Don't automatically assume that the speedo and odometer are off by the same factor. I just went through the same thing with my '95 Honda Civic and discovered that the old 175/70/13 tires, although they only measured .2% smaller than the new 175/70/13 tires (different brands), the new tires make the odometer read 4% too low. The old tires made the odometer read 2.6% too low. However, the speedometer reads exactly the correct speed regardless of the tire. I determined all this by using my GPS to measure my MPH and distance traveled.
Thanks, I didn't know about speedo/odo differences. I was thinking I would have to use a GPS for the best possible test I need to see if the feature set on my wife's GPS will show total miles travelled (not in a straight line). I am guessing they all do, I just need to read the manual.
Overall the tires are good. I still need to do a GPS test to get the odometer/MPG calibration right.
The one problem is that on freeways that are grooved in the direction I am traveling, the car "wiggles", aka the tread tracks into the grooves like a phonograph needle and the car has a noticeable wiggle. I had a feeling this might happen, but no proof until now. Thank goodness my main commute doesn't have this kind of freeway.
Back in the day it was much worse on my motorcycle, but it's still no fun in terms of road feel for new tires .
yeah the best thing to do is verify the odometer with GPS. Instead of reling in the specifications.
On my old Daewoo, the speedometer was right on with stock size tires, odometer off, then with oversize diameter tires, the speedometer off a little and odometer dead on.
The road grove following is a side effect of higher TP. Im my experience, it gets worse with more air. That is when you know you have reached the limit for that tire. Also sometimes you can "feel" paint stripes though the handling.
85 Chevrolet. 30 MPG or bust!
Soooooo, I think the GPS is telling me that my Odo is too slow by an additional 1%.
I think I will stick with 2% error for now, because I don't want to accidently inflate my numbers and tire wear will eventually bring this correction down over time (i.e. always losing tread => always reducing tire circumference => always reducing odometer error over time).