Wheels, Rims, and Tires

[Don]

If the i-MiEV can't correct the oversteer quickly the back end continues to slide out and the the i-MiEV loses its speed as you can see at 1:07 in the i-MiEV race video

He's losing his speed only because he tried to take the corner too fast and he finally lifted off the throttle, rather than run off the course. The iMiEV is understeering horribly all the way through the corner at 1:07 - He's going way too fast to hold the line and when he's nearly run out of racetrack at corner exit, he gets off the throttle and then suffers trailing throttle oversteer - No sign of oversteer in the corner . . . . he's understeering all the way through, can't hold the line and drifting wide. Classic understeer

At 2:02 in the video the i-MiEV's front wheels are straight and are not skidding. The back wheels skid and the car is oversteering. He's not understeering, he's just going way too fast to make that turn.

Robert, I love you too man, but the definition of understeering is . . . . "going way too fast to make that turn" - There is NO sign of oversteer in your video until he has exited the corners and then lifted to keep from running off the track. Trailing throttle oversteer trying to correct for his understeer through the corners. He does it several times

If you want a good lesson in an understeering car which suffers from trailing throttle oversteer when you let off and try to correct, read up on the rear engine Porsches . . . . they behave much as the iMiEV does in your video, but at much higher speeds. When you lose the front end of a 911 in a corner, things are about to get very exciting!

http://www.examiner.com/article/race-car-driving-techniques-101-handling-understeer-oversteer-and-other-racing-jargon

From the above link: "What to do when experiencing understeer depends on what sort of car you are driving. If you happen to be in a front engined, front wheel drive car then you will want to lift off of the throttle (accelerator) and continue turning which should get the back end to slide around and help you turn a bit more.
This technique works the same in a rear engined, rear wheel drive car as well. This is why you hear stories of Porsche 911 drivers going for a spin if they enter a turn to fast. They of course lift off of the throttle and in turn ignite the sort of pendulum / hammer effect that takes them for a spin."

Pendulum and hammer. At 1:07, the iMiEV is behaving much like a rear engine Porsche - Understeering and then oversteering badly when the driver lifts off the throttle to try to correct. He almost spins it off the other side of the course

I know, I know - You'll say no 911 could possibly understeer because they are rear engine, RWD and tail heavy (just like the iMiEV) but understeering is what they all suffer from . . . . until you lift the throttle mid-way through a turn trying to correct the understeer. Video proof of the iMiEV doing the exact same thing at 1:07 in the video

Again - Look at Joe's front tire. If his car wasn't understeering badly, his steering axle tires would have lasted longer than the drive axle tires . . . . but they didn't

Don

 

[Ozimiev]

Guys... I hope you realise...
Granturismo 5 'the real driving simulator' is a CG game.
Best not get sucked in.

 

[blownb310]

Guys... I hope you realise...
Granturismo 5 'the real driving simulator' is a CG game.
Best not get sucked in.

Bingo.

 

[alohart]

Granturismo 5 'the real driving simulator' is a CG game.
Best not get sucked in.

That giant sucking sound I hear is me being sucked in Pretty impressive CG! I wondered how it was possible to corner an i-MiEV on 2 wheels without the outer tires appearing to skid at all, especially considering its very low center of gravity. The answer is that it's probably only possible in a computer game.

 

[PV1]

The CoG of the i-MiEV in GT5 is rather high, but it's like that in all the cars on there. I've rolled the Tesla Roadster just driving up onto a bank.

That game is actually how I discovered the i-MiEV. Now I own one. :mrgreen:

 

[RobertC]

The iMiEV's ASC would make it pretty near impossible to oversteer the car, even if it had enough horsepower to make it want to, but you could compare Joe's front tires and his rear tires and quickly come to the conclusion that the ASC can't begin to do anything about it's understeer . . . . otherwise his drive axle tires would have worn out before his steering axle tires, because that's what oversteering RWD cars do - They wear out rear tires.

I don't see any information or pictures of Joe's rear tires, only his front tires.
Are Joe's rear tires worn out also?
Inflating your tires at the recommended psi will not cause the premature wear exhibited by Joe's front tires that were inflated at 60 psi. Inflating the tires at 60psi reduces the surface area of the tire that makes contact with the pavement.
My i-MiEV has over 24,000 miles and both front and rear tires are worn evenly, with just slightly more wear on the inside of the front tires and the outside of the rear passenger tire. I measured 4/32" tread remaining with a tread gauge.
The i-MiEV's tires are:
Front: 145/65R15 - Width 5.71 inches - 899 revolutions per mile
Rear: 175/60R15 - Width 6.89 inches - 866 revolutions per mile
The i-MiEV's weight distribution is F/R 45/55, which is the same as the F/R tire width. (5.71"/6.89" is 45%/55%)
All things being equal, the front tires on the i-MiEV should wear more than the rear because of more revolutions per mile and the additional stress that braking puts on the front tires.

The Yokohama AVID ENVigor tires available at tires-easy.com have a tread-wear rating of 560 (compared to the 340 rating on the Dunlop tires that came with the car) look like a good replacement. These tires have ultra-low rolling resistance and 60,000 mile warranty.
http://www.tires-easy.com/cgi-bin/rshop.pl?dsco=135&cart_id=81377003.135.8916&Breite=175&Quer=60&Felge=15&Speed=&LoadRange=&kategorie=6&Marke=&ranzahl=4&rsmFahrzeugart=PKW&search_tool=standard&details=Ordern&typ=R-232639
Front tires are $89.20 and rear tires are $97.60. Shipping to New Jersey is $60.42 with a total cost for four tires of $434.02

 

[RobertC]

Guys... I hope you realise...
Granturismo 5 'the real driving simulator' is a CG game.
Best not get sucked in.

I was totally fooled.
I have a Nintendo Wii U, however I was not aware that PlayStation video games could be so realistic.
I remember playing Pong at the local mall arcade when I was a child. I also remember playing Space Invaders on my home Atari with friends for hours when I was a teenager. I would have never imagined a that I would not be able to tell a video game from reality.

 

[JoeS]

The Yokohama AVID ENVigor tires available at tires-easy.com have a tread-wear rating of 560 (compared to the 340 rating on the Dunlop tires that came with the car) look like a good replacement. These tires have ultra-low rolling resistance and 60,000 mile warranty.
http://www.tires-easy.com/cgi-bin/rshop.pl?dsco=135&cart_id=81377003.135.8916&Breite=175&Quer=60&Felge=15&Speed=&LoadRange=&kategorie=6&Marke=&ranzahl=4&rsmFahrzeugart=PKW&search_tool=standard&details=Ordern&typ=R-232639
Front tires are $89.20 and rear tires are $97.60. Shipping to New Jersey is $60.42 with a total cost for four tires of $434.02

RobertC, thank you for identifying these Yokohama tires as I have not yet bought my replacements. I took photos of each of my four tires and will post them. In the meantime, is there anywhere on the Web where rolling-resistance comparisons were made that include our Enasave tires as well?

 

[JoeS]

Here are photos (taken on 30 December 2013) of the four tires which had been run at 60psi for 22,000 miles before I rotated them:

 

[jray3]

Thx Joe- wow, those treads are toast, but your rolling resistance will never be lower!
I also see some feathering on the outside edge of your front tires. Might wanna check the alignment when mounting the new ones. I rotated at 10k, was starting to see some feathering too, but nowhere near as bad as at 5k on the misaligned front end of my pigeon-toed first iMiEV.

 

[JoeS]

I just ordered a set of Yokohama AVID ENVigor, as they're the only available alternative to our Dunlop Enasave. I was told that Continental makes a front tire - it was used on some Smart cars, but not the rear. Will give an update once they're on the car. I had gone to my local independent tire guy (who is used to me coming in with weird requests) and asked him to find the LOWEST rolling resistance tires, at the sacrifice of everything else... after 1/2-hour of pawing through his computer, the Yokos and Dunlops were all he could find at all as a set.

 

[JoeS]

Note the very even treadwear pattern despite running these tires at 60psi

I think if you showed that tire to anyone with any expertise in tires, they would immediately tell you it has been run severely overinflated. All of the tread in the center is gone, while both outer edges still have tread - Pretty much the exact opposite of what you see on most worn out tires. The outer edges are designed to 'bite' in to prevent the tire from sliding sideways, so they are usually the first to go when the tire is run at the recommended pressure...

Au contraire, if you look at the depth of the three grooves you will see that they are uniform, with the outer tread simply showing where it goes around the corner. Just for fun, as the car was up on the rack and the wheels were about to be taken off, I asked the group of four 'professionals' (including the service manager) who were curiously admiring Mitsi whether they thought the rear tire wear reflected a correct pressure (neglecting to tell them I ran the 23,011 miles at 60 psi). The consensus was that indeed the treadwear was uniform and that pressure had been ok, although one of the four thought a very slight overinflation might have been present. Maybe they were wanting to make me feel good?

I had the Yokohama AVID ENVigors put on Mitsi this morning. $439 including installation/balancing with the 8.75% California sales tax on top of that. Each of the four tires is different: there is a LEFT and RIGHT tire, in addition to our differently-sized FRONT and REAR. Maybe that accounts for what I consider to be a fairly high cost for such small tires? That's evidently nothing compared to the Tesla which they said wear out really fast (especially their 21-inch tires) and cost a bit more than ours...

The five-mile drive home with the new tires set to 36psi on my curvy road left me thinking that the tire noise was perhaps a little higher than the worn-out Dunlop Enasaves and there seemed to be a thrumming sound emanating from the tires on the smoother straight stretches. The cornering response seemed about the same as on my worn-out tires, but I wasn't pushing at all. The service person had said it would take a couple of hundred miles for some protective coating to wear off.

I'm hoping that these new tires will now bring us some rain, as we're approaching drought conditions having had negligible rain around here in the last nine months. I'm also hoping to get more than 23,011 miles on these Yokohamas (although reviews on tire websites are not that encouraging). Just hope the rolling resistance is not higher than the Enasaves'.

Time will tell and I'll give an update of my subsequent impressions.

Photo of my new right front tire:

 

[Don]

I had the Yokohama AVID ENVigors put on Mitsi this morning. Each of the four tires is different: there is a LEFT and RIGHT tire, in addition to our differently-sized FRONT and REAR. Maybe that accounts for what I consider to be a fairly high cost for such small tires?

They should be noisier than your old Ensaves, Joe - Nothing is quieter than a bald tire . . . . no tread left to make any noise :lol:

The Envigors are a symmetric/directional tire, so there is no left or right tire, at least not until you mount them on the rims. The fronts are an identical pair and same for the rears, but they *are* directional tires, so once you mount them, you can no longer swap them side to side (without removing them from the rims and remounting them) because both would then be turning in the opposite direction they were designed to turn. Most all performance tires are manufactured this way, so that the tread can be designed to remove as much water from under the tire as possible and they do this by designing it to turn only one direction

"The AVID ENVigor radial's all-season silica tread compound is molded into an optimized contact patch featuring a five-rib directional pattern that blends performance with all-season traction"

If you check your car, the DOT code embedded in the tire will be on the outside of the tire on one side of the car, but it's on the inside of the tire on the other side of the car - Identical tires on both sides, but mounted so both are turning the correct direction

There *are* asymmetrical/directional tires which can only be mounted on one side of a car, so all 4 tires are different, but those don't have the symmetrical tread pattern, like your Envigors. With those, the tread to the left of center is different from the tread to the right. As you can see from your photo, the Envigors have tread which is symmetrical, left to right, so they can be mounted on either side of the car, so long as they are mounted properly so that they turn the correct direction

Here's an explanation of the 4 different tread patterns

Symmetric Tread Patterns A symmetric tread pattern is the most common and features continuous ribs or independent tread blocks across the entire tread face where both inboard and outboard halves feature the same pattern. Tires featuring symmetric tread patterns allow using multiple tire rotation patterns

Asymmetric Tread Patterns An asymmetric pattern is designed to blend the requirements of dry grip and water dispersal/snow traction where the tread pattern changes across the face of the tire. An asymmetric tread pattern usually incorporates larger tread ribs/blocks on the outboard side to increase cornering stability on dry roads by offering greater contact area. This also helps to reduce tread squirm and heat buildup on the outside shoulder. The inboard side usually features smaller independent tread blocks to aid wet and/or winter traction when driving straight ahead. Tires featuring asymmetric tread patterns allow using multiple tire rotation patterns.

Directional (Unidirectional) Tread Patterns A directional (also called a unidirectional) tread pattern is designed to roll in only one direction. It incorporates lateral grooves on both sides of the tire’s centerline that point in the same direction and result in v-shaped tread blocks. These grooves enhance hydroplaning resistance at high speeds by pumping water more efficiently through the tread pattern. Unless they are dismounted and remounted on their wheels to accommodate use on the other side of the vehicle, directional tires are to be used on one side of the vehicle and are intended to be rotated from the front axle to the rear axle. If different tire sizes are used on the front vs. rear axle, the tires become location-specific and prohibit tire rotation unless remounted

Asymmetric and Directional Tread Patterns Asymmetric and directional tread patterns have v-shaped tread grooves that are offset compared to the centerline of the tire. Tires featuring asymmetric and directional tread patterns must be treated as directional tires for tire rotation. However, if different tire sizes are used on the front vs. rear axle, they become location-specific and prohibit any tire rotation possibilities.

Don

 

[JoeS]

The Envigors are a symmetric/directional tire, so there is no left or right tire, at least not until you mount them on the rims.

Don, I stand corrected. You are right, these Yokohamas become LEFT or RIGHT after they're mounted. I found a ROTATION arrow on the side of the tire and had misunderstood what the tire person said when he pointed to it. This also means that in the future we don't swap the mounted tire LEFT to RIGHT in an attempt to even-up the tirewear. BTW, thanks for the tread pattern elaboration.

 

[Don]

You can rotate them, left to right, when they are about half worn, to gain increased life . . . . but you must have them removed from the rims and remounted

Don

 

[JoeS]

OK, ran for a couple of days with the Yokohama AVID ENVigors at 36psi. Noise level was low, roadholding was very good, and road irregularity shock absorption was excellent compared to my previous Dunlops at 60psi. I'm afraid I did miss the handling crispness and just now boosted the pressure to 50psi - really should go up to 60psi for a fair comparison, so the jury is still out on this one. Need to take a long highway trip to determine any effect on range, as running around town is inconclusive. So far, I'm happy with the Yokohamas.

 

[sandange]

I'm all ears Joe - will be shopping for tires this spring.
Thanks for the report

 

[Don]

I'm afraid I did miss the handling crispness and just now boosted the pressure to 50psi - really should go up to 60psi for a fair comparison, so the jury is still out on this one. Need to take a long highway trip to determine any effect on range, as running around town is inconclusive. So far, I'm happy with the Yokohamas.

I predict you'll like the Yoko Avids - I use them on both my Miata and my Protégé 5

I'm afraid I'll never understand your perceived benefit in severely overinflating them though

http://www.hybridcars.com/forums/showthread.php?101213-Dangers-of-Over-Inflating-Tires

Don

 

[JoeS]

Don, thanks for that link; strange blog site though...

I freely admit that the perception of improved handling and lower rolling resistance due to high tire pressures is completely subjective on my part, and in no way am I recommending this for others. I guess that my bias comes from half-a-lifetime of tossing cars around my winding roads home.

 

[Don]

If you Google 'NHTSA Tire Rolling Resistance' you'll see a huge PDF showing the results of Phase 2 of their testing and it will give you way more data on the subject than you ever wanted to know :shock:

I didn't read every page, but did learn a few things I didn't know before. Check out the 'Tire Magic Triangle' where Rolling Resistance, Traction and Treadwear are shown on the corners of a triangle. For a given tire, without changing it's chemistry or internal composition, improving any one of the three harms the other two. If you lower the rolling resistance by overinflating the tire, you get both less traction and less treadwear. Tire design engineers are spending millions trying to 'stretch the magic triangle' so they can improve any one of the three while doing less harm to the other two. LRR tires employ thinner sidewalls and less thread depth trying to maintain good traction while lowering rolling resistance - I guess that automatically means a shorter lifespan

One of the really interesting conclusions of their testing (found near the end) was that lowering the rolling resistance of the tires on a vehicle by 10% gave an improvement in fuel economy of only 1.1%. You can't get anywhere near a 10% decrease in rolling resistance by inflating a tire over the recommended pressure so the mileage gains (range in our case) will be truly insignificant, especially when you consider you're giving up both traction and tire life to get a few tenths of one percent improvement in range

One other thing I learned which is completely contrary to what I thought I knew is that for a given vehicle weight and tire pressure, wider tires have a lower rolling resistance than narrower tires do - This is due to the fact that since the cars weigh the same and are both supported by tires of equal pressure, the tire contact patch will be the same square area for both the wider and narrower tires. Therefore the wider tire will have a shorter longitudinal flat spot than the narrower tire, so the wider tire flexes less than the narrower tire when you roll it and less flexing means a lower rolling resistance

Don