Wheels, Rims, and Tires

[RobertC]

It appears the 3329 max weight rating is limited by the tires, specifically the tiny front tires. The car has an actual weight distribution of 45/55, F/R which means 45% of that 3329 pounds (1498 lbs) is resting on the tiny front tires, which are rated for a max weight load of 783 lbs each, or 1566 pounds - No reserve margin of safety left there at all :shock:

I'm not familiar with any other vehicle which cuts so closely to the absolute maximum ratings of it's rubber. More than ever, this convinces me that the suspension and tires were not really designed for this car, but for the 1960 pound I kei car they originally came on - This *really* makes me wonder how the Feds allowed this car to be sold in the USA!

The actual weight on the front tires is 1488 lbs (from the sticker in the door).

A little research found the following:
Mitsubishi i-MiEV: GVWR 3329 lbs; F/R 45/55; GAWR FR 1488 lbs; Front tire max weight 1566 lbs; Percent of max 95.0%
Chevy Volt: GVWR 4539 lbs; F/R 61.4/38.6; GAWR FR 2787; Front tire max weight 2,866; Percent of max 97.2%
Nissan Leaf: GVWR 4322 lbs; F/R 56.6/43.4; GAWR FR 2,446 lbs; Front tire max weight 2,558; Percent of max 95.6%
I'm not sure what purpose it serves for you to make unsubstantiated statements that the vehicle is unsafe and should not be sold in the US.
The i-MiEV received a 4 star NHTSA safety rating, the same as a Cadillac Escalade.

As an engineer I find the i-MiEV to be an engineering marvel. One of the things I love about it is how maneuverable the i-MiEV is in traffic because it is so much lighter than the other electric vehicles on the road and has torque on demand. I drove the Ford Focus Electric that weighs 3,624 lbs empty, and found it awkward to try to alter the course of all that momentum. I've put 14,000 miles on my i-MiEV in 11 months and have not experienced one episode of understeer, and I drive like an idiot. Also, the i-MiEV comes equipped with electronic stability control as a safety feature to prevent skidding.
The i-MiEV is not a sports car. It's a small four passenger commuter. It sits high. You are affected by sharp turns. I've driven the i-MiEV on the highway at the top speed of 81 mph and it performed well. When I was a teenager I had a 1970 Chevy Camaro with a 350 V8 and a 4-speed stick. You pretty much sat on the floor. Now that was a sports car.

Finally, the Japanese Mitsubishi i gas-powered kei car has a different rear tire 175/55R15 and has a higher center of mass than the i-MiEV with its 440 pound battery mounted under the floor. Both vehicles are rated for a top speed of 81 mph. Also, Edmunds tested the Mitsubishi i kei car in 2010 and it had a curb weight of 2,147 lbs, not 1,960 lbs.

 

[alohart]

Mitsubishi i-MiEV: GVWR 3329 lbs; F/R 45/55; GAWR FR 1488 lbs; Front tire max weight 1566 lbs; Percent of max 95.0%
Chevy Volt: GVWR 4539 lbs; F/R 61.4/38.6; GAWR FR 2787; Front tire max weight 2,866; Percent of max 97.2%
Nissan Leaf: GVWR 4322 lbs; F/R 56.6/43.4; GAWR FR 2,446 lbs; Front tire max weight 2,558; Percent of max 95.6%

The assumption that the F/R weight bias remains unchanged when a vehicle is loaded to its gross vehicle weight is not sound. In most vehicles, the additional load would shift the weight bias toward the rear where the cargo and rear seat passengers would be. As a result, the front tires would not bear as large a percentage of the gross vehicle weight as the above calculations suggest which would make their margin of safety greater than the above calculations imply.

Mitsubishi probably did what most auto manufacturers do which is to prefer understeer over oversteer. Oversteer may be more difficult to control with electronic stability control than understeer. So we are kind of stuck with a car that doesn't handle as well as it could but is probably safer in the hands of the average driver.

 

[DogMan12]

Hey, Don. Have you settled on and installed a set of wheels / tires? Do tell, and give us a pic, please!

Roll On - DM

 

[Don]

I bought brand new set of 4 OEM Mini Cooper 15 X 5.5 wheels. I like the look of them, but they're really heavy compared to the alloy iMiEV wheels

Long story short - You cannot put a 5.5 inch wide wheel on the front of our car, unless you space them out so far that you've increased the front track width well beyond that of the rears. The only real solution would be to have the front wheels narrowed to 5 inches . . . . at a further cost of about $200 per wheel. I've abandoned that idea

Not sure where I'm going next . . . . but I'm not going to buy any more wheels until I know for sure that they'll fit

Don

 

[alohart]

So summarizing, is it correct that the stock 15x5 i-MiEV rear wheel is the widest wheel with an acceptable offset that would fit on the front? I realize that some minor tinkering is required to fit these wheels on the front. If you also used the wider OEM rear tires on the front, that would certainly decrease the understeer at the expense of a tad more drag, but at least the same low rolling resistance tires could be used, and the tires could be rotated to help even out the wear. This seems to offer a lot of advantages.

 

[Don]

So summarizing, is it correct that the stock 15x5 i-MiEV rear wheel is the widest wheel with an acceptable offset that would fit on the front? I realize that some minor tinkering is required to fit these wheels on the front.

To be truthful, I'm not certain that's a valid statement

While both front and rear wheels have a 35mm offset, a rear wheel put on the front will still stick out half an inch more than the small front wheel does (and the tire even more than that) because it gains half an inch of width on both the inner and outer lip. It *might* work, but I think it would be better if a 5 inch wheel on the front had an offset of 45mm or so. Th BMW Mini wheels I bought have a 45mm offset and they would fit just fine . . . . *if* they were 5 inches wide

Don

 

[jray3]

Anybody done some rim swapping lately? Here's another possible rim supplier. I like the look of their SpeedStar MK-1, but our exact desired size isn't listed. Looks like they offer lots of customization though...
http://www.rd-tanabe.com/lineup/speedstar/mk1/smk1s.pdf

So summarizing, is it correct that the stock 15x5 i-MiEV rear wheel is the widest wheel with an acceptable offset that would fit on the front? I realize that some minor tinkering is required to fit these wheels on the front.

To be truthful, I'm not certain that's a valid statement

While both front and rear wheels have a 35mm offset, a rear wheel put on the front will still stick out half an inch more than the small front wheel does (and the tire even more than that) because it gains half an inch of width on both the inner and outer lip. It *might* work, but I think it would be better if a 5 inch wheel on the front had an offset of 45mm or so. Th BMW Mini wheels I bought have a 45mm offset and they would fit just fine . . . . *if* they were 5 inches wide

Don

 

[Barbagris]

Anybody done some rim swapping lately?

I, for a winter set of tires. But in Europe...

 

[justind]

To add a little more data to the wheels/tires thread...

I have a set of winter wheels (rims + tires) that I received from the dealer. I didn't realize this until after I put them on but the rears were the wrong size, one size too small. This affected the regen quite a bit. When slowing down from speeds over 60kph the regen would be applied for a second or two then the car would coast and I would have to use friction brakes to slow down. Sometimes the regen will try again. At speeds below 60 it would usually work as normal but not always. This happened with traction control on or off.

It was very unreliable and I took the rears off the next day. Dealer so far has agreed to get me the right size tire so I think all will be fine. But in case you were wondering what tire combinations to try I wanted to let you know what doesn't work.

I was given the TOYO Observe GI5 (front)145/65r15 with (rear)175/55r15; instead of the correct size of 175/60r15. The difference is approx. 3%

here's some numbers...
The original tires (Dunlop Enasave) have the following dimensions:
front 145/65r15 diameter=22.4"; circumference = 70.4"
rear 175/60r15 diameter=23.3"; circumference = 73.2"
ratio of front/back circumference= 0.962

The winter tires (Toyo Observe) dimensions are
front 145/65r15 diameter=22.5"; circumference = 70.7"
rear 175/55r15 diameter=22.6"; circumference = 71.0"
ratio of front/back circ = 0.996;

Not only are we limited by what tires will fit in the wheel wells but I think we also need to maintain the original ratio. ( Unless this can be changed through the computer)

Anyway I hope this is helpful.

Justin

 

[JoeS]

justind, thank you for your interesting observation. Although I've noticed significant regen erraticicity (love that word!) when driving over rough road surfaces, I hadn't considered that our ABS/ASC systems would have been that sensitive to wheel diameter front/rear mismatch. I mean, (0.996-0.962)/0.962 = 3.5%

My impression is that regen cut-out is caused by ASC, as disabling ASC seems to stop this when cornering on rough surfaces. Might be a good idea to try a controlled test to validate this.

Although I thought that perhaps a very aggressive tread pattern might confuse the ABS/ASC, the Toyo Observe GSi-5 tire tread pattern is not "knobby".

Do let us know how the properly-sized winter tires turn out.

 

[Barbagris]

Euro i-Miev mount 175/55R15 rear, (front same size of US model)

It's only programming, I think.

 

[Ozimiev]

Another tyre (tire) option....
http://forums.aeva.asn.au/imiev-tyre-wear-status_topic3671_post48256.html#48256
The Oz iMiEV had 145x65 R15 dunlop enersave 2030s on the front.
The Continental ecocontact 155x60 R15 goes on same rim with 0.4% change in rolling diameter, but with a very different performance in cross winds in particular.
I'd still like to know Mitsubishi's logic behind the 145x65 R15 2030s on the front. Power steering power consumption ?

 

[RobertC]

This car understeers pretty heavily, so it needs all the help in front that it can get.

Don. I love you man, but no matter how many times you say the i-MiEV understeers, it still doesn't make it true.
Watch this video of understeer and oversteer.
http://www.dailymotion.com/video/xzft6h_understeer-and-oversteer_auto
As you can see, oversteer is much more fun.
The i-MiEV is a rear wheel drive vehicle with a weight distribution of 45% in the front and 55% in the rear.
A vehicle heavier in the rear with rear wheel drive will oversteer.
Watch the i-MiEV race in this video!
http://www.youtube.com/watch?v=TfjGvTIZYd8
The back end slides out. Oversteer. But the i-MiEV does well in the race because it can take turns at high speeds (and the driver appears to be insane.)

Now having said all that, I've put over 24,000 miles on my i-MiEV and have not had the back end (or front end) slide out, except ...

A couple weeks ago I took my 14 year old daughter to the deserted mall parking lot after we got some snow. I pressed the Active Stability Control Off Switch for three seconds to turn the ASC off and when I went into a turn and pressed the accelerator pedal to the floor I was able to get the back end to slide out and do some nice spin outs. It was lots of fun.

When I was a teenager I had a 1969 VW Beetle with rear wheel drive and the engine in the rear. When I went into a turn and pressed the gas pedal to the floor I could do a complete 360 spin out in the snow.

 

[blownb310]

One other thing to consider regarding the rolling resistance of the spare tire you chose: it's not a radial tire. Bias ply tires are notoriously less efficient than radials.

 

[Don]

This car understeers pretty heavily, so it needs all the help in front that it can get.

Don. I love you man, but no matter how many times you say the i-MiEV understeers, it still doesn't make it true.

As you can see, oversteer is much more fun.
The i-MiEV is a rear wheel drive vehicle with a weight distribution of 45% in the front and 55% in the rear.
A vehicle heavier in the rear with rear wheel drive will oversteer.

Your video is comparing an understeering FWD car with an oversteering RWD car - Apples and oranges . . . . and the oversteering RWD car in the video is NOT tail heavy

The iMiEV race video is a hoot! - That car is plowing (understeering) so badly that he cannot even hold his line in most of the corners and when he gets so far offline with so much steering correction cranked in and the front end catches just a little bit of grip, the back end gets away from him under throttle. You've gotta hand it to the driver though - The solution to his understeering mess? Keep his foot in it and cut across the grass on the inside of the corners so you don't have to deal with them at all!! :lol:

On the next to last corner (at 2:02 in the video) he understeers it completely off the track and has to back out of it to keep from hitting the wall!

With my background driving old '50's & 'early '60's Corvettes, SS396 Chevelles, Toyota Supra's and 240Z's I am VERY familiar with oversteering cars (and how much MORE fun they are to drive than the iMiEV in the video) - Note that all 4 of those are RWD, front heavy and they oversteer like crazy. Most drivers prefer oversteer to under because they can control it with the throttle, while the only solution to understeer is to slow down, which is something that iMiEV driver wasn't willing to do, so he was all over the place. Weight distribution is a factor in whether any car will oversteer or understeer, but it's not the deciding factor - Within reason, you can set up most any car to over or under steer, regardless of it's weight distribution

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

When I was a teenager I had a 1969 VW Beetle with rear wheel drive and the engine in the rear. When I went into a turn and pressed the gas pedal to the floor I could do a complete 360 spin out in the snow.

No doubt! You could also have done the same exact thing if you were driving a RWD, front heavy, Datsun 510 :lol:

Google '911 understeer' to read about a car you would think (from your F/R weight bias theory) oversteers, but actually suffers from the opposite problem

Don

 

[RobertC]

On the next to last corner (at 2:02 in the video) he understeers it completely off the track and has to back out of it to keep from hitting the wall!
http://www.youtube.com/watch?v=TfjGvTIZYd8

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.
Here's another video that explains oversteer and understeer. Both vehicles are going too fast to make the turn. The vehicle that oversteers, like the i-MiEV, loses traction in the rear.
http://www.youtube.com/watch?v=zoICf55jED8
If you watch the i-MiEV race video at 0:30 you can see how sharply the i-MiEV can make a turn while oversteering. The only difference is that at 0:30 the i-MiEV is not going as fast.
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.
The driver corrects the oversteer quickly at 1:29 in the i-MiEV race video and maintains his speed, but by doing so he cuts the corner in the track.

If you watch this video you will see that the cars that understeer have the front end skid and can't make the turn, while the cars that oversteer, like the i-MiEV, can make the back end skid and can make the turn. However, like the caption in the video says, these cars are just going too fast to make the turn.
http://www.youtube.com/watch?v=OKuhNM5Q9Mg
If you are going too fast to make a turn and your front wheels skid, that's understeer.
If you are going too fast to make a turn and your back wheels skid, like the i-MiEV, that's oversteer.

 

[blownb310]

On the next to last corner (at 2:02 in the video) he understeers it completely off the track and has to back out of it to keep from hitting the wall!
http://www.youtube.com/watch?v=TfjGvTIZYd8

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.

Don is correct, at 2:02 the i-Miev is in terminal understeer going into the right hander. However, after the speed is scrubbed off, the car transistions into a tiny bit of oversteer at the end of that corner, just as he re -enters the track.

The driver actually took the incorrect "racing line" between those two right handers. The correct [dark] racing line is easy to see on the track.

 

[alohart]

Watch the i-MiEV race in this video!
http://www.youtube.com/watch?v=TfjGvTIZYd8
The back end slides out. Oversteer. But the i-MiEV does well in the race because it can take turns at high speeds (and the driver appears to be insane.)

The i-MiEV in this race might be the same one. The driver is just as insane But he must have set up his car differently. Would you call this oversteer, understeer, or rolloversteer

 

[Don]

I don't think it's the same driver - This guy is much more talented than the first one. The guy in the first video couldn't even get it around a corner without going through the grass

They have some serious rubber on the front of this car - It's set up about as neutral as I think you could get. No sign of oversteer and the only real understeer I saw was the corner at 1:55 in the video. The car is neutral right up to where it goes on two wheels and he's certainly making the most of it

After seeing this video, I think with some better front rubber and a good alignment, we could dial 90% of the understeer out of out cars and get them handling much better than they did when they came from the factory. But, as the video shows, even then the top heaviness of the car would limit what it can do

Don

 

[blownb310]

There's something weird about those videos. I'd swear that they were animations. Doesn't look real to me.