GW-Quote on Cat V system

[rohrt]

"Proper negative camber gain for this particular car requires a taller spindle. The stock spindle is too
short even with dropping the upper control arm pivot 1-inch. Negative camber gain is still not
generated, contrary to popular belief."

Well what the heck does that mean? Are they saying the Goldstrand mod won't give you Negative camber?

[Lowend]

If I remember the math right ... The Gmod will not actually produce negative camber under load, it will just decrease (or elminate) positive camber gain under load
By making the spindle taller you are changing the same relationship of angles as by dropping the upper a-arm. Since the a-arm can only drop so far in the mount the taller spindle allows even more angle correction.
BTW the CAT V changes a-arm angle and uses a taller spindle

[David Pozzi]

It's spelled Guldstrand please, the modification is named after **** Guldstrand who originated it.
The Mustang guys do a "Shelby Mod" that is very similar!

If my 67 Camaro rolls 2 degrees in a corner, it loses 1.39 deg of caster, and it has the Guldstrand mod.
BUT, if I brake into a corner and the car dives 1" in addition to rolling 2 degrees, the loaded wheel cambers out only .57 deg.

I see the forum software won't let me say ****, a shorter name for Richard! :)

[rohrt]

Sorry about butchering his name.

[Mean 69]

A little more info on the CatV system. I saw it in person finally at the Del Mar car show, and spoke to one of the guys about the setup (I think his name was Rich, an Asian American guy, pretty nice guy BTW). The spindle they use is a modified B-body spindle, the same as is used in the Chevelle setup that they market. Obviously, the B-body is a front steer car, so the spindle needs to be modified to accomodate the rear steer found on the first gen's. They basically cut the steering arm off, and weld a new piece on. I asked them why they wouldn't go to a fab'd spindle, or a new unit dedicated to the setup, their response was cost and complexity, they just weren't interested in changing from what they offer.

They didn't spill too much relative to the kinematics of the setup, but they did state that the system gains camber basically at the same rate of the C5 cars, which they described as "really" high. I guess it is all relative, the C5's, if I am not mistaken, gain at about .5 - .7 or so degree (negative) per degree of suspension roll, which exceeds the Gulstrand modified cars, but is a lot less than a late model Camaro (which gains at almost twice the rate!!!). The specific numbers I mention here might be off a bit, but you can get a basic feel for what they state the gain is.

Not a bad system overall, hard to argue with the success of it, they sell quite a few of them.

Mark

[galopin]

I talked to Doug N. about it several months ago. He didn't remember specific numbers but RCH is between 2-3" and the system has over a degree of negative camber gain for the first inch of dive (I didn't ask about roll). Part of the negative camber gain comes from the taller spindle, the other is due to shortening the length of the UCA and keeping the LCA at the stock length. He didn't remember RC migration during roll but said that the RC will move laterally no matter what you do, so they concentrated on doing what it took to keep the tire flat.

CAT5 uses the stock pivot points. Doug N. said that it was designed this way because at the time, many of his customers raced in associations that required the stock pivot points.

[dennis68]

Part of the negative camber gain comes from the taller spindle, the other is due to shortening the length of the UCA and keeping the LCA at the stock length. So they sacrifice FVSA for negative camber gain. By shortening an already extremely short UCA I would guess that FVSAL drops to somewhere sub 80" for sure. I wonder how short it actually is.

He didn't remember RC migration during roll but said that the RC will move laterally no matter what you do, so they concentrated on doing what it took to keep the tire flat.
Totally untrue and I have the documentation to prove it, my spindle/control arm design moves RC laterally .010" at 3* of roll and .75* of dive. JP's front suspension was limited to ~.25" of lateral RC migration I believe.

What he meant was that RC migration is eminent if you:
a) don’t understand suspension geometry, how it works, and what to do to fix it or,
b) try to fix it with what is available as a bolt on fix.

Just some necessary corrections, when will manufactures learn to either do it right or sell it for what it is-a bunch of junkyard parts fitted together and hoping for the best possible outcome.