Mooser

So I pulled the bolt out of one side of the spreader bar (and put in a couple of zip-ties) and went for a short drive around the block.

Road is pretty normal, a few cracks etc nothing major
Car has what I like to think of as a decent frame
Just drove around, didn't throw it into any corners or anything weird, watch the control arm and listen to how little the engine is working...

Here's a couple of sections of the video, You can see the spreader moving in-out around easily around 1/16"+


Now imaging what must be happening when a corner is made with some speed or aggression

I know this isn't a good demonstration or anything but it does show how the top of the frame where the control arms mount can move around even under old-man driving
M

resdoggie

Video is not working.

mortgageguy

I know nothing about SB. Are they intended to compensate for a weak frame, or as an upgrade for a good frame? What are the benifits? Are they needed for a cruiser?

Haggisbash

Doesn't surprise me in the least how much the frame flexes, you can feel it when travelling on our poorly surfaced roads here. I often thought that the original C1 frame with its X member was probably more resistant to flex. If you look at the lengths they went to strengthening the frame for road racing it highlights the issues of the standard item.

doorgunner

Now THAT video is interesting......no wonder some 45 year old frames have cracks in front suspension areas.

Thanks for taking the time!

oldgto

Well, basically, yes. I never thought about it until I started reading about them in the forums. But for about a hundred bucks, why not? EVERYBODY that has one, swears it has improved the ride, so I put one in mine..... even though I`m still building the car.

doorgunner

I accidentally "corrected" the frame sag on my project.....I used a floor jack under the main crossmember to lift the front end.

Now the measurement from rail to rail is within 1/16 inch....I'd better stick a spreader bar in there before it "closes" again.

I did...however....put a nasty concave dent in the bottom of the crossmember.........

(rookies...... )

ignatz

Great video, thanks Mooser. One of the forces that acts on the frame is camber thrust. You can see a correlation between control arm movement and the spreader bar, where I would presume camber thrust to be the major factor here. Any idea how much camber you have?

Mooser

I'm about 1/2 deg neg. but that's set in my garage using strings, levels and measuring tapes. Car needs to go for a proper alignment once I've stopped playing with various things up front.

The car is a big block so there's a lot of weight sitting between those arms but still, flex happens. I'm guessing there would be an easy 1/8"+ movement taking a normal on-ramp.

Hard to believe but when I bolt the bar back in the difference even pulling into the driveway is noticeable somehow.

Everyone says the bars make a difference, I wanted to SEE the difference.
M

7t2vette

Cool vids Mooser.

I am a firm believer in the positive benefits that a spreader bar offers these cars. I drive my car quite aggressively on a regular basis; several years ago I removed the spreader bar to do some other work, and the lack of it was immediately noticeable!!

One of the best "bang for your bucks" mods there is.

Tim 1973

I built one in a few min as part of my frame off.. Very simple to do and I'm sure it will help.

Thanks for the Video

Tim

63Corvette

Most street drivers will never notice it. However, when you put sticky RACE tires (slicks) on a C2 or C3, you will find significant frame deformation and suspension point degradation from spec. This will give you NO confidence in your car placement on the track, and therefoire slower lap times. It "may" also lead to premature (ya know, after 50 or 60 years) frame cracking. Flexing a frame hudreds of times per lap at 1.2 to almost 2 Gee will certainly wear that frame out quicker than on a street driven car. The Owens Corning race team treated frames as "consumables" and replaced them regularly.

CA-Legal-Vette

Great video Mooser. I'm almost surprised that there wasn't more flex. I was shocked at how much my handling and general stability improved when I added the spreader bar. This mod started me down the path of working on my suspension. I love the end result but no I ndividual change was as significant as the spreader.

cagotzmann

When I look at this video I agree it moves, but not enough to effect street handling. If anything suspension travel alone will have more camber change vs the amount this flex in the frame shows. When I did before and after with the spreader bar installed I could not feel a difference until I went out for a track day. And even then I am not sure I really could feel a difference. I think I need better tires than the Michelin super sport 18" tires to force more deflection.

I think the only real way is to have real time suspension measurements with and without the bar to see the change in the contact patch of the tire while cornering.

As for preserving the structure of the frame is were I put my, " I agree worth doing".

It may also help reduce body rattle noises, and rattle noises in the interior, again worth doing.

But for improving street driving handling I think this is a "placebo effect" were the driver pushes the car harder and this feeling is the wow factor.

After driving your corvette on the track with street WOW factor is hard to get.

My 2 cents.

oldgto

Interesting. Your comments make me glad I bought one. For now, I live in a crowded city, but plan to take the car to the mountains when I retire. (Think "Manhattan" versus "Dragon Tail") It may be a while before I will actually get to try it for myself, but we plan to run a LOT of very curvy roads, so it made sence to add one.

74Ken

Put mine in over a year ago, what a difference.
Now I am installing Steeroids, tired of that leaky control valve and loose steering.

ignatz

I would have to agree with cagotzmann on this. The lower control arm is pretty solidly mounted at a place that I wouldn't think flexes all that much. The upper is a different story. If you consider the camber change for 1/16" over the height difference between those two points, say 12", that is less than a third of a degree. Can't imagine that is enough to notice.

I suppose it is too late to ask, but when and how did these start to show up? It is indeed a great improvement.

63Corvette

I got mine from Dick Guldstrand in about.......um, 1969

jim-81

Very cool video... the things you can do with a GoPro! Really interesting to see that frame flex and the control arm moving. Next - take one of the trailing arm!

CA-Legal-Vette

Over the years there has been two camps in the spreader bar debate: makes a big difference and makes a small difference but is worth doing. I've also seen pics of broken shock towers due to metal fatigue. I tend to think that there is a pretty wide range to the degree of flex present at the time of the mod which probably accounts for the variation. Anecdotally, it also seems to make a bigger difference in convertibles though I'm not sure why that would be the case since the fame differences are in the birdcage area, not the front end.