Putting together the Jenex Aero 125SR wheels isn't rocket science, in fact it's more like working on a bicycle wheel.
In short, you need:
Talc the tube - I use a small plastic bag, put the tube in it with some talc, and shake. Push the air out of the tube, put the deflated tube in the tire, put the tire in one half of the rim, put the other half on, and *make sure* you don't pinch the tube. Make sure the tire sits squarely on the rim - some of the old ones were a bit ovoid. Make sure the valve stem fits in cleanly.
Assemble the nut, bolt and washers with washers on both sides of the assembly on the bolts opposite the valve stem, and only one washer on the nut side of the two adjacent to the valve stem for balance. Tighten the bolts in a star-cross pattern like you would a car wheel. Tighten them firmly, and inflate to 95psi, then let air out to 90psi. Even better, let the air out, knead the tire to make sure the tube isn't pinched, and do it again. Put a bead of slime around the valve stem and let it dry. This will keep it from chafing and wandering as much.
Make darn sure you have an accurate pump and keep them inflated to 90psi. Also, don't use the speed reducers any more than necessary - I think this does heat up the tire and may be one of the causes of premature failure.
Another tip is to make certain you have the wheels installed in the chassis straight. The mounting holes are intentionally slightly ovoid to allow for minor corrections (presumably due to crashes, etc). If your skis 'hook' or track in or out, this is a likely cause. Either use a long straight edge to lay against the wheels (deflated, of course), or at least hold the socket head firm and square against the frame while you tighten the nut. [Thanks to Zach Caldwell for teaching me that trick - MJ]