Caster

[cornfedbill]

I am putting the finishing touches on the front suspension of my 1974 Nova. It is a modified stock subframe with raised lower control arm pivots (1" higher than stock). I need to move the front control arm mounting holes rearward to get more caster.

I am thinking of 9 to 10 degrees of caster. The kingpin inclination is nearly 9 degrees. I do not want to lose camber as I turn. I also want a bit heavier feel in the steering.

I have more clearance than most because I have moved my subframe forward 2 inches from stock. I will not be hitting the firewall with the tires at full lock.

What is everyone else doing with First Gen Camaros and Third Gen Novas?

[David Pozzi]

I'd run around seven degrees if you plan on autocrossing. Caster increases in dive due to anti-dive angle of the upper A arm pivot axis in side view, so your static caster can be lower. I see 5 degrees often recommended by suspension parts manufacturers for street use.

[Mean 69]

Are you using the stock spindle - assuming so? As David states, there is interaction that should give you pause at going really steep with the caster angle. In addition to the increase in caster in dive (which can create in addition to other issues bump steer), the stock spindle is rather short, and it's effective length further decreases as you increase caster, which compounds the problem - although slightly could very well be detrimental. Have you thought about an adjustable UCA instead of changing the mounting location?

Mark

[cornfedbill]

I'd run around seven degrees if you plan on autocrossing. Caster increases in dive due to anti-dive angle of the upper A arm pivot axis in side view, so your static caster can be lower. I see 5 degrees often recommended by suspension parts manufacturers for street use.

Thanks for the input. I do not see a lot of autocross in my future. Some, but not a lot. I will be focusing on open road events like the Sandhills Open Road Challenge and the Big Bend Open Road Race. I will use local tracks here in Michigan to get some seat time without upsetting the local law enforcement.

I am running some pretty stiff springs. Also, braking in open road events is less severe than for autocross. There would be very little dive by comparison.

Good food for thought. Thanks.

[cornfedbill]

Are you using the stock spindle - assuming so? As David states, there is interaction that should give you pause at going really steep with the caster angle. In addition to the increase in caster in dive (which can create in addition to other issues bump steer), the stock spindle is rather short, and it's effective length further decreases as you increase caster, which compounds the problem - although slightly could very well be detrimental. Have you thought about an adjustable UCA instead of changing the mounting location?

Mark

Thanks for the reply.

I am using the stock spindles. Yes, they are very short. Based on the modifications to my subframe, tall spindles would necessitate raising the upper control arm pivot quite a bit.

I have given some thought to SPC adjustable upper control arms. I am a bit hesitant. They are good quality. But am concerned about potential breakage. I have heard of them breaking under street duty. Potholes in Michigan can swallow a small car, and are known for damaging suspension components. I am still looking at options.

Thanks for your input.

[Mean 69]

I don't know if the breakage stories are myth or reality. I'd do some things different with an adjustable upper arm personally (and am, for different application), but the basic intent is there. Having grown up in the Chicago area, I know first hand how the roads are in the Springtime!

Goes without saying, but if you plan on doing open road racing, safety is paramount with every detail. Horsepower is easy to make these days and as a result one can build a blindingly fast car, and things can go wrong in very short amount of time. Full cage, fire system, etc. Don't shortcut.

Good luck!
Mark

[cornfedbill]

I don't know if the breakage stories are myth or reality. I'd do some things different with an adjustable upper arm personally (and am, for different application), but the basic intent is there. Having grown up in the Chicago area, I know first hand how the roads are in the Springtime!

Goes without saying, but if you plan on doing open road racing, safety is paramount with every detail. Horsepower is easy to make these days and as a result one can build a blindingly fast car, and things can go wrong in very short amount of time. Full cage, fire system, etc. Don't shortcut.

Good luck!
Mark

Thanks Mark.

We will have all the safety equipment. One because I want to protect myself and my son who is my navigator, and also because they won't let me past the tech inspection without it.

I have seen photos of a broken SPC arm. I have also seen cars on the road with them and no issues. I used to live just up the road from them in Colorado before moving back to Michigan. It may not be a bad idea to revisit the idea. It would sure make adjusting things easier than the stock style pivots and shims.

[USAZR1]

I also considered the SPC adjustables but after seeing photos of two failures in the last six months,and the aftermath, I've decided to go with UMI control arms.

[Mean 69]

Do you guys recall where the failure was, and what the circumstance that caused it was? It's one thing if a part breaks in a wreck, it's quite another if the failure "caused" the wreck. I remember years ago that there was a knock off on the SPC arms that was seriously under-engineered that I wouldn't trust under any circumstance.

[cornfedbill]

Do you guys recall where the failure was, and what the circumstance that caused it was? It's one thing if a part breaks in a wreck, it's quite another if the failure "caused" the wreck. I remember years ago that there was a knock off on the SPC arms that was seriously under-engineered that I wouldn't trust under any circumstance.

One failure was posted here and did not involve an accident. It would be good to know the root cause. Failures can be caused by many things, including improper installation. I cannot remember the thread name or who posted it.

- - - Updated - - -


I also considered the SPC adjustables but after seeing photos of two failures in the last six months,and the aftermath, I've decided to go with UMI control arms.

I will take a look at the UMI parts.

[cornfedbill]

Do you guys recall where the failure was, and what the circumstance that caused it was? It's one thing if a part breaks in a wreck, it's quite another if the failure "caused" the wreck. I remember years ago that there was a knock off on the SPC arms that was seriously under-engineered that I wouldn't trust under any circumstance.

Take a look here: https://www.pro-touring.com/threads/96960-Heads-up-SPC-Adjustable-upper-control-arms-Snapped-on-street-tires-in-the-canyons?highlight=spc+failure

I cannot comment. All I know is what is written in the thread.

[Mean 69]

Got it. Thanks!

[a67]

Take a look here: https://www.pro-touring.com/threads/96960-Heads-up-SPC-Adjustable-upper-control-arms-Snapped-on-street-tires-in-the-canyons?highlight=spc+failure

I cannot comment. All I know is what is written in the thread.

According to that thread the issue was incorrect assembly of the SPC upper arms. Not only were the upper pivot shafts installed upside down, the ball joints were also installed incorrectly.

Bob.

[Mean 69]

I can't see a picture of where the arm actually failed? I did understand that they were incorrectly installed, but not clear what specifically failed. Did I miss something in the thread that stated what actually broke?

[a67]

From post #9 in that thread:

"First off the breakage was caused by vertical binding, flexing the ball joint plate until it fatigued and snapped off."

Bob.

[Mean 69]

Got it, thanks!