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Effect of rain and speed on the efficiency...

1364 Views 8 Replies 7 Participants Last post by  Fourdoor
This morning, we got a heavy downpour. I know already that my effective range is really reduced by more than 20% when it is raining hard. So I turned on the MPGe display to watch closely. My informal observation shows that I got very very bad MPGe <68, when driving at speeds of 35 mph and lower. The slower I get, the worse off the MPGe is on the display. When I go faster, the MPGe increased to about 90, in the heavy rain. The MPGe increased as I drove at 35 to 50 mph, then it starts to go steady from 50-60 mph and starts to go down again after 60 mph.

The MPGe pattern is dramatically different when the road is dry. The optimum speed is at 25 mph when I can get the highest possible MPGe and a bonus of 22% extra range compared to that at 55 mph.

Anyone else observed this?
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Warm tires roll easier. Water is excellent at cooling, much better than air. But at some point air resistance is going to win.
No, hydroplaning in a car is called "loosing control and crashing".

At slow speeds a lot of the water clings to the tire as it rotates, at higher speeds more water is evacuated from the tread due to centrifugal force. Combine this with the cooling effect mentioned by Qinsp and it makes sense of your observations.

You can hydroplane in a straight line... sometimes... briefly. But I doubt that what happened. I thought about it, but when you hit standing water it's like dropping a parachute. Not a minor loss, a major loss of propulsion.
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