Quote:
Originally Posted by mcrews
Again, I hate to beat the dead hoe.......BUT.......
to all:
1. The name of the game is rpm at 60 or 55 or what ever you 'cruise' at. In my Q45, w/ the 2.78 ratio and the one size up 255/45/18, I'm turning 1820rpm at 62mph. On a flat freeway, that will get me 30mpg all day long. At 2000rmp the mpg drops noticablly.
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245/45/18 to 255/45/18 changes the width not the height
Quote:
Originally Posted by mcrews
2. Again, why lower it. REALLY. why? I can tell you from firsat hand experience there is no noticable difference in mpg w/ lowering.
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"Active ride height that lowers the vehicle at speed, which Ford employed on the Lincoln Mark VIII and which appears on Mercedes-Benz vehicles with Airmatic suspensions. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."
Car Aerodynamics 101
To put Cd changes in perspective, Frasher put some numbers to a hypothetical sedan. Our imaginary car has a curb weight of 3,527 pounds, a Cd of 0.30, a frontal area of 23.7 square feet and 9 pounds of rolling resistance for every 1,000 pounds of weight. According to Frasher, "If we put a gas-burning engine in this car, expect reasonable performance and drive it on a combined driving cycle, we can expect to get 23.8 mpg…. Add 10 percent to the drag coefficient, we'll now get 23.3 mpg…. Take 10 percent from the drag coefficient, we'll now get 24.3 mpg."
Improving Aerodynamics to Boost Fuel Economy — Edmunds.com
65+ Vehicle modifications for better fuel economy - EcoModder.com
According to the book i have, a 1992 crown victoria has a drag of 0.34 and a grand marquis of same year has 0.36. Those are not bad numbers considering the size of vehicle.
Quote:
Originally Posted by mcrews
3. BUT your ride quality will suck. period. So knock your self uot. use lowering springs. what ever. But you will regret it. the spring is the major component in the suspension. the minimal change in tire size has very little impact on the quality of the ride. A 1 inch change in springs is not a little thing.
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I understand that; anti-roll bars, shock rates, and camber adjustments should be taken into account when modifying springs as well.
Quote:
Originally Posted by mcrews
4. Besides, if you measure the current ride hieght with the factory ride hieght, I bet the car sits 3/4" lower right now!
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Because of the saggy springs no doubt!
Quote:
Originally Posted by mcrews
5. a much better option (if you are convienced that you have to be lower is a front lip or airdamn. So of the truck-modders have really mastered the art of the lower front dam.
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A front air dam and belly pan is in the plans.
Fud2468, sorry for hijacking your thread.