mpg and weight

[MetroMPG]

According to the aero/rr web tool I made based on formulas and spreadsheets posted elsewhere on this site, adding 100 lbs to my car's stock configuration would drop its steady state 55 mph FE from 55.4 mpg to 54.74 mpg. Add another 100 lbs and it drops to 54.1.

Seems to suggest that (assuming the formulas are right) the added weight will have a not insignificant effect on rolling resistance.

http://metrompg.com/tool-aero-rr.htm

[Mentalic]

Originally Posted by Biffmeistro

To be utterly honest, when has anyone ever made a trip without touching the brakes once?

If anyone can tell me that they ever ONCE made a trip where they NEVER touched the brakes, only ever used coasting to slow themselves down, I will most definitely eat crow.

Don't think never is possible.. But I sure don't use them very much or hard. In 13 years I put 160k miles on an S10 pick up and sold it with the original brake pads with plenty of pad left..

[skewbe]

One trip Never using the brakes is definately possible, I'm sure its a pretty regular occurance in quieter areas. It's like playing pool (assuming you are not a "slammer"), it's about hitting the ball just hard enough so it stops where you want it.

[MetroMPG]

My '89 Accord had permanently corroded front rotors because I didn't use the brakes enough/hard enough to keep them clean. (And the VX rims let more water get to them.)

[Wyldesoul]

So you honestly have driven a whole trip without touching the brakes?

[skewbe]

Biff, you drive a much heavier car. A metro isn't a 3400 lb t-bird, and it slows down a lot faster. My saturn glides a lot farther than my metro and I have to use the brakes a lot more in it as a result.

[Wyldesoul]

I admit I'm quite impressed.

Crow eaten.

[MetroMPG]

The 133 mpg round trip I pulled off last summer was done with a mix of mostly rural highway driving (ie easy to not brake), with some suburban stuff at the beginning and end. I only used the brakes once - to stop the car in the driveway at the end of the trip.

I used the brakes once on the 133 mpg round trip, and that includes negotiating (ie. not "blasting through" approx. 14 turns at intersections, and 4 stop signs - which admittedly, I "rolled", but no more grievously than the typical driver.

http://www.gassavers.org/showthread.php?t=993

[lca13]

Adding weight adds to the RR in a linear fashion. With RR on the order of aero resistance at speed, a 10% increase or decrease in weight will yield approx. a corresponding 5% change in overall negative force applied to the car. So it is not insignificant even at highway speeds.

[Mentalic]

Originally Posted by skewbe

One trip Never using the brakes is definately possible, I'm sure its a pretty regular occurance in quieter areas. It's like playing pool (assuming you are not a "slammer"), it's about hitting the ball just hard enough so it stops where you want it.

Well if you have an auto you do have to at least press the brake to shift it out of park.
If you lived out in the sticks I'm sure it could be pulled off though. Drive from the North 40 to South 40, no brakes no problem.