LRR Tires.... 337 or 357 miles?

The 300 mile quote is for the standard rims on the 85 kWh pack at 55 mph and 320 miles for the aero wheels at same speed.

bluetinc said:

I tried searching high and low for any type of real numbers for the Goodyear and Michelin tires, but didn't manage to find anything. Does anyone out there have any data they have managed to dig up on them?

Peter

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Were you able to at least find some claimed savings (like an ad saying saving up to x%). That would give you an upper bound.

The DOE site actually has a good page on low rolling resistance tires:
http://www.afdc.energy.gov/afdc/vehicles/fuel_economy_tires_light.html
If you can find the rolling resistance coefficient for the tires you are interested in, you can probably get a good estimate of the max savings you can get.

On point to be aware of though, is that rolling resistance barely varies with speed. That means at higher speeds, it's going to matter less and less.

Okay I found a chart with RRC (rolling resistance coefficient) for popular tires:
http://onlinepubs.trb.org/onlinepubs/sr/SR286Rolling_Resistance_Data.pdf

The lowest Michelin Pilot Primacy tire they have listed have the RRC of 0.00833. The Goodyear Eagle GT HR (probably the closest to the RS-A2s) is 0.01217.

Plug this data into the formula given in the DOE page (using the highest 0.19 for Csensitivity taken from the HWFET cycle):
((0.01217-0.00833)*100/0.01217)=31.55
So the a 31.55% difference in rolling resistance.

31.55*0.19 = 6%
http://www.afdc.energy.gov/afdc/vehicles/fuel_economy_tires_light.html

If you use the more realistic US06 cycle, with a Csensitivity of 0.12, you get 31.55*0.12 = 3.8%.

stopcrazypp said:

Okay I found a chart with RRC (rolling resistance coefficient) for popular tires:
http://onlinepubs.trb.org/onlinepubs/sr/SR286Rolling_Resistance_Data.pdf

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The problem is that those charts are from 2005 and have absolutely no bearing on tires made in 2012--even if the tires are called by the same model name. Several rolling resistance improvements have been made to tires since then.

In addition, tire size makes a difference. A tire that has a RR value of X in size A will have a different RR value in size B. And because the tire manufacturers have fought and won the battle of not having the RR values and part of the UTQG system, the only way for a consumer to know is by actual experience on their particular car. It's unfortunate, but true.

Nokian, Yokohama, and Michelin all make low rolling resistance tires--although perhaps not in the Model S size (haven't looked it up yet). So far, I've had the lowest rolling resistance with Nokian eNTRYE in the Prius--but that's not to say they would be the best on the Model S. Most likely I'll try Yokohama next.

I'm pretty surprised that Low Rolling Resistance tires are not available from the factory, at least as an option.

bluetinc said:

All,

When I was at the store, the numbers shown were for only a 19" and 21" wheel option, and while it was not clear, it looked like the 19"s were not the aero wheel. (Edit, talking with the reps at the store, they say the numbers are for the standard wheels) Numbers where:
Speed(mph) 19" 21"
55 321 314
60 295 289
65 271 266

Given how close they are, it doesn't match the 5% gain from the Aero's (or the 1500 extra in cost) I was hearing about back at the factory...

Stopcrazypp, that's some great data you found, I wasn't even able to find that. It matches most of my rough assumptions, though I would love to find out the extra numbers for the particular tires that are out today. The MXM4's look to be a good leap forward from the MXV4's, with the loss of about 3lbs a tire in our size, and updated rubber and tread design. I'll try to hit up the manufacturers to see if they have any numbers that are available on request. At least the 19" tire size does have a few options shown by tire rack:

Tire Search Results

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Please forgive my lack of technical knowledge: Can you shed any light on potential range differences between a Performance and a Standard model with both on 19" rims (or would the range be the same except for potential driving differences with the faster drivetrain)?

I'm torn, in that I want the Performance but think I may run into problems during the Winter. We usually get a couple of decent snow storms and a few ice storms each year. Would it be sacreligious to put 19" wheels on a Performance model and would I be losing some of the Performance value?

jbherman said:

Please forgive my lack of technical knowledge: Can you shed any light on potential range differences between a Performance and a Standard model with both on 19" rims (or would the range be the same except for potential driving differences with the faster drivetrain)?

I'm torn, in that I want the Performance but think I may run into problems during the Winter. We usually get a couple of decent snow storms and a few ice storms each year. Would it be sacreligious to put 19" wheels on a Performance model and would I be losing some of the Performance value?

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They should perform the same if the driver treats the cars the same. Of course the driver of the performance may be more interested in feeling the acceleration so range will be impacted.

dsm363 said:

They should perform the same if the driver treats the cars the same. Of course the driver of the performance may be more interested in feeling the acceleration so range will be impacted.

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After of course you put performance 19" tires on the car.

zdre said:

I'm pretty surprised that Low Rolling Resistance tires are not available from the factory, at least as an option.

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I'd be surprised if there are any 19" LRR tires available. I don't think there is much of a market for 19" LRR tires.

goyogi said:

I'd be surprised if there are any 19" LRR tires available. I don't think there is much of a market for 19" LRR tires.

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Here are two:

Michelin Primacy MXM4 245/45R19 98 W

• FUEL EFFICIENCY = 10

Nokian Hakkapeliitta R 245/45R19 102 R XL

• Ultra-low rolling resistance saves fuel

Surprise!

Tirerack has even more. http://www.tirerack.com/tires/TireSearchResults.jsp?customSizeSearch=&width=245%2F&ratio=45&diameter=19

On the bottom left column there is a radio button to include only LRR tires.

bluetinc said:

Since I'm going to have the 21" wheels for summer, I want to put some decent all season tires on a set of 19" and if they can be an LRR that increases my mileage by a good deal even better. Unfortunately it's clear there is no way to find any real information to compare the tires for sale

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Unfortunately, that's correct. The tire manufacturers consider rolling resistance proprietary information and fought successfully to have rolling resistance excluded from the UTQG rating system. You'll find some old numbers around the Internet but the problem with those numbers is that they only apply to the tires made at that time (Rolling resistance is something that advances regularly. Last year there was a big jump in rolling resistance values.). The list would only apply to the specific sizes listed as well. So mostly it's a guess on which tire manufacturer you believe in.

bluetinc said:

I'm thinking this should be a lot easier then trying to compare this on an ICE.

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I don't really see how. Determining energy economy on a vehicle is a complex thing to do. About the only thing you don't have to do is put on a tank to hold a measured amount of fuel for the test run. All the other things still exist.

bluetinc said:

Do I need to drive the tires around for some distance before I can get valid numbers out of them to compare?

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Tires decrease in rolling resistance throughout their lifetime. I'd run the tires for 300 to 500 miles before doing this kind of test (and re-torque the nuts at this time).

bluetinc said:

Could multiple cars be used or would that introduce too much variability to the comparison.

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Multiple cars are generally the only way to do this kind of evaluation because each car will have it's own inefficiencies (such as alignment) so using two or more cars will tend to show only the tires. The logistics are a bit tricky. For example, if one driver opens the window, the other driver has to open theirs as well. Also the comparison has to be run on the same day for all the tires compared or you have to compare a base-line tire with each candidate tire. You can't really get in more than one test run per day so it will take a minimum of one day per tire tested.

bluetinc said:

What about variables such as outside temperature?

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Some tires may have less rolling resistance at higher or lower temperatures than other tires. However, the standard is 65F (18C) for almost everything related to tires.

bluetinc said:

Also, thoughts on tires to compare? So far I was thinking:


Bridgestone Turanza Serenity Plus
Michelin Primacy MXM4
Continental ContiProContact
Goodyear Eagle RS-A2
and of course the OEM 21"'s

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Nokian Hakkapeliitta R
Yokohama AVID ENVigor

jerry33 said:

Nokian Hakkapeliitta R

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Hakka R is a winter tire, not all-season.

jkirkebo said:

Hakka R is a winter tire, not all-season.

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You are correct, but it is a LRR tire and it would be very interesting to see how it compares to the other tires. Particularly if someone has a set of 21" tires for summer use.