When I went to get my wheels trued last weekend, I had to deflate both the front and rear wheels of the Thorn Nomad MK2, in order to take the wheels off the bike. Well, I have to do this when I try to fit the wheels back on the bike as well. I have 26x2.25 Schwalbe Marathon Extreme HS 402 tires on this bike and these guys ain't slim . Even after releasing the brake cable you still have to deflate the tires!
When I was taught to true the wheels at Trinity Bicycles, a secondary step of stress testing the wheel was also recommended:
Put the wheel on the ground, use knee to hold down the wheel, and apply pressure on the wheel with both palms to make sure the spokes were tensioned correctly. Move knee to a new point and repeat the procedure again, until satisfied.
Well, I did all that just fine, came back home, aired both tires and put the wheels back on the Thorn.
The next morning, I found the front tire on the Thorn was flat. I mean completely devoid of any air in the tube.
PS. Knock-on-wood, I haven't had a flat since 2008 --- except for this one mishap!