Maybe you taking that from there web site, other wise you would be saying that they were 37 3/4" be because that how a tape measure reads.
I have a set of 37" BFG's setting in my garage right now that measure 351/2" aired up with no load, that's right 351/2"
My 39" Mud Hog's are 381/2"
It all comes down to what the true tire & lift size is and if you really wheel it. Like the Goodyear MTR 37s are just over a 36" tall tire.
If your close to a true 37" tire and are going to run trails Like the Rubicon you need to cut about 3/4" at the back of the fender. theirs plenty of room...