Stop and think about it. Over time....the cradle collapses and when the front end is being aligned.....the shims for the upper A-arms are removed...so the upper A-arm is pushed back out to set the camber/caster. Over years and years...it can get to the point that there are NO SHIMS at the four upper A-arm shim points. THUS...the car can no longer be aligned.

SO...to answer your question...the dimension gets shorter...or tighter. And the dimensional measurement does not matter as long as you can align the front end...and when the spreader bar is installed...it basically prevents these two upper A-arm points collapsing in on each other any more. And as 'Mooser' stated...it basically stops movement and allows better control when cornering.

DUB

 

So if the a-arms are sagging inwards, do you put a load on the speader bar to push them back outwards over time? If I remember correctly, the instructions for my bar said to install it with slight tension on the arms and leave it. I imagined the benefit would be that it would prevent any more sag but not undo existing sag.

Could we use the an orthodontics analogy and say that a spreader bar isn't a set of braces designed to correct imperfections, but more like a retainer designed to prevent more change?

 

I measured my 73 frame at this area & get 26-5/8". I have no idea why it is greater than the factory dimension.

 

I have read enough good about spreader bars I want one, but I am curious is the more heavy duty VBP worth the effort of welding it for a SBC with mechanical fan. I find it very irritating that VBP cannot find a way to make their system adjustable as Speed Direct has. All they need to do is slot the holes. THere is NOT that much difference in manufacturing tolerance that they could not find a way....obviously Speed Direct did.

But, back to my original question...is the aluminum bar Speed Direct offers strong enough, ...I have heard of no failures, but it would not be pretty if it did!!

 

I suspect such failure would be more common if you try to crank that bar hard to push the arms back up or pull them back in. I understand the bar is not intended to influence alignment specifications, but only to help solidify the alignment values. Removing or installing the bar shouldn't impact your camber (you shouldn't be putting that much pressure on it), but should help your camber remain consistent once it is set.

I think with this in mind, the aluminum bar is probably plenty strong for its application. Please some correct me if I'm wrong on that. I have an electric fan setup.

I have the aluminum bar, but no mechanical fan that might grenade if the bar were to fail and smack into it.

 

DUB - with all this it begs another question - Do you continue to need shims with the spreader bar? I have no shims (at least not that I have found yet in the baskets of parts) so I am figuring I will have to buy a set. Unless they are not needed with the spreader.

 

I have a spreader bar. I took my C3 to a corvette specialty shop for an alignment. There are plenty of shims on my a-arm. The shims affect camber AND caster.

When I went through the process of installing the bar and playing with the tension I was quickly convinced that it doesn't do any actual camber adjustments... more just camber integrity.

 

I installed VBP spreader bar on my sbc. Plenty of room with the serpentine conversion and dual spal fans. I bought stainless steel shims for the front and rear alignments.

 

Yeah, I know about metallurgy, probably more than you. I've been a mechanical engineer for 25 years.

I'm saying that what you're describing wouldn't happen to a car in good shape. If the frame is rusted, then that's the part of the story that you left out.

 

I have a dumb question . Should my spreader bar be on the car during my alignment? Or should I take it of so the a arms can be adjusted correctly and then put it back on?

 

When the shop did my alignment, they loosened up the spreader bar, did the adjustments, then tightened the spreader bar back up while it was on the machine showing the measurements were good.

 

The final measurements should be taken with tension on the bar as it would be while driving.

 

Many years ago I had an alignment done by a well seasoned tech, during discussions with him, he said the '55-'57 chevys were bad for "sag" in the front end. (Not due to rust).
Some were so bad they could not be aligned properly.

His solution was to tie down both sides of the front frame and jack the middle up to take out the sag. He said that worked great.

The front end of a C3 is not that different.

 

By now there have been many opinions on the spreader bar. Most are in favor. I upgraded my 93 RX-7 with front/rear Cusco adjustable shock tower braces about the same time G-Tech upgraded their on-car accelerometer. My skidpad lateral Gs went from 0.95 to 1.15 and the car felt more predictable. The RX-7 has more steel and aluminum in the body and roof to make the car more rigid than the C3, but anything to cross-brace the C3 frame will make the car handle better. Anyway- my $0.02. RA

 

Yeah I've contemplated picking up some tubing and finding a buddy with a welder who wants to make a few bucks and start reinforcing the frame and cross members. I think it would make quite a difference.

 

YOU ARE CORRECT!!!!...and YES...the 'retainer' analogy is correct.

THERE IS NO WAY that this spreader bar will push your upper control arms back into position. The force to do that is very high. The spreader bar is not made for that. The spreader bar will STOP any further collapse...because ...if you think about it...HOW CAN the upper A-arms get closer together IF the spreader bar is installed and creating a basic triangle with the frame???? SO your thoughts were correct as I stated previously.

The cradle could have been stretched. That is what I do to get it back to where it needs to be so shims can be installed again....instead of using an off-set upper A-arm shaft that they make now. I can do it either way depending on the customer...install an off-set shaft or stretch the cradle to the dimension between the upper A-arms is good for shims.

Professionally speaking...I would not worry about what the measurement is..if it is wider...I would not bat an eye at it AND as long as when it is aligned..the nut is not at the end of the END of the bolt. I prefer not to have SUPER THICK shims packs. I would be more concerned with the alignment and if it can be aligned.

If I worried about every dimension that is NOT correct...I would be in the 'funny farm'.

If the alignment needs shims then obviously they are used. You will not know that until the heads are put on it and you read what it 'says' it needs...unless you are going to do an 'old school' alignment with gauges. SO YES...you want to have some way of getting the alignment where it needs to be. SO shims are needed. Then..when the spreader bar is installed...the alignment should stay put for a very, very long time.


"In good shape"???? The percentage of 1963-1982 Corvettes that I work on have SOME form of battle history is high.

RUST OR NOT. IT DOES NOT MATTER.... ONCE AGAIN..I guess you have forgotten about FATIGUE??? Trying to communicate to someone who wants to dispute events that I have experienced and have seen first hand is always a JOY. NOT everybody knows how to correctly support a frame when it is going to be off the ground for a LONG TIME.

And...even though I am NOT an Mechanical Engineer...I have 30+ years in dealing with steel and what happens to it FIRST HAND in a accidents and its properties....and how it has to be repaired. And I KNOW what happens when you have a car on a frame machine and do a pull....and WHY certain procedures are carried out in some areas while not in others. I guess you can tell me ALL about how to repair and straighten an aluminum frame on a Z06....with ALL of your knowledge. Funny thing about some mechanical engineers....they know all about how to build something...but not how to fix it.,,,or better yet WHY they are having to fix something that thy engineered and should be perfect.

I am glad that you are so knowledgeable...and if you do not want to accept what I wrote....then all well and good and you keep believing what you want to believe. I just KNEW that we were going to 'lock horns' on this. I just knew it.

I can not grasp how you still dispute/question this with information given by others that show how these frames are NOT as rigid as some may think. I am just amazed.

DUB

 

I have a question related to this thread: What amount of time is needed to cut a man in half at the waist with a M60 (machine gun). Please make sure your answer is accurate to (+)(-) 0.5 seconds.

And yes....there is a point to the question.

 

I have access to a MA DUCE if you care to be the subject of such a test I will néed someone to operate the timing equipment.

 

Let me google MA Duce.......

WOW.......It must cost about $500 per minute to fire that thing.

Hmmmmm.....50 Ca. ........that would do the job twice as fast!

So..............what's your time estimate on the M60?

(Sorry for the thread-jack!)

 

It's ok DG you said you have a purpose in this!


Quote from DUB
If the alignment needs shims then obviously they are used. You will not know that until the heads are put on it and you read what it 'says' it needs...unless you are going to do an 'old school' alignment with gauges. SO YES...you want to have some way of getting the alignment where it needs to be. SO shims are needed. Then..when the spreader bar is installed...the alignment should stay put for a very, very long time.

Ok then DUB, since my car is a LONG way from being driven to a specialty shop for an alignment, and yet I am wanting to setup as much as possible, should I put in any shims now or just leave that entirely up to the shop (is there one in IOWA???!!) (Will I be living in Iowa when I get it that far?) when it gets to that point? DO I tighten it up except for the upper control arms waiting for them to get weight on them - and is that weight sufficient with engine and tranny or does it need full body weight on it too?

And thanks guys I am learning ALOT!