Secrets of the Mirage

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Postby twistedwankel » Tue Jan 30, 2018 11:00 pm

Loren wrote: Everything fit PERFECTLY with about 1/4" clearance from the bottom of the ball joint to the wheel
Those front rotors look to be about 7" dia. That's the same size as my old Mustang Shamu. You want the box of Cherios I used for brake pads?
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Postby ImpostorDan » Tue Jan 30, 2018 11:52 pm

twistedwankel wrote:
Loren wrote: Everything fit PERFECTLY with about 1/4" clearance from the bottom of the ball joint to the wheel
Those front rotors look to be about 7" dia. That's the same size as my old Mustang Shamu. You want the box of Cherios I used for brake pads?
This explains so much.
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Postby Loren » Fri Feb 02, 2018 1:06 pm

Took a drive out to get some lunch. Noticed some rattling in the rear suspension. Also noticed that it looks like the rear tires are rubbing on the fenders. Figured I'd better give things a quick look back there.

Rear shock adjuster ring was loose. That was the rattle. Easy fix.

And, sure enough, the rear tires are now rubbing the fenders. They never did it before because the shocks were adjusted such that the rear suspension simply didn't move. It just immediately engaged the hard rubber bump stops, which probably never compressed more than an inch. The tires were probably right on the ragged edge of almost rubbing before.

Now that I've got the shock length adjusted to allow more compression travel, AND I've shortened the bump stop length by an inch... I've got a total of probably 2.5-3" of compression travel. And that's enough to get the tire up into the fender and rub a little bit.

It's not rubbing so much that I'm worried about it. I could roll the baby fender lip (it's only got like a 1/4" lip on it) for a little more clearance. But, instead, I opted to do what I was thinking about doing anyway, and just raise the rear of the car up another half inch, and then run the shocks stiffer. Hopefully, that will keep it from rubbing under all but the most extreme circumstances.

So, that's what I did. 1/2" taller. Dialed the shocks up to 3/4 stiff.

The ride is SOOOOO Smoooooth! (compared to what it was) Even with the shocks that stiff, it feels fine. Not harsh at all.

Still really itching to autocross the new setup!
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Postby Loren » Sat Feb 10, 2018 11:46 pm

Well, not an overly dramatic "reveal" today. The car performed as expected. Definitely feels better. Didn't get any photos or video of the front suspension in action. But, Joe Brannon said he was watching it in some of the more severe course segments and didn't see any wheel lift. So, that's good.

Hard to say if I was any faster based on today. The course was a fast "power course", which is not what this car is good at. And I ran the event with 7/8 tank of fuel because I filled up yesterday. Never checked the tire pressures. In truth, the only thing I did besides show up & run was adjust the rear shocks to full stiff.

I'm going to need to learn to trust the car. REALLY trust the car. It'll do a lot more than I think it will.
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Postby Loren » Sun Feb 11, 2018 5:27 pm

In my never-ending quest to find little things to do that will improve the car without going "full modified" on it...

Been thinking about seats. Factory height-adjustable seats are an option. But, they are not present on my base model. I've always felt that the driving position was too high. And, of course, lowering nearly 200 pounds of driver weight (and 40 pounds of seat weight) by a couple inches would help lower the center of gravity... which is a very good thing in this car. It's top-heavy, and 200 pounds is 10% of the weight of the car!

A set of nice leather Mazdaspeed Miata seats came up on the Miata forum this week. And I've been VERY tempted to buy them. Fab up some brackets, and then I'd have better (possibly heavier) seats and a more appropriate height. But, that's gonna cost me $300 for the seats, plus materials and likely some welding on the brackets. Figure $400 by the time I'm done. Not bad, all things considered. But, it's money that I don't need to spend right now. And, the downside is that my seats have integrated airbags. So, replacing the seat loses that (I don't really care much, I wouldn't hesitate to DD a vintage car with no airbags), and I'd have to find a way to cheat the system to ignore the missing airbag and still allow the others to function, and not trip a constant airbag light. That's usually not hard to do... but, it's on the list of things I'd have to do to go that route. (or accept that none of my airbags will work, and put up with a blinky light)

So, first, can we get the factory height-adjustable seats? Sure, we can. Probably around $200 or so for the driver's seat. But, good luck finding a salvage yard that's going to reliably sell you (and ship to you) the one you want with the height adjuster vs the one I already have without it! Could turn into a real pain in the ass unless I could find it locally and lay hands on it before buying it. And they might sell the seat base/bracket/mechanism part separate from the seat. It's possible I could get what I need for $50. Maybe. If was willing to run around searching for it. Meh.

A little research shows that the seat adjuster/slider/base thingy is a separate part, and can be bought from Mitsubishi. That would be easy. But, it's almost $600! I'll pass on that.

Let's go look at the car!

As mentioned, the seats are really tall. But, how did they accomplish this? Can it be modified? Well... yes! The seat bottom is pretty standard. A few inches of upholstered foam on a frame bolted to a pair of adjuster rails. The adjuster rails are mounted to the floor on pedastals. Simple bolt-on 3.5" tall steel pedestals! They can easily be modified or replaced with shorter ones. Too easy. Of course, that would never work... only THREE of the corners are on bolt-on pedastals. The inside rear corner is on a welded-in pedastal. Do I want to hack up and modify that pedastal? Well, aside from "no, I don't"... my class rules don't allow me to do that kind of modification. If it's not a bolt-on part, I'm stuck with it. Grrr.

But... what if I move the rails FORWARD so that I'm not trying to move it down into the location that the non-movable pedestal is in? Move it forward about 3 inches, then I can move it down all I want! The downside: I lose 3" of rearward seat travel. Some quick measurement shows that is not a problem for me! Anybody with significantly longer legs might hate driving my car (because, you know, everybody LOVES driving my car, anyway)... but, it would work for me. I could even work it so that it's more like only 2" lost. That could totally work.

So, what I need to do is create 3 basic pedestal brackets to go between the floor and the seat rail... and one bracket that will bolt to the top of an existing pedestal go down and forward to go under the now lower seat rail. Pretty simple, really. Might not even require any welding... though, I'll probably do some triangulation and weld in some reinforcements to make sure it's plenty sturdy.

Can probably do it with just $15-20 worth of steel. The welding is basic enough that I can DIY in my garage. Should be a cheap and easy project!

I needed another project.
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Suck Less - Drive something resembling a proper racing line.
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Postby twistedwankel » Sun Feb 11, 2018 6:23 pm

Not sure where you are going with the seat thing? I have a complete grey rx8 interior I picked up as a spare and never used any of it. They are standard grey cloth and very supportive. Come with the rails attached and all mechanical. DS has a pump up and down. Assuming it's low enough for you in the full down position? Has all the airbags in them and they were never recalled like the front of the car. Must not be Takita? Might have a blow up tube like on the airplane floation :lol: Concerning esthetics you might not appreciate the plastic pretend rotor in the headrest (hole for belts). I will be happy with $150 for both the front seats.
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Postby Loren » Sun Feb 11, 2018 7:23 pm

Thanks, Doug. That wouldn't be much better than the Miata seats I was looking at. I couldn't trust the airbags to be compatible with my Mitsubishi system (though they very likely would be... standards and all), so I'd still be hassling with the "airbag delete" issue.

Besides, making some simple brackets is a dirt-cheap and easily reversible solution. I just have to remember where I put the original brackets! (in the box with the rear wiper motor and the original control arms!)
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Suck Less - Drive something resembling a proper racing line.
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Postby twistedwankel » Sun Feb 11, 2018 7:39 pm

What did you do with the Fastiva seats? You might as well go all funky nuts. Mike takes off his entire exhaust each event. I hung my extra seats from my tire rack I got from Tire Rack in the missionary position. 8-)
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Postby Loren » Sun Feb 11, 2018 8:03 pm

Ben already offered me the Kirkey out of the FASTiva. Nah, don't want to go that route.

I'm apparently far more lazy on event day than Mike! (or busy... a little of both) I like to just arrive and drive. I don't even like to take the time to check my tires. I'm doing good to remember to put enough gas in it.

I even tried to leave the grid without starting my car Saturday! (and then, because I'd forgotten to start the car... I also forgot to turn off the traction control on my first run)

I'm on the fence about pulling out the back seat. I probably should. That's permitted in Mod. But, it makes the car a lot louder with rattles and clunks from the rear suspension. Even just removing the silly cargo cover over the area behind the rear seat makes it louder.

I should at least fold the seat down when I autocross to lower the CG. (not that the rear seat back weighs anything)
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Postby twistedwankel » Sun Feb 11, 2018 8:19 pm

I'm really trying to wrap my head around a 4dr with no back seat. That's like some sort of sin? If you take the back seat out you have to have Joe weld the doors shut and shave the handles. Also put in a roll cage since no one can get in there ever again. Monkey bars come to mind. Like a play area for people who don't check their tire pressure at least once a month. :lol: Whoa. This car with only two little front doors would make a great flower car for funerals or maybe even a hearst for double amputees? I digress. Oops. Where is the original "course design" for the Mirage? How do you ever know when you have achieved it? Mystery. :read:
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Postby Loren » Sun Feb 11, 2018 8:27 pm

Well, I didn't buy the car because it had a back seat. I bought it because it weighs 2000 pounds. Rear doors and a back seat were purely incidental!
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Suck Less - Drive something resembling a proper racing line.
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Postby twistedwankel » Sun Feb 11, 2018 9:04 pm

I get it now. I bought a three story semi-restored century barn once with 17 acres and they threw in a two story remodeled 1850 house - no charge.
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Postby ImpostorDan » Sun Feb 11, 2018 9:49 pm

Loren wrote:Well, I didn't buy the car because it had a back seat. I bought it because it weighs 2000 pounds. Rear doors and a back seat were purely incidental!
How much weight can you drop without the doors?
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Postby Loren » Sun Feb 11, 2018 9:52 pm

Maybe 100 pounds, but then I'd have to run in R1.
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Postby Rawkkrawler » Mon Feb 12, 2018 8:00 am

Loren wrote:Well, I didn't buy the car because it had a back seat. I bought it because it weighs 2000 pounds. Rear doors and a back seat were purely incidental!
Well according to Doug DeMuro, the back seat is terrible, it has to go! Kidding, I know how much you value his opinion. :)
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Postby Loren » Sun Feb 25, 2018 9:14 pm

Steve co-drove the Endurocross with me in the Mirage. We both beat on the car pretty hard. It didn't complain. We didn't complain. Apparently, I've got enough rear suspension droop travel now that it's not even lifting a rear tire... and the front is totally planted. Woohoo!

Been working on the Bump Steer issue. You can read all about that here.

I still have to make an adjustment to get the toe setting correct. Currently has about 5/8" toe in! But, with the bump steer kit, there is DEFINITELY a lot less bump steer. Really, feels like none. (that could be because what bump steer there is still isn't enough to overcome the amount of toe-in... so it never toes-out)

Have you ever dealt with a poor setup for so long that you got used to it, and when you fix it it feels wrong? That's where I was for the first 5-10 minutes driving after installing the bump steer kit. Bump steer is gone. Roll steer is gone. Steering feels curiously LIGHTER and more precise. But, I was so used to turning in and having to turn in MORE because of the toe-out... I blamed it on a weak steering ratio. Nope. And bumps... I was so used to feeling a bump as a movement in the steering wheel that NOT feeling a bump in the steering when I do feel it through the floor and seat... it was a strange disconnect. It's "right", I just need to get used to it!
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Suck Less - Drive something resembling a proper racing line.
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Postby Loren » Mon Feb 26, 2018 5:01 pm

Did a little final tweaking on the bump steer kit and got the toe adjusted to zero and the steering wheel centered. Feels good man.

Actually, I think I might go with a tiny bit of toe-IN. Why? Because I do still have a tiny bit of bump steer. It doesn't feel bad, but it actually felt better with a little toe in. Why? Because with a little bit of toe-in, when the bump steer tries to make it go toe-out, the result is very near zero toe. You FEEL the bump steer less.

But, the big difference is... when you turn into a really tight turn, it feels PRECISE. You're not guessing how much steering to put into it and constantly adjusting depending on how much body roll is happening. It's very consistent and just has a light & nimble feel about it.

I like it. I like it a lot. Would have really liked it on those turn-arounds on the Endurocross course. But, USPS had different plans.
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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 Native » Mon Feb 26, 2018 6:16 pm

Nice work, Professor!
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Postby Loren » Mon Feb 26, 2018 9:36 pm

Thanks, Steve!

After driving tonight, I'm definitely going to add a tiny bit of toe-in. It's subtle, but the car feels just slightly darty as it is. And I actually feel a hint of torque steer for the first time ever. (no, really!)

The Yaris was this way, too. The car was almost undrivable with any amount of toe-out at all. Still annoyingly darty with zero toe. It required some toe-in to feel right. Similarities between the cars: identical basic suspension design, very short wheelbase, fat tires, and electric power steering.
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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 » Tue Feb 27, 2018 9:35 pm

Here's a good max-G photo from the Endurocross.

It shows a lot of interesting things. Front camber is sufficient to keep the contact patch flat on the loaded tire. (this jives with data in the suspension simulator widget... it says that with -3.2 degrees camber at 4 degrees roll, I should have zero camber) Body roll is maxed out at 4.5 degrees. Rear wheel is only lifted about an inch. And most importantly, the unloaded front tire is obviously very light... but it's not lifting.

Would be good control the weight transfer a little better, maybe reduce body roll just a little more. I don't think doing anything else in the rear would have much of an effect. Stiffer rear bar would just cause the inside rear tire to lift quicker. But, once it's up, roll resistance transfers to the front. I could put a front swaybar back on. But, given that the car likes to try to lift the inside front tire, I don't want to do ANYTHING that's going to pull up on the inside front tire... which is what the front swaybar would do. The only thing that leaves besides shock adjustment (which I will play with) is front spring rate. More front spring would resist compression and thus body roll. I'm not ready to do that just yet. But, maybe eventually I'll bump it up a little. Front springs are only 224# right now. Probably wouldn't be horrible to go up to 275 or 300. But, stiffer in front = more understeer. So, I probably won't do it before I've fitted wider front tires.

Image
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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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