Quote:
Originally Posted by Blackdog
I moved up to 285 terra grapplers a little over a month ago. I have noticed a drop in mileage per tank, But........I have also noticed roughly 3 mph slow down on the speedo as compared to the GPS machine. I wonder if the miles per tank are really falling off that bad, or if the mileage is just not clocking accurately because of the difference in tne speedo calibration. Just a thought.
BTW I LOVE the Nitto TG's
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Bing, Bing, Bing - we have a winner.
The 285's are a larger diameter so your speedo and mileage will be off. Check out the miata tire size calculator to see exactly how much. It's around 4% IIRC. Lots of threads on this. A few ways to correct it. The easiest is a speedo correction gear available from Cdan, Christo and others. It trued up my speedo to exactly what my GPS reads. There's also the speedo correction box that allows you to program in different tire sizes if you run street vs off road sizes, etc. The correction gear is in the $40 range and the correction box just under $200 (all from ancient memory).