Front Derailleur$61.99 95g
160mm ICE Tech Freeza Rotor$121.98 228g
Cassette
• 10-45 XT$164.99 461g
• 10-51 XT$164.99 470g
• 11-36 105$87.99 391g
Chain$48.99 247g

*All weights claimed, provided by Shimano. Shifter/lever/brake weights are for complete set with right & left units including hose and caliper. Chain is CN-M8000 XT 12-speed chain. Complete group weight with two rotors for 1×10-51 with brake-only left lever, 172.5 arms w/40t chainring is 3,061.2g.

The new GRX is available now at these retailers:

Shimano 105 Mechanical now 12-speed, too

Following the 105 Di2 group’s move to more speeds, the new 105 12-speed R7100 group gets a mechanical option with all the latest gearing and features.

Key Shimano 105 12-speed features

Basically, this is the mechanical Shimano 105 you know and love, but now with a 12 speed cassette. It gets the same updates as the other 12-speed road groups, including:

  • easier brake bleeding
  • increased lever reach adjustment range
  • revised brake lever shape
  • 10% more pad clearance at the rotors
  • HG L2 cassette mounting standard
new Shimano 105 mechanical 12-speed road bike group

Specs and options are:

  • Crankset with 50/34 and 52/36 chainring options
    • 754g (172.5, 50-34)
    • $179.99
    • 160/165/170/172.5/175 crank arm lengths
  • 11-34 and 11-36 cassettes
    • 361g (11-34)
    • $65.99
  • Braze-on front derailleur
    • 96g
    • $44.99
  • Shadow RD rear derailleur with direct-mount attachment*
    • 249g
    • $64.99
  • Hydraulic disc brake shifter levers w/ calipers
    • 1,048g/pair
    • $354.99/each
  • SM-RT70 brake rotors
    • 133g/each
    • $45.99/each
  • Chain
    • 133g
    • $32.99
  • Complete 105 12sp mechanical group price & weight:
    • 3,026g
    • $1,005.92
shimano 105 mechanical 12-speed group shown on a bike with direct mount rear derailleur hanger

*Direct mount attachment? No, not the same as T-Type or UDH. Shimano’s rear derailleurs use a removable connector that lets it bolt directly to a special “direct mount” hanger used by some bike brands (as shown in photo above).

105 12sp mechanical groups and parts are available for pre-order at some of the retail links above, but officially shipping in October 2023.

Full details at Bike.Shimano.com.

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