First I want to thank you for posting the link:
Quote:
Originally Posted by CapriRacer
You would think that but the data suggests that there are other things that may have more impact. I've tried to catalog them here:
Barry's Tire Tech |
I was aware of and have a copy of the Smithers report as well as a few SAE papers and graphs.
I've been testing Sumitomo T4s on my NHW11 and have these lessons learned:
- GPS distance and speed - due to tire wear and geometry effects, we can not use the vehicle MPG because it is based upon wheel rotations WITHOUT compensation for the tire diameter change.
- tread width is NOT found in xxx/yyRzz - the "xxx" is a width of the inflated tire portion but the tread width is different. Go to Tire Rack and you'll find there is a column called "tread width" and there is considerable variability that tends to follow but is only loosely associated with the "xxx" metric.
Our 2003, NHW11 Prius has had these tires:
- 175/65R14 - Mastercraft (sears) brand suffered abnormal wear patterns that were corrected by fixing the rear toe and camber. The front right camber was off and fixed with the next set.
- 175/65R14 - Sumitomo T4s, 51 psi, were undersized according to the specs. This means the indicated speed was higher than true leading to lower true speeds. The indicated MPG was also high. But due to the tripmeter errors, the pump calculated MPG was probably high.
- 175/70R14 - Sumitomo T4s, running at 51 psi, slight improvement in stability and no change in the corrected, calculated MPG. The adjusted MPG showed no change from the previously 'optimistic' MPG . . . a true improvement of ~3%.
- 195/70R14 - Sumitomo T4s, 51 psi, largest that fit on the NHW11. No change from 175/70R14s although some evidence of more steering input.
Sumitomo T4 is listed as low rolling resistance by Consumer Report.