I noticed you posted this question on ToyotaVanPeople.com and I tried to answer it there, but for whatever reason I can't get my picture to display so I'll repeat the response here on this forum. Here it is:

Loosen the jam nut shown in the bottom figure, then tighten/loosen the adjustment nut until you achieve the dimension shown in the upper figure. Do this with the weight of the van resting on the wheels. You can jack up to loosen the jam nut and to get your tools figured out, but final adjustments should be done with the weight on the tires. It's easier if you put blocks under the tires (same thickness on all 4 tires), then just add their thickness to the final dimension. If you need to adjust a lot, it can be a PITA due to the length of the stud. Some people cut the studs off, but if you do that you won't be able to lower the van later (at least perhaps not to the degree you would like) and if you ever need to remove the bars it would be a real PITA to put them back on. When I cranked my bars up I needed to max them out (due to my heavy cargo) so I brazed (2) 7/8" deep sockets together. The 1/2" square drive hole is just big enough for the stud to fit up through the center of the 1st socket and I can crank away without any problems.



Here's a picture of my brazed socket:


THIS THREAD over on TVP has a lot of valuable info in it, so you may wish to review that as well. Tim