2x chainsets on a V2 Salsa Cutthroat: an exercise in frustration

NOTE: this article is a placeholder - I'll be adding photos once the bike has had the final tweaks done and I've collected it from my LBS.

Recently, I decided to pull the trigger on a Salsa Cutthroat frame - this is my first foray into carbon bikes of any description (original plan was a titanium Fargo, but I had my mind changed - cheers, Tom). I've been a fan of Salsa for a while, and my fixed-gear El Mariachi 2 in 'General Lee Orange'[1] is one of my favourite whips.

Since it's my plan to ride the Tour Divide within the next couple of years, I figured it might be good to spec up a bike based around a frame designed for that very purpose.

Full disclosure: I'm not a fan of 1x drivetrains unless they're fixed gear or hub gears. I have a Koga BeachRacer with a 1x drivetrain (38T - 11-32T) but I find the jumps between gears to be frustrating. 11-32T is just about bearable, running 11-42T made riding a chore as I could never seem to find the 'right' gear - plans are are afoot to change it to a 2x drivetrain.

But back to the Cutty ... here's what Salsa say about the drivetrain setup:

A road drivetrain paired with a mountain boost crank creates the best drivetrain and tire clearance for the unique needs of a drop-bar bike with 29” wheels: 1x mechanical-compatible using mountain boost cranks (max 40t chainring) and a road drivetrain in all other areas / 2x mechanical-compatible using Race Face mountain boost cranks and Easton direct-mount chainrings (max 50/34t, complete bikes ship with 46/30t) and a road drivetrain in all other areas / Shimano Di2 1x- and 2x-compatible / SRAM AXS 1x-compatible

That's some weapons-grade word salad - thanks, Salsa.

Now, one of the pre-built options is a GRX810 2x setup. However, like many people, I didn't read the fine print and naively specced a GRX810 chainset (30-46T) to find out that it doesn't work because it isn't 'road boost' - so many standards, so little time. 

Since I'd already bought the 2x11 GRX levers, going back to a 1x transmission wasn't an option (plus, as mentioned above, me and 1x drivetrains don't really get on)

This is where the frustration sets in - there aren't many 'road boost' chainsets out there, although there are any number of posts from people who've made up a 2x drivetrain from something like the XT triple chainset sans inner ring. The GRX chainset wouldn't work because the axle was too short.

After chucking round a load of possibilities, we eventually went with:

• RaceFace Aeffect-R cranks - this seems to be non-negotiable, at least at the time of writing, if you want to go 2x without fudging an MTB chainset. The important figure here is an axle length of 137mm. These are the cranks specced on the pre-built Cutthroat. Fortunately, the cranks are modular, meaning that we also need:
• RaceFace 64/104mm BCD spider - bit of an odd combo, this, but it gives you a reasonable choice of chainrings. A 104mm BCD asymmetric spider is also available if you want to stick with Shimano rings.
  
• TA Chinook chainrings - 30T 64mm BCD inner (the smallest that the front mech will handle without some hacking) and a 46T 104mm BCD outer. I'm going to see how I fare with this, but the option to switch to a 42 or 44 is there. Other makes of chainring are available, but I'm a sucker for TA stuff.
  

TL;DR - you need the RaceFace cranks, but you DO NOT necessarily have to get the Easton rings, which is handy as the UK distributor doesn't carry them (importing from the US is absolutely possible, but you'd get absolutely mauled in import duties and VAT)

The rest of the transmission is pretty much as you'd expect - GRX front and rear mechs (I'm running the long-cage mech since I've got an 11-42 cassette) and GRX levers.

Initial impressions are good - despite the inner ring being labelled as '8/9-speed', it works fine with an 11-speed chain. The outer is labelled as 10/11-speed so no problems there either - if you're going 2x12 then you're on your own (although given suitable info I can update this article). 

Shifting across the cassette is as smooth as you'd expect, although going back to STI after ages running SRAM DoubleTap on my Koga required a bit of a mental gearchange. Shifting between rings can get a bit noisy, largely because the pickup points on the TA rings are pretty aggressive compared to Shimano rings, so if you want ultra-silent shifting then you're probably going to be disappointed - even so, it works fine; time will tell how it fares on longer rides and/or with a gooped-up transmission. Shifting with 'proper' 11-speed chainrings would obviously be better but you gotta go with what you got.

What I will say is that the ergonomics of the GRX hydraulic levers are top-notch - they're extremely comfortable, even without gloves.

Despite 30T being about the largest chainring you can get in 64mm BCD, you'll not be able to go any smaller without hacking the front mech mount - in a situation like this you may well be better off with a 1x front and a stupidly wide-ranged cassette (11-51T seems to be the Thing nowadays)

[1] - That's 'General Lee' as in The Dukes of Hazzard.