So i was reading Jack Yamaguchi's book about the fd3s rx7. In the book there is a very comprehensive break down regarding the suspension geometry of the fd3s. It shows how the toe control functions for the front and rear suspension.

Front suspension:
Basically the 3 main points to look at here are the tie rod end, the upper control arm ball joint, and the lower control arm ball joint. When breaking hard the lower control arm rear bushing (which is liquid filled) seems to pivot on an axis that is related to the front lower bushing. It seems to be on a set amount of movement programed by the density of the materials used for the bushings. The tie rod stays in its place with regard to steering input and the upper control arm uses two sliding rubber bushings. This causes a toe out condition for greater stability. Under hard acceleration the front lifts which also causes a change in toe with regard to the same lower control arm bushings. My point of contention here seems to be in the front lower control arm. If you replace this front lower rear (liquid filled) bushing with say a "super pro" urethane bushing you effectively remove the front suspensions toe control ability if i'm not mistaken. As the front lower arm will no longer be capable of pivoting on a front to rear axis only on an up and down one. That actually seems like a bad thing to me.

The front upper control arms are just what is known as a sliding rubber bushing and should have no adverse effect from being replaced with urethane.

Rear suspension
The rear suspension seems to be mainly unaffected by this because many of the important bushings back there are actually ball joints (basically) and dont get replaced with bushings.

To sum this up, basically it seems to me that if you do replace bushings in these things that you should really leave the front lower control arms bushings alone. It seems to have a really nice purpose.

 

When I did my bushings I checked the front lower, and came to the conclusion that it would not be worth the effort to replace them. They seemed solid, and had zero play.

-Dan

 

i wouldnt think you would need the bushings replaced until 150k miles+

how many miles are on your fd?

 

I agree with the 150k statement. The thing is, i have never had any experience with a dynamic suspension like this. It is completely special when compared to anything else i have even worked on. The only thing that comes close is audi's 5 link front suspension. All the other cars i have worked on dont have as many adjustments on and off compression and rebound. So replacing bushings on non dynamic suspensions is an actual upgrade. Here it is starting to sound like not so much.

 

The only thing I have to say about this is if the rx7 does have this type of Dynamic suspension where it adjusts itself you could benefit from upgrading in the way that YOU will have totall adjustability it will no longer think for you instead you get to tell it what to do with the adjustments you make with sway bar links, toe link, camber plates and anything else you can put under there... For a regular street driven all the time car this is not needed... But if you go to the track and you want to be able to tell your car what to do when its put in certain situations an aftermarket set-up which give you the ability to make everything the way you want it is the way to go... Once you do this you know how to control your car in any given situation because its going to respond the same everytime... I dont think you get this kind of control with liquid filled bushings.

Chris

 

only diff and rear toe links are needed (worn)the car i well built out the box

 

My car has 80k on it, and I definitely felt an improvement. I it could have been the super pro bushings, or it could have been the pillow ***** (which were worn) that made the difference.

-Dan

 

The super pro is softer than the delrin. That being said, I'm sure that there is still some give. It would be interesting to hear from other people who have installed/replaced their bushings and their input driving it on a track.

 

There is no upgrade for the rear lower control arm bushing. Buy new ones from Mazda. These cars seem to go through suspension components faster than the average car. I suspect the stiff suspension and poor quality materials to begin with. At 50k miles most of these cars develop clunks, usually from the rear pillow ball bushings. Replace these with stock parts as well (don't forget new dust seals). For the rest oif the bushings I would do Super Pro or something similar. Delrin works great but it has no give, so you will lose much of that dynamic effect you refer to. Delrin will also transmit more vibration and needs frequent greasing. Even if you have low mileage, the car is still 15 or more years old so the rubber will deteriorate. I did delrin bushings in my last fd at 50k miles, and it made a world of difference. Had urethane bushings been available at the time, I would have gone that route instead.

 

Ihor is my post hero.....he's correct.