My knowledge/experience in this area is limited so I ask the Singletrack hive mind for its collective opinion.
Gravel bike is 1x with a 40t GRX chainset. This is fine for gravel riding but I want something smaller for the two or three bikepacking trips I do a year. So whats going to be the best way, and can you recommend parts required.

Option 1 – Get a second chainset with a 34 or 36 t ring that fits my existing BB and swap it out as and when required.

Option 2 – Get a new direct mount chainset that has a 34t or 36t and a 40t ring, I can easily swap between

As I understand it I would have to remove a direct mount chainset to swap rings?, so my thinking at the moment is swapping to another chainset is just as easy and it would be the cheapest option. Problem is finding one that fits the current BB, and has the correct chainline (49mm I believe)

What cassette are you running? Might be easier to change that than buggering about swapping chainrings/ chainsets

What cassette are you running? Might be easier to change that than buggering about swapping chainrings/ chainsets

11-42.

Yeah, bang on a Deore 11-51 for the trip.

Have you checked the back of your existing cranks to see if there is another set of bolt holes for a smaller/inner chainring?

Looking at the pics on Shimanos website the single ring and double ring cranks look the same except for the number or chainrings, might be possible to just bolt on another smaller chainring and just manually flick between the 2.

Double ring
https://bike.shimano.com/en-EU/product/component/grx-11-speed/FC-RX810-2.html

Single ring
https://bike.shimano.com/en-EU/product/component/grx-11-speed/FC-RX810-1.html

I’d say it depends on how much you like the GRX c/set.

If you do then I’d just pick up a cheap Shimano MTB chainset, either a 4-bolt (symmetrical or assym.) or the newer direct mount, and just fit that for the bike packing. The chainline will be a bit off at 51 but you may well be able to live with that?

If not, then splash out on a new direct mount c/set and swap DM rings as required. The chainline will be the same, and the only issue would be chain length when you drop to a smaller ring.

A mate chewed over this recently on his gravel bike and we considered, over a few beers:

– Hope RX
– Sram Force
– Rotor Aldhu and Vegast
– plus one other I can’t recall..

None would fit your current Shimano BB though.

If he’s 11spd then going 11-51 isn’t going to work…

New Shimano Deore 11-speed Gets Wide Range 11-51T cassette + 10-speed Updates

Even if it means a new chain, plus an eBay hanger extender for a couple of quid. No brainer. Keep your high gears, extend your low gears.

It’s only a no brainer if we assume an 11spd road mech can handle a 11-51 cassette, with a hanger extender.

Have you run this setup?

How does it shift when you revert back to the 11-42?

For me, extenders are bodges and shifting suffers as a result of the top jockey being set some distance from the sprockets, particularly on the smaller sprockets. That’s my experience but if you’ve run the 11-51 with a road mech then maybe you’ve had more success.