Should I lower the back end of my car? - Gas Savers

DRW · 10-11-2006, 10:19 AM

I have Eibach prokit lowering springs on the car now. They lowered the car about 1.25", but then I took out about 100 pounds from the rear of the car, so the back end sits a little higher now. I was wondering if you thought lowering the back end would help reduce aerodynamic drag? Plus the rear suspension does not bottom out over big bumps, so there's room to lower it if needed. Check out the pic.

PS yes I know it looks a little rough.

onegammyleg · 10-11-2006, 10:34 AM

Hi DRW..

I think its rite as it is.

If you look at your pik and run a straight line from the style line on the bottom of the door and sight it up against the front and rear hub centres , it only looks like 1/2 and inch higher in the back.

I think it looks higher in the back because of the shape of the wheel arches , its more a visual thing than anything else.

DRW · 10-11-2006, 07:47 PM

That's what I thought. I had to run it by you guys since I have this bad habit of modding stuff just because I can.

thisisntjared · 10-11-2006, 08:09 PM

sooo... take 120lbs off the front!

DRW · 10-11-2006, 08:51 PM

Quote:

Originally Posted by thisisntjared

sooo... take 120lbs off the front!

I don't want to make it look like a 4x4!

thisisntjared · 10-12-2006, 06:13 PM

but you know its the best when cars are looking sleepy. besides the best reason for aftermarket suspension is the stiffness so that suspension geometry is more resistant to change.

Compaq888 · 10-12-2006, 06:50 PM

I would never modify my suspension. One of the reasons is with a stiffer suspension the car behaves differently. That's why some people crash their cars after they switched to an aftermarket suspension setup.

Also the fact that it would draw attention to my car. Civics already have enough attention, I don't need to the point of where it gets stolen.

DRW · 10-13-2006, 09:33 PM

You can tell by looking at the paint, my car doesn't attract attention. Plus the 4" exhaust tip and fmic are painted flat black for stealth. No, I don't want to attract attention. I think I'll leave the back end up, stinkbug style!

onegammyleg · 10-14-2006, 12:21 AM

Either that or they are blind.

thisisntjared · 10-14-2006, 11:13 AM

Quote:

Originally Posted by Compaq888

I would never modify my suspension. One of the reasons is with a stiffer suspension the car behaves differently. That's why some people crash their cars after they switched to an aftermarket suspension setup.

yea my car is much more different after stiffening everything. it is much more responsive and has much more traction. its so much safer. although i wish it was maybe 1/2in higher...

onegammyleg · 10-14-2006, 11:20 AM

Hi thisisntjared

Some auto makers put super soft springs (seems mostly for the US market for some reason) compared to cars for other markets.
I think U.S. got used to limo style soft rides and expected that soft feeling even in small cars.
While soft is nice , too soft suspension can cause handling problems if there are geomotry changes with suspension travel. (which is the norm)

A car like this then fitted with what I would call normal stiffness springs can improve its on road performance dramaticaly., and if the spring maker did a good job at estimating the needed stiffness the ride shoudlnt be too bad either.

What is of concern is that some of the cheaper spring makers dont do much testing of their products , so you can actually get a handling package which is unsafe, especially when excess lowering is involved.

thisisntjared · 10-14-2006, 07:48 PM

ogl:

i agree with your points and often suspension setups designed for racing are very unsafe on the roads because they are too stiff and offer a steering bias that is unfavorable on public roads. i think we agree.

my point is that mildly tuning the suspension (properly) can improve the safety of the car as long as the driver knows how to work with it, in rebuttal to compaq888's post.

onegammyleg · 10-15-2006, 12:51 AM

Hi thisisntjared

I agree - A car with a well tuned suspension setup is pure joy to drive.

Ryland · 10-15-2006, 07:33 AM

I would first ask, how much weight are you going to put back in the car? I keep 100 pounds of stuff in the back of my car nearly all the time, so do I adjust the suspention for when I have the weight, or not? the extra weight is alwas going to be in the rear, and haveing the rear a little high is better then having it to low, I would pick that worst case hight (100 pounds of cargo) and leave it adjusted there.

red91sit · 10-19-2006, 01:02 PM

Hmm, 100 lbs, should lower the rear of my car 1/11 of an inch

It seems like a higher rear end would reduce the slope of the rear windshield and also turn the entire underside of the car into a diffuser?

DRW · 10-19-2006, 10:07 PM

Quote:

Originally Posted by theclencher

Lower it, test it, tell us what you find!

I'm feeling the need for a SuperMID and to develop a test route. I might do that someday soon.

Ted Hart · 12-09-2006, 04:31 PM

Quote:

Originally Posted by Compaq888

Also the fact that it would draw attention to my car. Civics already have enough attention, I don't need to the point of where it gets stolen.

If someone wants your car...and it looks like an "easy kill"...it's gone! Who sees a 1/2 inch angle? Relax! The angle isn't gonna save it! Or not....

LOL!

Ted Hart · 12-09-2006, 04:32 PM

Quote:

Originally Posted by red91sit

Hmm, 100 lbs, should lower the rear of my car 1/11 of an inch

It seems like a higher rear end would reduce the slope of the rear windshield and also turn the entire underside of the car into a diffuser?

Hmmm.... What planet do you live on? Can I come up & play?

red91sit · 12-10-2006, 01:06 AM

Quote:

Originally Posted by Ted Hart

Hmmm.... What planet do you live on? Can I come up & play?

Maybe, what can you bring to it? I dont' really understand your comment?

Silveredwings · 12-10-2006, 06:21 AM

Move the battery to the rear and maybe the weight will just about balance out evenly.

DRW · 12-10-2006, 08:19 PM

meh, I dunno about that. The spring rate on the rear of my car is 180 lbs/in. So if I add or remove 100 pounds it would lower/raise the back end by .56" My battery weighs 27 pounds, so that would lower the rear by .15" and raise the front by less than .15" , maybe about .1"? Nah, too much work for too little change. Lighter cars with softer springs might see a bigger difference in height for a given weight change. FYI my car weights about 2640 lbs with stiffer aftermarket springs.

Since I started this thread I've decided to leave it alone. I like the thought that a raised back end reduces the slope of the rear hatch. The tradeoff is that it increases the slope of the windshield. Overall I've heard the trailing edges are more important than the leading edges, but not by much. Luckily the transition from the front windshield to the roofline has a gradual taper, so airflow should stay attached either way. Unfortunately it's also the reason I can't see stoplights when I'm first at a light, the curve of the roofline blocks the view! Dang progress

I also like the thought that a higher back end creates lower pressure under the car, which should reduce drag. I know the car isn't lowered enough to keep air from sneaking in from the sides to fill the low pressure void, but I have to take comfort in something!

MetroMPG · 12-10-2006, 08:41 PM

Don't forget that if you change the car's "angle of attack" with a higher rear end, you also increase the projected area of the car (frontal area). Doh!

DRW · 12-10-2006, 09:24 PM

Quote:

Originally Posted by MetroMPG

Don't forget that if you change the car's "angle of attack" with a higher rear end, you also increase the projected area of the car (frontal area). Doh!

Hmmm... good call. This is good motivation to do a partial bellypan, then lower the back end to compliment it.

red91sit · 12-11-2006, 05:37 PM

Quote:

Originally Posted by DRW

meh, I dunno about that. The spring rate on the rear of my car is 180 lbs/in. So if I add or remove 100 pounds it would lower/raise the back end by .56" My battery weighs 27 pounds, so that would lower the rear by .15" and raise the front by less than .15" , maybe about .1"? Nah, too much work for too little change. Lighter cars with softer springs might see a bigger difference in height for a given weight change. FYI my car weights about 2640 lbs with stiffer aftermarket springs.

Since I started this thread I've decided to leave it alone. I like the thought that a raised back end reduces the slope of the rear hatch. The tradeoff is that it increases the slope of the windshield. Overall I've heard the trailing edges are more important than the leading edges, but not by much. Luckily the transition from the front windshield to the roofline has a gradual taper, so airflow should stay attached either way. Unfortunately it's also the reason I can't see stoplights when I'm first at a light, the curve of the roofline blocks the view! Dang progress
I also like the thought that a higher back end creates lower pressure under the car, which should reduce drag. I know the car isn't lowered enough to keep air from sneaking in from the sides to fill the low pressure void, but I have to take comfort in something!

This might be able to help with that.