No experience self-wheel build with a weird mix of stuff

I think you’ll be fine but I wouldn’t have worried about rounding to the next 2mm for spokes that only come in 2mm increments

The spokes might wind up/twist rather than tighten towards the end of the build, so watch out for that. Should still be fine, you might just want to be careful to destress the spokes before final truing. And lube the spoke threads.
Use brass nipples!

If you're not too heavy and not doing massive drops you'll be fine if it's well built. The high spoke count will help too

D-light spokes are what I use, and have on several 32h MTB wheels. No problems so far. I always find them a delight to build with.

Use brass nipples!

My alloy Sapim nipples have outlasted a set of rims, 2 snapped (Sapim) spokes and 6500km of often muddy wet Scottish gravel.

I think aluminium nipples have moved on from the days of seizing and crumbling, and most importantly they come in lots of pretty anodised colours!

Light spokes can actually be an advantage,

If you imagine what happens to a wheel when you land heavily,

With a stiff rim, the rim gets pushed up and the strain is all on the top spokes being stretched.

With a flexible rim the rim distorts and stretches all the top half spokes (i.e. the ones at 90 and 270deg are stretched as the rim tries to go a bit oval as well as just displacing upwards).

Light spokes are an advantage in that scenario because they stretch more for the same tension, which means the rim has to deflect a lot more before they go slack, and therefore the rims stays more evenly supported through the impact.

I think you’ll be fine but I wouldn’t have worried about rounding to the next 2mm for spokes that only come in 2mm increments

Yea, it makes naff all difference, 2 different calculators could have that much variance in the measurements. The DT calculator even implies you should use spokes that don't reach the top of the nipple with anything other than 12mm nipples.

They can't be too long ion modern double wall rims, the threads will bottom out long before the spoke reaches the inner bed and the tubeless tape.

Too short, sometimes spoke nipples crack if the spoke doesn't reach into the 'slot' part. But it's not a common problem.

For 2/1.8/2 or bigger spokes I'd always round up (i.e. 270.5 would be 272mm), for smaller spokes like 2/1.5/2 I'd consider rounding to the nearest as they stretch a lot more, so adding ~1.5mm might mean they're ~3mm too long by the time they're tensioned.

 I’ve only built one wheel before, and probably a decade ago, so don’t know what I’m doing. Hence why I’ve bought super-light spokes for the driveside of a rear mountain bike disc brake wheel, which I only just now discovered is probably breaking three rules of wheelbuilding simulataneously.

I'd just use the lightest spokes on the NDS rear where they're under least tension when built if possible, they're the lowest tension therefore benefit most from being the most stretchy.  Having them on the drive side is a recipe for a PITA wheel as the wheel will flex more towards the NDS side in use, so the NDS side will go slack.

If they're different lengths I'd just go out an get 16x 2.0/1.8/2.0 spokes for the drive side. Even at bike shop prices that's £16 well spent in the long run.

TBH having built a few wheels now and found a few things out the hard way, I'd always go one step up on the drive side (i.e. plain gauge if the NDS was 2/1.8/2, or or even chunky aero spokes) as a bit of an insurance policy.

Hmm, may be I was a bit fussy about spoke length. Thanks for the advice so far

So, I've used two different spoke length calculators:

One is telling me 287.9/286.6 for NDS and DS

One is telling me 289/288 for NDS and DS

The spokes I have are 18 D-Lights in 288 and 18 of the Lasers in 287, so may be I can just use them the opposite way around to what I planned?

The D-lights should be fine for the DS. But will the Lasers be OK for the NDS, given they are 0.9-2mm shorter then the calculators recommend?

I think the lengths say you should probably not use them the opposite way round. 2mm short is a bit too much, not enough thread in the nipple. On the other hand, half way between your calculations would probably be fine. How lucky are you feeling? Maybe build them up opposite, get them to final tension (if you can) then count the threads protruding from the nipple.

What length nipples have you got, buy some longer ones?

The D-lights should be fine for the DS. But will the Lasers be OK for the NDS, given they are 0.9-2mm shorter then the calculators recommend?

Like lesshaste I'd not go 2mm too short. As others have said, a bit too long is fine. Given the values from your spoke calculators, I'd have. gone for a whole wheel of 289mm. I class myself as a semi-amature wheel builder, but all the ones I've made have been no trouble.

What length nipples have you got, buy some longer ones?

I don't think the threads always go to the end of the nipple? I'm sure DT ones are all the same it's just the square bit on the end is longer so machines can grip it easier or it pokes through really thick / deep carbon rims.

Maybe another consideration... Have you measured the ERD of the rim or are you just using dt's published figure.

There can be a bit of variation, you could make a measurer with two old spokes cut to say 200mm screwed into nipples then elastic band to pull them tight onto a metal rule. This may help inform your decision if ycba. Or just go for it.... Let us know how it goes.

Ah, I stand corrected on nipple length, thought it was probably too easy.

I would be tempted to just order some more d-lites.

Also definitely worth measuring the ERD.

Also, do not use the sapim spoke calculator as it is all over the place.

As above, I always round up to the next available length. It's better to be slightly long rather than short.

With most nipples the thread starts about 5mm into the nipple.

However, TBF you don't need to engage the thread on the whole nipple, I'm normally happy if it's wound in 2/3 or more.

Just to check - you do have phr washers and compatible nipples to go with them? You need to use them otherwise you could crack the rim.

Personally I’d use the same type of spoke both sides of the wheel. I just use ACI double butted spokes from Cycle Basket as they tend to be the cheapest double butted spokes from a decent manufacturer. I always find Sapim very expensive in comparison, and DT Swiss are similar.

Pre Brexit you could get dt spokes cheaper from Rose Bikes but that got killed off. So I’m ACI all the way - even on a road bike wheel I re-spoked as the Pillar spokes kept snapping.

Joebristol +1I really rate aci double butted from cycle basket.

Thanks for all the advice again

I popped to my lbs to grab some more spokes (I'm in Switzerland so everything is expensive, hence my reluctance before).

They didn't have D-lights or a DT equivalent in stock. But they did have DT Revolutions, which are the same profile as my Lasers, so I've got some of them. Figured the lightness should be fine given there'll be 36 of them.

I do also have the PHR washers and associated nipples, so all good.

Might be worth mentioning that sapim now (quietly) specifically do not recommend the Laser for mountain bike builds. Myself, i think this is bollocks, it's comparable to a revolution (the Laser is literally the same spoke as the cx-ray with less forging, every Laser could have been squished flat and become fancy). I think they changed teh advice to stop people using them as cheap light spokes, personally.

In an odd twist Sapim's nipples are almost exactly the same shape as PHR nipples, I use them in all my DT builds just because special tools can **** right off, especially special tools that were designed for wheel building machines not for us.

last comment- building a whole wheel is way easier than straightening a bent wheel. It's more intimidating because you're starting from nothing but actually it's better to start from nothing than to start from bollocksed. good luck!

Well it is now wheel shaped and only wobbling about 2mm laterally.

Took me some time, particulary as I laced the first group of leading spokes incorrectly, and redoing them was a real faff without loosing phr washers in the cavity.

I'll prob build a front to match now, but won't ride them for a while -- will check back in when I do.

I should say that before this thread, I was not sure whether to use this wheelset as my trail/am wheels, or XC wheels. From the above comments I think I'm safer using them for the latter.