Quote:
Originally Posted by red-beard
Larger diameter wheels would lead to fewer miles recorded and lower MPG. The OD on the tires is around 33.4". Tread depth is 12/32. So losing 24/32 would mean a final OD of 32.65". That is a 2% difference if you use the full tread.
The GPS reading of speed vs. the ODB-II speed reading reading is also pretty close. The actual speedometer display guage adds another inaccuracy into things. I'm not using that. My old BMW had about an 8% high speed reading on the guage, but the ODB-II speed (A scanner hooked up) was very close to GPS.
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OBD2 speed could be exactly as inaccurate as the gauge....same inputs
GPS is more accurate because it isn't doing any math based on gearing, tire size, etc.
But you're right about the measurements and the 2%.... it's just a difference that your car cannot account for. Just pointing it out.
Some people can't understand why different tires make a difference in speed or fuel use.
Rolling resistance can make a big difference. Sounds like the LTX M/S2 does a good job reducing it.