what would happen if... (rears on front)

[fpage77]

Originally Posted by Suze

try that again with full sentences Jet - waddaya mean "...the impact zone for absorption..."?

I'm confused...

The wheels are suppose to absorb impact on our cars if we get hit on side.

[Bill Marshall]

I imagine that different size wheels & tires would not be compatible with the way that the esp is programmed. I imagine that it would also void parts of the warranty.

Frankly I can't imagine why anyone would change the equipment from the way it is spec'd. The manufacturer had a reason for designing it the way they did. Without knowing those reasons before making a change, I imagine that you'd just be asking for trouble.

[rfernatt]

Originally Posted by Bill Marshall

I imagine that different size wheels & tires would not be compatible with the way that the exp is programmed. I imagine that it would also void parts of the warranty.

Keep the outside diameter of the tire close and it shouldn't care. The OEM tires have a slightly different outside diameter front to rear as it is (about .25" I believe). 195/50 is right at the rear tire diameter and my car hasn't noticed or complained at all - ESP, ABS, TCS, etc. doesn't seem to mind. Keep in mind that the Brabus uses larger wheels/tires as well.

I've had warranty work done at a dealer after the new wheels/tires were installed and they liked the look and didn't give me a second's grief. Of course, YMMV.

[rolly]

Originally Posted by Bill Marshall

I imagine that different size wheels & tires would not be compatible with the way that the exp is programmed. I imagine that it would also void parts of the warranty.

Frankly I can't imagine why anyone would change the equipment from the way it is spec'd. The manufacturer had a reason for designing it the way they did. Without knowing those reasons before making a change, I imagine that you'd just be asking for trouble.

Manufacturers try to be conservative and put OEM parts on to make the car safe for the lowest common denominator driver.

STAGGERED wheel widths understeer (the most safe way a car to react) when a panic swerve is made by an average driver (they usually over react).
I put 6.5" Genius 15's on all corners and kept the stagger by putting 195 50s on the front and 205 50s on the rear. As recommended by Custom wheels, car rims, truck wheels - RIMS-N-TIRES
The offset on 2009 rear wheels allow stock rear to front mounting.

[Bill Marshall]

If you say so, Rolmeister. . . .

But I'd like to hear this from the manufacturer themselves. I don't see anythign conservative about different size wheels & tires on the front & the back. They must have had a reason to make such a radical design decision.

You can speculate about the reasons, but I can just as easily guess that it was to maximize mpg while still providing adequate support for the rear. I can also guess that it had to do with weight distribution since most of the weight in this car is in the rear & the center of balance is set back from the midpoint. There are other rear wheel drive/rear engine cars that have had problems with fish tailing & this may be an issue. It would be great to hear from MB on this one.

[jwight]

See post #5: Stiff suspension.

The wheel/tire size offset is there for a reason; not sure if there are any objective data on the results of using some of the "optional" wheel/tire size combos mentioned by forum members but I doubt it.

[SubSlr88]

I believe if you check, the Brabus models come with 175/15" front and 215/17" rear sizes. Lots of guys (and gals) are running the 175/15" rear wheel and tire combos all around with no problems or grief from the dealers. Many have opted to go even larger, i.e. 195/15"all around. . . which I think is about max for the front. Oversteer is reduced and ride is improved.
If MB can do it on the Brabus, why can't someone else on their standard Passion or Pure?
Geez, this question has come up many times in the past and it should be a no-brainer by now . . . except for the exceedingly nervous out there.

[Godfather]

"Exceedingly nervous" is the understatement of the year.

[rolly]

[QUOTE=Bill Marshall;223121]If you say so, Rolmeister. . . .

Bill, you've got a good point about maximizing miles per gallon on OEM tires.

I could be blowing smoke, (self hypnosis, because I spent so much extra $) but my butt tells me the car rides and handles better. Anyway, I switch back to stock wheels with winter tires because I drive in snow and ice for 6 months +- up here in "the frozen north".

[magilly00]

I went with four 185/60 R15's and that is about the tallest tire you can put at the front, the rears would be able to go taller but I wanted all four the same size so I could rotate them.Wayyy better ride now, if I knew it was going to be this nice with handling and bumps I would have replaced tires right after I picked up the car from the dealer.