The XX1 group arrived today.  The GXP bottom bracket went in smoothly with a spacer on each side (since the shell width is 68mm).

As I threaded the non-drive-side crank arm, I noticed how little clearance there was between the chainring (34-tooth) and the chainstay.

As I tightened it, it became apparent that something is not right.  Before even getting near the max torque on the crank spindle, the chainring started touching the chainstay.

I installed my old 3-ring crank to check whether it would have a similar issue.  Nope.  As is, it could possibly fit up to a 32-tooth ring.  Unfortunately, the two rings I’d swap between are 34t and 38t, so being limited to 32t max isn’t an option.

I’m almost certain I’ve seen the XX1 group on other MootoX’s.  Maybe the chainstay geometry has changed.  This frame is ~7 years old now.

Solutions?

Replace the 168Q crank with a 156Q crank and add spacers somewhere – on the spindle’s drive-side between the bb and crank arm?  I bet this would affect other things negatively.
Replace the drivetrain with a 2×10?  Expensive and painful.
Replace the frame for a new(er) MootoX?  Again, expensive and painful.

Update:

According to the Sram xx1 compatibility spec, each chainring differs by a 4mm radius every 2-tooth step.  A 32-tooth ring would probably fit my frame.  So that’s another option.
I tried shifting both 2.5mm bottom bracket spacers to the drive-side.  The 34-tooth ring fits with ~1mm clearance.  Since chain suck is not an issue with XX1’s clutch derailleur, I think it is enough clearance.

2014-07-10 Update

I now run a 30t ring up front, so can use the spacers as intended.  With the 34t ring, I shifted both 2.5mm spacers to the drive-side.  It ran fine for four months until I voluntarily swapped to the 30t.  I did notice that the drivetrain was slightly louder when in the granny gear with the extra-offset 34t ring.

The fork arrived in the mail today.  I chose a 2012 Cannondale Lefty Carbon XLR with 100mm travel and a remote lockout.  The fork was bought used, but it was recently serviced and stuffed with the newest internals.  I’ve been impressed by the ability of a Lefty fork to compress even while under lateral forces.  Soon I’ll be able to see for myself on the trail.

With the external cup headset, there was just enough clearance for the lefty clamps to clear the 5 1/2″ head tube stack height (and yes, I measured prior to purchasing the fork).

Next up – the drivetrain.  It should arrive tomorrow!

This frame was crafted in 2006 with a threadless 1-1/8″ headtube.  I chose Cane Creek’s 110 EC34 headset.  It’s a thing of beauty.

A Project 321 Lefty steerer tube is installed ready to accept a Lefty fork.  The fork, a 100mm 2012 carbon XLR, is on the way and should arrive this week.

I’m still undecided on which drivetrain and wheelset to choose.

I’ve been been in pursuit of a used Moots Mooto X YBB 29er frame for many months now – searching ebay, mountain bike forums, and craigslist.  Last week I finally found one for a relatively decent price.

This will be the bike on which I will finish the Colorado Trail.
This will be the bike on which I hope to race the Tour Divide in the next few years.
I’m going to build it 100% myself so it is mine through and through.

All components of my Rockhopper have been stripped and cleaned.  Being a 26er, there are some that obviously cannot be reused (fork and wheels).  Others I didn’t think of – the titanium tubes are smaller in diameter than the aluminum frame, so my front derailleur and seatpost need to be replaced.  I’ll gladly take any excuse to upgrade parts, though.

Hypothetical Build

Suspension
100mm Lefty – needle bearings just make so much sense.
YBB – duh.

Headset
Cane Creek

Brakes
Avid BB7 – mechanical for simplicity and reliability.

Drivetrain
Sram XX1 (1×11) seems so simple elegant but I’m afraid of the limited range of gears, especially for bikepacking.  If not 1×11, 2×10 is the next option.  3×10 (what my Rockhopper was running) was overkill.

Wheelset
No idea yet

Bars & Seatpost
I hear titanium is great, but we’ll see how the budget stands.