Running front tires on front AND rear

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Permalink Reply by Ptero on December 22, 2011 at 2:40am

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Permalink Reply by Ptero on December 26, 2011 at 6:45pm

I have a noticable mpg improvement with the narrower rear tires. The car feels a bit more skittish but i got used to it. I'm running 45 psi all around. Pulled the trailer 500 miles with a load. No problem. By the way, you state that the rear wheels carry "lots of weight." The car and empty trailer weigh 2000 pounds with me in it. The max load rating on the sidewall of the narrow tires is 827 pounds. That ain't a lot of weight, pal.

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Permalink Reply by Alan F. Webber Sr. on December 28, 2011 at 10:53pm

I love the way it left out what I said. The VW Bug also had skinny tires all the way around, no big deal. You could mount Vortex Generators to get rid of skittish feeling. How much was your noticable improvment in gas milage and how was the road bump handling compared to OEM?

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Permalink Reply by Ptero on December 28, 2011 at 11:56pm

Well, I like motorcycles and the Smart is fun to drive. With 45 psi it bounces around a little on rough pavement. At 32 psi it doesn't, so I consider that a personal preference. You have to pay more attention. As a hypermiler, I do and it doesn't bother me. I enjoy the challenge. I don't care for the OEM setup because it is a compromise. I want the real deal. With the trailer on a very slight downgrde, which I've traveled a 100 times, I achieved 65 mpg. Without a tailwind. I've never done that before. I also notice a 1 to 2 mpg gain without the trailer.No question in my mind that there is an improvement. Theory says there should be an improvement. I need more miles to analyze the improvement. Stay tuned.

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Permalink Reply by Gary Bryers on January 2, 2012 at 11:33pm

Just a couple things - not challenging your idea or anything:

1. Front tires have a small circumference than stock rear tires, and the speed and distance for the car, unless you have made an adjustment to the programming, will still think it has full-sized tires on the back. Using a smaller tire means the ECM thinks you are going faster than you are, and farther than you are - you will need to do the math to figure the difference. A tape measure will handle that quickly;

2. Over-pressure in the tires (45psi) will cause the tire to wear out much faster than a properly inflated tire. Weigh the cost of early tire replacement over the cost of gas saved, to figure out if you are doing yourself any financial good.

3. Smaller, narrower tires put less rubber on the road (and even less when over-inflated), meaning less traction. This will become most evident under wet-road conditions (I assume you don't get snow much). Take care not to put yourself in harm's way with your experiment, please.

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