Lower the rear

[bandit86]

Was looking at my jeep, the back is way high too high because the frot springs sagged. looked at several other vehicles, looks tha same way. Manufacturers raised the back to allow for cargo carrying capacity, and I think a lot of front springs sag on older vehicles, looks like if the back of most vehicles was lowered a half to one inch they would be more aerodynamic, the slanted roof creates too much downforce because it acts like a spoiler

now if you were to lower the back 2 inches, the grill would be more aerodynamc, the windshield would be on more of an angle, the roof at the windshield would be the highest point that would allow the wind to start falling off immediately

a lowered front air dam would cancel any negative effects of lowering he back

[Frank Lee]

It's generally accepted that a slight nose-down rake is best for Cd and I believe that applies to the underside. I suppose it's possible for a deep airdam to allow a nose-up rake to have better Cd... who knows, it might be kinda like the "banana car"?

[SentraSE-R]

I recall another recent thread where a Nissan SUV (Xterra?) owner complained about the dangerous handling of his vehicle in crosswnds. The previous owner had leveled it from the factory nose-down position. I speculate the previous owner's leveling allowed crosswinds to lift and lighten the front end. Beware unintended consequences.

[bandit86]

Originally Posted by SentraSE-R

I recall another recent thread where a Nissan SUV (Xterra?) owner complained about the dangerous handling of his vehicle in crosswnds. The previous owner had leveled it from the factory nose-down position. I speculate the previous owner's leveling allowed crosswinds to lift and lighten the front end. Beware unintended consequences.

DepEnds on the alignment, lots of offroaders lift he cherokee and grand cherokkees more in the front, that's what gave me the idea

[aerohead]

I would be hesitant to go beyond the factory,fresh springs inclination.The rake may be the only reason you have attached flow over the roof,as it is still 'attacking' the air up to the rear.Without the rake you might experience separation at the windscreen header.Very unstable! Very high drag!

[LeanBurn]

What about on a car? I have a 2009 Corolla and the back end sits 1 inch higher than the front. If I were to install a specific spring kit that evens out the ride as well as lower the car entirely by 3/4 inch would I have a good net result?

I have a lifetime average of 38mpgUS with a max of 46mpgUS so I want to keep getting decent numbers.

[aerohead]

Originally Posted by LeanBurn

What about on a car? I have a 2009 Corolla and the back end sits 1 inch higher than the front. If I were to install a specific spring kit that evens out the ride as well as lower the car entirely by 3/4 inch would I have a good net result?

I have a lifetime average of 38mpgUS with a max of 46mpgUS so I want to keep getting decent numbers.

Long ago HOT Rod Magazine published an article about findings reported by GM during inclination/drag tests conducted on a Chevy.Positive and negative rakes were investigated.Nose down was always better.But touchy!
I suspect that Toyota has fully investigated the Corolla and without a full-scale tunnel I would be hesitant to think I could outguess them.
It's true,that many really low-drag/high-mpg concepts have dropped noses only with 'active' suspension.
As far as I know,they NEVER reduce the amount of nose drop.
If you could lower both ends equally and maintain the stock inclination then that would be my recommendation.Watch your clearances though.Too low and the Corollas naughty bits may drag the ground!

[bandit86]

I still think my front springs are sagging, I'm looking for info on what the stock rideheight should be.

Doesn anyone have the article on this nose down vs nose up FE test?

[comptiger5000]

Rooster - That's part of it as well.

Bandit, what kind/year of Jeep is it?

[bandit86]

01 grand cherokee laredo, 4.0L

just waiting for a nicer day so I can take the luggage rack off. Why does almost every suv and van have roof racks, noone ever uses them. would be better if they left a bolt you could take out and screw in an I bolt to tie off to