The stock set up will run better in the snow, smaller tires tend to cut through the snow more than larger ones (I also recomend blizzacks or the Pirelli's stated earlier for tires in winter). As far as summer driving, having the larger tires on the front makes handling on your smart improve.
Having had the opportunity to run the Dragon in the same 450 on OEM 145/175 last year and 175's all around this year. The same tires all the way around perform worlds better, handling in the wind is better. I am running 34 PSI all around.
My concern on reading the posts in this thread is the difference in tire pressure front to rear that some of you are running with the same sized tires all around. The weight distribution in the car is pretty close, having a nearly 10 PSI difference front to back is going to hurt the way the tires work together.
Also running 40 PSI I would question, I know that in a 450 the ride would be brutal with that much air in the tires, the 451 soft suspension must help with this a bit. The big concern I would have is with how small your contact patch is with 40 PSI in the tires, you are negating some of the benefits of running the wider tires.
With factory suspension and 175 Hankook Ventus tires inflated to 34 PSI, I have very neutral handling, which is what I was going for. When the tires hit there limit the car slides quite controllably.
For winters this year I am going to run 145 Blizzack WS60 tires all the way around. I am expecting the narrower tires will cut through the snow well and give superior traction on ice and that I will retain my neutral handling.
With the OEM Continental snows in deeper snow I found the ESP to be constantly fighting to keep the back of the car under control, as the rears acted like sea anchors in the snow while the fronts cut through rather well.
If someone is trying out wider summer tires all around and think their car is handling worse, something is wrong either with you or your car's setup(tire pressure, alignment, etc).
I have just mounted, on the front of my 450, a pair of Conti Eco Contact EP 175/55 R15 tires on new OEM rear rims. When the wheels are turned to the maximum, or on tight cornering, there is some rubbing on the rear part of the front fender well liners.
I'll double check the tire pressures tomorrow and do another test drive.
Does anyone else have this problem?
RVGRINGO, the rubbing is coming from the fact that the offsets on the 450 for front and back are different. The 451's offsets on the front and back are the same which allows them to run rears on the front.
Because the 450's offsets differ from front to back, you will always get rubbing. You may should look at getting a spacer or something to keep from rubbing when turning.
I have just mounted, on the front of my 450, a pair of Conti Eco Contact EP 175/55 R15 tires on new OEM rear rims. When the wheels are turned to the maximum, or on tight cornering, there is some rubbing on the rear part of the front fender well liners.
I'll double check the tire pressures tomorrow and do another test drive.
Does anyone else have this problem?
Better to get a pair of Roadster front wheels, which are J5 width and will take 175/185 rubber and have offsets nearer to design spec.
My concern on reading the posts in this thread is the difference in tire pressure front to rear that some of you are running with the same sized tires all around. The weight distribution in the car is pretty close, having a nearly 10 PSI difference front to back is going to hurt the way the tires work together. ...
It was determined some time ago by corner scales that the curb weight distribution of a North American 451 is about 45% front-55% rear. One could assume that a 450 is close to that. The smart factory pressure when front 175s are used on the similar weight Euro pulse is 26 psi. A non-pulse rear 175 is 36 psi. -the 10 psi difference.
I think it is more important to have the front and rear tire pressures properly set to their respective loads carried than the pressure difference between them.
As people wheel-up, they are departing from set-ups that smart/M-B spent a lot of time on. They can expect handling to be altered (maybe unexpectedly too). Remember the Ford Explorer/Firestone Tire deal, when Ford decided to depart from Firestone's pressure recommendations for the sake of driving comfort.
In the way back when there were known M-B A-Class problems with the "Elk Test" (and quietly known problems with the nascient 450) the smart project was almost killed because of handling issues. The engineers actually working at MCC/smart couldn't solve it and engineers from M-B itself (offroad) were sent in to take over and save the day. I'm sure as much effort went into all of the later smarts.
About the only way you are going to know what an altered set-up actually produces is to hire time and collect data on a skid pad and slalom - otherwise it is all a guess and a hope. Maybe the various wheeler-uppers and pressure uppers-and-downers should throw some collective bucks into the hat and take the cars to Skip Barber or Bondurant to realy see what they have.
Last edited by Old smart; 10-03-2009 at 07:49 AM.
Reason: add
Yes, it is... curious that the 450 spec is 29psi front and rear, where the 451 was upped to 36 on the rear.
What I can tell you about the 450 is that my tuner, Eddy Lai, the "Flying Tiger" corner-balanced the car with my preferred 32/34 and using the Bilstein adjustables, lowered the front ride height very slightly to give me an excellent performance setup.
Thanks for all of your responses. After the first test drive, yesterday, I do like the softer feel of the larger front tires, especially on cobblestone streets, but the slight rubbing does concern me when turning hard; as into a parking spot, out of a driveway, sharp narrow street corners, etc.
Briansmart: What type of spacers do you mean? Something that would set the front wheels even wider apart? Washers under the lug nuts, or a spacer ring drilled to accept the wheel and lugs? I'll look at the offset link, but I'm not sure I'll understand it. How will increasing the offset eliminate the rubbing?
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