JoeS wrote:Can you imagine being a suspension engineer for Mitsubishi and telling management that they need to put in some seriously-skinny non-standard front tires on this vehicle? It must have taken some pretty compelling arguments (handling? rolling resistance?)
They had some very compelling arguments, so I'm sure it was a pretty easy 'sell'. I doubt rolling resistance was even discussed, but it was surely done in an effort to make the car handle the city environment it was designed for, no doubt about it. Much like a modern Porsche, it really needed the larger rear tires just to keep the rear end behind the front end
Remember, this was all designed for a car a foot shorter, 3 inches narrower, nearly 700 pounds lighter and extremely rear weight biased compared to our iMiEV . . . . and it had half the power. Truly a 'city car' designed neither for speed or handling Drivetrain
The i has a "rear-midship" engine mounted just ahead of the rear axle, a highly unusual configuration in a small car where front-engine design has dominated since the 1970s. The 3B20 three-cylinder powerplant has an aluminium cylinder block, a displacement of 659 cubic centimetres, and incorporates double overhead camshafts with MIVEC variable valve timing in the cylinder head. Initially only an intercooled and turbocharged engine was offered, until a naturally aspirated version was introduced for 2007.Suspension, brakes and tires
MacPherson struts are used in the front suspension, and an unusual three-link De Dion tube/Watt's linkage is used in the rear. Front discs with anti-lock braking (ABS) and electronic brakeforce distribution (EBD) are standard across the range. In common with many other mid- or rear-engined vehicles its fifteen-inch wheels have uneven-sized tires, 145/65 on the fronts and wider 175/55 on the rears, in an effort to minimize the chances of oversteer caused by the rear-biased weight distribution.
For the underpowered Tokyo city car it was designed for (which probably seldom saw 50mph) the minimal suspension made pretty good sense. For a larger, heavier EV cruising down the PCH at 65 mph, not so much
Now . . . . . Can you imagine being a suspension engineer for Mitsubishi and recommending that they keep this exact same set-up in a completely new car which is larger, wider, heavier, has a much closer to 50/50 weight distribution and more than twice the engine torque?? (The standard I car had 42 ft/lb, the turbo had 65 and our iMiEV has 133). If any suspension engineer thought this was a good idea, I'm pretty sure he would have lost his job before the sun went down! But, seriously, I doubt any Mitsubishi suspension engineer had any hand in this - I suspect it came directly from management as a cost cutting measure. "We'll stick an electronic ASC system on it (that the original car didn't have) which won't let it understeer quite as badly as it does without it, and hopefully nobody will notice that the suspension was designed for a completely different car"
I'm pretty shocked (and really disappointed) that it seems like they just took an existing automobile and converted it into an EV with so little thought as to what they were changing. Size, weight, C/G, F/R bias and power. The iMiEV is so much different in so many ways, yet they didn't make ANY changes to the suspension. How much more would it have cost to properly set up the now 2600 pound EV? Surely much less than it cost to completely redesign the body to add a foot of length and a few inches to the width just for the North American market. I'm all for keeping costs down, but this borders on the ridiculous, IMO
Show me any other 2600 pound car which uses 145/65 tires - There ain't one
What I can't imagine is . . . . how they actually managed to get a 2600 pound car with 145/65 tires past the Feds in the USA - Now that seems improbable. Put four 200 pound adults and some cargo in it and now you have a 3500 pound vehicle riding on 145/65 tires
Saving a few bucks here wasn't a great idea, IMO