Putting together 83 Reynard Lego set - Suspension question

[bucko3the7man]

I am at the point where I'm putting suspension back together on the car after removing all of the rust, priming and painting, and replacing most sphericals. The previous owner labeled nearly everything in baggies with decent instructions, but did not have pictures to provide me on how the car was before he disassembled it. Mostly I've been able to find answers on here as well as in picture references from Jason Fair, who also has an 83 Reynard and I've been lucky enough to have him send me lots of pictures when I've been unsure so far. In this case, he did not have the same spacers as me and thus I'm left with a choice.

I'm putting the front lower A arms on and the instructions I got were "Front bolt long 2 spacers Rear bolt short 1 spacer". Jason's car has two spacers sandwiching the sphericals, but with mine I get the choice of putting one spacer either above or below the spherical (and one seemingly superfluous spacer on the front?)

Unfortunately this diagram did not show the two joints I am talking about here - https://www.apexspeed.com/forums/sho...l=1#post623342

I'm building this to compete in CM autocross, and am curious how each of these choices will impact suspension geometry. From what Jason has said, I should make the suspension such that it gets to move pretty freely, and really use the mechanical grip that the car provides. I am planning on getting Anze 7500DA penskes and would like to be able to provide motion ratios prior to ordering them, this choice will impact those and I'd also like to generally understand what this choice will change for handling.

pictures here: https://imgur.com/a/vesvXks

[David Ferguson]

The height of the forward and aft inner A-Arm pivots will not alter your motion ratio, but it will affect the amount of "anti-dive" geometry. While covered in Carroll Smith's Tune To Win, it not clear if you want more or less.

This will be one of the tools you can use to tune the dive under braking. Certainly a case where autocross and road racing might have different directions.

[Dave Petzko]

This is from the 83/84 Reynard tech manual:

"The front wishbones are simple to fit providing fit the anti-dive spacers first, in
the proper place. The front anti-dive spacer is inserted above the Rose joint, and
the rear anti-dive spacer is inserted below the Rose joint."

Rose joint = rod end.

I had an 84 Reynard and don't recall having a split spacer on either the front or rear A-arm leg...but that configuration would allow you to fine tune the anti-dive. As David said, "autocross and road racing might have different directions". I road raced only so probably higher speeds and harder braking that might require more anti-dive (pure speculating as I have zero experience with autocross).

If you don't have the tech manual, PM me your email address and I'll send. The manual does a pretty good job discussing how to assemble an 83/84 Reynard.

[bucko3the7man]

This is from the 83/84 Reynard tech manual:

"The front wishbones are simple to fit providing fit the anti-dive spacers first, in
the proper place. The front anti-dive spacer is inserted above the Rose joint, and
the rear anti-dive spacer is inserted below the Rose joint."

Rose joint = rod end.

I had an 84 Reynard and don't recall having a split spacer on either the front or rear A-arm leg...but that configuration would allow you to fine tune the anti-dive. As David said, "autocross and road racing might have different directions". I road raced only so probably higher speeds and harder braking that might require more anti-dive (pure speculating as I have zero experience with autocross).

If you don't have the tech manual, PM me your email address and I'll send. The manual does a pretty good job discussing how to assemble an 83/84 Reynard.

Thank you very much Dave! PM sent.

[Gary Godula]

We have modified our 88 Reynard for zero anti-dive and zero anti-squat for autox, and we run the same configuration for road racing. There simply is not hard enough braking to demand any anti-dive and not enough excess power to require anti-squat. Without any real aerodynamic downforce, the need for extreme platform stability does not exist, so using anti-dive and squat geometries, with a mild compromise to suspension movement, to control the platform is not a justifiable compromise, IMHO.

If you look at the cars closely, you will see that most modern FFs do not utilize anti geometries, although their FC counterparts do for aerodynamic purposes.

[bucko3the7man]

We have modified our 88 Reynard for zero anti-dive and zero anti-squat for autox, and we run the same configuration for road racing. There simply is not hard enough braking to demand any anti-dive and not enough excess power to require anti-squat. Without any real aerodynamic downforce, the need for extreme platform stability does not exist, so using anti-dive and squat geometries, with a mild compromise to suspension movement, to control the platform is not a justifiable compromise, IMHO.

If you look at the cars closely, you will see that most modern FFs do not utilize anti geometries, although their FC counterparts do for aerodynamic purposes.

Thanks for the autocross insight Gary. Based on Dave's comment above, it sounds like the factory calls for pro-dive in the front. (spacer above the joint in front, below it in rear). Do you think I should just do that, or leave them at the same height?

[Gary Godula]

I would not set the front suspension geometry up with either pro-dive or anti-dive. You basically want the lower A-arm attaching points to be parallel to the front rocker pivot axis as viewed from the side. On our 88 Reynard, we aligned the front rocker pivots to be parallel to the chassis top and bottom rails (which are parallel), and then adjusted the lower a-arm mounts to be parallel with the bottom chassis rail.

Verify that the rocker pivot axis is parallel to the side of the chassis. We did this by inserting 4' long x 1/2" diameter steel rods thru the rocker mounts and positioned the sheer plate and rear rocker pivots so that the steel rods were parallel to the chassis and each other both in the top view and the side view. Any play in the sheer plate mounts might lead to the rocker pivot axis to not be aligned with the chassis or each other. Then we position the lower a-arms so that the mounts were parallel to both the steel rods and the chassis.

It is easy to make new spacers as needed to adjust as necessary on your Reynard. I would assume that the spacers would be the same for both a-arm mounts on your car. Since both the front and the rear a-arm mount heights can be adjusted on your car, some revision and development of the suspension geometry is possible with minimal fabrication. On our 88 Reynard, Keith Averill revised the lower a-arm rear mount to allow for a zero anti-dive mount as the original non-adjustable mount location had significant anti-dive as the car was originally constructed at a SF/FC/F2000 car and anti-dive was desired for that application.

Please let us know how this works out on your car.

[Gary Godula]

After spending more time looking at the pics, it appears that the front roll center on your car is most likely higher than on Jason's due to the spacer differences as currently assembled. I do not know if that is good or bad.....both the front and rear suspensions would need to be modeled and analyzed to make that assessment. I would continue with the assembly as is and go from there.

At some point, all of the suspension points should be measured so that a model can be created to determine what the roll centers are and if they could be improved for your application and tires.