Lowering my 01 Corolla...will 1.2-1.3" drop help aero?

[morkys]

I am planning to lower my car when I replace the struts. I have worn struts and I figure if I'm going to upgrade them, I may as well do a mild lowering too to improve handling. Just wondering if it will help my aerodynamics too. I have 195/60R 14 tires that are wider and taller than the stock 175/65R tires my CE came with, but lower than the height of the 185/65R tires than the S and LE models came with. My new tires (as of last year, this year newly installed on alloy rims)....are Evertrek HP from General...a Candian Tire exclusive tire, but basically just a slight variation of the Altimax HP). Also, the tread pattern is a nice smooth, non-blocky design and a stiffer H-rated tire with max 51 PSI. I'm experimenting with PSI. I have new alloy rims that are 1/2" wider than the stock tires, are lighter than the stock steel wheels w and they aren't smooth.

I LOVE the way the car handles with these tires/rims and the front strut brace I installed. I am hoping that lowering my car will help improve aerodynamics, and in particular, offset any of the negatives that the tire/rim combo may have cause, if any. I have to keep records and see how my MPG tracks. I hope to find a good balance.

[cfg83]

morkys -

I think you can do it. Based on this, the 195/60R 14 tires are almost the same size as 175/65R 14(?) OEMs :

(Miata) Tire size calculator

I wish I had done the lowering. I got new KYB struts in November of 2008, and that would have been a perfect time to "spring" for a set of Eibach lowering springs (ha ha). I could still do it, but it would be $200 for the Eibachs + in$tallation + alignment.

CarloSW2

[Deezler]

In my opinion it certainly should help aero to drop the car 1-1.5". Reference almost every "eco" branded efficiency car getting the lowering treatment from the factory.

However to ensure an increase in FE from lowering, I would recommend: Get your under-body flat, and clean up the front end of the car - including a sharp(er) edge at the bottom front, i.e. a lip spoiler / air dam.

p.s. Now that I know you have a corolla, don't go big on the ehxaust! haha.

[morkys]

cfg83...yep, I used many a tire size calculator. The stock Corolla tire size is 175/65R 14 for the CE and 185/65R 14 for the S and LE. The diameter of the tires compare like this:

175/65R 14 = 22.95
195/60R 14 = 23.21
185/65R 14 = 23.46

So you can see the tire is right in between...so overall, the size is not bad. I will get either KYB GR2's or Tokico HP's. As for springs, I am not going for a large amount of lowering, and actually want to keep the lowering to a minimum, if you get my meaning Either Tein H-techs or H & R...both around 1.2-1.25" drop overall.

Deezler,

I will clean up the front and underside of the car. I'm new to lip-spoiler / air dam's...but I'll look into it. I won't go too big on the exhaust. I had a 1989 Ford Probe GT turbo and needless to say, it wasn't great on gas, although, it was nice that you could drive it very conservatively and keep boost very low when driving normally. I installed a complete 2.5" stainless steel mandrel bent exhaust from the downpipe back complete with resonator, CAT and straight-through muffler and it improved my fuel-economy by approx 3 MPG. The boost is controlled by the ECU and the wastegate, so I didn't see more HP, but the increase from 1 7/8" diameter exhaust to a 2.5" mandrel bent exhaust must have removed some restriction to the engine. Anyways, whatever the stock exhaust diameter is, I won't up it nearly as much as I did the Probe....and that's something I'm typing about in another thread

Ok then, I'm going to research front lip-spoilers and smoothing the front and underside of my car. Also curious about tire/wheel fairings

[mcrews]

To get better mileage you have to lower rpm at cruise. That really is the bottom line. I run a 255x45x18 when stock was 245x45x18. It's a little over 3% in diameter larger.

The probe responded to the pipes because of the turbo. they are under-engineered for durability reasons. That 1.8 is not going to like larger pipes

I would focus on air flow after tire size. cleaning up the front and doing under belly pan work is not sexy, but it is the # UNO result getter on this forum.

[mcrews]

I will also suggest that lowering the car WILL reduce the ride quality. And the will be only ninimal increase in mpg. I had lowered my Q45 just 1 inch w/ lowering springs and replaced the with the stocks after 6 months.

If you lower you prpbably will hate the high psi. It'sa trade off. Granted I drive 35-40k a yr so ride is important to me.

[morkys]

mcrews,

Gotcha. Did you lower with the 245 or the 255 wide tires? What springs and struts did you use? Amazingly, using a tire calculator, your 255/45 ratio 18" tires have only a 1/10 th of an inch less sidewall height.

I realize lowering the car will reduce ride quality. I will consider not lowering the car, if but I doit will be as little as possible, mostly in an effort to maintain ride quality. The least I can lower it is 1.2". I started down this path to improve handling, but if a minor lowering improves aero too, then all the better. It may be possible to use coil-overs or otherwise adjustable springs to customize the drop amount, but they are expensive.

If I don't lower my car, I could just upgrade my struts and swaybars. The first strut upgrade option is KYB GR2's which are slightly firmer than stock. Next after that is Tokico HP's, which are firmer, and then after that you get into racing oriented stuff. I could try lowering 1.2" and if I don't like it, I could switch back.

I assume that getting a spring lowering kit that has a more uniform drop front to back is better for aero? Some lowering spring kits lower the front more than the back.

[Frank Lee]

Yeah, I was thinking +3% could almost be within mfg tolerances, or certainly within sizing tolerances among tires of the "same size" between brands... in other words, undetectable?

[morkys]

It's interesting that my car came stock with 175/65R 14 tires while the S and LE came with 185/65R 14.

Plus Zero

My 195/60R 14 is 1.13% taller than my stock size.
A 185/65R 14 is 2.18% taller than my stock size.
A 185/60R 14 is 0.92% shorter than stock...not good.

Plus 1

A 185/55R 15 is 0.27% taller than stock and I'd call it essentially identical.
A 195/55R 15 is 2.1% taller than stock.

So as you can see, there aren't many tire size to chose from that are the same or slightly taller. Shorter is no good as rpm's go up. Too tall = too big.

Sometimes I wonder if I should try a 185/65R 14 or a 185/55R 15 or 195/55R 15. The 185/55R 15 is an intriguing size because it is identical in height to my stock size and would have lower sidewall height, and most likely be an H rated or higher tire, meaning less sidewall flex. Not many tires in a 185/55R 15 size though.

Anyhow, as for lowering, I'll be putting it off a bit, but still researching.

[Frank Lee]

Maybe you'll come across one of the times I mentioned my lowered car vs my otherwise identical unlowered car.