Bolt-in rear suspension upgrade for '67-'68 Camaros

[Garymac69]

I just read about this suspension ugrade in this month's Super Chevy:
http://www.superchevy-web.com/technical/chassis/suspension_steering/0507sc_fat/

It looks very simple but elegant at the same time. What do you suspension experts think about it?

[nancejd]

Interesting, I wonder if there would be any advantage over a quality aftermarket leaf spring. Seems like ther would be some inherent bind in the system using a partial leaf and a panhard bar.

[wally8]

I'd say his analysis sums it up: "Did it handle like a slot car? Not really, because it wasn't set up that way."

How else would one set it up? I don't see much in the way of adjustment. With just a little more work they could have had a 3 link.

I'm sure it's just fine for the street.


Wally

[baz67]

Interesting.

It looks good for a cruiser.

For performance handling I am not sure. It looks like the PHB is angled down and partly above the center section of the housing. That may have the RC too high and cause some roll steer. The leafs add a RC component as well. That will have two competing RCs for the rear.

Like the thread about the airbag four link, they may be giving too much up for the sake of packaging and ease of install. Like I said for a cruiser it looks ok. A auto-x or sometime track car I would stick with a good set of leafs or custom link suspension.

[MrQuick]

that is interesting, but the leaf halves just act like links, flexible links. Also bind would not be (if any) as a bad as full leafs.

Panhard bar in that position is just for lateral location and not for RC positioning right?

[baz67]

Ya, Vince, I thought about them being just flexable links. For some reason that does not seem correct.

What this can be best compared to is a truck arm suspension. RC is determined by finding the two lateral restaint points of this suspension and drawing a line between them. That is the roll axis of the rear suspension. Where the roll axis crosses the veritcal axle centerline(CL) is the RC of the rear suspension. One point is where the PHB crosses the CL of the car in plan view(overhead). The other is the instant center of the links in plan view. That is determind by projecting lines forward until they cross. It is forward in the case of the first gen. Those two points are carried over into side view and a line is drawn between them. Where this line crosses the vertical axle CL is the RC.

In this case it looks like the PHB is along the vertical axle CL. If that is the case then it does not matter what the IC is of the links because the roll axis will always cross the vertical axle CL at the CL of the PHB. Then PHB height determins RC.

[chicane67]

Some bandaids are good and some are not..... I guess.

[Steve Chryssos]

Semi-eliiptical leafs are nothing new. You can crawl under a current generation Jeep and find them. I suppose the semi leaf/coil-over offers benefit in spring preload tuning.

But again (as stated) we get into the bolt-on packaging thing. And the funny thing is: These bolt-on kits all seem to require some welding. If you are breaking out the dark helmet (Spaceballs allusion), why not just go for it! Install a real 4 link/PHB or better?

Yeah this one's creative, but Terry Cole summed it up best: Ride improves and it sits nice, handling is so-so.

And do you see those turn downs on the end of the mufflers? Good luck squeezing tail pipes through that low crossmember and PHB.

[Serpa69]

A Little pricy but It does not cut up the car. I just got the catalog in the mail about this suspension set up. I like that there is not any welding on the rear. And if you want to take it out no problem. I have been looking for a good rear set up and I think that this is it. I like that it is simple in design and still gives some adjustment. I do not have to get new exhaust I put one on order and I will let you know how it does.

[Mean 69]

I would personally be vary wary of a suspension kit, or SFC, or any other significant addition/substitution that DOESN'T require welding. In our cars, hardware, even with locktite, etc, WILL come loose due to vibrations etc. If you don't weld it, make certain you follow up with a wrench periodically to insure things are righty-tighty.

On this design, well, it is pretty funky. The way I see it, the half-springs act as both a springing medium, and a longitudinal "link." Then you have the coil-overs to act as another springing medium? Beyond a bit of redundancy here, I don't see to much harm in that (double springing, that is).

I can't see all of the links, etc, but it looks as if the half springs are the ONLY longitudinal restraints? If so, I would be really concerned about a number of things. One, all of the torque will be transmitted through these springs into the chassis, alone. We all know that a leaf spring can wrap, and these certainly will. Effective length will change as a result, even though it will probably be slight, but what's worse(?) is that the axle housing will change pinion angle as a function of throttle and brake. It's clear why they did this, if you used a solid link in this location, the axle wouldn't roll, period.

Second and easily as important, in fact far MORE important, is the swing arm length. Normally, you would find this in the side view, looking at where the upper and lowers interesect (which also describes the instant center, at least at that "instant!"), but because there are only the lowers, the SVSA is the same as the length of the half-leafs. That looks to be about two feet or so, which I would argue is about two feet (or more) too short. No question, you will get a lot of forward bite, because the IC is so low and short, anti-squat will be well above 100%, probably quite a bit more. I wonder what the influence of the half-leafs would be on wheel hop though? But, more importantly, when it comes to really getting after the brakes, I would predict severe brake hop, and given that the links are springs, it would probably become violent and possibly uncontrollable brake hop.

From the PHB standpoint, it looks to be pretty steeply inclined but it might just be the pictures? If it is, you will get prounounced lateral movement of the axle in bump, at least relative to the typical (correct) case of a parallel-to-ground installation. RRCH is indeed defined by the intersection of the PHB with the vehicle centerline, and looks to be quite high.

Two benefits: basically bolts on, though I'd follow the suggestion of welding the cross bar in place. Second, you don't have to weld brackets onto the rear end housing/tubing, which WILL distort the alignment of the axle and WILL require straightening.

Mark

[wally8]

I agree. There doesn't seem to be any performance benefit whatsoever with this setup. You'd be better off sticking with the stock leaf spring arrangement.

The tip about using the air ride springs is a dead giveaway. The only real benefit here would be that you can adjust ride height. As a performance suspension it's an abomination.

I just can't think of a good reason to use the half springs as the locating link other than the fact that it's a convenient compromise. Like Mark said, they would definitely have a wicked affect on acceleration and braking. They probably hook OK (quickly since they're short) but heavy braking would have to be bad.

Another tip is the Fatman's is not a performance oriented manufacturer. If you want go fast parts you need to stick with folks who've proven their stuff on a track, even if you never plan to use it that way. Anything less is just a full bodied street rod. (Here's hoping I didn't start something......)

Wally

[Steve Chryssos]

A Little pricy but It does not cut up the car. I just got the catalog in the mail about this suspension set up. I like that there is not any welding on the rear. And if you want to take it out no problem. I have been looking for a good rear set up and I think that this is it. I like that it is simple in design and still gives some adjustment. I do not have to get new exhaust I put one on order and I will let you know how it does.

Serpa,
When the kit shows up, you should lay the parts out on the floor, take some detailed pics and post them. Let these guys analyze the design. They know what they are talking about, so--upon closer inspection--you may be sending it back.

[68Formula]

Why don't they ever do back to back testing on this stuff? If it's about acceleration they take it to a track, if it's about handling it's seat of the pants.

The only people I've seen putting any numbers to this stuff is PHR.

So how much is this gem?

[David Pozzi]

Want to have fun? take that setup and with an auto trans, step on the brake and jab the throttle off and on!
What happens? the same thing as a third gen vette, the rear pops up instantly, then down when you let off. Why? because when the brakes are locked the spring acts just like the vette "banjo" link, it is a fairly short arm and the axle torque will push right up on the body. The problem is, it works the other way when you brake into a corner, so you can get rear wheel lock very easily.

The panhard bar is too high, the roll center will be serveral inches above stock.
Look at the huge aluminum blocks on there!

[Serpa69]

Talked to the guy today and cancelled the order.. I am sick of chassis places! They said that they tested the set up on a 69 camaro and the kit is specific for that year because of the different bump stops. They said that it was ready to go then they called and said that it would be delayed 4WEEKS! I was hoping to have it installed the my next track day(2WEEKS) so I just got pissed and killed the order. In reference to the blocks, they are ment to take up the room of the leafs that is why they are so thick. The install you see in the mag is for a single leaf car so there is some hang out. I guess I call DSE and order there mini tub kit and go whole hog with the modification. The kit is cheeper any way. I was just hoping for getting rid of leafs.

[Mean 69]

In my humble opinion, you are probably a whole bunch better not running this thing on the track.

M

[joshuaweber]

would any one have a use for a bolt then weld on torque arm rear suspension for a 1 st gen f-body?