Independent or Solid...That Is The Question

[SGC48]

I know that this has probably been cover, but I gotta ask anyway. OK, here we go!

I have settled on an FFR. The question I am asking is this, is the independent rear that much better than the solid 8.8 3-link w/ coil overs? A bit about my plans ans activities might help so here ya go.

Will be installing a 427 side oiler, Tremec TKO 5-speed, 3.27 or 3.55 gears w/ 17" wheels and sneakers. I plan to use the car primarily for road use with an ocassional jaunt to the drag strip or track (by occasional I mean once to the drag strip and once to an SCCA event a year).

Any input to aid in the decision making would be appreciated. Thanks.

-SGC

[SGC48]

Somebody must have something to say about this. Anything?

-SGC

[Excaliber]

If I was doing primarily drag strip duty I would consider the solid axle for strength. DV was able to pull over 1G with his Double Venom and a live axle on a skid pad, pretty impressive.

Typically I GUESS one would have to conclude IRS is superior, certainly more difficult to "dial in".

Ride quality? Rumor has it the IRS offers a better ride. Again I think that applies to either unit WHEN their set up properly.

So it comes down to this:

IS the extra money an IRS set up cost worth the extra benefits you get?

Ernie

[RACERAL]

If money is no object, I would go with IRS... but if you want a little better ride, I would ditch the 17's and go with 15's.. you may want to try www.ffcobra.com
I have heard those folks are kinda fanatical about those FFR's

[SGC48]

Thanks for the help. I'll check out ffcobra.com. Any other thoughts?

[Bumpster]

SGC48 - You really need to ride in Cobras with each type of suspension, or preferably drive each. Only you can answer which one you will prefer. It's better to build yor car the way you want it than change it afterward, and much less expensive in the long run. I prefer independent rear suspension and I believe the majority of owners on this forum do also, but I don't know what percentage. There is a club in New York, contact them at www.upstatecobras.com, that may have some members near you who can give you a ride or a drive. You also might check over on the Factory Five Forum as most every member there drives a Factory Five and you can probably get a more informed response.

Bumpster

[John A. Simpson]

I agree you should check ffcobra.com. They recently had a thread on if people would do IRS again or not, just seach the topic. Also there have been several threads on the downsides of the live rear axle including binding and breaking u-joints, etc. The posts I've seen say they have zero problems at the dragstrip with the IRS, and I believe the IRS would be more liveable if the roads in your area are less than perfect.

[foothills gary]

After having several cars with sporting pretensions with IRS in the past,and having driven the back roads of Northern Ca. for nearly 25 years,I would say without equivication that IRS is the only way to go.Try driving a z-28,or Stang with solid axle on any back road with rises,potholes,offcamber corners,or s-curves and you will not even consider solid.Drag racing may be the exception to the rule.It will be a highly tunable IRS for me in my Cobra!

[Bill E]

If you are going to run a 90" wheel base car, you have tIo have an IRS. Their is not enough room for a drive line to work correctly, and binding of the splines is a real problem for a live axle. That is why we went to a 94 1/2" wheelbase we can run both effectively We much prefer the live axle ease of maintenance adjustability durability and E brakes that works and they don't brake and flip the car and can be made to pule over a G on the track consistently. We see a lot of cars at the track and the number one failure we see is the independent jag or 8.8 If you think this is incorrect go to a Shelby event at you local track and pay attention.

[grumpy]

SGC48,
Why waste the time, IRS is the way and the final answer. The 8.8 is the "9 inch" of the future right now and way more plentiful.
grumpy

[SGC48]

Thank you all for your help, I think I will be doing the IRS. Now, anyone got a T-Bird rear for sale?

-SGC

[JAM1775]

I am not meaning to throw a wrench in this discussion but I have a 8.8 live axle and I love it. I drive every weekend and have made 4-5 trips to the track with perhaps 25 passes. IMO the live axle is best for the street and straight track as it hooks hard and is extremely durable. The IRS is superior in ride quality and will no doubt out perform on autcross . I do not autocross . If my car rides harder or bumpier than IRS it does not matter to me because I prefer the off line or low roll traction trade off. I have never pushed my car through curves where I exceeded the limits of my suspension. I prefer the live axle because I drive under conditions that may favor it. My rear axle does not ever hop or bind, it was pinioned and centered at a chassis shop. It never goes out to the side and when over powered will drop 2 straight lines for as long as desired. The FFR 3 link is a great compromise between the two as if provides more live axle flexibility and is reported to hook very well. You have that 3 link option. The way we drive , what we expect in the ride and performance of our cars are personal preferences. If you plan on Autox got IRS.
Mine is primarily a sunny weekend street/highway and cruise night roller.

[speed220mph]

When trying to decide on solid vs. independent rear suspension it comes down to to basic factors; cost versus performance, with ride a major factor in performance.

Solid axles are definately less expensive and more durable. (That doesn't include the U-joints.) If you'll be drag racing only and driving on roads that are smooth as a pool table, go with the solid axle, providing you don't care about the ride and handling of a Cobra. But be aware that you've got to use relatively stiff springs to restrict wheel travel. With a short driveshaft, there will be a lot of driveline angle change with wheel travel, thus whipping of the driveshaft and U-joint wear.

On the other hand, an IRS is far superior to a bouncing axle in terms of ride and handling. And there are plently of them available such as the T-Bird/Cougar/LSC Lincoln setup with disc brakes attached. You can go with a much lower rate spring, which would give your car a smoother ride. Then there's the original Jag setup to consider, too. I have a friend who installed a Vette IRS in his Everett-Morrison, but I would stay away from that one.

For additional information, go to ERA's web site: http://www.erareplicas.com/427/427sc.htm#backfromfsusp . It will provide line drawings and information about why they went independent as did Superformance, Kirkham and others. As for why other manufacturers went the solid-axle route, it was to use the Mustang as a donor car, cost and/or ease of construction.

I hope that helps. By the way, I just pulled a complete Jag setup out of an '88 XJ6. Anyone want one?

[SGC48]

Thanks for the advice guys, I really appreciate it!

-SGC