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Old 10-14-2017, 09:39 PM   #1 (permalink)
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I'm thinking about lowering my Civic

I am thinking about lowering my Civic about 2-3 inches with lowering springs. How much would and why would lowering affect my Cd? It would probably not affect it much, if at all, but I am an idiot when it comes to aerodynamics, so I don't know. My 2005 Civic gets around 30 MPG highway. If I lower it, could I get 31 MPG highway? Thanks.

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Old 10-15-2017, 12:53 AM   #2 (permalink)
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MetroMPG appeared to have success with a ~3 MPG gain when he lowered his Firefly:
MetroMPG's 1998 Chevrolet Metro (Pontiac Firefly) mods & repairs kitchen sink thread

But no promises. You've a completely different car.

If saving $$ is your goal, you will probably have to own it a loooong time in order to offset the cost of lowering it. Especially if someone else does the install, and if you go for an alignment after.
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Old 10-15-2017, 03:27 AM   #3 (permalink)
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I secured a free set of junkyard springs for my 'Coupe and cut them myself, keeping the originals in case it was a fail. I align my vehicles in the driveway myself then get them "officially" checked at shops that offer free alignment checks; they've always been spot-on. So the cost of this mod for me has been nearly zero dollars; some gas for parts running plus my time and effort.

I am pleased with the look, ride (somewhat stiffer) and handling (corners better) of the lowered car. My mpg records and the ever-changing nature of my trips make it difficult if not impossible to make any fe claims for this mod. However it is indisputable that frontal area has been reduced a skosh.
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Old 10-15-2017, 08:51 AM   #4 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
frontal area has been reduced a skosh.
Can you put that in layman's terms for those of us less technically savvy?
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Old 10-15-2017, 04:37 PM   #5 (permalink)
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I'll try... I found out how what appears to be a nice level spot on a concrete slab isn't. By that I mean you can't do before/after lowering measurements from, say, the bumper to the slab and get a decently accurate value; those slabs are wavy. You have to measure from, say, the top of the tire to the fenderwell or some such.

IIRC I lowered it 2" so basically 2 x (tire width in inches x 2) /144 = Af reduction in sq. ft. There may be some additional reduction via the better tucked-in lower control arms too but I haven't looked at that recently.

Incidentally I lowered the car about 14 years ago and kept it that way. It got all new struts at the same time as the cut springs. I did experiment with different front roll bar strengths/thicknesses (I have three of the common ones) and decided to stay with the stock one as I couldn't discern any cornering improvement with the strongest bar but it did induce more ride chop. I installed the softest bar in a 4-door a/t Tempo and 14" wheels (softer bar than stock and larger tires than stock) and that one rides like a Cadillac.

P.S. The new struts were stock-type replacements. They've held up and work just fine.
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Old 10-15-2017, 05:16 PM   #6 (permalink)
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Don't lower it more than one or 2 inches. You'll regret that as you go over bumps. A very small air dam in addition to the lowering would help you, most likely.
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Old 10-15-2017, 07:18 PM   #7 (permalink)
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Quote:
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Don't lower it more than one or 2 inches. You'll regret that as you go over bumps. A very small air dam in addition to the lowering would help you, most likely.
Agreed. Also, I'm not sure how the suspension geometry and adjustment ability is on those cars, but usually lowering springs will increase negative camber. If you don't have any camber adjustment available on the OEM suspension, and you lower it too much, you'll have too much negative camber, which will increase wear on the inside edge of your tires. It will also reduce traction and braking grip (but may increase cornering grip if it's not too extreme). You'll probably need to buy camber plates if you lower it a lot, which will enable you to adjust the camber.

Your stock shocks will probably be outside of their ideal movement range as well, increasing the wear on the shocks if you go too low.

The new springs will need to be significantly stiffer than the stock springs so that you're not hitting the bump stops. The lower you go, the stiffer they'll need to be.
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Old 10-16-2017, 02:33 PM   #8 (permalink)
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I have read that cutting springs is not a recommended practice. The spring rate/handling as well as the metals' tempering may be adversely be affected beyond what the manufactures had designed.
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Old 10-16-2017, 04:35 PM   #9 (permalink)
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31mpg? Yes, if only by confirmation bias.

Assuming you stick to paved roads, the lower limit is set by speed bumps and the curb cuts to where they sell cheap gas. It triggers cRIPPLErOOSTER{sp} when people slow down for speed bumps. ...so, watch out.

There are certainly other benefits. If you only lower the front you have a better view.

Further to Frank Lee and twj347's comments: I have Macpherson struts but rear wheel drive on the Superbeetle (so YMMV), but I tried adjustable struts with stock spring rate and stiff as a Cockford Ollie. I combined lowered suspension with 50-series tires in the stock width. And a stress bar:



With the stiff springs if I drove with my elbow on the arm rest in 15 miles my collarbone would start to complain. Reverting to stock rate again ($$$) and the only downside is excessive body roll on those two lane left-turn freeway onramps and ground strikes on the edge of bridges on the Interstate.

To quote the skateboarders, "Let it grind".
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Old 10-16-2017, 11:18 PM   #10 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
I secured a free set of junkyard springs for my 'Coupe and cut them myself, keeping the originals in case it was a fail. I align my vehicles in the driveway myself then get them "officially" checked at shops that offer free alignment checks; they've always been spot-on. So the cost of this mod for me has been nearly zero dollars; some gas for parts running plus my time and effort.
As a skeptic of DIY alignments, I just tried it for the first time. It's not that difficult after all - the real time lasers make it quicker - not necessarily more accurate. I used a set square and digital level to check camber and set squares/ tape measures on the ground.

Are you using tape measures or string and axle stands or?

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