The Woes of a 2x Power Meter Cutthroat

I'm so frustrated.

Here's the design constraints on my current bike project - a crankset upgrade w/ power meter.

• Mountain bike standard spacing
• 42/28 gearing (or wider/taller, if possible?)
• 165mm crank arms
• < 30mm BB spindle

This is going on my 2016 Salsa Cutthroat, which has a 42/28 chainring setup stock on SRAM crankset. The cranks are a big chunker of weight, and they're too long for my legs, and I want a power meter on the bike. Turns out, satisfying these requirements is a huge pain in the ass.

I settled on the power2max NGeco spider power meter. Coupling this with either a SRAM GXP or Shimano 24mm spindle works. SRAM and Race Face cranks can work here, but they're a bit more annoying to install than I like, so I settled on  the Shimano XT FC-8100 cranks in 165mm. They're pretty and the shorter crank arm length is perfect.

power2max makes a 2x mountain-standard adapter for their spider, which has 104/64 BCD spacing. It's really easy to find rings for a 2x11 on the 64 BCD - but it's much harder to find a 42t ring for that spacing. There's a trick - a lot of the 42t rings in that spacing are designed to be the outer ring in a 3x system, not the outer ring on a 2x system. The ring dishes out, creating a large gap between the two rings. The chain will fail between the two rings instead of shifting into the small one.

So what are my options?

1. Find an appropriate chainring?
2. Washers or spacers to move the chainring inward?
3. Go to a 1x
4. Get a different frameset

1. Appropriate Chainring

It's difficult to even determine what might work here. The stock cranks use the 120 BCD rings, and most 42t 2x rings are designed for that BCD.

The Blackspire Supre Pro MTB Series come in 104/64 BCD, and are advertised for 11 speeds. They make a 42t ring! And it's the right spacing! But... they mention "middle and outer chainrings" and the 38/48 rings are advertised as "2x only." Is the 42t another outer ring? Who knows?! It's not advertised. So I've got them on order and I'll figure out what's up when they arrive.

The Spécialités TA Chainrings offer a 42t 104 BCD ring, but it's very hard to find and out of stock almost everywhere I look. Peter White Cycles can do an order if you call them up, so I may do that and see what I can find.

The Vuelte SE Plus offers a 42t 104 BCD ring, but the picture shows five bolt holes?? But the reviews show four bolt holes? Let's see how this works, I guess...

2. Spacers or Washers

This feels pretty dicey and hacky. If I could go into a bike shop and fuck around with their tools, stands, and parts, then I'd be willing to try this. It's a bit too unlikely to work for me to be ordering parts from Amazon and just hoping it'll work out.

3. The Dreaded 1x

My gear range is nice. I like it a lot. 42/28 rings and a 10-42 cassette give me a gear range from 0.67 to 4.20, for a total range of 627%. Suck it, Eagle. Nothing even comes close to that. I'm going to lose a ton of range on either end by going 1x, and I don't really want to do that - the bike currently handles everything from loaded bikepacking to fast roadie stuff well. Sacrificing any part of the range will harm that versatility. But let's investigate. After all, there are advantages to this.

At 120rpm cadence, I'm spinning out at 42.6mph on my tallest gear. And I can go a mere 4.5mph at 80rpm in my smallest gear. So let's compare the 1x ranges and see what I can do.

OK. So the biggest 1x ring I can run is a 38. A 38x10 has me spinning out at 38.6mph - while a bit sad to lose that top end, that wouldn't be awful. With my current cassette, I'd be at 6.1mph with an 80rpm cadence - a 0.90 gear ratio, which feels a bit tall for loaded bikepacking. Even a 50t cassette is only a 0.76 ratio, or 5.1mph at 80rpm - even if I can find a 10-50 11 speed cassette, that's a big weight gain and a huge amount of wear and chain to be messing around with.

A 34t ring and a 50t cassette gets me to 4.6mph at 80rpm - so we're just a tiny bit less easy than my current setup. With my current cassette, I'm at 5.5mph climbing. Which is a whole mph more than I'm currently doing. But, that's... also the gearing on my Woodsmoke, and I'm pretty happy with it - even on the paved road stuff I was doing recently.

I could also go oval. Unfortunately the biggest ring I can run oval is probably the 36t, and the smallest oval I can run with the power meter spider is a 34t. So that isn't really worth changing things for. Except maybe the Boost spacing on the spider means that I should be able to run a 38t oval...

Anyway, there are other benefits to a 1x. Simpler system. Less maintenance work (though the 2x setup really isn't much work when it's setup). Lighter - probably a pound less weight. Less finicky to get replacement parts - this is really the big thing IMO.

I wish folks made an 11 speed 10-50 cassette. The E13 cassette 9-46 is great, but reportedly not super durable, and for a bikepacking rig, that's a bit of a problem. Shimano's 12 speed cassettes are up to 10-51, which is great, but huge cassettes are kinda... problematic. And I can't do 12 speed road yet. I could do the new SRAM Rival AXS paired to an Eagle GX AXS rear derailleur for a 10-50 12 speed cassette. But, meh, that's so much money... 

4. A New Bike

I really don't want to do this. I love my Cutthroat. It finally fits perfectly, it's comfortable, fast, light, fun, amazing. The framebag looks so cool and I want to just use the damn thing. But let's not act like this isn't really annoying, and it's not going to get any better - the standards aren't getting any newer.

I'd need to replace my framebag, the wheelsets, and probably most of the other component upgrades I've done. But these options come to mind readily.

1. G2 Cutthroat
2. Fargo
3. Woodsmoke?
4. Road bike?

4.1. G2 Cutthroat

This is the most obvious thing to do. The new Cutthroat can run a 46/30 crankset using their "Road Boost" business. That gives me a much bigger gear range, which is super cool. And I can relatively easily get a power meter in there. Plus it has Boost wheel spacing, which means I can share wheels with my Woodsmoke! That would be super fun. The G2 can also have a fully-bolt-on framebag, which is super slick looking and reduces abrasion. And the teal/orange color is so pretty.

But, it does mean that I'd need to get new wheels. Or replace the hubs, or Boostinate them, or something, for my current stuff. And that's a big expense and hassle. But I am a little unhappy with the rims on my gravel wheelset, so selling and rebuilding wouldn't be the worst thing I've done there.

4.2: Fargo

The Fargo is a cheaper option. It would be a lot easier to work with, since it has external routing, and it's a bit more standard of a build. But it's considerably heavier and slower, and wouldn't make as nice of a road bike. So that kind of sucks. But it would make a fantastic bullet proof bikepacking rig, and if I sprung for Ti, it wouldn't even be that much heavier. But... if I'm thinking mountain bike... let's go full bore.

4.3: Woodsmoke

I have a small frame Woodsmoke. I love it. It's so cool and so fast. And it's great for bikepacking, and it's comfortable, and checks all my boxes... but wait. It's a flat bar bike. Why am I even talking about it?

Well, I'm no stranger to drop bar conversions, and there's a Medium Woodsmoke frameset for sale right now on Craiglist with a rigid fork - at $1800. What if I had two Woodsmokes?!?!?!

It's crazy. But the Small frame Woodsmoke would work great with drop bars and a rigid fork, and the Medium frame Woodsmoke would probably be a more natural fit for me with flat bars. Stack goes up 9mm, reach goes up 17mm, and standover goes up 39mm to 773mm. That's the most worrying figure, but it's still 27mm less than my Cutthroat is now, and that's with 29x3 tires. 

I'm running a 80-100mm stem on the Woodsmoke now, so it's not like increased reach is a bad thing. I could easily have a lower stem position, too, so it's not like the added reach is bad, either. I feel comfortable with the M Woodsmoke frame size for a flat bar setup. What about the drop bars?

The Cutthroat has a frame stack/reach of 619.5/375.6, vs the Woodsmoke with 606/409mm. So I'm losing ~13mm stack and the reach is 34mm longer. I've currently got an 80mm stem with 16 degree up angle. So I'd need to have a seriously angled stem to make it work - 30 degrees or so - and this is definitely a thing. Then my geometry is totally the same!

The BB drop is 62mm on the Woodsmoke vs 70mm on the Cutthroat. That puts me slightly higher off the ground for a comparable tire size. But I could definitely run the roadie wheelset I've got now on the Woodsmoke + a gravel wheelset, and then I could share front wheels for a dynamo setup, and have the same tire clearance...

The biggest ring the Woodsmoke can take is a 54t in a 1x, and a 36/24 setup with a 2x. I'd probably run a 1x on both bikes.

Actually hell yeah let's build this out, I'm going to make a spreadsheet.

4.4: Road Bike

The problem with a Fargo (and with my versatile Cutthroat build) is that it won't handle road stuff very well. Which sucks. So... what if I did a road bike? Or a really fast gravel bike? It would be lighter and faster than the Cutthroat anyway. And I'd have a Fargo, or a more bikepacking optimized Cutthroat, or shit just use the Woodsmoke.

But this is something I'd do if I already had a more mountain oriented bikepacking setup. And I do - the Woodsmoke. But the Woodsmoke isn't what I want for longer distance riding.