I couldn't let that statement stand. I just don't like Mac Struts, they aren't 'nice' engineering. If it weren't nearly impossible to design a beam axle with a low enough roll centre, a front beam axle might even be a better bet than a Mac Strut.Originally Posted by Bludger
LOL
was waiting for your post
That's because I'm not all that familiar with the detail of these different suspensions.
I have to assume that one basic design is similar to that of my CB7 Accord, in having a radius rod forming the forward part of the lower 'wishbone', and the other is like that in my nephew's EG Civic, having a lower control arm rigidly attached to and in front of another substantial forging, these two forged components forming the lower 'wishbone'??
If so then as a matter of principle I prefer the radius rod design because the radius rod is loaded only in tension / compression and as a result is reasonably light (less unsprung mass, always good). On the other hand the heavier forged leading arm of the EG Civic style wishbone (from memory) seems to be largely loaded in 'bend', and relies upon it's rigidity in bend to resist deflection of the wishbone (which will be most highly loaded under heavy braking).
This is because the second forging is shaped to allow clearance of the tyre when the inside wheel is turned to it's fullest extent. To make a steel component rigid in bend requires it to be rather substantially massive, or of a rather substanially proportioned hollow section. I suspect that despite it's size, this forging possibly won't be stiff enough to give as high a resistance to deflection as the radius rod probably will...
The problem is that it's hard to package a simple and lightweight radius rod behind the LCA because it will interfere with the amount of steering lock that is possible when the inside wheel is turned, i.e. before it's been steered all that far the inside front wheel will come into contact with a straight radius rod located behind the LCA because the inside wheel needs to turn much more than then outside wheel (because of Ackermann geometry).
The only ways to avoid this are to minimise the Ackermann geometry, minimise steering lock (and thus maximise the turning circle), to attach the radius rod to the LCA half way along it's length instead of nearer the outer end of the LCA (which will massively increase loadings on both the LCA and the radius rod), to reduce the distance between the points at which the LCA and radius rod attaches to the chassis (which will increase loadings on the radius rod), or most practically to use a substantially robust forging shaped to clear the fully turned inside wheel as a substitute for a radius rod.
When using a lightweight straight radius rod, it's easier for steering clearance if the radius rod is located in front of the LCA. The only downside is that a substantially rigid location must be provided for the attachment of the front ends of the radius rods, meaning that a more robust front cross member must be fitted.
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