[Holicow]

Yes, there are numerous threads discussing different tire sizes and models. I have even done my own experimenting, with mixed results to say the least. I have decent knowledge of tires in general.

My questions are: (finally)

What is a Low Rolling Resistance Tire? At what threshold of rolling resistance is a tire now deemed LRR?

Is there any source that shows the rolling resistance of current tires?

 

[Rick Reece]

My understanding is that LRR is like low fat. In other words its not an absolute value of a particular rolling resistance but rather a reduction of something like 30% from the Non LRR tire. I have looked and have not been able3 to find absolute numbers. Have fun, Rick

 

[Rick]

Here's what I am aware of when a tire is said to be LRR. From the weight of the vehicle the bottom of the tire is flattened some which is where it comes on to contact with the road. So the tire is not perfectly round. For ideal low rolling resistence you'd want a perfect circle, but then that brings in the saftey issues of loosing control too easily. LRR tires use a extra strength side wall so they don't deform at the bottom as much. They can also incorporate different compounds in the tread which make the tire easier to turn. Soft rubber takes more power to spin than hard rubber.

Unfortunately there is really no rating of LRR. From what I've seen the Potenza is going to be the lowest rolling resistance of any tire your going to find. As I've mentioned the Goodyear Integrity is close behind it. Generally if you look for reviews on tires and find ones that have bad reviews as far as traction it's a hint that they are LRR. Also if you look on the manufacturers page sometimes it will say something like designed for better fuel efficiency.

Like Rick Reece has posted before he tried some skinny 155 (was it) tires on his Insight that were not LRR and mileage was about the same or actually took a hit if I recall correctly.

 

[Rick Reece]

I used some 145/80 Goodyear's for about 1000 miles. (I thought they would help considering the smaller patch in contact with the pavement). The taller tires helped the ride a bit and they didn't follow groved pavement as bad but they weren't as good as the bridgestones for mpg. Have fun, Rick

 

[Holicow]

Thanks for the replies, and that reinforces what I had thought:

There is no such thing as "Low Rolling Resistance." There are only tires that have lower resistance than others, on the rolling resistance continuum.....

I guess one way to tell if a particular tire is more efficient is to look at whatever models are OEM for high-mpg cars, eh?

 

[Rick]

Yeah, their engineers probably get to consult with tire manufacturer engineers and then buy a few different types and experiment. One of my other goodies I have are some slides from the original GM EV1 concept car, the Impact. One picture shows the wheel and tire. Goodyear specially made them a set of LRR tires that could be inflated to 65 psi. That car had more range than the final production car did even.

Here are a few other LRR tires I know of:
Michelin Proxima EV1 tire, no longer made
Tigerpaw something, used on the EV trucks, no longer made
I think Nokian makes a LRR tire as well, kind of hard to get though.
Honda had some special LRR tire on their EV+ too, but I don't have a clue what they were.
Now I'm kind of curious as to what kind of tire is found on the production RAV4 EV's.
Dunlop A20, used on Civic Hybrid

If you look on the electric vehicle discussion list a while back a person knew someone who owned a tire shop so he rigged up a device to push his car with a constant force so they mounted up a bunch of different tires and found the Goodyear Integrity was the lowest RR of the group.

 

[cakley]

LRR would be hard to measure or at least rate without one person using the same method along with many different tires. And the key difference would be tire pressure.

The stock Insight tires might be called LRR but put 32psi in them.. For that matter put 52psi in any tire, mount it on a 1800lbs car and it would probaly be LRR.

My .02 is that Tire companys make tires to be used on normal cars. IE cars that weigh at least 1000lbs more than the Insight. So the tire they make/design has to handle the weight at Xpsi. Put the same tire on the Insight and the PSI could be increased above the max.

 

[Holicow]

Reviving this thread with a link I got off the Honda Hybrid yahoo group:

http://www.greenseal.org/recommendations/CGR_LowTireResistance.pdf

Has some interesting info, and also snow tire recommendations. Unfortunately, does not mention our OEM tires, or GY Integrity that some are considering.