FWIW, Wolftooth make a 36T NW ring to fit GRX, and I’d expect 34T ought to be possible, but nobody makes one. 36x52 gives a slightly higher low gear than for instance 28x42, so won’t lower the bottom gear much further than can be done with 2x. Tolerance for gaps between gears matters too, and the fewer rear cogs there are, the bigger these will be…
I’m pretty sure I’ve maxed out my 11 speed 2x GRX groupset, I swapped out the chainrings for some from TA at 44/28 and I pair that to a 11-40 cassette. No goatlink needed, just a tiny bit of b-screw adjustment. The shifting is fine, it works well cross chained as well even though I try to avoid that. It’s great as it gives me some good gears on basically all terrain.
I carefully calculated the maximum capacity of the derailleur beforehand and I knew I could push it a tiny bit further than Shimano recommend (40) and I had been using a total capacity of 43 for a while before I upgraded to 45.
I’ll be honest, sometimes on the long steep climbs I even wish I could go smaller 
Interesting. At the time I was looking (18 months ago, to be fair), 38t was the min I could find, and I was told by Garburuk 36t wasn’t possible with that BCD (they still don’t make one).
If you can get a Microspline cassette onto the wheels in question, then a 12spd GRX 820 series long cage rear mech will work with a 10-51t cassette - I ran that on my drop bar MTB experiment with a 32t 1x front chainring, but you could go even smaller up front too.
1 Like
At this stage, an e-bike is in the planning but prob not in time for the next trip (they are expensive, as will be the trip!). 
My initial looking at long term hires (eg 5/6 weeks) has been less than successful and most I find are upright trekking bikes.
If anyone has any leads on hire e-gravel bikes in Frankfurt (where we’ll be flying in/out of), that would be great.
But for now I’ll look at an 11-40T 10sp cassette to help a bit more in the interim.
Something to look at is the new Trek e-gravel bike (Checkpoint+). It’s a mullet drive train, essentially a MTB 1x drive train and it has the TQ e-bike drive train. This should be set up like our Domane+ e-bikes where you can remove the main battery (360Wh) and then take along one or two 160Wh range extender batteries.
I’ve looked into this and you should verify with your airline, but most airlines allow you to carry on up to 2 each of a 160Wh battery. - I know Delta does. If your bike has no battery, it flies just like a regular bike (we’ve done that a ton). Our experience is that the TQ drive system is so intuitive, and it is so well integrated, that she could turn it on and off as we do. I just today did a 20mi ride and only briefly had the boost on to clear a busy road section. I used 3% of the battery. Bike rides fine without boost.
My wife has essentially the same AXS drive train on her acoustic bike as on the Checkpoint+ and she has done 3 tours through the mountains of Norway with it. Add in the TQ motor and it would be beyond awesome.
2 Likes
Hi, I have run GRX 11 speed 48/31 with an 11-46 cassette and wolf tooth Roadlink., works perfectly.
1 Like
This is exactly why I keep ranting that f$cking bike industry needs to standardise batteries. (I can dream…)
Having seen so many e-bikes touring in NZ, I reckon it’s a really good solution - EXCEPT for that bloody battery transportation problem.
We sure could’ve used more power on our laden mtbs in NZ
I’d love to get an NZ or US spec’d e-bike with 32k speed limit and then have batteries in each continent. I guess it’s easier to just buy multiple bikes 
.
I realise I’m late to the party but I’d recommend checking bikepacking.com for gearing options. I have bookmarked this page because this is something I’m constantly wishing to improve.
I’d get a Classified hub except we need to mount our tailfin racks on our rear axles.
I know this isn’t what you were asking for, but it may be good to have in a pinch
I use these with my kids on hills and they love it.
If you have a difference in power, this slows you down and speeds her up, keeping you together.