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I have a 91na w/93 turbo swap (including rear suspension setup), soon to have tokico illuminas and tein s-techs. What is going to be the best setup for everyday and the occasional autox. Should I get a front sway bar, crash bolts (just fronts?), or anything else? Also will getting the alignment with in specs of http://web.mitsi.com/auto cross/faq.html result in excessive tire wear?
 

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The MR2 will eat up rears no matter what. The fronts on my car don't wear that bad, and I've run as much as 3 degrees upfront.

It's also my daily driver, for reference.
 

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haha sorry for the almost pointless post, but i just realized that we have almost the exact same car MR2biker91, and we're both 18, well one of us is 19 t'day = )

i also daily drive my autoX car... crashbolts arnt necessary... if you daily drive the car, and you dont want to keep paying to have the front tires rotated and remounted, then you can get a max camber of close to -1.5 which is fairly decent. You might experience a bit of understeer w/ just a front sway bar.. but hey, that might be what you want... um, a custom alignment will make a NIGHT and DAY difference, which is what im running. Be sure to get maximum caster out of the front wheels, which will make the car more stable under cornering... *and that's something that only 91/92's can do stock = )*.

good luck

- Nathan
 

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Be sure to get maximum caster out of the front wheels, which will make the car more stable under cornering...
No it won't, but knock yourself out if you like it.
 

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I thought the increased caster would give more dynamic camber while turning which would give better turn in. If not, what does it do for you ?

John
93T, 88 SC
 

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I thought the increased caster would give more dynamic camber while turning which would give better turn in. If not, what does it do for you ?
Yes, you can get more dynamic camber with more caster. But you don't need more, and in the meantime, you've increased steering effort and screwed up your bump steer and Ackerman geometry. And the alleged benefit isn't sharper turn-in, anyway, it'll do exactly the opposite to your turn-in. The only theoretical benefit is greater camber on the outside front at high steering angles.

And that just isn't worth the penalties. It's worth considering that there might be a good reason why Toyota went to the trouble of re-engineering the front suspension to remove caster-adjustability in '93.
 

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hillman said:
Yes, you can get more dynamic camber with more caster. But you don't need more . . .
It has taken me awhile to realize that this is the crux of the caster argument. If you run enough static camber, then you don't want more camber when the wheels are turned.

It's worth considering that there might be a good reason why Toyota went to the trouble of re-engineering the front suspension to remove caster-adjustability in '93.
Why did they go to a new design when it would have been easy to make the old design non-adjustable? I think their motivation had more to do with possible binding at the leading edge of the strut bar at max. bump/rebound. IMO, adjustability disappeared because it would have added cost to the new design.
 

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i think it would be better to have more dynamic camber instead of more static camber. Why? Straight line braking suffers when you have more static camber. But of course, the most camber that you could gain would be 3 degrees of gain at a 45 degree wheel angle if you have 6 degrees of caster. The problem is, who ever runs full lock? Then again, if you already have 1.5 degrees of camber, getting that extra degree of camber would only need a smaller steering input with more caster. Of course, that gain is small.
One thing that is helped with caster, is steering feel.
FWIW, i flipped the strut top mounts on my 93T for more caster, and i liked it better with more caster.
 

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Dr. Pepper said:
FWIW, i flipped the strut top mounts on my 93T for more caster, and i liked it better with more caster.
IIRC there was a protest on that at Nationals in Es and it was found to not be legal.
 

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i think it would be better to have more dynamic camber instead of more static camber. Why?
In theory, this makes sense. In practice, consider a fast slalom that only requires small steering inputs. You never turn the wheel very far, and never get much dynamic camber, and you probably push. As you said, who ever uses full-lock? Also, I really don't find braking to suffer much until you get over -3 degrees of static camber, IME.

Brakes aren't very important in autocross ( they only slow you down ;) ). You'll gain more time being able to stay on the throttle through one decent slalom than you would sacrificing that for better braking.
 

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StrokerAce said:
IIRC there was a protest on that at Nationals in Es and it was found to not be legal.
it was just an example...just stating my experience with more caster. I don't run in stock. Heck, I don't even run SCCA rules. :) I'm from Canada, eh!
 

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hillman said:
In theory, this makes sense. In practice, consider a fast slalom that only requires small steering inputs. You never turn the wheel very far, and never get much dynamic camber, and you probably push. As you said, who ever uses full-lock? Also, I really don't find braking to suffer much until you get over -3 degrees of static camber, IME.

Brakes aren't very important in autocross ( they only slow you down ;) ). You'll gain more time being able to stay on the throttle through one decent slalom than you would sacrificing that for better braking.
I agree with all of your comments. I was just dishing out more info, wether it be autocross specific or not.
Most regions do not have hard braking zones, but the regions that i race in often do have hard braking zones into a very short stop box, in which case braking is a huge factor. With the relatively light front ond of the MR2, i find that it does make a very noticeable difference in braking power when changing the amount of camber that is being run up front. But like you said, braking doesn't play a huge role on most autocross courses. This doesn't seem to effect the front heavy mustang guys though. :)
 

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I am fixing going to compete in my first autocross within the next month or so. I know that the alignment is way out of wack. I am running the newer wheels I beleive they are 15 inches, with 205 and 225s. I am not worried about tire wear, I am worried about the best performance. My friend goes to an automotive school right now so he can do anything I want to my car for the cost of parts. So what would the ideal settings be?
 

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The real issue on the mr2 is the lack of camber gain from bump travel. Any time you have the wheel turned you also have body roll. Camber gain from caster and camber gain from bump travel go hand in hand. Our MacStrut setup is just this side of horrible as far as camber gain goes. We aren't even close to compensating for body roll, degree for degree, I think it's something like 3:1. Fix that, and caster will become much less of an issue, and 3 degrees of static camber won't be necessary. Once that's done, adjusting the length of the tie rod to minimize bump steer is probably the next step. But this is all outside the realm of stock.
 

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Dr. Pepper said:
i think it would be better to have more dynamic camber instead of more static camber. Why? Straight line braking suffers when you have more static camber. But of course, the most camber that you could gain would be 3 degrees of gain at a 45 degree wheel angle if you have 6 degrees of caster. The problem is, who ever runs full lock? Then again, if you already have 1.5 degrees of camber, getting that extra degree of camber would only need a smaller steering input with more caster. Of course, that gain is small.
You're missing a big part here. And in actuality, I don't think we gain any camber at all when the wheels are turned. I think we actually lose just a little bit. Humor me....

We measure caster as the angle made by drawing a line through the strut top and the ball joint when looking at the car from the side, right? Max caster that we can acheive is somewhere in the 6 degree range. That means that this line is 6 degrees from vertical.

Now, look at the car from the front, and draw the same line from the strut top to the ball joint. On a stock car I believe this line is approx 6 degrees from vertical as well (on my car it was somewhere around 8 I think because of camber plates). Let's use 8 just so we can distinguish between the two. Let's call this angle "A", it's the more important one because it's perpendicular to the wheel. Let's assume angle A is the one always perpendicular to the wheel.

What does this mean? You don't carry the 8 degrees (the amount the strut leans toward the center of the car) with you if you were to turn the wheel 90 degrees (it's not 6+8=14). At 90 degrees the 6 degrees of caster becomes your angle A and the 8 degrees of your old angle A becomes your caster. At 90 degrees you actually LOSE 2 degrees of "camber". So, if we assume lock is at 45 degrees, you would take the average of the two (6+8)/2=7 to get the new angle A, which in this case results in a net loss of camber of 1 degree.

I don't think we gain any camber related to caster within our stock adjustability range. I think all we are doing is minimizing the camber loss by adding more caster. Adding more static camber via crash bolts doesn't effect this loss (doesn't change the angle between the strut top and the ball joint), but adding more camber via camber plates does because it increases angle A when the wheel is pointing straight, causing the delta between angle A and caster angle to grow greater, meaning more loss of angle A (camber) per degree of turn in the wheel.

On the flip side, camber plates do a good thing by increasing angle A: they increase dynamic camber gain related to bump travel/body roll. They effectively shorten the "upper arm" if we were to imagine our suspension as double A-arms. Race cars use the length of the upper arm in this way to control camber gain relative to body roll.

The question I'm battling with now is: when I increase angle A with camber plates, do I also want to push the camber plate rearward to increase caster as well, and why? I'm wondering if my ideal camber plate would actually have a 30 or 45-degree slot in it (sliding inward and rearward) vs. the popular setup where it only slides inward.

Please think about this guys and poke holes in my reasoning where necessary. These are all new discoveries for me and I haven't completed the full circle of reasoning in my head just yet, in case it wasn't obvious ;)
 

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I dunno, Randy, that sounds pretty plausible. A showroom stock road racer had suggested to me that I would get more camber in turns by trading static camber for caster on my Miata. So when I took my car to Jack for an alignment, I asked him to give it a try. He was skeptical, but humored me. With the wheel turned like I was going around a corner in an autocross, he fiddled with the alignment cams. Nothing he did resulted in an increase in camber over what was there with the suspension set for maximum static camber. I thought that it was odd, but I think you may have found an explanation.
 

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Randy,

Jesse wanted me to take a look at this and so I'm throwing in my 2 cents.

You've just discovered k.p.i. king pin inclination..... angle (I wonder why it's not kpia...). Anyhow, it's been a while since I mucked with this stuff, but I believe kpi tends to camber a wheel positively as it turns either direction, where as the caster angle tends to negatively camber the outside tire and positive the inside. Had I known any mathmatical relationship between kpi, steering angle, caster, and the billion other variables, I would have long forgotten them. Since I'm racing a stock car with very limited amount of prep that can be done, I don't care enough to look it up, all I know is general trends. I do know that kpi also increases steering effort since it is pushing the wheel down, the weight of the car tries to center the wheel (though I think caster is much more effective).

As far as what I think one should do for "setup" with this info? In the case of autocross with a car that lifts the inside front, fcc be dammed, but it doesn't f'n matter what that inside wheel is doing as long as it isn't hitting a cone. Braking, though handy sometimes, isn't a big deal in autocross... especialy in an e-stock car. The problem with trying to build camber with caster is that it is corner speed sensitive... a high speed corner, you don't turn the wheel that much, but you do in a hairpin. Ideally you want to pull the same amount of G's and thus get the same body roll, but in one situation you could have more camber than the other. I think the easiest and 95% effective solution is to run less camber and a _____ load of roll resistance. If you try to up the camber gain curve then congrats, you know have 6 degrees of camber when the nose dives when you hit the slow pedal.

Too bad pizza delivery makes it fiscally unadvisable to build a street-mod car, it would be fun... but I'll have a degree soon enough..

BTW no one here probably knows me, my name is Jim... and I'm codriving with Jesse again this year.

p.s. technically kpi may be the total angle of inclination, thus some math relationship that I've forgotten between caster and you angle "A"... pathagoreon theorom or something... not too sure though

edit: sorry about the bleep... I cussed, I tried to be creative and get around the bleep but it got me... let me just say it was a "boat" load of roll resistance
 

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Oh so to answer your question... I think crash bolts are a better way of changing the camber... if you want to mess with kpi, caster, and suspension geometry then strut tower plates are handy.
 
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