Improvements in modern LRR Tires

[CapriRacer]

Originally Posted by rmay635703

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

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 ......

Originally Posted by rmay635703

....... 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.

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.

[rmay635703]

Originally Posted by CapriRacer

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.

[Chrysler kid]

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

[Vekke]

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.

[MeteorGray]

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.