Improvements in modern LRR Tires
 

So there's lots of information available as of 4 years ago on some of the best LRR tires out there..... but each list and comparison i come across doesn't seem to be conclusive. I hear a lot of people preferring to use snow tires, yet all the tire rack tests and such only pick tires from the touring categories... Not only that, most of the tires in these tests are no longer made! Or at least there's been a modification of the compounds.

So.... anyone have any idea what the end all be all is of a LRR tire available today? I'm currently shopping for new rims for my CRX HF and i need to know if i need to stick to 13's, 14's, or 15's too, so the tire size availability will probably determine that.

Until the us government requires an lrr metric and rating you only have a best guess.

13" are poor lrr but usually light,

14" the only choice is the re92, the others are designed for heavy cars and not as efficient

15" is Ecopia but their discontinued in that size

You can debate and compare tread patterns and rubber compounds all you want, but the real action is in the gross geometry. The advantage goes to tall and narrow:

http://ecomodder.com/forum/showthrea...-25208-13.html

TL;DR

If you have a 5x112 or 5x120 BCP and 27+ inch diameter it's a fairly straightforward fitting. These are as new as the BMW i3. You can get Moon disks in that diameter, too.

Yes.
The European market requires rolling resistance testing and their ads post a letter indicating relative LRR performance. Unfortunately for us North American drivers, most of the tire model names sold over there are different from what's sold here. AND, if you ARE lucky enough to find a make/model/size sold in EU with good LRR performance, that same model sold here in the US could have different characteristics. Makers are under no obligation to provide the same tire here as over there, even if the name is the same.

To find overseas market tires, I've google searched using "tyre". The UK spelling. That way I get results in English. And yes, shipping tires or tyres from overseas is costly and sometimes cumbersome. I investigated briefly. You need a "Freight Forwarder".

That said, I'm partial to Michelin for LRR. They've been offering LRR tires longer than most (all??) makers, and seem to at least have some idea of how to get results while simultaneously still building a great tire in other regards.

I can't speak for tires at large. I'd like to, and I've looked for data, don't get me wrong.

My personal experience: In the 14" size, Michelin Defenders, which are relatively new, perform no better than the 16 year old RE92's. Most Insight owners agree they're worse, but it's marginal at best. They do last 2-3x as long, at the expense of being (subjectively) a bit more noisy.

My winter tires, Nokian Nordmans, are not rated for low rolling resistance, but I've seen 100mpg @ 50mph during the winter with the car fully warmed up, which is basically what I get with RE92's in the summer.

I just bought a set of 15" Michelin Defenders (green) and am very happy with them. The coasting distance is much greater than the previous tires. So much so that I've had to adjust the start points for coasting to all the stop signs on my route. Where I use to start coasting left me still going 30 mph at the stop sign.

PS: just noticed you're in San Antonio. I'm in Rockport, so we should have similar results.

First, there is a technology triangle involving treadwear, traction, and rolling resistance. To get better properties in one area, one or both of the others have to be sacrificed. That's why OE (Original Equipment) tires - the tires that come on new cars - have such a poor reputation. They were designed for good rolling resistance, and the treadwear and/or traction were sacrificed to get it.

Further "LRR" is a relative term. It means better rolling resistance compared to other tires with similar wear and traction properties. It does NOT mean absolutely low rolling resistance. In fact, many LRR labeled tires will have fairly high RR values - some higher than non-designated tires.

So why hasn't the US government required labels for RR (fuel economy)? Because the tire size plays a large role in what the value is and the regulators (NHTSA) want to use RRF (Rolling Resistance Force) which makes smaller tires look better (which also means overloaded tires), where the tire industry wants to use RRC (Coefficient of Rolling Resistance), which makes larger tires look better. The courts have ruled that NHTSA's proposal is unacceptable, but NHTSA has not yet issued a revise regulation.

14" insight wheels and re92's

So what you are saying is that nobody wants to rate the tire so you can tell what affect on fe it will have?

I would think you would load the tire to 75% of its rating and measure the drag it creates and test the amount of wind drag at a simulated 65mph fender less drive.

Then weight the two measures appropriately to create a drag metric.

One could then subjectively compare a real metric as opposed to one that is likely meaningless.

No, I am saying the government has not issued the rules that need to be followed. All the tire manufacturers have agreed that they will follow the rules once they are published, but until they are published ......

It's the issue of meaningless that has prevented the issuance of the rules.

There are some things that the regulations must address:

1) The test: The good news is that pretty much all RR tests correlated to one another, and a single test point (Load/Inflation/Speed) can characterize the RR of a given tire.

2) Comparing test locations: This is bit more difficult, but there is a way to compare tests from different locations - the SRTT (standard Reference Test Tire) - a carefully constructed and carefully stored tire that has very good and stable properties over time. It is used for traction testing, treadwear testing, and other types of testing where the testing conditions might vary, say, with the weather or testing surface.

3) RRF vs RRC - this is a biggie. As explained in an earlier post, NHTSA wants to use RRF and the tire industry wants to use RRC, and the courts have ruled that NHSTA's proposal isn't workable, but NHSTA hasn't agreed to use RRC.

4) How is the data to be presented: A number? A Red/Yellow/Green bar graph? A combination? Something else? That's up to NHSTA to decide - and they haven't.

5) And the problem of tire size needs to be addressed. Ya' see, RR varies according to tire size. Both RRF and RRC are different for otherwise identical, but different sized tires. Do the tire manufacturers need to test every size of every tire line they make? If so, it would take over 3 years working 24/7/365, and nothing else could be tested. Realistically, there aren't enough testing facilities available. So how to handle? This has barely been discussed with no obvious solution in sight.

In the meantime, Congress has been cutting the budget, meaning there just isn't enough money to work on every project - and this one is a low priority. It seems reducing the amount of traffic fatalities is more important.

So if you want the tire manufacturers to publish RR ratings, send a letter to your congressman. Tell him you are willing to pay more in taxes to get this accomplished.

I would strongly support a variable gas tax that would stabilize gas prices.
Aka the tax becomes higher when crude goes under a certain price threshold and lowers when crude is more expensive.
Charge it at the supplier level so it can be reactive and hold a price floor, eliminate it entirely when prices jump.

During windfall times roads could be fixed and bs pet projects funded, during hi fuel seasons the tax would lower reducing the surge and road budgets would be reduced.

Unstable road funding should force a nimble reactive workforce.

Defenders are great, the price tag for $100 each for a set of 14's is rediculous.

I just bougth yesterday my next efficiency test tires. They are Continental ContiEcoContact 5 in size 195/55 R20 95H XL. That means they have A rolling resistance. Many brands to choose for A level RR in this size.
- They are narrow so drag is lower.
- They are tall which also lowers RR

They can be fit to cars like Tesla Model S or Model Y, Audi A8D3 etc. I think best fit would be the a8 model weigth wise, but my plan is to test them on Tesla Model S. Estimated energy consumption reduction is 15-20% on the model S.
10% comes from aero of tire (width 195 vs 245 on Model S)
5% comes from lower RR
5% comes from aerodynamic wheels
I am at the moment searhing the best wheels to buy for the test. I have found a nice option for later use if and when the test works like I have estimated.

Minor problem is that maximum rear axle mass is 1500kg which is little bit more what the wheels or tires can at the moment handle. But if you know that then there is no problem to use these in model S.

I installed a set of Bridgestone Ecopia EP422 tires on my Mazda3 a few months ago. I "believe" they are a LRR tire which should help a little, but I haven't been doing enough driving to really tell yet, thanks to The Virus from China.

I did increase the already tall legs of my Mazda3 a bit with the new tires, going for 20565R16s to replace the factory's 20560R16s. This bit of extra circumference slowed my RPMs down by around 3%, which theoretically will yield a small increment of fuel economy, but probably not measurable except under laboratory conditions.

With the new tires, my 2.0L engine is now turning at about 1670RPM at 60MPH, compared with about 1720RPM before. Slower RPMs generally helps fuel economy by reducing the level of internal engine friction and allowing the engine to loaf a little more, as long as, however, the tipping point isn't reached where the extra load from the slower engine overcomes any benefits from the fewer revs per mile.