A little late, Bridgestone implemented what I had to do on our former Prius by tire testing and substitution. Source: ologic | Bridgestone Now if we could just fit them on a Prius . . . Bob Wilson
Same kinetic energy at the same speed? True... But...only if wheels kinetic energy of rotation is the same... 1/2 I.w^2...
Larger diameter would affect speedometer, odometer, & mpg making them even more inaccurate I have not heard of ways to re-calibrate a Prius for different tires. I believe Bob got tires to match his Prius calibration at one time.
It looks like that tire was designed to work on the BMW i3. do we know anybody to test Bridgestone’s “ologic technology” hits the road
Correct and I've even identified the replacement tires for the Prius Prime that will minimize the error between indicated and true speed and MPG. As for the "ologic" tires, true the ones for the BMW i3 won't really work on our Prius as they are too large. So I've been thinking about another approach to reduce the aero drag: leading and trailing 'mud guards.' If you can keep the air somewhat laminar around the tires, it should make a measurable improvement. Something to test with a cardboard prototype. Bob Wilson
Vehicle mass: Prius Prime mass ~= 1,527.3 kg Prius Prime tire mass ~= 30.9 kg Although not insignificant, tire mass >> vehicle mass which also includes the linear mass. Even though the wheels have a polar moment of inertia, both cars have tires of approximately the same mass and the geometry effects would be 'in the noise.' Another approach to reduce tire drag: AutoSpeed - Modifying Under-Car Airflow, Part 2 Bob Wilson
Long wearing, less rolling resistance tires. Vs. Tires that reduce braking distance. Personally I prefer the second option. Some say, inches matter....haha. There are many options in tire sizes, pressure and technology and the more info the better for all of us.
Geometry makes a lot of difference. Worse city mileage (aero drag is minimal, only rolling matters) and less acceleration is true - here you have it, the inertial effect - when comparing 15in and 17in Prii. I was particularly keen in pointing out that the experiment needs proof when stating "equal energy" in both Leafs in the video.
Exaggeration of displayed mpg is a marketing ploy I would think. The speedometer "error" is legislated, in an attempt to reduce speeding, however hopeless. The odometer however, with stock tires, should be roughly accurate. I can't see your logic: to stray from the design tire outside diameter, to "fix" speedo and mpg display? And throw off the odometer in the process? Seems like tail wagging the dog.
Actually it also fixes the odometer and trip meter distance measurements. It turn out one single metric, the revs/mile is all that has to be adjusted. That one fix corrects mph, MPG, odometer distance, and trip meter distance. BTW, testing is required to make sure the slightly larger and wider tires clear the rear wheel well. Due to turning, the front wheel wells have abundant clearance. Only the rear wheel wells have less clearance. Bob Wilson
Maybe different with the prime? With our 3rd gen: Liters/100 km, calculated vs displayed: displayed 7.5% optimistic (very closely tracked, pretty much since purchase) Speedometer: 2~4% high (purely seat-of-pants, watching displayed vs Garmin GPS indication of speed) Odometer: never checked, but I would assume it is reasonably accurate, and erring on the low side, to avoid warranty debacles.
The trip meters have 1/10 th mile resolution so it is fairly easy to drive down a highway with mile markers and see the error. With 10.0 miles, the least significant digit is ~1% (+/- 0.5%). Take a 50.0 mile drive and it is ~0.2% (+/- 0.1%). Do 100.0 miles and you've doubled the accuracy. I suspect the standard unit displays have a similar, fraction of a km display. BTW, I did the same tests with our Gen-3 and Gen-1 Prius. In the case of the Gen-1, I actually put the largest I could fit on the front to implement a type of 'over drive.' Yes, acceleration was impacted but it was an experiment. The only problem is the resolution was too low to verify a mileage effect. I continue the experiment because when I was driving the indicated speed limit, the car was 'keeping up with traffic' which in area tends to be over the speed limit. In some cases such as posted 40 mph roads, this was enough to let the car run in 'hybrid mode' because it was below the 42 mph threshold although the true speed was closer to 44-45 mph. Bob Wilson
it's too bad they didn't name the competitors, i bet michelin energy savers weren't tested. are cars really identical? maybe they should swap tyres and do it again.
