I am lucky that there is a place near me that does this, so I go every few months. The caliper test for me was off by 7% and NOT in the right direction!
When I went to get dunked, the owner told me that he has tested people that the calipers are off by as much as 17%!!
Here is the link to the place I am aware of. They have mobile units all over the place. Might find one near you.. http://www.getdunked.com/home/default.asp
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