I'm thinking of running a reserve air tank on my truck to allow for fast tire inflation with a small pump. The only 2 plausible locations to put it are where my spare tire goes (and is staying), or in the cab (which is space I use often). Can other ideas. THis is for a 4dr. 4Runner.

 

have a roll cage? cap the ends and tap for air fittings.

 

Thats a pretty good idea, unforunately I have a 2nd gen and I don't intend to install a roll cage in the near future.

How safe is a homemade air tank that is basically a long steel pipe that could be fitted in the stock rear bumper, or along a frame rail (away from exhaust heat) etc?

 

Depends on the pressure.

Alot of people user sliders and bumpers as air tanks. So long as you control the pressure you will be fine.

 

My front bumper is airtight with fittings.

But the thing here is that you need a HUGE tank to really help - tires contain A LOT of air.

I would highly recommend looking into a CO2 setup with the small compressor as a possible backup.

 

I have some 2.5 gallon tanks that fit just in front of the spare tire, use some plumbing strapping to hold it up to the bottom of bed:
http://www.4crawler.com/4x4/CheapTri....shtml#Storage

 

I found 7 gal of air at 100psi just barely filled a 31x10.5r15 to 30psi. If I recall correct that is.

Anyone attached a York compressor to a 22RE? There's plenty of room for one I think.