90's Touring Car Front Macpherson strut? What am I looking at? Toyota's Superstrut?

I was reading up on JGTC and Asian Touring Cars, and I just saw a recurring mysterious front MacPherson Strut layout.

As you know, Mac Struts look simple AF.  There's a balljoint at the bottom, there's a strut top... uhh... up top... and it is at those two points where the whole assembly turns.



The new Civic Type Rs have a different steering axis from the upper strut top and lower balljoint, but even that is still simple to understand with a diagram.

But lately, I've been looking at some 90's JGTC and 90's Japan and Asian Touring Cars. Notably the SW20 MR2 in GT300 class for JGTC, and an AE101 Sedan in Touring Cars.
 

They both have this thing going on in the front end. And honestly, I'm not sure what I'm looking at.


My guess is that it's Toyota's Super Strut, but adapted for racing using billet parts. But honestly, I don't even really know how Toyota's Super Strut works, and what its advantages are. Furthermore, I guess it reveals another thing about Touring Car and JGTC rules: You can adopt a suspension you didn't have on that specific road car you're racing, as long as you have it on "a" road car you have. To my knowledge the AE101 sedan and SW20 only ever had basic MacPherson struts, and did not have limited editions with super struts, but the ST205 Celica GT4 definitely had. Edit to add: AE101 20V 2dr Coupe also had Super Struts.

page:
Toyota's Super Strut, and why I have trouble visualizing it.
https://global.toyota/en/detail/7829158






 

Ok. This animation works better than the drawing I guess.

https://www.youtube.com/watch?v=4t375GCEyIU

Oh snap!  Youtube to the rescue

https://www.youtube.com/watch?v=y4uBKQyXzck

Too many balljoints. Looks like a nightmare during suspension refresh time.

Seems like a really weird way to raise the roll center without affecting the steering axis inclination.  If I'm reading it right and picturing how it affects track width vs a regular strut setup.

From what I've heard of the superstrut suspension is does handle better than an ordinary macstrut, but it was only tried in a few JDM oddities and there is that ridiculous number of balljoints and bushings to service. If JGTC teams are running them that again suggests that they work. It's supposed to have a better camber curve and steering geometry than a macstrut but with similarly tight packaging.

The new Civic Type R's Dual Axis Strut suspension looks similar but works in a very different way, it looks like the wheel camber is still locked relative to the angle of the strut as with a conventional macstrut setup and unlike the superstrut setup, but it separates all the steering geometry from the strut angle. Superstrut does the same thing as well, so you could look at the Dual Axis Strut as a simplified Superstrut.

In reply to GameboyRMH :

I'm a suspension geometry nerd so all of this is utterly fascinating 

You can get most of the benefits of the Toyota setup from simply moving the top of the strut inboard.  That makes the camber curves more favorable for sporting purposes, reduces scrub radius if you move camber back by adjusting camber at the knuckle, and raises the roll center a bit.  But there will be an increase in steering axis inclination, which may not be favorable, and you run into packaging limitations.

The nice thing about the Toyota setup, as well as the separate kingpin setup used by Honda, as well as the 2nd gen Focus RS and optional on the Buick Regal GS, is that it all bolts in to the standard pickup points so the cars can all use a common tub and subframe.  That's even more important from a mass production standpoint.

And yes, when the bushings wear, everything goes to hell alignment wise.

I finally found a camber curve graph, complete with comparisons to Double Wishbone and normal MacPherson Strut.  Yay!  The Japanese YouTube link had one, but I didn't understand the values and it did not have comparisons.

https://lamertonsimulation.com/kinematics_super_strut.php

Actually interesting how much of a linear straight line it is.

In reply to randedge :

My mind wonders how long a piece of string is, too   Some MacStrut suspensions gain an amazing amount of negative camber in compression because of how acute the control arm/ball joint/strut top angle is.  Some don't.

Likewise, some wishbone setups have really sharp camber curves, I am thinking of the 86-89 Accords.  For the next generation Accord, Honda made the camber curve much closer to that of a strut car.  Later when rising beltlines eliminated the whole reason Honda was doing that, they just went back to struts.

And then there are all the older American cars with inverse curves... camber went negative in droop and positive in bump.  They really really wanted your car to understeer at the limits.

What I think of when I hear superstrut.

In reply to randedge :

While the Super strut model claims to be based on measurements from an actual car, they simply state the Mac strut and double wishbone as being a generic 'standard' model for each type. From what I see there, neither is 'optimized' for our purposes in any way, and both are at what I would consider opposite design extremes. It's very conservative for the Mac strut and very (overly on a front suspension) aggressive for the double wishbone. Better optimized, all 3 would be much closer to each other at the 0.04m mark. So few real conclusions can be made by comparing the values and angles directly to each other. The most meaningful and interesting takeaway I see is simply that the Super strut line manages to curve down like the double wishbone, rather than up like the Mac strut.

In reply to Driven5 :

Macpherson strut suspensions don't curve up until the control arm-balljoint-strut top angle goes past a right angle.   Before that, the angle of the strut (which the wheel is attached to) is still moving towards negative camber even as the ball joint is moving inward.   For this camber curve reversal to happen you tend to need a combination of very short control arms and very wide strut top spacing.

Which are, admittedly, both hallmarks of the space limitations imposed by a transverse drivetrain.

One eye opener when trying to cram Subaru GC/GD suspension geometry into a Mini R50/R53 chassis was that the Mini's ball joints were two inches closer together, and the strut tops were something like six or eight inches further apart.   To do it "right" would have required making new strut towers entirely.  Subarus have excellent camber curves as strut cars go, Minis not so much.

In reply to Pete. (l33t FS) :

Curve up as in the overall direction curvature, not the angle of the the curve relative to horizontal at any given location on the curve. Not sure what a better term is, but even when it's angled down, the Mac strut line is curving less negative and more positive. The double wishbone and Super strut both do the opposite.