Classic Roadsters - Ind. rear?

Double Venom · #1 (**permalink**) 12-06-2002, 06:00 PM

All right then, lets get this thing in fast forward.

If you had a choice, which would you take? Or would you want either one?

#1 - a modified independant, ie; T-bird, or some other. Well built single wishbone rear for say...$3,500.00 including brakes and shocks

#2 - a double wishbone independant rear end, actually designed for the Classic Roadsters frame and front suspension. Includes your choice of coil overs and Baer or Wildwood Brakes
say... $6,500.00?

See, I told you our independant rear was exspensive!
DV

Excaliber · #2 (**permalink**) 12-06-2002, 06:35 PM

Heres the deal for me (and I'm glad you asked)!

#1. Reason I want IRS is my PERCEPTION that if offers better ride quality than a live axle. BUT, am I wrong on that count? I mean is it REALLY noticeably better?

#2. Reason would be the POTENTIAL for "better handling". BUT, the live axle in my Excal was no slouch, that bad boy could hang with the best of them on the track. Could I "feel" the difference with IRS? I wonder........

I had the Excal live axle so STIFF (sway bar\springs) it rode like a dam truck! Sure cornered flat though!

Is the IRS then really "that" much better? Enough to say:
#1. Single (cheaper) IRS is better than "live" for $3500 and worth the investment in TERMS of ride quality and handling.

#2. Is the double wishbone offer noticeably better performance than the single wishbone IRS and thus warrant it's $6K price?

My guess is it would HARD to tell from a single to a double wishbone IRS setup. Would it be easy to tell from a live axle to ANY kind of IRS? Or is that smoke and mirrors too?

The re-sale factor: Hmmmm,,,,tough call. I think the fact that it had IRS in general would "up" the value of the car. Single or double wishbone I don't think would be a major factor in re-sale.

OK, I'm going with single wishbone as soon as someone CONVINCES me it has superior ride and handling and thus warrants the additional $3K price! I'll pass on the $6K setup and spend the money on a good soft top, lol.

Ernie

mr bruce · #3 (**permalink**) 12-06-2002, 06:44 PM

Ed, the JR GT 40 is almost done, so I'm lookin' for a new challenge. Get me a Classic frame over here in the 'Burgh and I'll put a C-4 Vette rear under there for you.

petek · #4 (**permalink**) 12-06-2002, 06:46 PM

Well, if you could get the T-bird setup down to $2.5k I think you'd have a popular product!

Frankly I just don't see a market for a $6k mod ... no matter how good.

Double Venom · #5 (**permalink**) 12-06-2002, 06:55 PM

Excal...
In MY opinion, on the street it makes little or no noticeable difference.
On the track it's a different thing - NOT a Drag Strip! Keep the 8.8's.

Proof is at the track. Professional testing showed my DV Cobra, esesentially set up just like any other big block Cobra with a 9" pulled a .78 G with Cooper Cobra street tires. With our engineered Double Wishbone set up, same track, (TRC-Honda's test track), same driver and tires, we pulled a plus 1.2 G's. The facts are in.

On a course I can tell the difference from the single and double wishbone, but mostly only from the clock. To ME the double wishbone is a major safety issue. So there you have my 2-cents worth.

This is obviously cutting my own throat, "we" Classics by Elite, have been designing and building what the customer wants and needs for over 30 years. BUT, does a CR's NEED an independant? Does any Cobra NEED an independant? I don't think so, but I want a LOT of things I don't NEED!

Mr. Bruce...fella it's time we talked again. For more reason than one

DV

Excaliber · #6 (**permalink**) 12-06-2002, 07:31 PM

Well put Ed,

I think my next Cobra will focus more on street driving than track driving. But WOW, those skid G numbers ARE impressive!! I guess IRS really DOES make a difference!

Is the safety issue:
If you loose a half shaft on the single, you chances of a crash are much greater than with the double? I assume the half shaft (axle or what ever you call it) is the MAIN component holding the suspension together? If thats the case, a guy would have to ask himself,,,is the added safety worth the price? depends on the guy and how you drive to a large degree I guess.

Ernie

Double Venom · #7 (**permalink**) 12-06-2002, 08:02 PM

Excal..
To me, that is exactly the issue. Normal cars using a single system really don't have an issue. Years ago, I really never gave it a thought either. Just wanted an independant. Then along came Run n Gun 1998(?). A Cobra coming down the straight, broke a weld, (apparently not assembeled correctly per the story) dropped the half shaft, folding the rear wheel in, driving the half shaft into the ground, throwing the Cobra in the air, rear in first, back down then back up. When it came down the sesond time it was still sunny side up, but this time the tank was ruptured and the car caught on fire.

Driver was extremely shook up, but aparently OK. From that incident alone, my mindset went to the Double Wishbone rear end.

I really do like breaking unbreakable axles, bullit proof rear ends, guaranteed U-joints and drive shafts but, I don't want my wheels falling over when I do it!

DV

Ken Greene · #8 (**permalink**) 12-07-2002, 05:09 AM

being someone on the long road to buying/building my firt cobra, I would really want an IRS now if i was building a car that was going to be seeing alot of track time i would want the same setup you did on DVII. and i suspect that is the $6500 price tag. money well spent. but for a car that may see an autocross or at a big stretch a track day a year $3500 seems to be where i would go.
If money was no issue you would be building DVIII

Double Venom · #9 (**permalink**) 12-07-2002, 05:23 AM

Ken,

DV I's are just awesome, DV II's are incredible.... A DV III model?
I'll have to think about that one for awhile!

DV...now tha's worth a chocolate chip cookie!

Jack21 · #10 (**permalink**) 12-07-2002, 10:50 AM

My $0.02,

Double wishbone only. For reasons stated above, you don't want the axle doing double duty as part of the suspension, such that if it breaks, your rear suspension folds up.

Would like double wishbone, T-Bird 8.8, retrofit capable; weld-in, or bolt-in, hub to hub. brakes and coilovers optional. Choice of diff's, Eaton, Torsen, etc. 31 spline standard. Possibly leave the option for builder to procure his own center section diff.

Suspect the big block drag racing folks would use the Ford 9", or Dana instead of the 8.8.

Don't have a feel for a price tag. Have looked over the FFR, and SPF IRS's and they don't look overly difficult to make.

Is there any economy of scale in manufacturing these?

Anyway, list me as a potential buyer if the cost can be kept in the $2500 - 3500 range.

Bob Putnam · #11 (**permalink**) 12-07-2002, 02:33 PM

Our rear suspension is a fail safe design.

And this is only $4500

Double Venom · #12 (**permalink**) 12-07-2002, 02:39 PM

Bingo!

If you run a single "wishbone" this is the way to do it!
Bob, I was hoping you would jump in here, thank you.

DV

shnookie · #13 (**permalink**) 12-07-2002, 02:44 PM

The T-bird is a double wishbone. Won't fold up like the Jag will if the axle or joints go. Weakest point is the small axles. I am currently looking for someone who will build me a custom shortened set for a reasonable price. Modified T-bird mounts/cage shouldn't cost more than $2,000.00 less the rear.

mr bruce · #14 (**permalink**) 12-07-2002, 02:52 PM

The T-Bird settup is NOT double whishbone. It has a single strut on the top. All accelerating/decelerating forces are taken by the lower part of the hub carrier. Worked fine on a stock 'Bird , but a Cobra with big tires and HP.? What's the fatigue cycle of aluminum ?

shnookie · #15 (**permalink**) 12-07-2002, 02:58 PM

BY GEORGE Just Went out and looked and your right. My feeble old memory fails me. Haven't heard of a failure in a SF yet. Are they using bird carriers or making their own?

mr bruce · #16 (**permalink**) 12-07-2002, 03:10 PM

Ain't heard of one breakin yet, but did read some posts of some cars suddenly verring left or rite. Maybe torque wraping up the soft rubber bushings induced rear steer.F5 must have noticed it, they have a horizontal shock holding the upper arm, but what it's supposed to do is questionable. Lots more to it than just bolting any old settup under there. Look at the graphs on the camber curves etc. on JBL's website. Front must work with the rear. Wheelbase, engine placement, weight transfer on turn in, tire size, man ,there is lots to look for.

Excaliber · #17 (**permalink**) 12-07-2002, 04:17 PM

I'm surprised at how many live axle Cobras are out there (having scoured the "used Cobra" market intently for awhile now). All though I was "kind of" aware of the single arm failure it really hadn't jelled until now. And that makes a strong case for covering important areas such as this from yet another angle.

Those skid pad G numbers DV referred to just blew me away! Combine that with the "potential" danger of a single arm setup and I'm convinced. Double arm or modified like the ERA design is the only logical choice. IRS is a must have in my book now!

Ernie

Edit: By the time I finish my "must have" list the car will cost an impossibly high amount, ha ha!

Double Venom · #18 (**permalink**) 12-07-2002, 07:27 PM

I left, thought about my last post and I have to add, with nothing taken away from ERA or Bob Putmabn, but it is NOT normal that the welds will break, it's the U-joints that can snap or the shafts being twisted in half! Ask Gary Proia, R&G winner '97(?). Twisted his half shaft in half and it WAS a modified Vette.

Like my first post indicated, you want one that will work, or do you want one that is engineered to the car as Mr. Bruce eludes to? "IT AINT JUST CUTTIN' AND WELDING MY FRIEND!"

DV

Ken Greene · #19 (**permalink**) 12-08-2002, 06:00 AM

now in my search for a stretched cobra i ran into the now, i believe, defunked Johnex out of Ontario. They had a colpete IRS that i "think" was a "double" and it was designed by CMC also in Ontario. From what i understood it was a total custom design for their car but it sure did look pretty. I believe they designed the complete chassis for Johnex.

mr bruce · #20 (**permalink**) 12-08-2002, 06:00 AM

Rite-o DV, It ain't the welds ,it's the u-joints, then you're in deep kimshi. The best off the shelf settup rite now has got to be the C-5 Vette, but by the time you narrow it, chop the wheelbase, to fit a Cobra, you're throwing away a few Million $$$ GM spent making it work so well.