What do you guys feel would be acceptable tolerances on a used trials wheel?

Roundness?

trueness? (side to side)

Don't know the "right" answer, but my personal opinion is you can get away with alot. I'd be happy with under 10mm side to side and 5mm up and down. That's a big tolerance, but I've ridden ones worse and barely noticed.

I was figuring about 1/8" and you would not feel it.

I guess I am wondering more, "what amount of out would it take before you felt it on a trials bike"?

I would think a high speed road bike you could feel some pretty small deviations.

I have ridden some trials bikes though that the wheels were scary out, and never felt it, or maybe realized how I was feeling it.

That's my impression too Alan, The combination of ultra slow speeds, ultra low tire pressures and rough, loose terrain make much less significant.

In fact, even on MX bikes, 1/8" out of true is barely noticable to mere mortals...damn the tires aren't even that true most times

Now, on a road bike, with a solid surface, higher speeds and direct connection to the road surface (not the looseness of dirt), the difference is very noticable.