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

[forestacademy]

Originally Posted by holliwud

what would happen if i bought some rear oem wheel and tires and put them on the front of my 09 pure. i was just wondering if they would rub and won't work out good. any advice you have will be very well appreciated. i don't really care for rims, i just want to replace my front skinny tires.

The car will drive backwords?

[Alan Smithee]

Originally Posted by Bill Marshall

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...

Bill, staggered wheel/tire widths are not unique to the smart. Most (if not all) of MB's and BMW's 'sport' package and performance models have wider rears to induce understeer for 'sporting' drivers not experienced at driving on the limit of adhesion. This on cars that (especially in the case of BMW models) have nearly 50/50 weight distribution.

(Inducing understeer is also why factory recommended tire pressures are lower for front tires on RWD cars, whether staggered or not. FWD cars typically have ~60% of the weight in front, therefore understeer is a given.)

Even without sporting pretentions, with such a short wheelbase and rear weight bias, everything possible is done on the smart to reduce the chance of oversteer. Otherwise the smart would have four narrow 'front' wheels/tires for optimal fuel economy.

As somebody else mentioned, along with the wider rear wheels/tires and higher rear pressures, severe negative camber for the rear wheels on the smart also increases rear grip in order to further induce understeer.

Unfortunately, chances are slim that you will find a salesman, dealer tech, or customer service rep well versed in vehicle dynamics to confirm this, but it is common knowledge among car tuners, racers, etc.

[holliwud]

big wheels at the front works great. you don't get shoved around on the highway. i have 25-30mph winds out her. the wind was pushing me back and forth. now i feel the wind hit the car and i don't move. thats a big plus

[Godfather]

Gee, I changed mine because as delivered it was an understeering pig. Like most economy cars where the manufacturer tries to balance cost versus performance, and safety for the masses versus handling for those of us who can actually drive. Enjoy your stock smart Bill, if that's what makes you happy. It's a free country.

[redbluff]

I have a Pure and keep the rear tires the same and just put 175/55 identical to the rears on the stock front wheels. Wheels are not as wide as the rear wheels but the 175's fit fine. I did this to rotate tires and stability. Also having had the Passion and the Pure the steel wheels on Pure's alreeady help with the harsh ride.

[chieftmc]

Originally Posted by redbluff

I have a Pure and keep the rear tires the same and just put 175/55 identical to the rears on the stock front wheels. Wheels are not as wide as the rear wheels but the 175's fit fine. I did this to rotate tires and stability. Also having had the Passion and the Pure the steel wheels on Pure's alreeady help with the harsh ride.

That's exactly what Randy Zimmer did! He said it works perfectly, but his is a passion

[tabevan2052]

OK folks---

I got as set of stock rear rims. I took the 175/55 R15's and put them on the front , I had 205/50 R15's mounted on the rear. LOOKS GRRREAT!!!

The ride is great , the steering is "twitchy". Side winds raise heck with steering... The ESP kicks in if any quick moves are made at or over 60 mph....

Any ideas as to where to run the air pressure?

MPH is actualy 66.25 at 65 mph reading

[SubSlr88]

[QUOTE=tabevan2052;235722]OK folks---Any ideas as to where to run the air pressure? </QUOTE]

I'm running 175x15's on all four corners on all 'rear' sized rims. I currently am running 36psi on the rear tires (stock specs) and 33psi for the front set. That seems to be a good spot . . . at 29psi they seemed to cause the low-speed steering to be harder. And at 33 they still tame the pot holes and such. . . good luck.

[RussBarnes]

[quote=SubSlr88;235761]

Originally Posted by tabevan2052

OK folks---Any ideas as to where to run the air pressure? </QUOTE]

I'm running 175x15's on all four corners on all 'rear' sized rims. I currently am running 36psi on the rear tires (stock specs) and 33psi for the front set. That seems to be a good spot . . . at 29psi they seemed to cause the low-speed steering to be harder. And at 33 they still tame the pot holes and such. . . good luck.

I have four Michelin 206/60-15's on equal wheels. I run the fronts at 28/29 and the rears at 35/36. Ride here in TN is fine, still wanders, but much less, may need to check toe-in. With my power steering I haven't noticed hard steering.

[fpage77]

Basically after reading this whole thread OEM fronts are 155/60 15 and rears are OEM are 175/55 15. The rears being larger, having camber and higher PSI (36) give you more grip than the fronts. The fronts being smaller than rear and having lower PSI (29) helps give you more reduced grip. These things are what total up to give us our whole of what understeer is in car from factory. I now have 175/55 15 on my rear in front and as I see it I should still have some understeer left. I still have the advantage camber and higher PSI (36) on the rear which helps increase grip. The fronts have lower PSI (29) which should reduce some grip. The way I look at it using that line of logic I should still have some understeer left but I would lose some (not all) due to the tire size no longer being staggerd. I hope I have made some kind of sense here as my brain hurt from hard thinkin.