[jimnotgym]

Thumbscrews are plenty accurate enough imho. I an only interested in mountain bike wheels so... I would rather have a highly tensioned wheel than a very true wheel, and as wheels get to very high tensions they are harder to true, so it is a compromise. That's why lots of mechanics steer clear of high tensions, it its easier to go slacker.

[toss1]

Yes, one can get really finicky with a decent thumbscrew.

Good point on the tensioning - higher tension makes the trueing really finicky. I haven't done my Mtn Bike wheels, but my current thinking on tension is that I'd probably go with fairly tense on the rear wheel to minimize power losses, but on the slacker side in the front. High tension wheels are also much closer to catastrophic failure or folding, which I really don't want anywhere near a situation where my wheels are taking a big impact. I've also been surprised a few times how well my bike was riding after discovering that my spokes were quite slack - kind of like it creates a bit of suspension action. Just thoughts on things to try next...

[jimnotgym]

> High tension wheels are also much closer to catastrophic failure or folding,

Another way to look at it is that the higher tension gives more force holding the rim where it should be. Catastrophic failure or folding is a result of heavy impact, not tension. Unless you jump off buildings on your bike this should be very rare. Are you really seing these kind of failures with modern mtb rims from quality manufacturers. Even at downhill I would expect most wheels to be replaced due to denting or heavy buckling, not folding?!?

> I've also been surprised a few times how well my bike was riding after discovering that my spokes were quite slack - kind of like it creates a bit of suspension action

Interesting, I hate that feeling because loose front wheels deflect sideways in corners, which is kind of what you pay money for suspension not to do! Your money, your choice.

[toss1]

>>Another way to look at it is that the higher tension gives more force holding the rim where it should be.

Sort of. I'm pretty sure that the situation is basically a pre-load on a spring, and the spokes are tension springs. So, yes, you pre-load a spring and it will make the mechanism stiffer upon the initial force application. But, the spring is also that much closer to it's failure limit both in available travel and available force absorbtion capacity.

What I noticed was that I've been surprised on a good number of occasions to find little noticeable deflection even when I've checked my spokes on coming home and found them looser than I expected. They aren't sloppy loose or anything, but just loose enough that a good finger squeeze of two spokes would yield a few mm of motion, instead of twanging like a piano string. And I've been lazy enough to go out after noticing that a few times before re-tensioning them, with no ill effects. Hence my thought about really tight rear, and (slightly) loose front tuning. But yeah, something to test, not just go with ;-)

The other thing that I've noticed is that one can get a wheel so tight that it will fail catastrophically if one spoke/thread/seat fails - that gap in the tension structure can cause the pull from the other spokes to be so out of balance that it'll fold the rim. Seems to be on low-spoke-count lightweight wheels. So, I'm a bit skeptical of that approach.

[jacquesm]

> Unless you jump off buildings on your bike this should be very rare.

That's true, but kerb impacts are pretty common when cycling a lot in traffic, especially the rear (though, intuitively I would assume that that detensions the spokes rather than that it tensions them). For the front not so much, you can usually pull up the front in time. But on a bike heavy with shopping you may not always have that luxury.

I think I understand where you are coming from: competition MTB is a pretty interesting niche and it allows you to really max out on the bike for those conditions. But it makes me wonder how long such a very tight setup would last in everyday use over 10K km / year or so. Because that's my application, I've never done any MTB / offroading and at a guess stuff breaks and gets replaced far more frequently in that setting.