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Old 09-19-2007, 09:30 PM   #1
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Anyone experiment with spring heights to change aero?

I'm curious about the affect on aerodynamics on many vehicles by playing around with the front dan rear ride height differentials. I wonder if there are some cars that would be way if the bumpers weren't so level whether they tilted the vehicle forwards or backwards.
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Old 09-19-2007, 09:45 PM   #2
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Cars are often tilted down for down force. I wouldn't be surprised if some cars worked better with the butt dropped instead... but I know that dropping the nose would be a common situation. Still, it would be fun to have numbers for how many cars do and what the ideal front rear ride heights are.
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Old 09-20-2007, 06:48 AM   #3
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An oft quoted optimal ground clearance is 3.3"- I don't know the source or the validity of that.

If there was a gain from loweriing my car, it's damn small.
So it's desirable to have some air flowing under the car? I have my VX very low, and I wonder if that is worse aerodynamically.
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Old 09-20-2007, 04:00 PM   #4
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So it's desirable to have some air flowing under the car? I have my VX very low, and I wonder if that is worse aerodynamically.
measure it on level ground. i bet you still have at least 5 inches. my civic rides at 8 inches and it is lowered a lot of people think their cars are a lot lower than they really are.
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Old 09-20-2007, 04:49 PM   #5
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So it's desirable to have some air flowing under the car? I have my VX very low, and I wonder if that is worse aerodynamically.
Yeah, you get a ground effect which produces extra down force which increases rolling resistance. This is caused by higher velocity air moving under the car which means lower pressure (Bernoulli) - so low pressure under the car, high pressure above the car -- net downward force. Useful for high speed cornering and traction, not so much for P&G.

I suspect there's head and nozzle loss too along the leading edge of the portion of a car very close to the ground.

One F1 car used a fan to actively increase ground effect pressure http://en.wikipedia.org/wiki/Brabham_BT46.


I actually need to do research on this very thing for this year's human powered vehicle... When I eventually find some numbers where height becomes a factor, I'll report my findings
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Old 09-23-2007, 09:06 AM   #6
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I thought I read somewhere that lowering the rear helped out (simulating a heavy load) by minimizing the effect of the windshield angle. Dropping the nose down seems like it would increase downforce but also increase windshield angle (increasing drag). An airdam in the front would keep airflow under the car to a minimum.
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Old 09-23-2007, 06:25 PM   #7
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adjusting the rake of a car for fuel economy really depends on the car. the bottom line is that you do NOT want to increase the frontal area.
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Old 09-23-2007, 07:35 PM   #8
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measure it on level ground. i bet you still have at least 5 inches. my civic rides at 8 inches and it is lowered a lot of people think their cars are a lot lower than they really are.
i got about 8 inces of ground clearance and i have taller tires than stock on my explorer, id feel like **** if a civic was that high. ive seen plenty of civics that were less than a coke can off the ground.
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Old 09-23-2007, 10:59 PM   #9
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Tempos are pretty tall stock and they are only 5.something off the ground. Where are you measuring to come up with 8?
the ground to the lowest point of my vehicle (rear shock mounds in my case)
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Old 09-24-2007, 05:57 PM   #10
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Tempos are pretty tall stock and they are only 5.something off the ground. Where are you measuring to come up with 8?
hmm... i dont remember honestly... i thought i remembered measuring my old 4 door civic when i first lowered it. but now i realize that was over about 7 years ago and i bet my memory is shot.

when i measured it was from the bumper to the ground.... i will have to measure where my civic rides now...

also where the shock mounts to the control arm is not a good place to measure ground clearance because it is unsprung. i would measure the lowest part of the sprung chasis to the ground. this would probably some cross member or something.
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