OT but relevant: Jag IRS How To...

Great thread .... thanks for your efforts posting this info.

Now all I gotta do is find one of these $200 donor cars I keep reading about here on the HAMB!

 

Thanks,Don't need the info right now but saved for future referance.

 

The XJ IFS are used in a lot of different cars/rucks. I have one under my 49 F-1 truck. They can be soft mounted as originally done by Jaguar (I soft mounted mine) or welded in. The front crossmember has everything attached to it. You just have to build upper shock mounts. When you set the IFS under the car, use a level front to rear on the top of the crossmember. With it level your front end geometry will be correct.

 

what spring rates for a single coil over in the rear per side have people used?

Since there is the leverage issue of where the coil overs are mounted with the independent rear suspension, I have found you need more spring rate.

I have 400s in the back of a 29 coupe. Where I would probably just have run 250's if it was a straight axle.

wil

www.sakowskimotors.com

 

well there has been alot of jag irs conversions over the years.. and I would just like to say that the pumpkin thats in there is the british version of a dana 44 I believe the only difference is the carier bolts are smaller.. but you can drill and tap so that standard dana gear sets will swap in.

 

and hell i traded my 79 xjs sbc powered car for a 81 honda 3 wheeler lol

 

got alot of ands here today.. if you solid mount the rear you don't need the trailing arms either...

 

On my Buick I used the stock rate as the weight of the car was the same as the Jag.

 

Well not the originals for sure.
But you do need some.

See tech article here.

http://www.uk-hotrods.co.uk/v2/tech/jag_rear/tech_jag.php

.

 

Do you have a brand/stock number on those units?

 

X1000

A very common mistake is when the folks solid mount the rear and then add trailing arms that mimic the originals. They are really only needed if you rubber mount the cage with the original rubber mounts.

If you really really really think you need trailing arms with a solid mount, then the front of the arms must intersect exactly the axis of the lower inner fulcrum arm bearings. You gotta be tits on. There is no interference motion with these rears as everything is mounted on tapered roller bearings.

 

Plus if you don't use any trailing arms you are relying on the bearings and the shocks to keep the wheels in the right place.

Eventually they will fall off

Had a car like that and the axle whip was really bad until I installed trailing arms.

 

Not so. If you had problems something else was bent or worn out.

The Jag lower arms are tugboat strong and the inner mounts are wide enough to triangulate. Those pieces are DESIGNED to do what they do, and it is a design that the Brits really got right.

Many, many Cobra kit cars, for example, cars with healthy Ford side-oiler motors, used solid mounted Jag rears with no arms. They did just fine.

Stock Jags mount the rear in a cage that is rubber mounted to the unibody. The trailing arms are mounted in really soft rubber bushings - way too soft to locate the rear fore and aft - but just firm enough to introduce a modicum of rear steer when cornering hard, one of many reasons that these Jags handle as well as they do.

If you solid mount a Jag rear and then replicate the stock trailing arms with bushings or hard links you are asking for trouble as there is no provision for interference motion with these rear suspensions. You will be forcing the center section to walk clockwise-counterclockwise (as viewed from the top) as the suspension works, and that is not a good thing.

 

There is no "really really really think" about it.
Seen way too many rear end problems with them being left off.
But agree, they need to be mounted spot on to create the perfect triangle.
See my earlier link for details.

 

So, that concept of the perfect triangle is really really really REALLY important.

Most of the Jag IRS installations you see just mount the trailing arms any old way. And that is really really really bad.

I stand by my statement that they should not be needed, but I have absolutely no problem with them being there if you really really really really really have that perfect triangle!

 

Agree

 

Thanks collecting info.

 

One question... what was the rear tire diameter on the Jags? Gary

 

I use a solid mounted 420 Jag IRS in my 35 Chevy along with the stock Jag coil overs. Given that coilovers are old and soft, it rides a treat. I set it up with all OEM specifications without the cage. It took a while to set up correctly but was well worth the effort. I use a sway bar which improves handling immensely. I also used a lower arm rear bush on the front of the lower trailing arm, no binding whatsoever as they mount as per OEM. You definitely require front and rear tie bars , bottom plate and forward reinforcement rods to stop the centre reacting under acceleration and braking forces. I've seen others run them forward so as the pivot point intersects with line from lower inner axis.

 

Thanks, some info I was searching for for my TVR, yours is the first that gave info on the stub axles!!! Printing and saving to hard file!
Thanks, and Thanks again, Hugh

 

This varies a bit between different years and models, but sixteen inch steel rims are the most common on the original cars. The tires also vary a bit, but around 25" to 26" rolling diameter would be about right.

 

Wow, Thanks for the great info!

 

Really appreciate that you took the time to scan all these Bash'n'Weld<SCRIPT type=text/javascript> vbmenu_register("postmenu_4141123", true); </SCRIPT> . THANKS

 

The one in my sedan is solid mounted. It was originally an early 70's build, The ride is real smooth.

 

15 inch rims and overall tire diameter, IIRC, of 24"

 

I must say, warpspeed, never seen any 16" rims around these parts.
All of mine are 15"

 

Yes all the older Jaguars such as XJ6 mostly use 15 inch steel rims,
The more recent ones like Xj40 , V8 and V12 Jaguars use 16 inch rims with alloy wheels and lower profile tires.

 

In case it helps.
Here are a few links to Jag rear end threads.

Have a look through these threads.
Everything you will need to know .. and more.

http://www.jalopyjournal.com/forum/s...ad.php?t=77729

http://www.jalopyjournal.com/forum/s...d.php?t=296583

http://www.jalopyjournal.com/forum/s...d.php?t=333423

http://www.jalopyjournal.com/forum/s...d.php?t=160436

http://www.jalopyjournal.com/forum/s...d.php?t=381637

http://www.jalopyjournal.com/forum/s...ad.php?t=24785
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Not sure why the wheel size is such a big deal. Bolt pattern is 5 on 4 3/4 just like a Chevy. Most regular rims will fit, just check the center hole size first. Supremes fit awesome.

 

Thanks again for scanning these....Looks like i'm fixing to jump in feet first.