Secrets of the Mirage

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Loren Williams
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Secrets of the Mirage

Postby Loren » Mon Jan 22, 2018 2:42 pm

I'll just be knocking the high-spots off with the grinder and smoothing things out. Joe did a nice job, it really doesn't need much.

I bought a cheap ball joint and kept it threaded into the sleeve during welding. That prevented any distortion and kept any slag from getting in the threads. It still threads in like butter. 8-)

Not a race car until I do something that can't be undone. This is a spare set of control arms, I can still put the stock ones back on the car. So, this is really no more "race car" than the coilover kit was!

(but, I can get groceries really fast)
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Postby Rawkkrawler » Mon Jan 22, 2018 5:40 pm

100 and 240 grit flap disks on an angle grinder are you best friend, makes things pretty. Great work!
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Postby Loren » Tue Jan 23, 2018 3:30 pm

Flap wheels are cool, but I find them a bit too expendable. So, I did my little bit of clean-up with the bench grinder and "polished" with the wire wheel. Little bit 'o paint, and we have this:

Oh, "snap ring". Sometimes the words just don't come.

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Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
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Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Sat Jan 27, 2018 9:36 pm

Good autocross today. Probably the last on the current setup (should have the new control arms on this week).

What I learned:
1. I really need to remember to turn off the traction control.
2. The car really does put down power better with the rear shocks at full stiff.

I sometimes get lazy and don't adjust the rear shocks. I drive with the rears full soft on the street (and the ride quality still sucks). Sometimes I forget to set them for autocross. Sometimes I just don't feel like doing it. If the car feels "good enough", I'll leave it. Today, I was having traction problems in a couple places. So, I dialed the rear shocks up to 50%. It helped. So, I went full stiff (okay, 14/16... I don't like maxing things out) and it helped even more. Gonna have to commit to that one.
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Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Mon Jan 29, 2018 3:31 pm

:bouncy:

New control arms are installed! The change in roll center is definitely noticable, and feels good. I'll try to explain in a bit.

Image

First, by the numbers:

New control arm and ball joint setup places the outer pivot point about 1" lower than stock, and about 1/4" further out. This raises the roll center from about -0.5" to +3.0". Which should reduce body roll, move the wheel out 1/4" (and/or increase negative camber depending on how I adjust things).

Everything fit PERFECTLY with about 1/4" clearance from the bottom of the ball joint to the wheel. The only difference between the cheap aftermarket control arms and the stock ones is that some of the holes (not the critical ones) are not properly deburred on the cheap one, and believe it or not, there are more welds on the cheap one. Mitsu was trying to save weight and money on this car. There are places where they just welded one side of a joint, and the aftermarket part is welded on both sides. So, the stock part is lighter by that much, and had one less step in manufacturing. Interesting. That's how you make a car lighter, and how you can sell it for less money. Oh, and the factory ball joint doesn't have the snap ring holding it in. It's just a tight press-fit. (one less part, less machining on the ball joint, all replaced with one machine-crimping process)

I checked camber before I started. It was just under 3 degrees, call it 2.95. After the swap, it's right at 3.5 degrees. So, a gain of about a half degree. I'll probably dial that back, but maybe not. I've not been getting crazy camber wear at 3 degrees, even with the trip to Dunnellon, and driving it back and forth to St. Pete a couple times per week. As long as my toe is close to zero, I'm probably okay for the amount of autocross that I do.

I didn't check toe before, but I know it wasn't more than about 1/8" total toe. After, it was 3/4" total toe! (of course, that jives with the change in control arm length) Extending each tie rod end by 1 and 4/6 turns got the toe back to zero. Actually, it has just a breath of toe-out. Like 1/16" total toe. Good.

Didn't bother checking caster. It's not adjustable, and I didn't move the ball joint fore/aft, so it should not have changed the caster at all.

So, that's the math. That's what we've done. NO change in spring rates, ride height, or anything else. Just a significant change in roll center, and a minor change in camber.

Now, the FEEL:

Man, it's hard to explain. A lot of this will be lost to time. Once I get used to it, I'll forget what the difference was. So, I'm going to try to document it as best I can. First, yes, there is a definite difference that you can feel IMMEDIATELY. There is less body roll per the amount of steering input, but there's more to it than that. The body roll is still there. If you hang a turn, it rolls as much as it did before (more or less... probably less, but with larger steering inputs, it's hard to say "how much" less). But, smaller inputs, less roll. More precision.

That less roll and more precision feels really good in transitional maneuvers. But, the car also feels more "composed". This is a subjective thing. "Feel" is really hard to quantify. But, it feels like the front end is more connected to the road.

I can relate it to a caster change in a way. If you've ever played with Caster, you know how more caster angle gives you a sharper steering feel and more steering effort. And less Caster makes the car feel a little numb, but the steering effort goes way down. This sort of feels like less caster. The steering does feel a little more numb in a way... and yet, more precise at the same time.

Sidebar: One of the things I read somewhere (either in the Milliken book, or in one of the engineering forum discussions) is that if you could get your roll center and your CG at exactly the same height, you'd eliminate all body roll. Steering input would generate a force straight sideways. No body roll. As a driver, you'd HATE it because it gives you no feedback. A little bit of body roll is a good thing, it gives the driver's senses something to work with. So, by raising my roll center, reducing my roll couple -- I've reduced body roll, decreased one aspect of the driver's steering feedback, and translated more of the steering input into sideways force at the tire instead of into body roll. It's like a complicated balancing act. I definitely haven't gone too far with it. I have plenty of steering feedback, and body roll is still occurring. But, I can feel that more of my steering input is going into the tires vs. the body roll.

I can also relate it to a swaybar change in a way. You know how when you fit a fat front swaybar, your steering is suddenly WORLDS sharper and you have WAY less body roll? I'm pretty used to that one. This feels a little like that. Steering is lighter, but more precise. Swaybar would make it a little heavier, and more precise. But, there's a strange disconnect. The big front bar feel is accompanied by a change in ride quality. It's not "supposed" to. They say that a swaybar won't effect ride quality unless you hit a one-wheel bump. Well, guess what, you almost never hit a bump with both wheels at exactly the same time! So, yeah... a stiffer swaybar will, in my experience, always be accompanied by a somewhat harsher ride. So, that's the disconnect for me. If this was a swaybar change, I'd feel a lot of the same stuff... better steering response, less body roll... but, what I'm NOT getting is that harshness in the ride. My rear suspension still sucks, but the front... it's buttery smooth! The input and body roll feedback feels kinda sorta like a big front bar would, maybe with less steering effort increase... but absolutely no change in ride quality. Pretty cool.

Just puttering around on the street, so far I think that what the net take-away here will be is that because more energy is being fed to the tires in a sideways direction (rather than body roll trying to lift the inside tire), the front tires are staying more equally loaded. The reduced body roll and inside tire lift will hopefully solve my stability problem and make the car less scary to drive... or to watch. More evenly loaded front tires should increase cornering ability at the same time.

Any way you cut it, this is DEFINITELY an improvement. Very glad I did it so far!
Loren Williams - Loren @ Invisiblesun.org
The "Push Harder, Suck Less" philosophy explained:
Push Harder - Drive as close to the limit of your tires as possible.
Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Mon Jan 29, 2018 5:19 pm

In other news... since I was experiencing a bit of motivation today...

The rear of my car has been obnoxiously stiff and rough riding especially since I lowered it. I was thinking of raising the rear a little bit, but I got to looking at it today and remembered some things.

When I initially installed the shocks, it was with stock springs, and the ride height was WAY outside the range of the shocks. I made up some spacers to effectively make the shock rod a half-inch longer so that it could extend more. And I set the length of the shock body as long as I possibly could. Even with that, there was only an inch of extension available before the inside tire lifted. But, that was the best I could do.

Also, I opted to use the stock bump stops because I was on stock springs. Seemed like a good idea.

When I decided to go ahead and fit the lowering springs and lower the car, it was a rush job. I just did it really quickly and didn't put much thought into it. On the rear, the springs are separate from the shocks. I didn't have to do anything to the shocks (other than pull the bottom eye bolt to allow the axle to drop) to fit the springs. So, I didn't. I put the springs in, set the ride height, and off I went.

So, the situation was... I still had the shocks set up for maximum extension, meaning not a lot of compression travel. AND... I still had the stock bump stops in there. They're 2.25" long! That means I was ON the bump stops, artificially inflating my spring rate, and I was probably running out of shock travel, too. That would explain the overly rough ride over bumps.

The fix: I removed the spacers so the effective shock rod is as-designed, and I put the bump stops (which are only 1.25" long) and boots that came with the shocks on there, too. I also shortened the shock body by 12 turns. I didn't measure it, but that's probably somewhere between 1.25 and 1.5"

Net result, I should have about 2.5" of additional rear suspension travel before hitting the bump stops. For daily driving, I can keep the shocks soft and have a reasonable ride. For autocross, I can dial the rear shocks to full stiff, and it pretty much doesn't move, anyway.

And I could still raise the rear a half-inch if I wanted to make it even better.
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Suck Less - Drive something resembling a proper racing line.
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Postby Rpwolf » Mon Jan 29, 2018 10:46 pm

That's awesome, can't wait to see it in action.
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Postby Loren » Mon Jan 29, 2018 10:51 pm

I can't wait to drive it in anger!

No local events this weekend, dammit.
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Postby Native » Tue Jan 30, 2018 8:52 am

Good stuff.
Be curious to hear more about how it performs "in anger."
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Postby ImpostorDan » Tue Jan 30, 2018 10:48 am

It just hit me, needs some box fenders next...
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Postby Loren » Tue Jan 30, 2018 11:22 am

We're still in stealth mode.
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Postby ImpostorDan » Tue Jan 30, 2018 11:58 am

How many times did anyone get pulled over in the festiva?
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Postby Loren » Tue Jan 30, 2018 12:15 pm

:lol: I don't recall anyone ever getting pulled over in the FASTiva.
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Postby Native » Tue Jan 30, 2018 1:30 pm

...lots of pointing and laughing though...
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Postby jbrannon7 » Tue Jan 30, 2018 2:47 pm

I saw it pulled over once, cause it was out of gas.
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Postby mymomswagon » Tue Jan 30, 2018 4:54 pm

you still won't be able to haul 24 bags of mulch
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Postby Loren » Tue Jan 30, 2018 6:42 pm

It could haul 24 bags of mulch... slowly.
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Postby twistedwankel » Tue Jan 30, 2018 9:16 pm

Loren wrote:I can't wait to drive it in anger!

No local events this weekend, dammit.
They list a double event this weekend Feb 3,4. Maybe one of the Mikes can help get you in one day? Certainly a huge piece of concrete to learn on.
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Postby Loren » Tue Jan 30, 2018 9:22 pm

I know there's an event in Ft. Myers, and one at Sebring, and one up in Jacksonville. None of those are "local" enough for me. I'll just wait until Feb 10.
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Postby twistedwankel » Tue Jan 30, 2018 10:44 pm

I signed up for that one too :thumbwink: There are points involved :contract:

Even tho' I haven't changed anything on my cars. I bet Philip cannot drive the Mirage now. Too stiff.

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