The Cobalt XFE as well as a couple other GM cars receiving tweaks for 2009 now have "low rolling resistance tires"... what exactly does this mean?

There must be a down side to them otherwise everybody would be using them.

I'm guessing maybe they're designed to be inflated to a higher PSI or at least have a stiffer tread and sidewall so maybe they have a rougher ride? Or is it something else? Worse traction? Worse tread life? The tread life reduction thing would make them pretty pointless since you'd save more on gas but pay more for tires. And if they cost any more than regular tires that would suck too.

Anyone know anything about them?

 

Whenever I think of low rolling resistance I just think of skinnier tires, maybe tires have made enough progress that you can get skinnier tires but similar traction, especially on lower performance cars.

 

I imagine they're harder compound.

My question is, how much benefit do the low-resistance tires give in fuel economy? Is this something that the average consumer will know about when buying replacement tires at a local store? And like you said, Threxx, what about price? Cheaper? More expensive?

 

I was under the impression they were harder compound tires


http://en.wikipedia.org/wiki/Low-rol...sistance_tires

 

Think about this... "less resistance".
Kinda like "less friction", huh?
As in "more sliding", "less heat", "less sticky"... basically all the things you want your tire to provide - especially for performance.

Harder compaounds, blow them up to 44psi or more, and roll-on.

 

Nothing new about them. Hell, the EV1 had tires designed for reduced rolling resistance. Everything is a compromise. You want superb grip and speed capability, you get more rolling resistance and much lower tread life.

Most cars geared toward fuel efficiency have tires with structures and compounds that lean toward efficiency over performance.

 

In other words, give up braking distance and maneuverability (avoiding potholes) for a gain in fuel economy... Wikipedia says between 1.5 to 4.5% gain.

 

Many hybrids have them as well.

EDIT:

Read some more on them...
Looks like these tires are going to be more common on vehicles as they improve fuel economy. New CAFE may mean these tires will be everywhere.

My guess is that it won't be on Corvettes, but we might see these on V6 Camaro's and other cars that are supposed to be large volume.

 

No big deal, I suppose, as anyone who wants to can just buy stickier rubber. This will hurt the numbers in magazine reviews, though.

 

I was just having a discussion about this on some Liberty forums. The Goodyear STs (the standard non-optional liberty tires) are low rolling resistance tires. After installing some new all season tires several months ago (after the old ones were virtually bald in only 25k miles) our fuel economy dropped about 5-6% and stayed that way (we check fuel mileage *every* fill up). The ST's we kept @ 35psi, the new ones we keep at 40psi. I wonder if we would have done even better had the STs been kept @ 40psi.

 

Toyota uses such

"stiffer tread and sidewall so
maybe they have a rougher ride?
Or is it something else?
Worse traction?
Worse tread life"

tires on much celebrated Prius.

 

Since they're harder, you'll likely get longer tread life out of them. But, traction will most certainly be compromised, if only a little.

Michelin pitched the MXV4 tires as "low rolling resistance," although I'm not certain they meet the strict definition. They're a 15 year old tire tech that was OEM on lots of Hondas, though.

I don't see it as a bad thing on most vehicles.

Here's an interesting tidbit-

I picked up 0.5mpg and WAY WAY easier roll-on ability when I switched from my 245/50/16 BFG Comp TAs to the 275/40/17 Goodyear Eagle F1 GS tires (the OEM 2000 SS tires). I couldn't believe it.

 

Those were just my guesses at what compromises could be... sounds like based on this thread the only real issue is reduced traction. Tread life may actually be better it sounds like. Sounds like for an economy focused car they're a very good choice.

I never was impressed with the MXV4/+ tires OEM on Hondas... especially for what they cost to replace with the same tires. Fairly noisy and rough, OK tread life, very expensive.

 

For some reason, I want to say low rolling resistance tires will also create more audible road noise in the cabin, but that's just a guess.

 

How low in "low rolling resistance" is the question, I know in the 90's and even today Michelin has been working on low rolling resistance tires, all the Green-X stuff had lower rolling resistance compared to other designs.

I think at some point rolling resistance is supposed to be added to the UTQG ratings in the future.