Suspension: Springs

[vintage prep]

Bryan,

You need to lower the front outer (lower) ball joint to keep decent geometry. I've heard that Jack Beck makes modified front uprights with an extended lower portion that uses the stock ball joint. It sounds a little scary, but then I did the same thing to my 64 Falcon vintage road racer and never had a problem. The geometry would not be as effective as the above adaptor mod, but it would be better than stock and it has a stock appearance to the novice inspector

[davbert]

Quote:

Originally Posted by George Willet I hate to disallusion you, but that spacer on top of the arm doesn't change the pivot point. Changing pivot points changes geometry. And it looks from the lower picture that the coil over is mounted on the inner of the ball joint bolts. Not to the spacer. The spacer might be there to change negative camber angle, and widen the track.

[vintage prep]

Like I said, Jack Beck of Orion motorsports has made a more stock appearing version using the original ball joint. $350 per pair exchange.

www.orionmotorsports.com

[genericwood]

I can vouch for Beck's modified uprights. Jack lengthens the lower part an inch and shortens the upper an inch. It lowers the car an inch with practically no change in suspension geometry. Of course, most of us will lower the car further using shorter springs. But the ending roll center will be higher than if you used springs alone. The welds are beautiful and I have never heard of a failure.

The rod end with aluminum block modification pictured earlier , when used with a stock upright will lower the car another 1 1/4 inches or so. But one thing you would want to consider is that it will lengthen the upright 2 1/4 inches unless you somehow modify the upper ball joint. This is probably a little bit more lengthening than you get with a knuckle-riser. You can feel confident with Beck's modified uprights, but I wouldn't go the rod end route unless you are willing to do a lot of research and use a suspension program. It's easy to get some really screwy lateral movement of the roll center if you aren't careful.

Finally, I have been investigating a way to make the upper ball joint location fully adjustable. It involves knocking out the ball joint and boring the housing to accept a spherical bearing. You could then move the pivot up and down to fine tune roll center and camber gain. Better yet, it would look almost stock!

Erik

Quote:

Originally Posted by vintage prep Like I said, Jack Beck of Orion motorsports has made a more stock appearing version using the original ball joint. $350 per pair exchange.www.orionmotorsports.com[/url]

[bryan]

so I'm just starting to really process what you guys are saying... and the front wheel rate ratio is 1:9 approximately. So the factory spring (somewhere between 300 and 385 depending upon who you talk to) would yield somewhere between a 34lb to 42lb wheel rate. And the stock rears are around 70-80. Does anybody else find this a remarkably odd front/rear ratio for a front heavy car, not to mention the unbelievably low rates in general?

[darth dino]

Quote:

Originally Posted by bryan so I'm just starting to really process what you guys are saying... and the front wheel rate ratio is 1:9 approximately. So the factory spring (somewhere between 300 and 385 depending upon who you talk to) would yield somewhere between a 34lb to 42lb wheel rate. And the stock rears are around 70-80. Does anybody else find this a remarkably odd front/rear ratio for a front heavy car, not to mention the unbelievably low rates in general?

[vintage prep]

The motion ratio is 1 to 3.2 with stock steel wheels. Wider wheels with more positive offset would make this ratio slightly worse.

Inboard pivot to the center of the tire is approximately 16". Inboard pivot to spring centerline is approximately 5".

[George Willet]

Hi Paul and All

I have been trying to find something in my books and the web sites to verify what we all believe to BE TRUE!, that the wheel offset has an effect on the wheel rate. So far I havn't found any thing one way or the other. None of the formulas have the wheel dimnensions in them. They seem to indicate that the wheel rate is measured at the outer pivot.

Maybe what we are looking at in our minds eye is the lever arm reaching to the inner pivot (on the lower A arm); but the "pipe we put over the spindle" is really moving a mechinism (upper and lower arms connected by the spindle) and what the outer pivot recieves (wheel rate) is the same amount of force needed to raise the pivot regardlless of the moment arm (pipe) we added.

If we accept this premis, then maybe the spacing of the wheel farther from the pivot would have an effect on the moment arm of the roll center of the chassis, giving the suspension greater leverage against roll.

Well this is my story, and I'm sticking with it At least for now.

[60sRacer]

Good morning George!

I think the load carried by the tires is the same whatever spacer is used - its the weight of the car. So wheel spacers could have a small effect on the force seen at the spring.

I suspect that the formulas all assume that the wheel force is loaded thru the 'kingpin axis' - the axis about which the steering rotates. This can't be far off the ball joints or they would carry a non-axial load that they are not designed to do. Also, the toe in or out and caster forces would be very big.

So there is perhaps an effect of wheel spacers, but the formulas assume that the spacers are to correct the rim offset to center the wheel force....

blah, blah, blah....

Anyway that's my thought of the day...

Robert

[bryan]

Quote:

Originally Posted by vintage prep The motion ratio is 1 to 3.2 with stock steel wheels. Wider wheels with more positive offset would make this ratio slightly worse. Inboard pivot to the center of the tire is approximately 16". Inboard pivot to spring centerline is approximately 5".

[jgates]

How about this for a theory for wheel rate. Wheel rate is the spring rate divided by the square of the leverage. The leverage is the movement of the spring divided by the movement of the wheel. Easy enough to figure the ratio of the ball joint to spring ratio by measuring tape. The contact patch movement is defined as an arc with the center at the instantaneous center. The ball joint is part of the definition of the instantaneous center. The ball joint moves at a ratio to the wheel defined by the distance from the instantaneous center to the ball joint, to the distance from the instantaneous center to the contact patch. Gonna be small, maybe .95 or so. Apply this to the ratio of the ball joint to spring to inner pivot ratios, and a wheel to spring ratio can be figured. Of course this changes slightly as the suspension moves, but that should be left to someone who actually passed in calculus.

John Gates
Enumclaw, WA
'65 Spider Arrugginito

[vintage prep]

George,

If you want to prove it to yourself, put the car on jack stands, remove a front wheel and Jack the car up by the ball joint, measure the wheel travel between some point on the hub and the top edge of the fender (at lift off from the jack stand), then jack the car up with the jack under the outboard edge of the hub (carefully) and measure the wheel travel. The distance measured to the fender should be less when jacking the hub (indicating more wheel travel hence more spring compression).

Bryan and Dion,

I don't understand the 9:1 or 10:1 ratio you are talking about, did I miss something?

PS I hope I'm not having a Homer Simpson moment, Doh!

[darth dino]

Quote:

Originally Posted by vintage prep Bryan and Dion, I don't understand the 9:1 or 10:1 ratio you are talking about, did I miss something?