IRS vs live axle

[The Dark Side of Will]

BTW I'll have a Z rear FS this winter - I'm putting Jag suspension under my V 8Z.

Having seen both, I really have to wonder why...

[Series8217]

BTW I'll have a Z rear FS this winter - I'm putting Jag suspension under my V 8Z.

Having seen both, I really have to wonder why...

They're strong and readily available. A lot of kit car (read: Cobra) builders use(d) them.

[Tha Driver]

:salute:
sayonara

[The Dark Side of Will]

Plus, I have *really* wide flares, & don't want to run 14" wide wheels.

Why ever not? :thumbleft:


Cobra builders used Jaguar hardware because at the time the Cobra kit industry started, it was conveniently available. It's also modular... the entire thing comes out as a unit and it's pretty compact. It also rides well even when stiffly sprung because of the very low unsprung weight thanks to inboard mounted rear brakes (why is the only modern vehicle like this the freaking HUMMER?)

The Z's have the R200 diff (Fuji? Mitsubishi?), which is pretty strong. I think there's a kit out there someplace to install the Z32 300ZX R230 diff (VERY strong and has viscous limited slip) in place of an R200.

The Jaguar suspension is an interesting design, but it has a few points I don't like.
The entire suspension MUST be rubber mounted in order to work correctly. The H-arms have hard bearings and track straight up and down relative to the cage. The trailing arms are rubber mounted to the chassis and describe an arc as they move. When power is applied to the suspension, the ENTIRE cage will twist upward on its rubber mounts (almost like a sold axle) in order to load the trailing arms.
I haven't analyzed the geometry, but I don't think there's much camber gain.
The H-arm has the aforementioned hard bearings. At the inner end these are needles that last forever. At the outer end they are tapered rollers that last 30-50K before needing replacement. The outer could be re-engineered to accept the needles like the inner.

Struts aren't bad because they're struts. They're just frequently compromised by other things, like drivetrain components (see 1988 Fiero rear). I thought my dad's V8 280Z handled VERY well and was VERY easy to push to the limit and hold there. He had Koni struts, poly bushings, 14x7 MkII Supra wheels and a very slight rear tire bias.

To make the Jaguar suspension to my liking, I'd hard mount the cage and replace the H-arm & dual coil overs with a pair of lateral links. I'd add an upper trailing arm to better deal with high power... but then I'd have something that looked suspiciously like C4 Corvette IRS.

The Jaguar front is a pretty nice setup. It's rubber isolated in the Jaguar, but can be hard mounted without causing problems. If you use S2 knuckles with S1 calipers, you can increase your front brake rotor size significantly (maybe to as much as 12") and only have to find rotors to fit... The money saved on calipers would get some nice Wilwood 2 piece rotors with custom hats.

[Tha Driver]

:salute:
sayonara

[The Dark Side of Will]

The Jaguar suspension will NOT work well if hard mounted. The hub carrier moves vertically; the trailing arm moves in an arc. There MUST be compliance in the cage mount or you end up flexing the cage or H-arm, which aren't supposed to flex.

There was a somewhat well known twin-engine car built some years ago that used two complete powertrains side by side. It used Jaguar suspension in the rear, but was all but UNDRIVEABLE because it did not use the trailing arms. The cage and H-arms can and will flex to the detriment of your alignment at the rear.

[Tha Driver]

:salute:
sayonara