Been reading over that well known C4 suspension tuning chart, as I'm kicking around making some tweaks to the C4 suspension under my '69. Looking for some help on a few questions if possible.

1) Except for '84, are the front bars interchangeable, or are they different between the early and later suspensions? (If different, what are the differences?)

2) Two of the sizes (24 and 26 mm diameter) are listed as tubular. Is there any information anywhere that states the wall thickness? (I'm currently using a tubular front bar off a Firebird, and I'd like to do the math to compare the rates,)

Thanks for any help here!

 

I think doing a search you can find most of those answers. But for your car I would think you would be looking at the 32mm front bar or the 35mm aftermarket bar. Long time no see for one of the few with a C3 with C4 suspension.

 

84-87 front bars are narrower, or mount to the LCA's further in, than do later, '88-'96 front bars.

IDK the wall thicknesses.

 

and as eluded to in op first post, 84 is a one year only and very strange looking!!

 

Not sure if this data would help? An old post of mine had some numbers.

https://www.corvetteforum.com/forums...l-options.html

Post 7.

I have the VBP 1.25" and 1" tubular bars on mine.

I called Addco for info on the rates. Lots of these bars are made by Addco (which VBP sells?), in their chart there is a 1/8" difference in dia. between the tubular and solid. The tubular being larger.

http://02bbfb5.netsolhost.com/Buick-....htm#Chevrolet

http://www.addco.net/

800-621-8916 main
800-338-7012 tech

A 1 1/4" tubular bar will be the same rate as a 1 1/8" solid bar. So for the front if you buy the 1 1/8" bar you're just adding extra weight.

Some figures, 1 1/8 solid = 1464 lb/in deflection (34" mid section, 6" arm), 1 1/4 tubular = 1464, 1 1/8 tubular = 914. 1 1/4 solid bar = 2231!

A tubular bar will be the same rate as the next size down solid bar.

 

Yeah, I've been busy elsewhere trying to get the car back together to hopefully get in some track days yet this summer. (Aided by some time at camp. )

I'm trying to go a little softer (and lighter weight) on the front bar. The present tubular bar is about 30mm, and has one of those center offsets (to clear the radiator/shroud in F-body cars, I assume). I've got the car down to 2700#, and am also modifying a C5 aluminum LCA crossmember to work with the C4 arms, to pull a couple more pounds off the front end. A possible issue is that the C5 crossmember and the Firebird swaybar's center offset section might be competing for the same real estate, so I'm in the market for a simple shape bar that will package easier. I have a dust covered 24mm bar on the shelf that came with the suspension when I bought it a hundred years ago, but the C4 chart shows a 26mm tubular bar also. That might be a decent size to ponder for the next iteration.

 

I appreciate the width difference info.

 

I'm poised to learn-a-thing, today! I thought all were same '84-'87? Got a pic?

 

I don't have a picture at the moment, but if you recall in McLellan's book how he mentioned they tilted the '84 radiator forward to reduce the radar signature (WTF??). They pulled the bottom of the radiator rearward to accomplish this, which then put the bottom of the radiator shroud right in the way of the sway bar torsion length. They then put a BA bend in it to drop the bar center section under the shroud. They then moved the radiator back to vertical in '85, whether due to needed room for the air filter, or just a return to common sense.

 

Here you go👍

 

Sweet! Thanks for the pic, and @69427 thanks for the excellent description and refresher from the book. I'd forgotten about that deal w/the radiator. Great flow of information.

 

Well, I did some searching around different internet sites for a C4 26mm bar, and found that the great majority of sellers are damn proud of that part they were selling. I said screw that, I'm not paying that kind of money for a decades old used Chevrolet part that isn't exotic metal. So I hit up a large junkyard within an acceptable drive distance to look for a close substitute that I could get reasonably cheap and then modify to fit my application. While wandering around the place I found a couple candidates that might work but then stumbled upon a unicorn '89 Corvette sitting in the yard surrounded by similarly damaged Impalas and Cavaliers. Surprised the hell out of me. Measured the bar and luckily it was the 26mm piece. Other than dealing with 30 some years of rust on the bolts it came off without much headache, and the best part is the price is the same regardless of what vehicle it comes off of.

Just gotta get some 26mm poly bushings now.

 

LOVE the JY finds!! Score.

 

I agree. I have several later model lighter-weight parts on my car that I've gotten from a variety of junkyards. In addition to finding parts, roaming a junkyard is like a mini vacation or a spa day for me. It just kinda recharges my battery.

I got the 26mm front sway bar cleaned, painted, and mounted up, I did weld a small tab on the arm ends so I could hook this bar to my adjustable heim links. Took it for a drive, and things felt decent, so I'll keep it on for the next track day. The bar is two pounds lighter than the previous bar, and that weight comes off from in front of the front axle line, so that's always nice.

The rear of the car is a bit over-sprung with the weight I've taken off it over the years. I ran the '84 Z51 spring for a while, and then ran the "softer" base '84 spring for several years. I just took that spring off today and put the only other/softer spring I have, which is the uber soft NYR spring. I don't know if this spring will necessarily be soft on this car, as the rear weight (less driver) is about 1300#. Will see how it rides later this week. But while I've got a couple members reading this thread, if someone can tell me what the broadcast (three letter) code is for the Z51/Z07 rear spring I would appreciate it. That would help me if I need to find a spring that is between the base '84 (BMF) and the later base spring (NYR).

Thanks for any help.
Mike