Quantifying the aerodynamic impact of lowering a car? (drag coefficient Cd)

[lowglider]

You haven`t told us how much more the new springs would cost. Lowering does improve mpg but I doubt it would pay for itself. If you go for it, I strongly recommend using progressive or soft springs, so that you do not ruin the already not not so smooth ride quality. It can never ever pay for itself if it ruins your back, even if the signs will show in the distant future, it`s just not worth it to risk sacrificing your health.

[aerohead]

Lowering,by itself,may not achieve the lowest Cd.Low drag concept cars as the Probe-IV not only lowered the nose,but also raised the tail for out-of-town driving,configuring the 'rake' of the car for overall lowest drag.This is something which a full-scale wind tunnel would be handy for ascertaining.
I'd be inclined to maintain a 'factory' suspension.

[320touring]

Originally Posted by lowglider

You haven`t told us how much more the new springs would cost. Lowering does improve mpg but I doubt it would pay for itself. If you go for it, I strongly recommend using progressive or soft springs, so that you do not ruin the already not not so smooth ride quality

New springs= £80

New Shocks another £80 for fronts only.

New cheap coilovers £155 (front and rear)

Originally Posted by aerohead

Lowering,by itself,may not achieve the lowest Cd.Low drag concept cars as the Probe-IV not only lowered the nose,but also raised the tail for out-of-town driving,configuring the 'rake' of the car for overall lowest drag.This is something which a full-scale wind tunnel would be handy for ascertaining.
I'd be inclined to maintain a 'factory' suspension.

Duly noted- this being the week before payday, I'm in no position to pay for the bits to alter anything!

interesting re the probe- maybe a front only drop would have similar outcomes?

[LeanBurn]

Careful with the cheap coilovers...I have heard stories where they break and/or leak fairly quick..often made with inferior materials...especially cautious if made in China.

Why not some Eibach, H&R or other proven name brand that while lowering the chassis they actually are designed to improve the handling dynamics of the vehicle. Helps with maintaining momentum and keeps more control on windy highways, not to mention can add a little fun back into the driving experience. Also can work with factory shock absorbers with a minimal impact on life expectancy.

[ultimx]

I would go with some eibach linear springs not progressive. They come inane different spring rates and are cheap, atleast state side. Just make sure u have the proper Id of the spring u want to fit onto the coil over and don't get cheap stuff like mensioned before

[Varn]

When I was a poor student I decided that my new 73 Toyota could use some lowering. I pulled the front coils and cut a full turn off the coils. I was interested in fuel economy as gas was sometimes over 50 cents but was mainly interested in handling.

Reducing a coil will increase the spring rate. I have done it many times on off road motorcycles. If you want to maintain ride height you have to put in a spacer.

[Varn]

If you have 10 turns on a front coil and it is 10" long then removing one turn will increase the spring rate by 10/9ths and reduce ride height by one inch.

Usually stock springs are way cheaper than aftermarket.

[aerohead]

Originally Posted by 320touring

New springs= £80

New Shocks another £80 for fronts only.

New cheap coilovers £155 (front and rear)



Duly noted- this being the week before payday, I'm in no position to pay for the bits to alter anything!

interesting re the probe- maybe a front only drop would have similar outcomes?

Too bad for us that Ford never published a drag breakdown of the Probe as it transitioned from 'urban' to 'highway' configuration.
Dropping only the nose would,in essence,effectively raise the boot,taking some bite out of the rear contour.
I suspect that it would lower the drag.I just don't know how to predict a numerical value for it.
If you had access to a closed course,along with instant mpg readout capability,you could substitute rigid links where the shocks go,fixing the ride height at your new target,then drive it only as long as it took to get your new mpg reading.If you liked the number,then it might justify a proper modification.
If the numbers didn't pan out,you'd be out very little time and money.

[Sven7]

I ran with cheapcheapcheap coilovers on my Rabbit for several years and never had a single problem. The ride was rough, though not unbearable. Handling was dramatically improved. Grease the sleeves if you drive in the winter.

You might be able to find some used H&R's or similar for much less money. Look on vwvortex, local VW forums or your local Craigslist type site.

Otherwise the popular cheap brands are Vmaxx, Raceland and Rokkor.

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If anyone in the Michigan area has a Scangauge they'd be willing to lend for a weekend I would very much like to plug it into a car with air suspension (I could probably find someone on MIVE) to get real-time readouts on MPG as a function of ride height.

[aerohead]

Originally Posted by Sven7

I ran with cheapcheapcheap coilovers on my Rabbit for several years and never had a single problem. The ride was rough, though not unbearable. Handling was dramatically improved.

You might be able to find some used H&R's or similar for much less money. Look on vwvortex, local VW forums or your local Craigslist type site.

Otherwise the popular cheap brands are Vmaxx, Raceland and Rokkor.

==============================

If anyone in the Michigan area has a Scangauge they'd be willing to lend for a weekend I would very much like to plug it into a car with air suspension (I could probably find someone on MIVE) to get real-time readouts on MPG as a function of ride height.

Man,that would be a great contribution.We could also look at mpg as a function of steady road velocity and begin constructing mpg vs speed tables.
Hope that falls together!