Testing rolling resistance of the Various Tires of the Suzukiclone Fleet (RE92 wins)
 

http://forkenswift.com/album/23-gt-w...re92-tires.jpg
(ForkenSwift sporting the winning tire: Bridgestone Potenza RE92's, OEM low-rolling-resistance tire of the 1st generation Honda Insight.)

So, on the weekend as you may have seen already, I did some rolling testing of the six (6) different sets of tires that are currently in the Suzukiclone fleet. (Seven sets, if you count the spare tire donuts, which I also tested.)

I wanted to find out which tires had the best rolling resistance performance (and which ones had the worst).

This info probably may not be particularly useful to anyone else unless you have the same tires. (Which is unlikely, with the exception of the Bridgestone Potenza RE92's, which are still available. And maybe the Goodyear donuts. :D)

All the wheel/tire sets were mounted on the same car (ForkenSwift), which was rolled down a gentle hill onto a flat run-out.

Long story short, here's what I learned:

http://forkenswift.com/album/8-results-chart.gif

Order of testing - it was sort of an "A-B-C-D-E-F-G-H-A" test... :)

http://forkenswift.com/album/8-resul...er-testing.gif

The how

• All testing was done by mounting the wheels/tires on the ForkenSwift

• Tires were set to 51 PSI

• I drove each car the same distance to an empty parking lot with a small downhill entrance/exit opening on a level run-out area

• Start: car was stopped with the hand brake at a marked position on the hill, transmission placed in neutral and the brake released

• Finish: after coasting to a stop (max speed < 10 km/h / 6 mph) each run's "end" position was marked on the road with chalk.

• 3 - 5 runs were done for each set of tires

• drove back to the shack, swapped the wheels/tires

• the hydraulic brakes were not used at all during the testing, to avoid as much as possible having the front brake pads dragging on the brake rotors after use

• rinse and repeat

Conditions:

24 C / 75 F - clear & dry
wind WSW 12 km/h (~7 mph)

Here's a pic of the test area, with an accurate representation of the RE92's average finish position compared to the average finish for the donuts (@ 70 psi):

http://forkenswift.com/album/8-re92-...t-panorama.jpg

You can see it wasn't that steep a hill. Maybe a 2 foot elevation change. (From: Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Poll Results )

Moral of the story: obviously... tire choice can have an enormous impact on vehicle efficiency!

Stuff I learned:

• I was surprised how much better the RE92's were - not only did they have the best result overall, but they also had the biggest improvement when looking at the difference between each set of tires.

• I was surprised to see the big, beefy Michelin snow tires in 3rd place. With lots of deep-siped, blocky, squishy treads! (Then again, we know some snow tires can have LRR qualities - remember Chang Ho Kim's modified CRX winning the AMEC mpg rally with Nokian winter boots on?)

• The spare tire/donut performance surprised me. Part of me hoped they would have magical properties. Instead they were awful.

• PSI over 50 seemed to make little to no difference with the RE92s:

The next day I did a test of tire pressure vs. rolling resistance using the RE92's in the same parking lot. I went from 20 to 70 PSI in 10 PSI increments, 3 runs per increment. From 20-50 PSI, there was a measurable improvement each time. At 50, 60 & 70 PSI, there was no significant change in finishing position - the ending 9 chalk marks (3 PSI x 3 runs each) were mixed & clustered together along a 4.5 foot line.

I've done a test like that before: www.metrompg.com/posts/tire-pressure-rolling-resistance.htm

Interesting test, and kudos to you for mounting and unmounting your wheels so many times just for some real data.

Yeah, it took a stupid amount of time to do this.

Initially I just wanted to know if the RE92's were better than the Blackfly's Invictas. But then I just kept going :)

Oh well, it made for a neat picture.

I'd love to see these kinds of tests with current popular LRR tires like the Energy Saver A/S, Fuel Max, Ecopia EP100, dB Super E-Spec, ContiProContact w/EcoPlus, Nokian enTYRE, etc.

If only we were rich huh? lol

Yup, that would be nice.

Supposedly official LRR ratings for new tires are coming for the US market - but I haven't been keeping up with the details.

FYI, I posted the details & charted the result of this test in this thread: http://ecomodder.com/forum/showthrea...tml#post265379

That's an awesome post.

Been looking at some Nokian Hakka C Van tires to replace my Kuhmo's.

Awesome job! But the "donuts" in the pic look a lot like yellow GTi wheels! :D

Good eye. Yes, they look a lot like Suzuki Swift GTi wheels photoshopped to be yellow for that picture. :)

Aside from the pic below, I didn't take profile pics of the different wheel/tire combos...

http://forkenswift.com/album/8-spare...angles-800.jpg

from: http://ecomodder.com/forum/showthrea...uts-19094.html

It would interesting to do a city route then a highway route with the donuts at 70 psi vs the Stones at 51. I would be willing to bet that based on your previous experiences with donuts that they would shine bright on the highway route based on lower aero drag and the stones might, or not, shine on the city route.

Seems like a load rating/aero drag compromise is what we are looking at.
If so, then the skinniest tire (preferably tall) with a high load rating is what we are after for overall performance.

FYI, I just happened to calculate the "real world" (ie. not scientific) impact of switching to the RE92 tires on the ForkenSwift:

• 345 Wh/mi ... 10 drive/charge cycles before switching tires
• 285 Wh/mi ... 10 drive/charge cycles since switching tires

That's a 21% increase in range. (Or a decrease in battery discharge for the same distance driven, with associated benefits to pack life.)

FYI, I'm not actually planning any more tire tests. I will just aim to use RE92's wherever I can on the Suzukiclone fleet.

Also, for a pile of reasons, I am DEFINITELY NOT suggesting that other people will see anything close to this efficiency increase if they switch to these tires.

What's the weight of that vehicle?

What's the load rating on the RE92's vs the donuts?

ForkenSwift: 2070 lbs

RE92 Max Load: 937 lbs.

Donuts max load: 1025 lbs.

I lost that bet. Could have swore the RE's would've had a better load rating.

So why are the RE's better? This is the burning question as we have been sold on load rating for RR (according to most test data) and your results lean away from that.

Or is it a case of psi (weight of each corner of car) acting upon the pavement?

Construction materials would be my first guess. Higher silica content, orange peel oil or what have you. Load is not the only factor that determines RR. :)

As a matter of fact, load rating is a minor player compared to the differences in tread compound - which, of course, varies considerably from tire to tire.

I did a search to see the availability of these bridgestone potenza RE92's. I see they are available everywhere, new and used. However I don't see this tire being advertized as a low RR. What's up with that? All they advertize about it is that its popular cuz it came stock with toyota camrys and other vehicles.
Could it be the bridgestone potenza RE92's that I see for sale at all these online tire places is not the same tire as the ones used in the OP's tests?

Just type "bridgestone potenza RE92" into google and u get a whole bunch of vendors advertizing these tires. Not one of them mentions low rr

What's up with that?

You are correct.

The size (165/65 R14) of RE92 made for the first gen. Insight is definitely LRR, and is unlike the other RE92 sizes available.

If you view the listing at Tire Rack for the Insight sized RE92, it identifies that size as Low Rolling Resistance.

But if you view the 185/60 R15 size of that tire (I picked that one at random), it does not list it as LRR.

The only size that is LRR is 165/65R14 that came stock on the 2000 to 2007 Honda Insight and from what I remember people claim a 4 to 7mpg affect from using these tires, in other sizes of tires there are brands that have LRR models as well but most of them span most if not all of their sizes in that model.

Just a note: keep in mind that a 4-7 mpg difference on an Insight won't equal a 4-7 mpg increase on a different car (should you try those tires on something else).

If the Insight's baseline is, say 60 mpg, that 4-7 mpg increase represents about a 7-12% change.

If your baseline is 20 mpg, that 7-12% change represents 1.3 to 2.3 mpg.

Just putting that out there.

Damn you math!!!!!!

Just a question... aren't donuts supposed to be inflated to about 50-70 psi anyway? So if you're using the other tires at their max sidewall rating, which is usually in the 45-50 psi range, wouldn't the equivalent for donuts be around 90 psi (my donut is)...

Except that donuts have a short designed lifespan - on the order of 50 miles - while regular tires are designed for a lifespan up to 100K miles. That means the casing for donuts is designed weaker and additional pressure is much more likely to cause fatigure problems.

Also, the max sidewall pressure on the donuts is 60 psi. I should have posted that.

Awesome work and results. Only problem I see is that you had 13 inch tires and 14 inch tires, leading me to believe you had to use different wheels.

My Civic VX wheels are super light 13", steel wheels are very heavy. For an apples to apples comparison did you use the same 13" wheels for each 13" tire, and the same 14" wheels for the each 14" tire?

Also what were the weights of said wheels?

Don't get me wrong, the work sounds awesome, and i'm super happy I bought insight tires for my VX swapped EK hatch ( I ended up using semi hollow miata wheels that are like 11-12lbs and 14", I couldn't find a set of insight wheels to use). Just curious on the wheels used.

All were conventional steel wheels (all the 13's were in practically identical), except the RE92's which were on light aluminum wheels.

I didn't try to estimate how much of an effect this would have had, if any.

Keep in mind the testing: a couple of feet elevation change, meaning acceleration to & deceleration from a top speed of about a brisk walking pace.

Ah. Ok. Mine are bigger (replacement for 195/50R16), so that may be a factor.

Again, great test. I've been meaning to suggest this to some friends doing official tests on a "fuel-saving" tire from another manufacturer. They measured consumption as the average consumption over dozens of (tightly-controlled) laps over a closed circuit versus a control tire. Was going to participate, but had prior engagements. Was thinking they could also test rolling resistance directly, too.

Steffen, could you please post an image of the Miata wheels that you are talking about there?
And do you happen to know the lug spacing on them?
Thank you.

If these are the famous hollow-spoke Miata wheels, probably these:
http://www.miata.net/garage/mx5wheel...poke_front.jpg
Typically 100x4 lug spacing, full hollow spoke 14" are about 10 lbs, semi-hollow in the 11 lb range, solid spoke in the 12+ lb range.

Julian's Home Page - The secrets of the '94-'97 MX5 OEM Wheels: Hollow Spoke and Solid Spoke - November 13, 2002

ROTA also sells really light cheap wheels. They have a set of 15x6.5 wheels that are 10-12 lbs, called AutoX... but I doubt you can find them secondhand as cheap as Miata wheels.

If your PCD is the same as the Miata's, I've always found this page helpful:
http://www.miata.net/faq/wheel_weights.html

Which ones are these?
http://i94.photobucket.com/albums/l1...1/IMAG0134.jpg

Look like first generation (NA) Miata wheels, to me.

Do you know what these weigh?
I don't have any Miata wheels yet but I am considering them if they will fit a Ford Focus.

About 12 lbs each. Should fit if the PCD is the same, but our Focus is different from yours, so I don't really know.

Well, I had a few issues with this thread from the getgo so I figured I would post my scientific (lol) set of data points for comparison on another totally different vehicle.

In any event my testbed was a Miles ZX40 EV, its top speed determined by the 48v motor and single gear is 30mph summer and 28mph winter (clean road)

I did a test in front of my folks house to see how far the car would coast from 5mph to a stop.

I tested the stock Powermax 769 - 155x65r13 and some randomish Honda 115x70x14 space savers, last year at this same time I was running some antique Goodyear continentals 155x80r13's and will include a bit of antidotal from them. All tires were tested at 60psi. I did want to test some 125/80r13's (because I have always had excellent luck with them) but I had none that fit the miles lug pattern. :(

In any event on flat ground and a huge 30 degrees, wind was nearly calm with a couple MPH here and there with a very thin layer of slime on the road

Powermax 769 155x65r13s coasted a whopping
35' 3" (both runs were only a few inches off, must have been dumb luck) These are the stock tires from miles

Honda 115x70r14 space savers on front only a whopping
39' average (1' variation, 2nd run was further)

I then tested top speed, unlike any other vehicle on the road the Miles ZX40 cannot change gears or increase power output and tire changes are easy to test based on WOT top speed.

Results
Powermax - 28mph (on the normal stretch we run everyday)
Spacesavers up front - 29mph (same place)
Old Goodyears - 29mph (speedo corrected but also at 5-10% higher energy draw due to the size change no doubt)

So given the set of tires I have available I noted no significant difference besides a bit of traction difference and of coarse some major road noise on the spacesavers (rather agressive tread for a bald tire actually).

Also before size is brought up although the space savers "should" be a smaller diameter (1/3") I did note the car sat higher because the tires are more like old balloon tires, car sat a bit higher on the space savers than with the regular tire and side to side comparison off the vehicle same deal, look more like moped style tires. It is also worth noting that the car is about 2400lbs and actually has a tad more weight to the rear.

Ah well. When summer comes along maybe I can do a more convincing test with clean roads and warm temps.

Something worth noting is that the Miles Zx40's alignment is not significantly affected by the space savers, I have noticed some space saver designs when put on my cobalt or commuta caused visible deflection due to the really strange offset on the rim, I would think this would have more affect on how far you coast than the RR because it messed up your alignment. But I digress.

Happy coasting.

Finally got the RE92's on the Firefly/Metro
 

http://ecomodder.com/forum/attachmen...1&d=1436795199

Happy coasting indeed!

After 4 years, I finally got around to sticking the "winning" Bridgestone Potenza RE92's on the Firefly. (Because the car that was wearing them -- the ForkenSwift electric car, top photo this thread -- was retired last year).

Despite the presumably worse aero of the slightly wider tires (165 vs. 155) plus air-blender alloy wheels vs. the car's stock, smooth-ish 13 inch wheel covers, the car got much better mileage on a round trip (back roads) to a cottage:

• 76.8 mpg US (Goodyear Invicta) round trip
• 82.5 mpg US (RE92) round trip

Notable: that was with a 3.2 km/h (2 mph) higher average speed on the RE92 trip. (Similar weather & traffic conditions ... mostly deserted back roads driving, 87 km / 54 miles round trip.)

(Note: the RE92's have a ~1.4% smaller circumference than the Goodyears. I didn't apply this correction to the speed/distance figures here. Even corrected, the MPG % difference is much larger than the measurement error.)

Most of this was driving with load (DWL) on rolling terrain, but I definitely made use of the obviously better coasting ability of the RE92's when approaching most turns & stops (engine off).

Of course, in fairly typical ecomodder fashion, I changed more than one variable: the car also has a brand new air dam on it. So I can't say how much of this improvement is from the tires alone. It seems unlikely it's all from lower rolling resistance. (But I plan on A-B-A'ing the air dam...)

Oh, and PS:

I really like the look of those wheels on the car. But I'll be covering them up with smooth wheel discs soon.

I agree, it looks nice with those wheels.

Nice MPG too!

I got a new set of wheels and I'm thinking, given the cost of unmounting and remounting, and mounting the new ones, I might just as well get a new set. They're 15s.

I checked the Portenzas and they are only available in one or two sizes in 14-, 17- and 20". The front tire I'm rolling now is 165/50R15 Federal Formosa FD-1, with the stock 165(70?)R15s on the back. I'd like to find a LLR 15" tire with that 50(or55)/70(or 80) split in aspect ratio to preserve the drive axle gearing. Any suggestion?

I was hoping my next set of tires would be i3 Ecopia 600s, but that takes a 4x19" wheel.

The potenzas are lrr in the 165/65-14 size only