How to convert your Z to coilover suspension

[Guest Anonymous]

If you have been considering a coilover conversion, you might find this web site useful. It explains the theory behind spring rate selection and offers a spring rate calculator. Additionally it has a fully illustrated coilover instructional as performed on a '72 240z.

 

Bregards,

Brian Holdeman

 

Brian's Garage

[pparaska]

Brian, thanks that's an excellent write-up and the spreadsheet is cool!

 

BTW, from looking at the calcs in the spreadsheet, it looks like you assumed the spring rate is the same as the wheel rate. Did I get that correct?

[Guest Anonymous]

Hi Pete,

 

Yes, that's correct. This assumption will make the suspension feel a little softer than as calculated by the spreadsheet. I have assumed that the sprung load is transfered in a vertical direction and through the center of the wheel (as if the spring were setting directly atop the center of the wheel). Obviously, the strut is attached inboard of the wheel and not through its center.

 

The spreadsheet also neglects the hysteresis effects of the control arm bushings. This will tend to slightly counter the difference between spring rate and wheel rate (but not entirely).

 

I should probably make comment that an additional 1/10 of a Hz (i.e. 0.10) should be added to the design frequency to compensate.

 

Bregards,

Brian

[pparaska]

Sorry, it's just the consummate engineer in me, but I'm always going down into the details.

 

I see what you mean about the bushing drag adding to the overall wheel rate.

 

I put my springs in and I get around 1.9, 2.2 Hz. Uhoh... I guess I'll be jiggling around a bit until I get some sense into my head and get lighter springs.

 

Great effort on the springs pages and spreadsheet!

[Guest Anonymous]

Brian ..... I am waiting for your next installment on the transmission mount! Heavy duty info on driveline to trans/diff. phasing angles. Griffin radiator installation is very interesting. Great speedometer analysis! Definitely required reading in SBC V8 into early Zee and one of the better "how to web" pages. My only concern is that the camera or photographs(?) was not up to the quality instructions and directions provided. Excellant site.I gotta get an angle finder now that I got an idea how to use one and where to use it (and what for)!!!!

[Guest bang847]

sorry.. but what is the difference between coilovers and the original suspension? not really mechanically inclined...

[DavyZ]

Excellent info, Brian!! I appreciate the link and the very useful information, with great photos too ,that I can use for my own project.

 

Davy

[Tim240z]

Bang,

The use of coilovers offers full suspension adjustability, from ride height to spring rate. Also, the springs are much smaller in diameter so wider wheels (which would foul with the stock setup) can be used.

Tim

[katman]

Actually Bang the stock suspension is a "coilover" in a loose sense, although technically it is Mcpherson strut whether the spring seat is adjustable or not (actually Chapman strut in the back if you want to get anal about it). Coilover usually refers to a double wishbone or other suspension where the spring mounts to the shock but does not include the spindle. Whatever.

[katman]

Actually Bang the stock suspension is a "coilover" in a loose sense, although technically it is Mcpherson strut whether the spring seat is adjustable or not (actually Chapman strut in the back if you want to get anal about it). Coilover usually refers to a double wishbone or other suspension where the spring mounts to the shock but does not include the spindle. Whatever.

[Guest Anonymous]

Mr. ljohnson,

 

Many thanks! You may be waiting indefinitely on the remaining parts of the motor swap series. I started that long ago, and it keeps getting put on the back burner. Eventually, I would at least like to add the technical information regarding wire harness, gauge & sending unit, electric fan, alternator, etc. modifications.

 

Yes, you're right. Most of the pictures were taken with a 1st generation Sony Mavica (640x480). Additionally, I try to reduce detail to enable a faster load time for those of us with dial-up connections.

 

Brian