Three and half link rear suspension (3.5link)

[takai]

Heya guys

I thought i would just post in here as im trying to chase down some info regarding 3.5link rear suspension.
From what i understand this is a more effective setup over the traditional 4-link setup, due to having less lateral binding force. However, i havnt been able to find a huge amount of literature regarding the idea.

Anyone got some links or can explain it better.

Cheers

[Wojtek]

Hi,

Sorry, I haven't heard of a 3.5 link suspension. Can you elaborate please.

Wojtek.

[takai]

So far as i know its a modification on the traditional 4link suspension.

Either through drilling holes in a nolethane bush on the LHS Upper Diff Mount. Or replacing it with a standard rubber mount.

Apparently its to stop binding due to lateral forces (which i thought a panhard rod would do).

[Wojtek]

I still don't understand what is being done, or it's simply too agricultural approach for me to comprehend. I don't think we'd be doing something like this, but like I said, I don't understand exactly what this modification involves. Or more to the point, what is the reason for this modification? Is it simply a band-aid fix to overcome a poor bush design? It just doesn't make sense to me. I think you are basing this on a Toyota Corolla AE86, which has a very common 5 link rear suspension, 2 upper trailing arms & 2 lower trailing arms locating and controlling the longitudinal position and angle of the axle (pitch centre, squat properties), and the 5th link is the penhard rod which locates the axle laterally and determines the roll centre position. Discarding any of these would only compromise the geometry.
Just on the margin, a 5 link solid axle configuration as described above using panhard rod has by design a migrating roll centre, which is less then ideal. A Watts link is much better.
But, I very happy to learn and be corrected... Can you show me a picture?

Wojtek.

[takai]

Mmm, sorry i cant. I know about the inbuilt migration of the roll centre, and i think this is what it may be to prevent in racing situations.

Im certainly no suspension expert, and ive only heard this being talked about at a few events ive been to, and from some other respected suspension people i know. But it seems to be somewhat of a dark art, since they dont know why it works, it just does.

Ill try and dig up more info.

EDIT: this wasnt soley on the AE86, although it was discussed for fixed axle 5-link (as you call it) cars.

[Wojtek]

maybe this was to fix the migrating roll centre... ???
interesting... very much looking forward to more information.

Wojtek.

[takai]

From what i understand from a limited resource base its to keep the traction down during cornering. A limited type of IRS style movement one can only assume. Allowing the side of the diff which is tethered by the panhard rod to slip a bit more up and down.
Completely unsure of the physics though.

[Wojtek]

Originally posted by takai
A limited type of IRS style movement one can only assume.

:eek:

i think it's time for some more research.... for all of us.

Wojtek.