So I'm looking at new front tires in the next year or so. Right now, my criteria are: Max Inflation - 50% Min Revs Per Mile - 30% Min Tread width - 10% Max Tread depth - 10% In today's market, the leaders are: Yokohama Avid - 51 psi, 837 rev/mi, 6" tread width, 10/32 tread depth Fuzion Touring - 44 psi, 840 rev/mi, 5.5" tread width, 11/32 tread depth The Yokohama Avid is clearly ahead by max psi and lowest rev/mile. Tread width adds 1" in profile area and tread depth is slightly lower. But this is a city commuter, not a highway, cross-country car. Any experience with the Yokohama Avid tires? Bob Wilson
Does O.D. (or Revs Per Mile as you put it) have a significant impact on the Prius? Won't its CVT adjust for optimal economy automatically? Wouldn't adding 5% to the O.D. offer most of the downsides of a taller tire without the economic positive?
It has an effect but I have yet to quantify it. The "CVT" or Power Split Device (PSD) is the gear that connects to the engine crankshaft. There are gear stages that reduce the rpm, multiply the torque, until it reaches the differential that splits torque to feed the two drive wheels. By increasing reducing the 'revs per mile', we turn these multiple gears slower at any given true speed compared to the OEM tires. This reduces stirring losses from the transmission gears having to 'move the oil' about between the teeth and part of the rolling drag. There is also a reduction in tire rolling drag because the rubber hysteresis at the contact patch is reduced in frequency (i.e., the rate the tire rotates) and displacement (i.e., a larger tire has a lower angle change than a smaller tire.) This is solid theory but hard to quantify, yet. Bob Wilson
Ah, I did not think about stirring losses. Has anyone quantified this? Yes, there would be a slight rolling-drag reduction as well, but very very small. I was just thinking the added height of the car, weight & rotational inertia of the tire would counter-act any gains would see from the above. FWIW, I did have Yokohama Avid H4s on a previous car. Awful awful tires. But at the time my goal was not mpg... so not really a fair opinion.
I would also consider the Nokian WRg3 (max PSI 51) Size/Speed Rating Weight (lbs) Rim Width Overall Diameter Overall Width Tread Depth (32nd) Revolutions Per Mile 185/65R15 92H XL 15.1 5-6.5 5.5 24.4 7.4 12 850 195/65R15 95H XL 17.2 5.5-7 6 25.0 7.9 12 832 see: Nokian WRG3 - The new Nokian WR All-Weather tires offer a virtuoso combination of safety and carefree driving pleasure for every season. / Nokian Tyres JeffD
Thanks, It looks like they have a 185/70/14, 14" rims, that might work but finding them south of the Mason Dixon Line has been a challenge. I haven't given up but I'm reminded that one of the best ways to hide information is the Internet. <GRINS> Still, I have three leads: two in Tennessee and one in Michigan. We'll see what pops. Bob Wilson
Hi Bob I also need tires and been reading and watching this thread. Great information but bit too complicated for me. My question is on 2001 prius and 2010 prius what tires will you buy and what inflation Psi you will keep to get max mileage per gallon? I have read some people like defenders and you seem to like Yoko,s . I wanted it to be specific so we use your experience to buy tires which will give me higher miles per gallon and decent ride in town. Please give your thought. I do need new tires pretty badly. Thanks again for such wonderful information you put put out for us. Thanks
I optimize my ride for maximum MPG and don't really do much for 'ride quality.' So I just had the rear pair of Yokohamas installed on the 2003 Prius. The front pair were too large for the rear wheels. So after checking for rear wheel clearance, I'll 'fully' inflate them and restart my stunt drive. I went with Yokohama's because they are the only ones that support 51 psi on 14" rims. I started with P195/70R14 but they only work in the front where they are mount today. The rears have P185/70R14 that from the specs should work just fine. Their tread width is the same as the Sumitomo T4 P195/70R14 that I had been running. Both sets are larger diameter (i.e., lower revolutions per mile) so I'll be using a Garmin as the GPS speedometer. My first test with just the front mounted Yokohamas showed a 107.2% overdrive effect for the 50 miles initial calibration check. This was before fully inflating them. So I am reasonably happy with my set but they might cause you grief. A relatively low-cost way to approach tire testing is to buy just one pair and put them on the front. This will let you see the handling and ride without having to buy the full set. If they are OK, buy a rear pair. If not, buy your next choice for the front and move the others to the rear wheels. GOOD LUCK! Bob Wilson
