A topic thread about this a few months back mentioned a Kobalt air compressor for $50 from Lowe's that many here recommended.
I looked at one a few weeks ago and have been planning on picking one up soon!
Here is a link:
http://www.lowes.com/pd_146781-40883-KL12120_0__?productId=3522750#img
I could have used it two weeks ago on our last campout as I picked up a piece of metal in one of my truck tires while we were out 4-wheelin and had to drive 12 miles in to Gunnison, CO to get the tire fixed with a half inflated tire!
I might just go pick one up tomorrow.
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I have a Porter Cable--
Link. I've had it for eight years and it still works great...a little cheaper eight years ago.
I have a Sears Craftsman air compressor of similar size that I bought for use in the RV, but I've found it too heavy to haul around (even though it is small) and it blows a circuit in the trailer if I plug it in to the outside power outlet of the trailer.
Plus, even though it has a 100psi tank on it, I still have to run it to fill the tank for every tire I want to top off!
Even our mountain bike tires!
Which is why I will be getting the Kobalt air compressor I posted about above.