I wanted an extra 'granny gear' So from a 45 x 19 combo to a 39 x 19 combo seems the best option and gives me the 13.33% gearing reduction ie  one full lower gear. Additionally, I read that 'Rohloff only make steel splined sprockets for up to 21 teeth' 22T sprockets are intended for Gates belt drives.
I'm not considering a chainglider.

So, unless I wanted to gear lower again the 39 x 19 combo seems like the best option.
Interestingly the price of a new sprocket or chain ring is about the same in UK.

Many thanks for the helpful posts, appreciated.

Depends on several factors. The first thing is to decide what gear range you want.

Then you can usually get there by changing either the sprocket or the chainring, or maybe both.

If you want to fit a ChainGlider, that limits the options. There are only a few possibilities for compatible chainring size, Chainglider front parts are 38, 42, 44 and 48 IIRC. Same goes for sprockets, with the constraint that smallish sprockets need the special Rohloff compatible Chainglider rear part, which IIRC is different for threaded and splined sprockets. Large sprockets 19,21,22 are in practice compatible with the standard Chainglider rear part as used for Shimano Nexus 8 hubs. Another thing to consider is that Chainglider front parts aren't necessarily compatible with all the rear part options, IIRC the 48T front part won't work properly with the 19-22T rear part. Chaingliders also work best with thin chainrings, the Surly stainless steel chainrings work well for me and are reversible. But I have one bike fitted with a wide TA ring using  1/18" chain and a 1/8" sprocket, this works OK with a Chainglider but needed a "breaking in" period.

Changing the chainring can be economique if you have a stock of spare chainrings. I did this with my Raven Sport Tour, swapping out the 50T TA ring for a 42T TA ring I had in my spares box and leaving the 19T sprocket in place. This also allowed me to fit a Chainglider as I then had a 42x19 combination.

When I lowered the gearing on my Raven Tour I kept the 38T Surly chainring and changed the sprocket from 16T to 21T. I also had to change the Chainglider rear part.

One minor consideration is that for a given gear range a large sprocket/large chainring combination wears more slowly than a small sprocket/small chainring combination. That was the reason I originally chose 50x19 for my Raven Sport Tour. But a transmission that is partially protected by a Chainglider should last a lot longer than an unprotected transmission.

Hi
Would you mind taking a look beneath the bottom bracket and sharing the letters and numbers you should find there. They give the actual size and maybe an LA ( indicating the UK frame builder) Photo might be easiest.
TIA

Reluctantly selling my Thorn Nomad Mk3 58L Rohloff, custom built by SJS Cycles in 2024.

This is a high-specification expedition/touring bike with 2,537.8 km on the clock — according to Garmin!. It was built specifically for me by Thorn and the original invoice total was £4,138.61.

I'm selling because recent marriage has curtailed my long-disance touring career 

Specification

* Size 58L
* Colour Red Imron
* Rear wheel: Ryde Rival 650b 32h disc Rohloff 14spd CC Disc Hub, 17T sprocket (QR)
* Front wheel: Ryde Rival 650b 32h disc SON dynamo hub (thru axle) — (dynamo supplied by me and has done a further 7000 km)
* Chainring: Thorn 42T
* Brakes: Shimano Deore XT BR-M8100
* Crankset: Thorn 104/64 PCD Triple Crankset MK2 - Black - 170mm
* Handlebar: Surly Moloko 735mm handlebars with cork tape with cork flecks and gel backing and Ergon GC1 grips
* Brakes: Shimano CUES hydraulic 2-pot disc brakes with 180mm rotors
* Saddle: Brooks B17 black leather with rain cover
* Chain: KMC E1 Rohloff-compatible chain
* Tyres: Schwalbe Marathon Almotion EVO 27.5 x 2.15
* Mudguards: SKS Chromoplastic (not fitted in photos)
* Lights: Sinewave beacon front light (supplied by me and has done a further 7000+ km) / SON rear light
* No pedals

As indicated above, the SON dynamo hub and front light were supplied by me rather than being new components. They had previously done around 7000 km.

Condition

The bike has covered a little over 2,500 km and is mechanically in perfect working order. However, I want to be completely upfront about the cosmetics.

There are a number of scratches and marks on the frame and forks from riding and from air transport. There is also a small dent in the downtube. I have had the dent assessed and have been quoted £60 to repair it, unpainted, by Argos Racing Cycles in Bristol, a company recommended by Thorn.

I've deliberately not had the dent repaired before selling the bike. I'd rather the buyer sees the bike exactly as it is rather than having a repair carried out immediately before sale. I'll provide clear photographs of all the scratches and the dent, so there will be no surprises for the buyer.

Size

58L, suitable for a taller rider. The bike was built for me at 186 cm / 6'1" tall.

The SJS build sheet records:

* Height: 1860mm
* Barefoot saddle-over-height: 850mm
* Arm length: 1885mm

Documentation

Original SJS Cycles invoice and build specification included.

Frame number: N580L23008

Fork number: 480623

The original invoice records the complete build and a total paid of £4,138.61.  The purchase of the dynamo hub and front light are not included in that price.

Location

Nottingham, UK

I'd prefer collection so that the buyer can inspect and ride the bike before committing to purchase, but will consider delivery at buyer's expense.

Price

£2,600 ono

I'm not looking for silly offers, but I'm happy to have a sensible discussion with someone who is genuinely interested.

I can provide plenty of photographs and answer any questions about the build, condition or sizing.

I guess that unless an emergency situation arose any sort of ad hoc/ thought-fart solution should be considered very carefully. What's that thing about the law of unintended consequence? Owing to a very inconvenient  slow flat ( aren't they all!)  I had to transfer my loaded rear panniers on to my front rack for a sort of get me home solution. I tried riding with it for a very short distance but it was so unbalanced and unnerving I got off and walked the rest of the way.

PS Currently posting from Chiang Mai and wishing I had my Nomad with me. Next time!