Flex-a-Form Fiberglass F-body springs

[CarlC]

For those interested there is a new section on my webpage that shows the new 250 #/in Flex-a-Form fiberglass rear springs. They have been modified to use a spherical plain bearing system (similar to CAT5) on each end.

[Taylor1969]

For those interested there is a new section on my webpage that shows the new 250 #/in Flex-a-Form fiberglass rear springs. They have been modified to use a spherical plain bearing system (similar to CAT5) on each end.

Carl,

I planned on purchasing rear springs soon and would like to know if you can go into a little more detail on what is necessary to complete this setup.

Did you purchase directly from flex-a-form? Can I purchase the rear cat5 bushings from GW and put them directly into these springs? I am looking to drop the car as well. What does the ride height look like with these springs? Are Qa1 12 ways the best shock to get with this setup?

Thanks,
Chris

[CarlC]

Did you purchase directly from flex-a-form? Yes, it's the only way.

Can I purchase the rear cat5 bushings from GW and put them directly into these springs? No. As noted on my website the spring eyes must be bored to fit the spherical bearing housing.

I am looking to drop the car as well. What does the ride height look like with these springs? 14 1/2" from the center of the axle to the bottom of the fender lip. Another 3/4" - 1" lower is possible by flipping the spring eyes over.

Are Qa1 12 ways the best shock to get with this setup? I don't know, but a friend has the same setup with adjustable QA1's and it seems to work well. I don't know what the on-track reliability of QA1's are.

[Mean 69]

Very cool, Carl, and as always, thanks for the open and candid feedback.

The spring rate seems pretty high, and I read that you felt it rode smoother than the softer Gulstrand springs, which is cool. How was it in terms of putting the power down though? I run quite a bit softer rate on mycar (different suspension, as you know), and with tighter springs there is more of a tendancy to spin the tires on corner exit, etc. Just wondered if you had an impression on that specific attribute. I was a little surprised that there was a bit more lateral movement, I wouldn't have guessed that.

Mark

[Lowend]

I'm curious to know what you are using for shocks?
In my experience fiberglass springs need massive amounts of damping, more than an off the shelf shock can offer

[CarlC]

Mean,

Corner exit is similar to the previous springs. For low-speed exits, like many at SOWS, I have to be careful not to overpower the tires during acceleration. Higher-speed corner exits still exhibit quite a bit of aft weight transfer (see the pic on the Alcino's Bachelor Party post in the Racing Events section). It squats close to 2-1/2" in that photo.

The shocks are Bilstein AK2074. I need to call Bilstein and talk to someone about having them re-valved, if needed. So far, they work pretty well. Lap times are the best so far, and the track temperatures were 40* warmer than the previous best. Same setup on the car except for the spring change.

[rattus]

Carl,
Thanks for the info. I'm curious why you chose Flex-A-Forms over Hyperco's composite leafs (as they offer 250 lb/in leafs)?.

Another thing: Does you Flex-A-Form offer higher (than 250 lb/in) spring rates?

And finally, could you give some more detail on the parts you used to construct the spherical bearing ends?

[CarlC]

Hyperco's were my first choice, but the spring eye does not appear ridgid and does not completely encapsulate the bushing. The FAF ends are a very beefy alumunum extrusion and can be bored from 1.555" to 1.600" to fit a GW CAT5 bushing.

For spring rates you will need to talk to George at FAF directly.

All of the parts in my setup are hand-made except for the bearings. QA1 offers a bearing that is ideal and is reasonably priced. There are plenty of others available in the industrial power transmission world that will work as well.

I do have an Excell spreadsheet that I used to make a drawing. I can send it to you if you would like, but in all honesty after the time and materials cost I would rather buy the parts from GW. There's a lot of machine time, some fairly precise bore diameters, and anti-corrosion coatings required to get things right. Either way, the spring eyes need to be bored with a boring head to match the bushing housing diameter. With all of the parts needed to do the job + eye boring you're looking at close to $800 total.

[Steve68]

Carl, Gulstrand can revalve Bilsteins for you, FYI,

[chicane67]

The shocks are Bilstein AK2074. I need to call Bilstein and talk to someone about having them re-valved, if needed. So far, they work pretty well.

Something like..... 250/90 would work with that rate. Looks like its time to give Shane a call and mail a package to Poway. :woot:

[Steve68]

Tom whats Poway?

[chicane67]

Poway California.

And BTW, Guldstrand will pretty much only do the valving that they know for their own, known spring rates. Anything custom, rate to damper, is going to be handed to Mr. Hindorf via Shane. Its much easier to cut out the middle man in this situation.

[alcino]

How much are those spherical bushings from globalwest? I found pics of them but they seem to be part of "cat 5" spring package. Do they sell them seperatly? I guess I could call them, but thought I would ask here.

Did you get a chance to ride the Flex-a-forms with the original bushings to compare the ride to the sphericals?

[Mkelcy]

How much are those spherical bushings from globalwest? I found pics of them but they seem to be part of "cat 5" spring package. Do they sell them seperatly? I guess I could call them, but thought I would ask here.



Global West website listings for first generation Camaros:
"Part # 115SH ----- This a category 5 bearing and shackle kit. It converts your stock system over. Cost $460.35"

[Stu Seitz]

By going from a solid bushing, in both front and back, to a spherical bushing in the rear and a solid in the front. Would this require a sta bar in the rear?

[wendell]

I think the reduction in roll stiffness from a monoball in the REAR spring eye is going to be marginal and won't require a sway bar.

[6'9"Witha69]

Carl, good to see you got those in and had some fun on them. Since the day you showed them to me I have been thinking about doing the same.

[Steve68]

Tom, I see, yes I understand cutting out the middle man,

[CarlC]

I did not try the springs with the standard, as-supplied bushings. Frankly, the as-supplied bushings were terrible. The diameter that fits into the spring eye was "customized" with a belt sander to fit. For me this did not matter since it was decided to go with the spherical bushing from the get-go.

The bushings are installed in both ends of the spring so roll bind is basically gone. Anti-roll bar requirements will depend on how the car is set up, but I went this route to get rid of the Hotchkis bar, which has a low effective rate but helped the car a bit.

GW will sell just the bushings separately. I already had the upper GW del-a-lum bushings and shackles so all I needed were the spring eye bushings. Doug sold these to a friend of mine for $350. If the advertised CAT5 kit has the frame del-aa-lums as well, it's a pretty good deal.

[rattus]

It appears that Global West will no longer sell the spherical bearing kit (they say they're only available w/ their Cat5 springs).

However, Deaver Springs offers these:

http://www.deaverspring.com/BajaBushing.htm

[Mkelcy]

I ordered a set of 225 lb/inch Flex-a-Form springs for my '68 Camaro. I told George I had the Hotchkis springs on the car now, so he sent the Flex-a-Forms to me with the spring eyes flipped over to lower the car. Unfortunately, I have 15.25" or so from center of the axle to the fender lip and the stance (and maybe handling) is pretty screwed up.

I'm leaving for a long road trip with the car in a week and don't have time to return the springs and get replacements, and the ride with the Hotchkis springs and the DSE subframe connectors is just punishing. So, is there any reason I shouldn't use lowering blocks with the Flex-a-Forms? The ride even with the higher rate of the Flex-a-Forms, seems materially better than with the steel Hotchkis springs, although I'll know more when I take it out for a longer drive tomorrow.

[CarlC]

Mike,

Mine is 15" with the ends in the normal position, that is, the flat part of the end is facing down when installed in the car. This is with less than 1/4 tank of fuel. There is the equivalent of a 1/2" lowering block due to the angle shims. I think a small lowering block should be fine, but yours seems high at 15-1/4".

If you are using the FAF supplied bushing one thing to try would be to loosen each through bolt on the ends of the spring. FAF's QC on my bushings was terrible, and it would not surprise me that yours might be binding if the overall width of the bushing was greater than the steel sleeve insert.

[alcino]

I was told that I could use a lower block of up to 2" without puting excessive strain on the springs

[Mkelcy]

Carl: I loosened the lower bolt on the rear shackle with no appreciable change in stance. (I haven't tried loosening the front eye bolt yet, and may not bother trying to get the Flex-a-Form bushings to work.)

Rattus: The Flex-a-Form spring eyes are 1.53" in ID and 2.53" wide, so I'm considering using the Deaver spherical bushings you mentioned. I'll contact Deaver on Monday and see what they say about fitting the Flex-a-Form spring eyes and durability in street use.

Alcino: Thanks for the lowering block info. I've ordered 1.5" lowering blocks just in case my ride height isn't the result of the Flex-a-Form bushings.

That said, the difference in the rear suspension is amazing. They seem to track over bumps much better than the previous Hotchkis steel springs. I took it up the Angeles Crest this morning which has a lot of corners with a lot of frost heaves. The Flex-a-Form rear suspension is much more stable over these sections, with less tendency to step out over the bumps than before, even with the badly worn tires that are on the car now. I also didn't notice any increase in lateral deflection, although this was only a street driving situation.

All in all, I'm impressed.

[CarlC]

What's your final ride height target? Also, what size front tire do you have and what is the distance from the ground to the center of the front lower A-arm bolt?

[Mkelcy]

What's your final ride height target? Also, what size front tire do you have and what is the distance from the ground to the center of the front lower A-arm bolt?
My target is a car that's just a bit lowered and either level or with the rear ever so slightly higher than the front. The distance from the ground to the center of the front lower A-arm bolt is 7.5" with 245-45-17's. The distance from the center of the rear axle to the fender lip continues to be 15.25".

[CarlC]

As a point of referance, mine is 9-1/4" with a similar tire diameter. To minimize steering geometry changes the center of the sphere in the lower ball joint should be 1/2" lower than the center of the front lower A-arm bolt when the car is on the ground and at full weight. 7-1/2" is pretty low. Are there any ground clearnace problems or darting under braking?

[Mkelcy]

Are there any ground clearnace problems or darting under braking?

I haven't noticed any problems, but I haven't tracked the car, and don't use the brakes that aggressively on the street.

[Alan66ss]

Carl,

I see on your web site you worked on the eyes of your faf springs. When you removed them - what was the insulator material that you used when you reinstalled the aluminum eyes back on the composite spring? I would greatly apreciate the info.

Thanks.

Alan

[CarlC]

There was no insulating material. They are bonded using a fiberglass construction adhesive + bolts.

[rattus]

Awhile back I bought a set of custom FAF springs (350 lbs/in 2.5 free arch). I finally installed them along with Deaver's "Baja Bushings" mono-ball inserts. The bushings fit perfectly except the FAF eyes are about 0.030" larger diameter than the bushings. I used shim stock to take up the difference.

Distance from center of wheel to fender lip is 13.5" (275/40-17 wheel/tires).

I haven't road tested them yet.

[CarlC]

Sounds very interesting.

Do you have side view pic?

[Mkelcy]

Awhile back I bought a set of custom FAF springs (350 lbs/in 2.5 free arch). I finally installed them along with Deaver's "Baja Bushings" mono-ball inserts. The bushings fit perfectly except the FAF eyes are about 0.030" larger diameter than the bushings. I used shim stock to take up the difference.

Distance from center of wheel to fender lip is 13.5" (275/40-17 wheel/tires).

I haven't road tested them yet.

Deaver bushings installed, front, rear or both?

[rattus]

The bushings are installed in front and rear spring eyes. The bushings cost ~$150 / pair.

[Mkelcy]

The bushings are installed in front and rear spring eyes. The bushings cost ~$150 / pair.

Have you felt a need for (or do you have) a rear sway bar?

[rattus]

"Have you felt a need for (or do you have) a rear sway bar?"

No rear sway bar. I haven't driven the car on the new springs yet, so I don't know if one is needed.

My previous rear leafs were probably stock and they were sagging pretty low. In the above pic my front is pretty low (too low) and with my old leafs the rear was equally low.

The front springs are currently 700 lb/in (5" x 9.5" Hyperco with upper pocket adjusters) and are too soft for what I want (and probably a bad match for the 350 lb/in rear leafs). I have 950 lb/in fronts that I'm going to try out.

[Jeremy]

With those spring rates, do you plan to run on the street? How is the ride with rates that high?

[rattus]

"How is the ride with rates that high?"

I don't know yet. The car will be ~10% street.

[wendell]

Rattus,
Those are high rates for a first gen. How did you come up with them? For reference, the dedicated race 1st gens that I deal with are 650#/ 210#on the high side. These rates are coupled with the relatively soft side wall of a bias ply tire.

[rattus]

"Those are high rates for a first gen. How did you come up with them?"

I developed and simulated a somewhat detailed model of front and rear syspension dynamics. I targeted the front ride frequency to be ~1.8 Hz, then set the rear ride frequency (somewhat higher) to give minimal pitch jerk at ~80 mph. These are the rates I came up with (at ~40% critical damp.).

The rates are to a large degree experimental.

[silver69camaro]

"Those are high rates for a first gen. How did you come up with them?"

I developed and simulated a somewhat detailed model of front and rear syspension dynamics. I targeted the front ride frequency to be ~1.8 Hz, then set the rear ride frequency (somewhat higher) to give minimal pitch jerk at ~80 mph. These are the rates I came up with (at ~40% critical damp.).

The rates are to a large degree experimental.

That's somewhat the approach I take, and I came up with 200-250 lbs/in springs (leafs are a bit tricky to come up with an exact rate). So far, I'm right on the money.