Here's a link to 4Lo.com where they have tire size/gearing caluclators. You can plug in the diameters of your tire sizes and figure out exact speedo and gearing changes. Going from BFG 265/70s(30.6") to BFG 265/75s(31.8")results in a 55mph speedo reading actually being 57.2mph. This calulator is also handy when figuring out R&P changes. My truck came with a 4.30 R&P and my tire diameters changed from 30.6" to 32.7" so 4.56 R&Ps got me to a 4.27 effective gear ratio. Brew <img src="/forums/images/graemlins/cheers.gif" alt="" />

Last edited by Brew; 06/21/07 03:03 PM.
98 T100 SR5 4x4 3.4L auto, TRD Goodies, Bilsteins, engine/TC skids, 2" body/d.train lifts, F/R ARBs, 4.56 R&Ps, Aisin hubs, 255/85R16 Dunlop Rover RVXTs (street), 16x7 +8mm offset wheels, custom bumpers, Warn M8000, Master-pull synth. line