Jag IRSs

[jagirs]

Hello to all Members,

I want to introduce myself and my company to you. Since I've been a member for over a year, I think everything is in place to do an intro.

I have a small company, JH Engineering, that manufactures brake kits for the venerable Jag IRS along with other services. jheengineering.com

With the exit of Mike Bontoft at C.W.I., it left a definite void for the Jag IRS enthusiast. I don't/won't ever claim to be on a level with Mike. He probably wouldn't remember me...I bought a couple of IRSs from him back in the late '70s when he had his shop in Costa Mesa, CA. to start my courtship with the Jag.

All I want to say and do is to provide the Jag enthusiast some great brake products that have been CAD designed and CNC manufactured.

I am open and covet any and all input you can give me...after all, it is for your benefit as well as mine.

Looking forward to hearing from all of you Jag guys out there.

Thank you,

Jim

[Brooklyn-427]

Do you have a alloy 4 pot conversion for the big jaguar iron 4 pots ?

[jagirs]

Sorry...

Not sure what you mean by an "alloy 4 pot". This is new terminology to me and I've been around Jag IRSs for over 25 years.

If you will explain, I will try to answer your question.

Jim

[DanEC]

I think he means 4-piston calipers.

If you have any brake upgrades for the Jag IRS, in-board rear brakes - there would probably be some interested parties on this forum.

[mickmate]

He has upgrades (alternatives) for the Dunlap (Dunlop) and Girlock (Girling) brakes. The calipers are only single piston floating but at least they are using vented rotors. If a solid shaft is stronger or better than a tubular one then most people in the drive shaft and auto manufacturing haven't done their calculations or testing. I have been making the tubular axles with a heavy wall DOM 1020 tube. These axle designs have been well tested used and proven and are a fail safe design as even if the weld shears the axle is held together by gravity. An axle that has been welded together to length and then ground off scares me, especially when it looks like it has a hole in it.
Looks like a few nice pieces of hardware available.

[jagirs]

Hi, Mickmate,

Thanks for the input!

The OEM half shafts are forged as you probably know,...but have not been not modified as you have suggested...there are no holes?? In the narrowing process they have been annealed and re-heat treated.

Many Rodders and Resto guys prefer to keep the original look. I just did a set or a well known Jag Dealer/Resto shop, nostagic racer.

As far as calipers....we've gone where the interest has been...Rodders more than Cobra guys, looking for show as well as improved brakes.

To go to the big rotors(over 103/4) to get to the big 4 piston calipers would take modification to most installation cross members...clearance is the issue, so we have been limited to the 103/4" rotor.

Thank you again for the input,

Jim

[RICK LAKE]

jagirs Jim #1 thing is stronger stub shafts. CWI used to sell 30 spline stubbies. I am on my 2nd set. First setup was stub shafts made down under and they twisted over time of hard abuse. I have gone to a detroit locker with 30 spline from the Jeep world. This rearend has held up for over 13 years of autocross and road racing. Adding a support cover to this center section would be another option to help support and control the caps in the housing. Yes Jeep world and have one. The stock salibury rear carrier needs to have 27 spline side gears removed and 30 spline gears install. Not easy but we have alot of good mechanics here that can do this job. I modified a Dana 44 carrier to work in my cobra. Getting a good price on Quieffe rear carriers would be another plus. Most guys here up the power levels over the years. I started with 348hp and 446 ft of torque and now in the all most 600+ feet of torque and 500 hp with a 484 motor. I am going into the 600/600 range on the last motor, and then some. The torque load on these rearends is the failure problem. The Salsbury is safe at the 450/450 level. The CWI went to the 600/600 level. Need to get back there. Tires are getting better and some cars are pulling 1.1-1.3G's on accel. That's hard on a rearend.
#2 Brakes for this rearend. I have solid rotors and when racing the brake pedal gets soft. Too much heat going down the trans tunnel and cooking the rotors and pads. Fluid almost boiling. The finned rotor kit for the inners would be another great option. I don't want to goto the outboard system for about 3-4K$$$. I don't know if the finned rotor kit really worked.
Anyway here a good place and projects to look at and what CC members want. IF you can rebuild a unit, this is a plus at a good price. Good luck Rick L.

[Brooklyn-427]

Rick.. you can go out board rears using later xj40 and xj6 (x300) or xj8 (308) rear hubs and brakes. Also the rare later xjs 6.0 rear out board brakes or Aston martin DB7 rear.

[jagirs]

Hi Rick,

Thank you for your input!

Agreed! Have been trying to locate a source for 40 spline stub axles for the Jag IRS with no success. If any one out there in Cobra land has any info, please contact me!

Sometime back, I emailed Mike from CWI, to get his input and hopefully some sources to fill his huge void, but for whatever reason, never heard back. I'm sure he had some sources in Britain that I haven't been able to find. Mike has/had a brother there as well.

It would seem, that with such extreme braking conditions to cause such rear brake problems, that there should be some way to duct air across the rear brakes to aid in cooling...but I'm not a body or sheet metal guy.

Back to the big rotor/caliper issue. There are other limiting factors with the Jag IRS. rotor to LCA clearance. Even with our 103/4" rotors, there is a small amount of relief grinding required.

Also, there is limited room on the front side of the Jag IRS, so space is a very limiting factor on caliper size...ala our rear mounted kits. The best option at this time is our rear mounted Corvette calipers with integral Ebrake. Corvette used them until the '97 model change, so they must have adequate to have used them for so many years.

Since the big percentage our customer base/market is for brake systems with some kind of Ebrake to meet state safety inspections/regulations. caliper selection is very limited. We feel there are better solutions for Ebrakes than drive shaft Ebrake systems.

There is way to go to 1"/1,1/8" x 12" rotors, but would require a whole new LCA approach. Like all "for profit" companies,we are limited to demand to off-set the high development costs. In other words, market demand dictates products/development.

One last thought on half shafts, we don't believe in "butt" welds.

[jagirs]

Rick,

Would your email me?

I would like your info on 30 spline side gears. Also have not been able to find Quieffe Co for rear carriers other than dealers.

jhe@inebraska.com

Thanks,

Jim

[joyridin']

My rotors are over 11" in diameter and .944" wide without any LCA clearance issues. It is all in the offset.

[jagirs]

Hi Joyridin,

Thank you for your comments.

With a deeper hat to do that with a truly 11" rotor, would put the rotors closer to the the differential...putting the rotors and their heat closer to the stub axle seals. Heat is what causes premature failure and leaks... one of the problems we have strived to improve by moving the rotor further away from the diff. a truly 11" rotor would require more relief grinding to the LCAs for clearance. All solutions are sometimes a trade-off, so it is a matter of what your deem most important.. Heat problems with a 11" rotor over a 10 3/4" doesn't seem to to be worth it to me. 10 3/4" rotors are commonly called 11", so I'd ck on that.

Jim

[joyridin']

Yes, if you use a design that requires the use of Wilwood rotors. Using another common off-the-shelf rotor will actually put the hub of the rotor further from the seal and give you more room for air circulation around the seal area itself. I did not grind anything off the LCA.

Not here to argue. Just pointing out that stating anything more than X diameter is not possible is not necessarily a true statement. I was originally going to use Wilwood rotors on the back, but the dimensions they show in their books (going back as far as 2008) do not match the actual dimensions on the product I bought. When I called them 5 times to discuss this, they just kept telling me all the books and online information was wrong. My guess was the rotors were machined wrong...but that was just a guess.

Good luck! We definitely need more people doing Jag IRS improvements!

[jagirs]

Hi joyridin'

Amen, we are not here to argue, but to discuss ideas. I appreciate your input.

A comment on your thread which confused me…you stated a .944" rotor, I assume vented. Being a Wilwood and AFCO dealer and reseller for other rotor companies, none, to my knowledge, have a .944" rotor, so I am gong to assume it might be sold as a 1" rotor?

I haven't found any off-the-shelf rotor company the manufactures a vented rotor for the Jag IRS….Wilwood and AFCO don't and non of my suppliers do. Are yours from a one-off supplier?

Some comments about our logic and reasoning. Keep in mind, that in custom work, there are always compromises/trade-offs. We have tried to address these for the best possible out come for brakes on the Jag IRS.

Let's look at one of the problems with the Jag IRS…stub axle oil seal leaks. The most common complaint we get from our customers. I have personally had Jags under my 2 of vehicles,... both developed this problem.

What is contributing to this?
One major culprit is HEAT. A well documented history.
With OEM installations you have a small solid rotor with a HAT that puts the rotors in very close proximity to the diff and stub axle seals. Another problem with this, it limits air flow to the area.

Our solution...
Putting the rotor further away from the diff would do 2 things…get the rotor heat further away and have less restrictive to air flow over there area.
Use as big of a VENTED rotor as possible w/o interfering with the cross member and mount it as far away from the diff as possible.

How…
Wilwood 10 ¾" VENTED rotors mounted DIRECTLY onto the stub axle flange with NO HAT, allowing better air flow as well as putting rotor heat further away from the diff.
Compromise/trade off…the rotor is very close to the LCA requiring a small amount of relief grinding that doesn't weaken the LCAs.

Our second biggest complaint…inadequate braking with the OEM Jag calipers.

Now that we have a different rotor set-up it allows us to look at new caliper options. The options turned out to be few….
First option, calipers with an integral Ebrake to satisfy state safety regulations.

There were only 2 with an integral Combination P/E-Brake, Wilwood and Girling Corvettes. The Wilwood was for a 13" rotor, so it was out…leaving only the Vette which was huge.
Compromise/trade off…the Vette calipers hit the rear cover requiring it to be dimpled for clearance, with NO other options on rear covers.

Second solution…separate calipers for braking and parking.
Again, due to room and clearance problems with the diff, both give front and rear limited choices. Wilwood has 2 Parking Brake calipers, 1 for a 13" rotor which is huge and desirable, but it was too big to mount on the front hitting the diff. On the rear, it just didn't fit the 11' rotor….so it was out, leaving us with the Aluminum caliper we are using, front mounted.

Front mounted caliper selection was really hampered by the amount of room due to hitting the diff. Rear mounted caliper choices were few also. The only workable calipers we could find were single piston. Our choice,…Giriling Vette, being tried, finned for additional cooling, floaters, off- the shelf, inexpensive and showy when polished. Much cheaper than any of the few Wilwoods.

This leads us to solid rotor kits…found only one outstanding caliper with an integral Ebrake, Girling race caliper with a casting number 1 off the the '84 Vette Girling's casting number.
Compromise/trade off…It is big enough to only allow finned aluminum rear covers….no faux Quick Changes rear covers, hard to fit front mounted do to size.

With enough inquiries, we developed a front mounted caliper with Ebrakes on the Series II diff to allow the show guys run their faux Quick Changes rear covers on the solid rotor.
Compromise/trade off…it is such a tight fit it requires relief grinding on the diff for clearance for the Ebrake cable bracket.

Overall trade off…very expensive development costs. Please keep in mind that all of our products have been CAD designed and CNC manufactured. All brackets and adaptors are CNC machined from BILLET STEEL, not aluminum.

if anyone has comments, it might be easier to just email me, jhe@inebraska.com

All of the products and services are viewable at jheengineering.com.

[Brooklyn-427]

I actually knew Mr Bob Knight that designed the Jaguar IRS for first use in the E Type, Unfortunately Bob passed away may years ago. i know it didnt take him long to come up with that design. When i questioned him about the unpredicated use of his suspension in Hot Rods and Replicas, he replied "I designed it to be universal in sports and saloon cars"

[Brooklyn-427]

The already known format for the rear vented disc conversion uses a off the self production car rotor. I did actually know what that specific rotor was but now unfortunately its a faded memory.

[jagirs]

Great history.

A wonderful design!!

Too bad you can't remember the info on the off the shelf rotor. Would be nice to latch onto a set and evaluate them.

[Tom Wells]

jag,

I have Mike Bontoft's vented rotors on the Jag rear in my Cobra. If my memory serves, they are Porsche rotors. They came with caliper spacers so we had to split the Jag calipers and insert them to gain the extra width to accommodate the thicker vented rotors. The calipers use the stock Jag parking brake setup.

I have worn out sets of pads on the setup both on the track - many road course sessions - and 30K++ miles on the street without problems. I am also still using the differential Mike prepared.

I found the EBC Redstuff pads to be quite good for both kinds of use, giving good stopping and low wear and dust rates.

Mike supplied custom hats for the rotors. I think he may have machined the Porsche rotors a bit to adapt them. Perhaps the wishbones had to be clearanced too; it has been almost 15 years so you can forgive me for not having that bit of info available

Mike's now in England doing kart stuff - I think if you go to his web site you could contact him directly for more accurate details: http://bontoftkartengines.com/contact

Tom

[jagirs]

Hi Tom,

Thanks for the up-date on Mike...last info I had on him he was in the Setyle area, but was boat racing in Englnd...his Dad's pasion the eventually kiled him, if memory serves me.

My original rotoreSwere Porsche..ala the Street Rodder giVe awAy TBucket in 1987 ...see my web site link on the home page. I'm not sure, but if yours were Porsche, the rotor info possiblity was probably info I shared with Mike when he was in Costa Mesa, CA... he was still there than.

Yes they took some machining and an adaptor, but the cost of Porsche rotors is why I looked in a different direction.

I just sold the last one of my kits using the Porshe rotor to clear out my inventory.

Thanks for sharing,

Jim

[cycleguy55]

Originally Posted by jagirs

Hi Tom,

Thanks for the up-date on Mike...last info I had on him he was in the Setyle area, but was boat racing in Englnd...his Dad's pasion the eventually kiled him, if memory serves me.

My original rotoreSwere Porsche..ala the Street Rodder giVe awAy TBucket in 1987 ...see my web site link on the home page. I'm not sure, but if yours were Porsche, the rotor info possiblity was probably info I shared with Mike when he was in Costa Mesa, CA... he was still there than.

Yes they took some machining and an adaptor, but the cost of Porsche rotors is why I looked in a different direction.

I just sold the last one of my kits using the Porshe rotor to clear out my inventory.

Thanks for sharing,

Jim

One would think that, after all these years, there would be a plethora of after-market suppliers of lower cost rotors to fit Porsches, thereby somewhat alleviating the cost issue. This could be attractive, should it be a better technical solution - especially if the OEM calipers could be re-used by inserting a properly machined spacer between the two halves of each caliper.