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Discussion Starter #1 (Edited)
For Suspension Geometry Expert!

How would this affect my handling? Pictures link below:

photos.yahoo.com/[email protected]

under "87 MR2"

The driver side is a hybrid suspension from part '85 and part '87. (knuckle and strut is '85, suspension bracket is '87 .. tie rod is half '85 and '87 to it can fit)

The passenger is a standard '87.

Notice the angle of the tie rod .. standard 87 is similar to any mr2 angle.

The hybrid is at the opposite angle and that's why I ask .."how would this affect my handling?"

To cut down on stupid questions I know people would ask:

Why do you want to use 85 suspension part when the 87 is fine?

Ans: I used to have an '85. The suspensions on it were H&T bushing, ST spring and Koni yellow shocks. Since I couldn't sell it (didn't accept lowball offers), I decided to install it on my 87 even I know there are some differences (IMO, there is ALOT of differences). (Front went straight in. )

I couldn't use the 85 suspension bracket since only 2 of the 4 bolts line up .. as a result, I forced to use the 87. I'm also forced to use the 85 knuckle since it will only fit to the 85 strut. The tie rod near the knuckle is 85 but the other end is 87 because the 87 is wider. Lower control arm and strut rod is 85 (it had the bushing installed already so I didn't want to swap it) but it's the same as 87

Su
 

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I viewed it twice. Since you're making the tie rod longer than the suspension arm you are going to steer your rear wheels in compression. It should toe them in making it understeer more.
 

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Discussion Starter #4
Red 20V said:
I viewed it twice. Since you're making the tie rod longer than the suspension arm you are going to steer your rear wheels in compression. It should toe them in making it understeer more.
Actually, when I was bouncing the car on the hybrid suspension, I notice it toe out under compression. When I was bouncing the standard '87 suspension, it toe in under compression.

I will need to look at a standard '85 but I believe an '85 will toe out under compression.

Su
 

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The hybrid suspension is seriously jacked up. You want both arms to be parallel to eachother (or at least really close) for starters. The way it's setup on the hybrid one will give you massive toe out on compression and massive toe in on rebound. To understand how this happens, look at the arcs that the control arm and the tie rod swing as the wheel moves up and down. Know that when the line between two pivot points is horizontal, the outboard point is at it's furthest horizontal distance from the inboard point.

Now, as your suspension compresses, the control arm becomes more horizontal, pushing the lower part of the knuckle (and the center of the wheel) outward. At the same time the tie rod becomes less horizontal, thus pulling the rear of the wheel inward, creating toe out. Under rebound the opposite happens: the control arm becomes less horizontal and pulls inward on the center of the wheel, while the tie rod becomes more horizontal, pushing outward on the rear of the wheel, creating toe in.

A good rule of thumb is: the angle of the arm dictates whether the outboard point on the arm is going to move inward or outward when the suspension moves in a given direction. The length of the arm dictates how much. The relationship between the tie rod and the control arm is what causes toe in/out (what we call "bump steer") as the suspension moves.

You either need to go with an '85 inboard mount, or go back to the '87 outboard knuckle. Do not drive it with the hybrid setup. If you can actually SEE the car toe in and out as you push on the suspension, it will be dangerous to drive on the road. We measure extreme toe as about 1/4" of movement (1/8" on the front of the wheel and 1/8" on the rear), or about half a degree. I'd be willing to bet you're watching the front or rear of the wheel move 1/2" by itself (1" total toe change) when you bounce the car. You will wear tires like mad, and the back end will be very, very loose under throttle.
 

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Randy is right. I'm dealing with the same issues using a 93T front knuckle arm on the front of my MK1. Just lengthening and bolting up the MK1 steering arm to the MK2 knuckle gave a similar seriously "jacked up" geometry with about 1/4" of toe change (per side!) per 1" of suspension deflection. I couldn't believe how unstable and darty the car felt on the first (tenative) test drive.
 

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We here at G.R.P. , believes in what it takes to make it work, for as cheaply as possible. But!!! Yes, Buttt! The engineers at Toyota hired some very bright individuals to help them design a suspension for the toyota sports car that sold nearly unchanged for four years. G.R.P. does design and modify parts, but never have we change the geometry of the suspension. If it aint broken yet don't fix it; just strengthen it, but don't change it!! If you are going to try and make parts fit, use the parts that toyota thinks will fit, or some that are nearly dimensionaly identical. Sorry, we don't approve of drastic suspension dimension/angle changing. I don't belive what you are trying will safely offer you any performance.
 
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