I finally saw a Jag IRS setup

[olddog]

Originally Posted by cobred

If you are that worried about it just dont get one with a jag rear, there are many other choices.

I wanted to make sure I wasn't totally wrong about how I assume it works. That's why I put this thread out. If it works as I think, I wouldn't buy one, simply peace of mind for me.

Also if this thread causes someone to go check their car over and they find and fix something that was about to break that's a good thing too.

Sorry if I come across as tossing rocks for no reason. That wasn't my intention.

[G.R.]

There have to be hundreds, if not thousands, of street rods/hot rods and Cobra replicas running the Jag rearend.... let alone in original Jags since "62 or so.
Sure some have failed...due to maintence, negligence or fatigue .... or ignorance/stupidity on the owners part.

It must be he!! to be an engineer (no offense meant if you are one)
If I worried about every little niggly thing about any car I drive I would never drive it, be it the replica or the daily driver.

[olddog]

Originally Posted by Tom Wells

olddog,
Also, if you really look closely at the Jag rear, you'd notice the lower arm/hub construction will restrain a couple of degrees of freedom if the axle does come adrift. The result is probably not as catastrophic as you anticipate.

Since I only looked at the thing and did not have the ability to take it apart, I may well have missunderstood some things. I could tell that the hub would not turn left or right, but it looks to me like the top will tilt in with nothing to restrain it (no axel). Am I wrong?

It does look to me like ERA modified the design to minimize my issues.

I can say if it works like I assume, I wouldn't choose it, but if I already had it I would use it. I would be cautious with it, but that's me.

Buy the way I like the bumble bee analogy. You may have me pegged, but again I wouldn't design an air plane based on the bumble bee as a starting point with so many other better examples out there.

[Yetiman]

Well, breaking the axles can be done.


Happened during an autocross speed shifting very hard from first to second. The car simply rolled to a stop and would not move on it's own power (which kind of surprised me with the limited slip).
This is a 1962 XKE rear, which has weaker axles than the later ones. They were replaced with chromoly axles and no problems since with the same kind of treatment and worse.

[Lowell W]

Old Dog,

I raised the same issue last year sometime and got pretty much the same response: "Well, yeah, it probably could, but I don't worry much about it...".

Some of the Jag-based IRS setups do have an upper link, which seems to me to be a good idea.

Lowell

[badrich]

Yetiman: I used to speed shift regularly back in the day, but the first time I did that autocrossing in my 365 HP Stingray with some brand new 11" slicks, I stripped my spider gears and had to limp home, clunkedy, clunkedy, clunk. I may shift my Cobra quickly when necessary, but now the right foot comes off the gas, ever so briefly. I have beefed up my Jag rear end considerably and so far it hasn't given me any grief. Rich

[olddog]

Well thanks to all who responded. It did help me get some things straight in my head. More comments welcome.

29 years of working under safety taken to ridiculous levels has had its impact. To give you a hint, I can be fired for not holding onto the hand rails, when walking up or down steps. Ladders require three points of contact at all times, both feet and one hand or both hands and one foot.

So the Jag IRS is out for me, and a scatter shield around the clutch. Drive shaft enclosed. Rev limiter about 6500 RPM. What will Ernie think of me now? I must be a whimp.

[rdorman]

One thing is for sure... when you are done with your car, it should be sturdy! Sounds like a street driven spec racer with a solid rear is the way to go for you. Don't forget 'real' seats, the six points and arm restraints Not a darn thing wrong with being safe (of course, consider the source, a guy with no roll bar and a jag IRS).

[427 S/O]

767Jockey, they were purchased and came with brackets for the emergency brakes, I don't recall the manufacture. I'll contact you if I can find my receipt.

[427 S/O]

767jockey, the calipers are wilwood forged dynalite.

[avanti-176]

427 S/O-767jockey,
I think these are what you are looking for.....

http://www.cwiinc.com/brakes.htm bottom of page.

I just talked to them the other day and the setup is about $700. I will probably get it within the next month or so.

Dan

[427 S/O]

Mine are a little different and cost much less.........

[avanti-176]

Originally Posted by 427 S/O

Mine are a little different and cost much less.........

really?? Boy,if you could dig up the info I would really appreciate it. This is the only kit I have been able to find.

Thanks,
Dan

[427 S/O]

If I can find the receipt I'll pass it on...

[Tony Ripepi]

Hi Guys,

I had a Jag rear end in my Unique with a 427/Tremec combo, upgraded axels, rear link and beefed up the mounting and it worked great. George Petrus in SoCal company name Accurate Machine makes a version on the JAG rear that takes it a major leap forward from there.

Take a look at these.

http://www.cobraracing.com/ProductsAMP.html

TR

[427 S/O]

Nice stuff TR, IMHO it's more for a show car than a driver. I purchased some high end center section bolts from CWI a couple of years back, during the phone order I ask which rear end was best, they said the 89-95 HE was much stronger. I picked up one at a local salvage yard for $500, it has the aluminum cover.

[cobrashoch]

Olddog - I too understand your concern with the Jag setup and in my mind it is valid, SORTA. Yes these guys are right, there are few failures reported on the Jag setup, but if that's your only problem with this setup then you can tie off the upper hub with saftety cables to keep the wheel upright if a halfshaft breaks. Another solution would be to to fabricate a upper control arm to the hub or some kind of trailing link. Of course there are other double/wishbone arm setups out there, but that's another thread. My question is this though. Why a Jag setup in the first place? I will repeat what I have said many times and I know this will draw fire. The only advantage ANY independent setup has over a live axle setup is it gives you more suspension travel for when things get really rough. PERIOD! Virturially everything else is compromised a bit with independent setups, from a hot rodders viewpoint. A fact not lost by the NHRA or the SCCA for that matter. So if the ride on your solid axle car is rough, the chances are it is in a overspring condition, or something else is wrong, because even they can be made to both ride soft and perform. Don't forget that Factory Five spec racers use a live rear end setup most times, as does several other sports cars. For further example, the majority of the pro street rods out there use a mono spring setup for heavens sake, and some of those cars are both heavy and have well over 1,000 horsepower.
So my question to the original question is still valid. Why the Jag setup in the first place, over other designs? As with all engineering designs there trades to be made. So you do's your research, pays your moneys, and takes your chances. The Jag setup is relatively inexpensive and has history, but its not perfect.
cobrashock

[strictlypersonl]

Originally Posted by cobrashoch

...
So my question to the original question is still valid. Why the Jag setup in the first place, over other designs? As with all engineering designs there trades to be made. So you do's your research, pays your moneys, and takes your chances. The Jag setup is relatively inexpensive and has history, but its not perfect.
cobrashock

If your primary use is hole shots, then by all means stick to a solid axle. It's been engineered over the years to work pretty well, and it's hard to beat zero camber for traction.

On the other hand, a standard wheelbase Cobra replica with the engine in the proper place has a driveshaft that's only about 12" long between joints. If you stick to the recommended maximum joint angle, that translates into about 4.5" wheel travel, total of jounce and rebound. That's OK for a smooth track when you're using stiff springs, but not so good on real-world roads. Maybe my (in)tolerance for bottoming out is less than yours, but I think that a car whose suspension can't soak up normal bumps is not acceptable. I can only grit my teeth so much.

It's much easier to control the roll center height on an IRS, so that there's less jacking and more predictable handling, and the lower unsprung weight allows softer damping without losing wheel control.

RWD high performance production cars universally have IRS because it combines good handling with good ride, something that's much harder with a solid axle.

[cobrashoch]

strictypersonl - we can debate the various engineering advantages and disavantages till the cows come home, and in the end it comes down to personal choices. I know what you are saying, and agree only partially with what you said above. For example, there are many ways to make that drive shaft longer, (mine is 24") and there are many ways to incraese and control travel in any kind of suspension setup. The guys that run Baja would love to read your thread too, and this only illistrates that the various types of orthodoxy in use out there is only limited by that orthodoxy. Yes, most Cobras are built using some sort of limiting orthodoxy, but it's fortunate for all of us there is other ways. I stand by what I said. Note; I didn't say the Jag setup was not any good, I only said it has advantages AND disadvantages and IRS setups are in most cases overkill. BYW- in some cases some rear camber in a drag car is a good thing, as they hook up and the rear end is driven down. My Cobra is a drag car.
cobrashock

[82ACAUTOCRAFT]

Originally Posted by cobrashoch

strictypersonl - we can debate the various engineering advantages and disavantages till the cows come home, and in the end it comes down to personal choices. I know what you are saying, and agree only partially with what you said above. For example, there are many ways to make that drive shaft longer, (mine is 24") and there are many ways to incraese and control travel in any kind of suspension setup. The guys that run Baja would love to read your thread too, and this only illistrates that the various types of orthodoxy in use out there is only limited by that orthodoxy. Yes, most Cobras are built using some sort of limiting orthodoxy, but it's fortunate for all of us there is other ways. I stand by what I said. Note; I didn't say the Jag setup was not any good, I only said it has advantages AND disadvantages and IRS setups are in most cases overkill. BYW- in some cases some rear camber in a drag car is a good thing, as they hook up and the rear end is driven down. My Cobra is a drag car.
cobrashock

I agree, the jag IRS, having owned several E-Type has 3 main flows
1) it's heavy
2) it's complicated, difficult and expensive to service. (in-bord brakes overheat easily) It cost me $2K 20 years ago to fix a frozen parking brake on an E-Type to pass Connecticut inspection. The whole rear end had to be brought down to get to the parking break mechanism. The convertible does not have an access panel in the trunk.
4) it's suffers from too much camber change on turns and has to be set up extremely stiff for good handling on the track.

That said when set up properly, it's a great an very reliable system. For a drag car, a solid axle is a much better system for the reason stated above. Less overall weight, you can use a much beefier differential, and both tires are alway perpendicular to the ground.
Actually, when you look at Jaguar racing history, they always used solid axles even for the D type which was their most successful racing car.