Tire break in and rolling resistance?

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nthach

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So Costco refused to replace my year-old Bridgestone Potenza RE960AS since my MPG has not recovered back to its norm of 18-19mpg. The guys at the tire shop say the tires need to break in for a bit but I have about 6,000 miles on them. Does rolling resistance improve as the tire is used or no?

I'll guess the evil streets of San Francisco need to chew these tires up, I don't like them...
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It's not a break-in issue, but mileage does improve as the tread wears down. More tread mass equals more fuel consumption. For optimal fuel economy, you need to find a tire with poor traction, poor treadlife, or both. OE tires and low-rolling-resistance tires are best for that.
 
I did not notice a significant drop when putting 960AS on my saab 9-3 compared to the Pirelli P6 OE tires they replaced. Quieter though...

What has the economy dropped to?
 
I usually got 17-19mpg normal driving, 25 or so highway like up to Tahoe. Now, it's dropped to 16/22.

The tires are on a Lexus LS400, I had Michelin Pilot Exalto A/S before.
 
Why should they replace your tires? Tire break in is not an issue. Your car gets,what it gets,with those tires.
 
If you look at the thread pattern of the RE-960 and the Exalto they are different. I bet the Bridgestone's handle better but b/c of the this thread pattern, you're losing a little mileage. Both are great tires. Also, it's winter. You tend to lose a few miles per ga. I don't see why Costco would replace your tires after 6K mi.
 
One thing I can assure you of is that the RE-960 does not handle better than the Pilot Exalto. I've driven both tires, on identical cars, and I'll take the Michelin without hesitation.

All UHP tires generate poorer fuel economy numbers compared to a traditional all-season type. It's just the nature of the beast. New tires will also provide lower fuel economy numbers than their worn counterparts, due to things like tire mass and tread flex.

If fuel economy is a major priority, then I'd suggest something like the Continental ProContact ECOPLUS +, or the Michelin Energy Saver A/S. Performance tires just aren't going to cut it if you're trying to hyper-mile it.

Oh, and just as a note, a tire doesn't come with "threads". Unless the manufacturer is giving away some spiffy wearable swag with your tire purchase...
 
The car did feel lighter on the Michelins - and one thing was that the Exaltos did share Radial XSE construction with the Energy MXV4 and HydroEdge series, I noticed the newer Exaltos also carry the Green X symbol as well. With the Bridgestones, it feels a little squishy.

Well, since the car sees a commute to SF and Tahoe roads are a little rough and the Potenzas have a softer compound I'm sure my MPG will slowly bump up as they wear down. I'm just not happy with the extreme MPG drop. We just got a set of Primacy MXV4s on the Prius and it has seen a slight drop but it's still pulling in 48MPG.
 
Agreed, it's "tread". Not "thread". Gah, that really annoys me...
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And what everyone else said... The tires *should* give you better MPG as the tread wears down... but a performance tire isn't usually focused on MPG's...
 
The RE-960's are rated 400/AA/A. Softer compound. Trade-off's. I see a slightly lower mpg's vs. the OEM Hankooks which were on my Focus. The Exalto's cost slightly more. If you don't put too many miles on per yr., the longer lasting tire may not be an advantage.
 
Mpg will rise with most tires as they wear down but with the Bridgestone RE960's they have a stickier compound underneath that gets exposed as the top layer is worn off so it remains glued to the road. I had these same tires on my Mercedes and I tore it up pretty good on I 280 and US 101 in SF. It stuck to the road. Only issue was that it was very loud for me after you put more miles on it. They wore out before 30,000 miles for me. I have Michelin Primacys back on now and they sure ride better and with less noise. I do notice that the sidewalls are much softer now. So with any tires...its a little give and take depending on what kind of performance you seek.

What pressure are you running your 960s at? I always kept all 4 corners at 35 psi.
 
35 psi fronts/ 32 psi rears. Mileage is slightly less w/these tires compared to the OEM Hankooks. But, the mileage trade-off for better handling, superb steering response, etc, etc was more than worth it.
 
Originally Posted By: FZ1
No,boys. You don't get more mpgs as the "tread wears down". Think about it.

Personal experience with commercial trucks, running millions of miles coast-to-coast, tells me that you haven't a clue what you're talking about.
wink.gif
 
After 40 years of running a few miles or so and a tire or two purchased, I definitely do believe there is an improvement in rolling resistance as a tire ages/wears.
 
rolling resistance results from the tire resisting to flex as it contacts and releases from the contact patch. Stiffer rubber, ie, higher treadlife tires, typically have higher RR. CapriRacer has a great explanation somewhere out on the 'net.

soft rubber = better traction & Lower RR, but at the cost of lifespan.

As a tread wears, the dia decreases, which will make the computer think you are getting higher MPG, AND there is less rubber to flex, so yes, worn tread can provide better and "fake better" mpg. the amount of the effect will vary based on vehicle itself, tire size, which is why perhaps the commercial driver above hasn't observed this behavior... tire resistance may be way to small to calculate in a commercial vehicle, while in a lightweight commuter car or Kroger's-bound SUV, can be a real factor.

Going from oem, soft (lasted only 30,000 miles) to a harder compound All-Terrain (50,000 tread warranty) I've lost a solid 2 mpg, as echoed by MANY surveys on tirerack.

M
 
Originally Posted By: meep
rolling resistance results from the tire resisting to flex as it contacts and releases from the contact patch...........


Ah......Mmmmmmm......Not exactly

Originally Posted By: meep
.......Stiffer rubber, ie, higher treadlife tires, typically have higher RR...........


Ah......Mmmmmmm......Not exactly

Originally Posted By: meep
...... CapriRacer has a great explanation somewhere out on the 'net.......


Thanks - and here it is:

http://www.barrystiretech.com/rrandfe.html

Stiffness and hardness are 2 dimensional and RR is a 3 way property - traction and treadwear being the other 2 legs of the triangle.

And, yes, RR gets better as the treadwears away - less mass!
 
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