Plenty to think about

For now, I've got 26-inch wheels front and back, but with a much wider rim on the front.

Velocity Dually 26”
https://www.velocityusa.com/product/rims/dually-559

This has a 39mm internal diameter compared to the Ryde Andra 30 which I think is 19 mm internal diameter on the rear.

It makes a noticeable difference to the tyre profile with more of the tread in contact at the front.
(it also lets me run tubeless at the front with pepi tire noodle, insert so that when I'm not carrying lots of luggage upfront, I can use a lower tyre pressure).

For interest, I'll probably end up trying the 27.5" Front wheel after seeing how this current set up handles for a few months.


While theoretically this might all make sense; on my E bike which I use for commuting with moderate load. I've got 27.5 inch wheels front and back but a much wider front tire.
2.35" at the back and 2.8 at the front"

Since making this change to a much wider front tire on the E bike the handling has felt much more stable and giving me a lot more confidence on my commute. (about 15 miles each way half of which is off-road on relatively rough tracks)

However, I did make other changes to the E bike at the same time, such as bamboo handlebars and a redshift suspension stem.

Will report back in a few months once I've made a comparison.

Ewan

Did SJS say what length nipples they use with those spokes?

I am not sure why there would be a difference, but I remembered hearing in the past that SJS used a different length.

I built up my wheel with 36 spokes and I think SJS only does 32, so I never asked them what to use, I used the table from Rohloff.  This table is dated 2019, I built my wheel in 2014, so I do not know if there is a difference.
https://www.rohloff.de/fileadmin/user_upload/erd_32_36_Speichenlaenge_03_2019_de_en.pdf

Different topic, if your hub is an old one that did not come with the flange reinforcing rings, you might consider adding those at the time you build your new wheel.
https://www.rohloff.de/en/company/news/news/flange-support-rings

I added the rings to my hub, even though I was not rebuilding the wheel at that time. I have ridden into remote areas where I did not want a wheel failure.  The rings do not make the hub flange stronger, but if a spoke pulls out a piece of the flange, the ring will hold it in place so you can keep riding, then fix it later.

What do you make of this description of the way the force vectors change with a larger font than rear wheel from mullet cycles
https://www.mulletcycles.com/mullet-bike-technology/

These mullet guys are describing a bike specialised for a gravel road without either crosswinds or other traffic and no close ditches or berms either. It has nothing to do with touring bikes because they are trying to shift even more of the bike's weight onto the rear axle, which on a touring bike like your Nomad, if Andy Blance had done it, we'd ask if he was all right on the day. (Yeah, I know, Mr Blance wouldn't, he is too experienced; I'm making a dramatic illustration.)

For those who're already put off by this sort of theoretical discussion, you can discover where the mullet guys went wrong by searching in the link E-wan gives for the word hysteresis. You won't find it, because the mullet guys say nothing about it, but it is what makes the tyres of all other bikes, except only bikes on a loose surface like gravel, work so well. Hysteresis is technically defined as an effect lagging its cause, and describes the compound of the contact patch on the tyre resisting change of direction or any other input, nibbling itself into the changed state. Okay, now you don't need to read the rest, because you don't want to turn your touring bike into an awkward duckling under perfectly normal circumstances for a tourer (weight distribution, crosswinds, heavy traffic close by your bike), even dangerous if you go too far.

The mullet guys even tell us it is a pure marketing exercise:

Bike Geometry is a standard of measure used to market how a bike is supposed to handle.

Remember when I pointed out that, regardless of what ERTRO permitted the clowns among the manufacturers to do for cost reasons, a "29-er" with rims less than 40% of tyre width across the rim beads was not, repeat not, a 29-er, but a fashion-victim's acceptance of his fate.

In the very next sentence, the mullet guys give away the game:

However, geometry plays a very small part in how the bike’s tires contact & react to the ground while in motion.

This is goldtropchen slurry-grade manure. The geometry of the bike, and all its dynamic vectors and all its weight, and all the inputs by the cyclist, react only through those two contact patches. But the misleading statement goes with "marketing" if you want to sell something else. That they contradict themselves in the very next sentence is par for this sort of marketing guff, five bob each way, but is too late. They've already given away the game.

I can do the same analysis sentence by sentence but there's no point. I'll just pick one more lowlight:

One major factor left out of traditional bike design is how the rear wheel turns & reacts with the terrain.

[my emphasis]

This is more prejudicial nonsense. How the rear wheel turns and reacts with the terrain is automatically arranged in the standard safety bicycle (whose distinctive feature in contrast with the penny-farthing is its two equal-size wheels) by hysteresis as described above, a valuable safety feature in that it automatically adds understeer. And also, I might add, on gravel or loose sand by the "terrain" shifting under the tyre, an analogue for hysteresis. The mullets substitute "scrub radius" but the effect is the same.

The mullets know exactly what I'm talking about, and tell us so when they mention "dirt bike geometry" and label the symmetrical bike (same size wheels and tyres) a "safety bike". It's apples and oranges -- and only the dirt bike will benefit from the mullet, and be a trailer queen if you live some distance on busy roads away from the dirt. Nothing to do with touring bikes.

If you're still with E-wan and me, try looking at the mullets' illustrations, which are pretty good conceptually, if you're planning a dirt bike. Again, nothing to do with touring bikes. But note that the steering vector of the rear wheel is faster on the mullet, which is less safe than on the safety bicycle.

WHY IS THE MULLET NOTHING TO DO WITH TOURING BIKES?
A touring bike, or a utility bike for that matter, needs first and foremost to protect the rider, which by definition means same size wheels and tyres (or very small differences in tyre diameters and/or widths) with understeering geometry. The touring and utility bike needs to be ridden on any road surface the cyclist might meet, which the safety bike does superbly well, especially if fitted with fat tyres. Finally, the touring and utility bike must be intrinsically safe in all its designed elements which, besides relaxed geometry, means a centre of aerodynamic pressure well back on the bike (and permanently behind the centre of gravity otherwise the bike will swap ends in a blink at the slightest crosswind--or suck you under a passing truck), and predictable in response which also means understeer which in turn requires a rising couple towards the rear for the centre of gravity.

I hope you won't think I'm a neanderthal luddite, E-wan. It's your bike; you do what you want. I put up these articles for information to everyone, but I'm not trying to persuade anyone of anything. In fact, I enjoy hearing about other people's experiments; the guys who're taking one for the team always get extra kudos from me. If you're doing it anyway, I for one would love to hear your impressions.

Someone is going to have a great summer riding this beauty.

Thanks for your thoughts

I wasn't really considering running different tire sizes, front and rear

I'm happy enough with the 26×2.5 Surley extra terrestrial front and rear tyre.


What I am considering is running different wheel sizes front and rear with the same tyre size
(there may be a slight difference in tyre profile as the internal diameter of the rim on the rear wheel is narrower)

What do you make of this description of the way the force vectors change with a larger font than rear wheel from mullet cycles
https://www.mulletcycles.com/mullet-bike-technology/

By running at 27.5 wheel at the front of the 26 inch wheel at the back the front axle will be about 10 mm higher than the rear axle.

Given that, I am running a different front fork which is 10 mm shorter than the one intended for the nomad mk2, running the 27.5 wheel Front and 26" back would return the frame geometry to its original intended angles, albeit with a different size front wheel.

Ewan