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Kirkham Motorsports

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  #1 (permalink)  
Old 11-27-2022, 12:38 PM
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Default Jag rear upgrades

Since the ERA rear is temporarily unavailable I was wanting to start a thread about Jag rear upgrades that folks could do that could be beneficial for those that are more track oriented. I plan on tracking my car as much as I can (autocross/ track days at COTA) and I would like to fix some of the minor issues with the Jag rear.
This is meant to be an open thread for those that have done some modifications or have suggestions for areas of improvement.

Brakes: I know the one issue is having the brakes inboard is not great for cooling as well as serviceability. I do plan on upgrading to vented rotors and adding the remote bleeder. I believe I have seen somewhere that there is also a wilwood caliper replacement as well....not sure on that though. Also could add some custom brake cooling ducts to help with temps.

Adjustability: I dont know if anyone has tried building there own adjustable lower control arm (similar to the ERA rear). I think I might give that a try. I do plan on adding the upper track bar (again, similar to the ERA rear). I think that would be pretty straight forward. Make an attachment bracket that bolts to the top of the OEM jag hub carrier. If I sandwich steel plates on the inner and outer of the aluminum carrier I believe that should be plenty strong enough.

Any other suggestions or thoughts on above mods would be appreciated.

My last effort down the road would probably be a complete DIY rear using a fabricated 9" center section/ quick change rear, CV shafts and custom upper, lower control arms. Would also require a cnc'd hub carrier at that point.

Anywho, just curious if anyone has upgraded their jag rear and what success you have had with it.

Thanks
Jason
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Old 11-27-2022, 01:09 PM
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Jason,

I'm sure you'll get much more learned replies, but that doesn't stop me!

I have an Everett Morrison that uses a Jag rear. It is stock, including 3.8S axles (length == longer than XKE but shorter than XJ) and PowrLok differential. It was built years ago by Mike at Concours West and has lasted many track and street miles, having at present 43K miles under it so far. I don't know if Mike put any special bearings, seals or limited slip friction materials into it.

It does have vented rotors which use custom hats and slightly machined Porsche rotors.

No other mods I'm aware of.

I use a proportioning valve to reduce the pressure to the rear brakes. If you have dual master cylinders you'll use the balance bar to get the fronts to lock up first.

I've worn out a couple or three sets of pads doing track days at Daytona, Sebring etc, but no problems otherwise.

One thing the thicker rotors did require was a tweak of the emergency brake linkage and cable setup. Not difficult but it was necessary to keep that function.

The main thing is to enjoy the ride!

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Old 11-27-2022, 01:20 PM
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The only part ERA can't get is the hub carriers.

Why not machine or modify existing Jag carriers to fit the ERA rear?

John

Last edited by Grubby; 11-27-2022 at 01:29 PM..
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Old 11-28-2022, 05:09 AM
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There are some interesting kits to build 9” independent rears.

This could be an opportunity to build something better than the ERA rear.

Maybe use upper and lower adjustable control arms like modern cars. Could easily be stronger and more adjustable. You could likely use the Jag hub carriers.

John
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Old 11-28-2022, 08:26 AM
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I’m surprised that ERA hasn’t sourced new hub castings.
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Old 11-28-2022, 11:52 AM
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In todays climate I am not surprised it is getting harder to source parts. The small business that do these type of things are starting to get few and far between.

In the end I am still getting the independent rear with the 6 pin hubs. I like to think I am fairly decent at fabrication and actually kind of enjoy it.

In regard to the ERA rear with jag hubs, I dont think the inboard brakes will fit in the custom aluminum cage and I would still have to make the bracket that would bolt to the Jag hub.

I would like to move forward with using a quickchange rear and CV shafts. I think I am going to try and work on drawing up a 2 piece hub carrier similar to modern vehicles. I need to contact DSS or Mark Williams to see if they are able to make the outer CV splines to match the Jab hub...10 spline that way I could keep the 6 pin hubs. Thinking about if I went to a 2 piece hub carrier I could use a c6 upright and just have a custom bolt in hub that accepts the correct bearings. I think that would be a lot simpler.
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Old 11-28-2022, 02:56 PM
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Could you not use the narrower E Type rear with outboard discs?
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Old 11-28-2022, 05:39 PM
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Image17 - Club Cobra Photo Gallery
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Old 11-28-2022, 10:09 PM
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Exclamation Outboard brakes!

The 94-96 XJS, and some other models, used the same basic Jag rear configuration, but used outboard brakes. This is what I used on my Unique Motorcars 289 USRRC. There are a couple of important differences between the two: the outboard u-joint mates two different size yokes, as the stub axle is different, and the lower control arm pivot bolt on the bottom of the hub carrier is slightly smaller diameter on the newer unit.

Here are a couple of pics of mine. I made a jig to be able to move it easily, otherwise it is a bit gangly without the frame around it!



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Old 12-08-2022, 09:33 AM
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On the 2nd ERA Cobra I built, I installed Tilton calipers. They made a kit for the inboard mount. They have all the components to ensure front/rear bias, etc.
Don't worry about the inboard feature, they mount in the rear position and I cut our a large window in the trunk and installed an aluminum cover with aircraft Dzus fasteners and used their hand tool for quick removal & attachment.

Keep in mind that the rear brakes are only doing about 30% of the stopping power, so heat buildup in club track days (10 lap session) will not be a major issue. The emergency calipers still remain in the front.

If you think heat buildup will be a major factor in longer lap sessions, you could install two electric fans (one for each rotor) just above the drive shaft tunnel to blow cooler air from the cockpit area into the critical heat zone.

Also, attached is business located in La Habra, Calif that makes compete Jag IRS suspensions using either a Ford 9 style 3rd member or a Quick change 3rd member. They have everything from flange face to flange face in several different widths. They are well know in the streetrod world with a great reputation. Some of the biggest car builders in LA, like Chip Foose, use Kugel rearend assemblies in their vehicles. kugelkomponents.com
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Old 12-09-2022, 05:28 PM
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Here you what I did..
https://twitter.com/JohnMaddison2/st...S_4uAWOpw&s=19
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Old 12-10-2022, 06:47 AM
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I put Porsche 11.5 vented rotors on the rear. The calipers were from a 72 Jaguar I think and were the 2 piece design with the split down the center. The rotor fit perfectly and I just added a spacer between the caliper halves. The e-brake had to be moved to the driveshaft. Looking back, I probably should have used GM calipers with the e-brake in them. It would have been cleaner and easier.
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Old 12-11-2022, 09:03 AM
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You could have just used the Jack calipers the same way and just put a spacer between them and break
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Old 12-18-2022, 05:20 PM
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Call Jagbits
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Old 12-19-2022, 06:20 AM
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Quote:
Originally Posted by CHANMADD View Post
You could have just used the Jack calipers the same way and just put a spacer between them and break
Huh? They are Jag calipers and they are split. The e-brake won't work because the rotor is too big.
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Old 12-19-2022, 07:41 AM
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I had no issue with the stock Jag e brake with the wider vented rear rotors. I used this kit.

https://mossmotors.com/rear-vented-d...conversion-kit

I did have to grind some clearance on the Girling calipers and the top inboard lower control arms for the wider vented rotor assembly.
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Old 12-19-2022, 10:33 AM
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Probably depends on the diameter of their rotors. I think mine was a bit over 11" in diameter. I built/machined everything myself. If there was a way to make it fit, I would have done it.
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Old 12-19-2022, 07:38 PM
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Default Jag rear upgrades

My vented rotor kit had the same diameter as stock plate rotors I believe but the diameter of the adapter plate created an interference at the e brake mounting area.

Club Cobra - mvanhorn8893's Album: Contemporary Front Caliper Interference - Picture


This plate diameter also caused an interference with the lower control arm. In retrospect this may never have been a possible condition with the shocks and coil over springs installed as the car is not likely to ever bottom out enough to allow that to happen.

Club Cobra - mvanhorn8893's Album: Contemporary Front Caliper Interference - Picture

Club Cobra - mvanhorn8893's Album: Contemporary Front Caliper Interference - Picture
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Old 12-19-2022, 08:25 PM
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Jason,

Before you begin a modification program you might want to look at Morris' gallery and how he did his rear end. Morris' car is a Kirkham which means it uses a Kirkham version of the Dana 44 but otherwise similar to the Dana 44's you are considering.

While I haven't seen your car and your gallery does not provide any pics of it, I suspect that the Kirkham which Morris uses would perform credibly in the race events you are considering. If that is true you will find a wealth of rear end and considerable other information in his gallery. He is also quite generous with both sharing what he has done and why he has done it.

The best aspect of using Morris knowledge and experience is that, it is track tested. I am going to go out on limb here and suggest his race track performance, which the car has to deliver, would likely be at least comparable to what you are considering.

The investigation might save you monies, avoid false starts, and produce a finished product that could even exceed your expectations. Check out his gallery, I doubt you will be disappointed. He is also easy to talk with and very upfront about sharing his experiences.
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