Suspension Questions

[sirelesar]

Hey guys,
Got a few suspension questions for you.

I have a B&B w/ a 302 engine, T5 setup, and a solid 8.8 (SN-95) rear end with 17" wheels. I am running the QA-1 coilovers both front and rear. The B&B uses the Mustang II type front end, where I have aftermarket tubular A-Arms. The rear is a SN-95 with aftermarket rear control arms with polyurethane bushings. The front coil-overs are the QA-1 (365#/in) springs. For the rear springs, I began with the 170 #/in coilover springs, but after reading an article (www.rqriley.com/suspensn) I lowered them to 110 #/in. The ride got better, but I am still looking to improve it.

In an ongoing effort to improve the ride without sacrificing performance, and without having the opportunity to test-ride other Cobras, perhaps some help on these questions may shed some light on my suspension-tuning quest.

Is anyone using sway bars (either front or rear) with these setups? I know that it is only for cornering, but perhaps the tradeoff of softer springs with swaybars would quiet the ride while maintaining performance.

What are your experiences from going with the solid rear axle to the independent suspension? Is it that dramatic of improvement? I know by the before-mentioned article that lessening the unsprung weight ratio is a significant factor to ride quality improvement on paper. Before I went and spent the excessive effort in the modifications, I would like to hear some real experiences.

Thanks ahead of time for the input.
Darren

[Clois Harlan]

am running a 1 1/8" front sway bar with 600# front springs and Carrera coil overs and tubular front A arms. I like it a lot my ride is more of a performance ride but I prefer it that way. I had a softer ride in the beginning but when I switched from SB to BB I stiffened everything up.

I tried a rear sway bar and didn't like it with my live axel. I am runnung after market upper and lower control arms and an 8.8 rear end. In race situations the rear sway bar caused too many problems. I felt like I was going to wreck at any time with it attached.


Clois

[HighPlainsDrifter]

Hi,
The unsprung weight issue is real and the easiest way to noticably improve lap times. I run centerline billit aluminum wheels, they are 15 lbs lighter each than average cast wheels. I also prefer a stiffer sping like Clois and no sway bar for the cobra, completely opposite from my mustang, don't try to use the same setup.
Good Luck,
Perry.

[sirelesar]

Thanks for the input Clois.
Great car Perry, I have seen the pictures of the paint. Awesome.

The stiffer front springs would most certainly be required with the BB. The question of the sway bars was raised after going thru the Corvette museum this last weekend in Bowling Green, KY. The C5, even with its low CG, has sway bars both front and back (independent front and rear suspension). It got me to thinking that it might have other advantages in load distribution, even in the straight away. To further that analysis, if one wheel hits a bump in a straight away, it would tend to transfer that load to the frame thru the sway bars, acting as additional spring, and a secondary distributor of dynamic load. I realize that this car is an engineered item, and is also significantly enhanced by the active suspension system. That is why I was even further intrigued by the use of sway bars.

It would sure be nice to put that active suspension system on my Cobra Also of note, I was surprised to see transverse leaf springs being used on the C5 (and C6) rather than coil-overs.

Enough of the Corvette. We are building snakes here.

I am beginning to get the impression that the independent rear suspension is the real key to ride/performance enhancement. It has a significant impact on the unsprung weight ratio, more than lighter wheels or any other single component could.

Darren

[sirelesar]

Disregard this entire post. After looking at the trees thru the forest, I finally have realized that my bump stops on the B&B frame needed to be cut back. 1/4" of travel in the rear is tough on a suspension.

Signed,
Feeling like a dweeb

[speed220mph]

Darren: Your questions would take an entire book to give you a straight answer, but the bottom line is ride quality is directly proportional to wheel deflection and travel. And contrary to many misconceptions, a soft suspension doesn't mean a bad handling car in most cases. If a suspension is stiffened, it's done beacause a compromise had to be made, i.e., solid rear axle in a Cobra. Why? Because a lot of wheel travel would mean a lot of u-joint angle with that short driveshaft, which would result in frequent u-joint failure.

The IRS setup in the rear improves everything in the suspension department: ride, handling, trunk space, originality . . . providing it's done correctly. Wheel travel can be increased, suspension can be softened (give a lower ride frequency), unsprung weight is reduced, camber gain keeps tire patch flat on ground, sway bars provide roll control, and you can redo your trunk for more space like was originally done.

To get a real lesson in high unsprung-to-sprung weight performance, drive an empty pickup truck--not too fast--around a curve on a dirt road with a washboard surface and notice how the rear end wants to pass the front end.

Get Fred Puhn's book How to Make Your Car Handle to learn about this stuff.

Simple

[sirelesar]

Thanks Tom,

Great input. I raised my bump stops to an appropriate level, and am looking forward to testing the ride. That is, after I figure out what I fried by welding on the vehicle, even with both battery terminals unplugged, and the computer/MSD hot at the starter for constant voltage unhooked. (Out of the frying pan, into the fire).

I am highly considering the independent rear suspension. Have you heard much about the Thunderbird? I have a connection to one, but they do not know the rated torque, axle length, etc. I will need to do a little more digging.

Once again, thanks for the input.
Darren

[speed220mph]

Darren:
Superformance uses the T-Bird rear suspension. It should do the job. Also, check ERA's web site. They go through the mods done prior to installing Jag rear suspensions. Very informative. ERA will sell their rear-suspension cradle for the Jag setup and their improved IRS. It's worth a look.

Check it out: http://www.erareplicas.com/427/rsusp.htm