Effect of Yokohama S. Drive tires on range

Summary: Compared to stock, S. Drive tires probably reduce range by no more than 11% when driving on LA freeways.

A few weeks ago, I installed new Yokohama S. Drive high performance summer tires on my new Spark EV, replacing the barely driven stock tires. I wanted to know how the S. Drive tires would affect range, so did an experiment. Before installing the tires I did a round trip drive during the day on the freeway, measuring energy usage before and after each leg. After installing the new S. Drive tires, I repeated the drive at night (less traffic), and during the day (more traffic).

Details:
The start, destination, and end points were all less than one third of a mile to the freeway ramps. The free-way has no large hills. The efficiency listed is the “Driving and Accessories” efficiency (i.e. energy used for AC is subtracted before calculating mi/kWh).

Start -> Midpoint: 21 miles
Midpoint -> End: 21 miles

Stock tires day trip:
Start to Midpoint efficiency: 5.1 mi / kWh
Start to Midpoint average speed: 45 mph
Traffic: Moderate. No large slowdowns. Speeds around 40-50 mph due to traffic density.

Midpoint to End efficiency: 5.6 mi / kWh
Midpoint to End average speed: 40 mph
Traffic: Heavy to moderate. One slowdown to speeds of 15-30 mph.


S. Drive day trip:
Start to Midpoint efficiency: 6.5 mi / kWh
Start to Midpoint average speed: 37 mph
Traffic: Heavy to moderate. Multiple slowdowns to 20 mph or less. Max speed was about 55 mph.

Midpoint to End efficiency: 5.5 mi / kWh
Midpoint to End average speed: 37 mph
Traffic: Heavy to moderate. Multiple slowdowns to 20 mph or less. A few sections of 55-65 mph.


S. Drive night trip:
Start to Midpoint efficiency: 4.8 mi / kWh
Start to Midpoint average speed: 55 mph
Traffic: Light. No slowdowns. Kept speed at 65 mph or less.

Midpoint to End efficiency: 4.7 mi / kWh
Midpoint to End average speed: 49 mph
Traffic: Light. Was behind bus going 40 mph for part of the journey.

Sources of error:
The energy usage was taken from the “energy details” screen. These numbers are only reported in 1% increments which adds quantization error. Also, except for the S. Drive day trip, the average speed is probably not very accurate.

Probably the biggest uncontrolled variable is the traffic. The two legs of the S. Drive day trip for example had the same average speed (37 mph), but their energy usage differed by 1 mi / kWh. The less efficient leg had more fast and slow sections, while the more efficient trip was slow throughout.

Analysis:
Since going slower should be more efficient, the unexpected 0.1 mi / kWh between the S. Drive night trips is probably due to “Climate Setting” quantization error. Also, I think that the S. Drive day trip Midpoint to End efficiency should be closer to 5.7 mi / kWh for the same reason.

Comparing the S. Drive night trip Midpoint to End efficiency of 4.7 mi / kWh to the Stock tires day trip Start to Midpoint efficiency: 5.1 mi / kWh:
4.7 / 5.1 = 0.92 = 8% loss
Considering quantization error, the Stock tires day trip Start to Midpoint efficiency might have been as high as 5.3 mi / kWh:
4.7 / 5.3 = 0.89 = 11% loss
Since the night trip was significantly faster (and the headlights were on), this is only an upper bound on the range loss.

Conclusion:
Doing a range test is tricky. Since the stock tires trip had traffic, I will probably never be able to accurately replicate it. Because of quantization error, the mi / kWh numbers are probably accurate to no more than +/- 0.2 mi / kWh. The range loss from S. Drive tires is probably less than 10%, so since I have the fast charger and live in an area with plentiful chargers, range is not an issue.

If I were to do this experiment over again, I would do the stock tire test at a time when there is little traffic, so I could use cruise control for the entire trip. I would also do the trip with the stock tires at least twice to see if I could get consistent results.

another factor: tires have more rolling resistance when they are new.

Other fun measurements could have been:
0-60 times.
60-0 distance.
Lateral G's.

All this would require accurate measuring equipment like the car magazines use.
Although, , there are phone apps that use a OBD-II to Bluetooth adapter that would give somewhat accurate measurements.
And securely mounting the phone vertically the app could measure lateral G's.
I use 'Torque Pro', but I don't use all these features.

Also you don't mention tire pressures.
Hopefully you'll explore the Yoko's at higher than the car's spec of 38 psi.

Car and Driver did a skidpad test on a Leaf, and the S. Drive tires increased lateral acceleration from 0.79 g to 0.84 g.
https://www.youtube.com/watch?v=tOIAk8TA6b4

For my test, the tire pressure as measured by the sensors was around 41 psi for the stock tires, and between 38 and 41 psi for the S. Drive tires. The tire installers said they inflated to 35 psi, so I don't know how accurate these numbers are.

greenspark said:

... The tire installers said they inflated to 35 psi, so I don't know how accurate these numbers are.

Click to expand...

Why did they under inflate them? The door sticker is right there.

You know these tires are probably rated to 51 psi.
What have you got to lose trying the high end of the range?
You might like it !!
And then run your test again !

NORTON said:

greenspark said:

... The tire installers said they inflated to 35 psi, so I don't know how accurate these numbers are.

Click to expand...

Why did they under inflate them? The door sticker is right there.

You know these tires are probably rated to 51 psi.
What have you got to lose trying the high end of the range?
You might like it !!
And then run your test again !

Click to expand...

My door sticker says 35 psi.

What will you lose by over inflating tires? Traction and the center tread will wear faster

Zoomit said:

...
My door sticker says 35 psi.

What will you lose by over inflating tires? Traction and the center tread will wear faster

Click to expand...

Oops, just saw 35 on my app. I was thinking Volt....

You won't lose traction if the tires are much stickier than the stock rubber and responsiveness goes way up with stiffer sidewalls.

Steel belted radials do not 'wear the center' more when run near their max rated pressure.
That's old bias-ply tire thinking. Look it up. Radials just shorten their contact patch front to rear with higher pressures.

NORTON said:

Steel belted radials do not 'wear the center' more when run near their max rated pressure. That's old bias-ply tire thinking. Look it up. Radials just shorten their contact patch front to rear with higher pressures.

Click to expand...

My experience with modern tires does not reflect that perspective.

It appears others also feel same:
http://www.bridgestonetire.com/tread-and-trend/drivers-ed/tire-tread-wear-causes
http://www.tirereview.com/reading-tire-wear-patterns/
http://www.procarcare.com/includes/content/resourcecenter/encyclopedia/ch25/25readtirewear.html
https://www.pepboys.com/tires/treadsmart/typical_treadwear_patterns/
https://blog.allstate.com/tire-wear-patterns-what-do-they-mean/

OK,, that's a lot of good sources. I have NEVER experienced that and I always run my tires on the high side of the spectrum.
Maybe because I flog the car in corners I wear the edges faster creating the appearance of normal wear !?!
Car manufacturers always factor 'Comfort' into what they say is the magic number.
Can anyone really feel ± 5 psi? Normal temp rise is that much in some climates.

A lot of people I know agree with this. One guy is my pal, the +2 million mile bank courier guy. He goes thru tires like most people change oil.
The Spark EV racing guy on this forum also agrees.

Anyway, here's another aspect of running on the high side:
(from a google search, this is from a Prius forum.The links didn't copy....)

The only good experiments that I have seen were based on rolling distance in a coast down test. The higher the pressure the further the tire rolled before it came to a stop. The further a tire will roll with the same energy input the better mpg will be in most circumstances. Some road surface types could alter this.

Mythbusters gave these results from their test:

Control, 35psi (manufacturer recomendation)
tires at 10psi = 3.7% increase in consumption
tires at 30psi = 1.2% increase in consumption
tires at 40psi = 6.2% decrease in consumption
tires at 60psi = 7.6% decrease in consumption

MythBusters: Tire Pressure Test : Video : Discovery Channel

Here is the test done at Ecomodder.com
Experiment: coast down distances (rolling resistance) @ various tire pressures - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

PSI/Distance in feet

20 / 479.3
25 / 524.8
30 / 621.0
35 / 621.0
40 / 639.6
45 / 687.5
50 / 702.0
55 / 699.3
60 / 702.0

NORTON said:

Can anyone really feel ± 5 psi? Normal temp rise is that much in some climates.

Click to expand...

I can feel 2 psi over/under on my cars. On my bike, I can feel 1 psi, being under on a bike has big consequences for handling. And over or under on the bike will have a big impact on wear.



But I digress... :lol:

You can feel a 2 psi difference?! I they change more than that in the first 15 minutes of a drive and the rubber is stickier due to temperature.
You may feel these small differences.
Only a blind taste test would prove this claim!

NORTON said:

You can feel a 2 psi difference?! I they change more than that in the first 15 minutes of a drive and the rubber is stickier due to temperature.
You may feel these small differences.
Only a blind taste test would prove this claim!

Click to expand...

yep, I can tell when they're down 2 psi. So can my wife.

NORTON said:

And you both can taste the difference between a $13 bottle of wine and a $55 bottle too, I'm sure....

Let the blind taste testing begin testing begin !!!!

It will require an air compressor, a good tire gauge and a neighbor with too much time on his hands.
You and the wifie retire to the back yard while he prepares the car for at least 3-5 test runs, with a sticky note taped over that display, right?

I call BS

You know there is a huge traction difference between 38 psi tires at 30° and at 100° , right? Can you also tell the temp of the rubber compound?

Click to expand...

hey, know what? f off.

K


edit: Sorry. I get carried away sometimes. I watch too much 'Myth Busters' and 'Penn and Teller's BS' and fancy myself a man of science.
If you feel it, you feel it. That's all that matters.
Love the Fog Light mod !! I'm going to copy it !

Sorry to do some thread necromancy - but I'd like to know your experience with the S.drive tires specifically with the insane nanny that the T/C and Stability control is on these cars. Do the s.drives actually reduce your wheel spin to any noticeable degree? Currently I have brand new Kumho Ecsta 4x IIs on and the grip just isn't enough to stop that damn nanny from cutting power.


Norton, as for the tests of decreased consumption at ridiculously high tire pressures...of course, you are reducing the contact patch.

SciroccoTDI said:

Sorry to do some thread necromancy - but I'd like to know your experience with the S.drive tires specifically with the insane nanny that the T/C and Stability control is on these cars. Do the s.drives actually reduce your wheel spin to any noticeable degree? Currently I have brand new Kumho Ecsta 4x IIs on and the grip just isn't enough to stop that damn nanny from cutting power.

Click to expand...

The S. Drives definitely increased traction compared to the stock tires. On flat ground the wheels might slip a little when flooring it depending on the road. On a flat road I don't recall the T/C ever limiting power. By "limiting power", I mean that the power from the motor is significantly reduced for several seconds, not that the T/C light flashes.

With the the S. Drives, the wheels will still slip when accelerating and turning uphill. This is what I wrote about it in my 5 month review:

Near where I live there is a right turn onto a road going up a hill. This right turn is a worst case scenario for front wheel drive cars since the intersection is tilted, and the corner is concrete while the rest of the road is asphalt. This means that unless you turn very slowly, the front wheels always slip. After turning, you need power to accelerate up the hill. The problem with the Spark EV's traction control is that it limits power after the wheels slip. So I approach the intersection, stop, wait for a gap in cars, and turn right. The wheels slip while going around the turn. I then step on the accelerator to get up the hill and get up to speed but I can't since the traction control has limited the power.
[...]
I have resorted to turning off traction control while making this turn.

Click to expand...

I don't know how the traction of the Kumho's compares to the S. Drives, but it would be concerning if you get significant power limiting when flooring it on a straight and flat road in good conditions.

greenspark said:

SciroccoTDI said:

Sorry to do some thread necromancy - but I'd like to know your experience with the S.drive tires specifically with the insane nanny that the T/C and Stability control is on these cars. Do the s.drives actually reduce your wheel spin to any noticeable degree? Currently I have brand new Kumho Ecsta 4x IIs on and the grip just isn't enough to stop that damn nanny from cutting power.

Click to expand...

The S. Drives definitely increased traction compared to the stock tires. On flat ground the wheels might slip a little when flooring it depending on the road. On a flat road I don't recall the T/C ever limiting power. By "limiting power", I mean that the power from the motor is significantly reduced for several seconds, not that the T/C light flashes.

With the the S. Drives, the wheels will still slip when accelerating and turning uphill. This is what I wrote about it in my 5 month review:

Near where I live there is a right turn onto a road going up a hill. This right turn is a worst case scenario for front wheel drive cars since the intersection is tilted, and the corner is concrete while the rest of the road is asphalt. This means that unless you turn very slowly, the front wheels always slip. After turning, you need power to accelerate up the hill. The problem with the Spark EV's traction control is that it limits power after the wheels slip. So I approach the intersection, stop, wait for a gap in cars, and turn right. The wheels slip while going around the turn. I then step on the accelerator to get up the hill and get up to speed but I can't since the traction control has limited the power.
[...]
I have resorted to turning off traction control while making this turn.

Click to expand...

I don't know how the traction of the Kumho's compares to the S. Drives, but it would be concerning if you get significant power limiting when flooring it on a straight and flat road in good conditions.

Click to expand...

Thanks for the response greenspark - sorry I missed your thread. Indeed, the Kumhos slip like something crazy in a straight line, they have decent cornering grip, however disabling T/C and Stabilitrac does nothing, it comes RIGHT back on when wheel hop is detected.

I've started a new thread asking about the Dunlop Direzza ZII Star Spec extreme performance tires...hoping someone has experience.

http://www.tirerack.com/tires/tires.jsp?tireMake=Dunlop&tireModel=Direzza+ZII+Star+Spec&partnum=955VR5Z2SS&vehicleSearch=false&fromCompare1=yes

-Eric

I've got Dunlop Direzza DZ102 for summer tires.

What you probably need to realize is that if you put performance tires on the Spark EV, it is because you want to use them harder than stock, and the way you drive will cut your range by much more than the choice of tire.

That said, this summer I never saw more than 72 on the GoM after I swapped out the tires for the Dunlops. Maybe 76 on OEM tires, so 5-10% is a good guess for loss of range.

(BTW, I also view a 2lb. difference in tire pressure as obvious)

EldRitch said:

I've got Dunlop Direzza DZ102 for summer tires.

What you probably need to realize is that if you put performance tires on the Spark EV, it is because you want to use them harder than stock, and the way you drive will cut your range by much more than the choice of tire.

That said, this summer I never saw more than 72 on the GoM after I swapped out the tires for the Dunlops. Maybe 76 on OEM tires, so 5-10% is a good guess for loss of range.

(BTW, I also view a 2lb. difference in tire pressure as obvious)

Click to expand...

Indeed, I have a very short commute (20 miles round trip) so even driving hard (which honestly seems what this little hot hatch likes) I'm not worried about range decrease - I'm going for grip.

On my autos, I can sense a 2 psi over/under. I can feel 1 psi on my bike, and riding a bike with less pressure has serious handling implications. Additionally, riding the bike over or under will significantly affect wear.