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10/29/2011 10:27 pm  #1


Narrowest Jag rearend

I know the series-1 E-type was the narrowest factory Jag IRS, but is there any documented case of one being narrowed even further?

The geometry of these things seems pretty simple, is there a formula/spreadsheet for camber change with bump/droop travel by arm/axle length?   

How different are the inner LCA pivots on the XJ40/X300/X308 setups?

I have in mind an application that, ideally, could stand to be approx 1.5in narrower than the E-type configuration.

Thanks.

 

10/30/2011 1:23 pm  #2


Re: Narrowest Jag rearend

I know that the Jag IRS has been used quite a few times on MGBs and the track width on those is some where around 50"   It should easily work in the widths you are talking about.


If it isn't broken..... modify it anyway!!!!
http://dazecars.com/dazed/JagArmssignature.jpg
 

10/30/2011 2:55 pm  #3


Re: Narrowest Jag rearend

Here's a project for someone with a bunch of Jag bits around: weigh up the bits and post the component weights. 

An assembled hub carrier.   Control arm.   Caliper.   Diff pumpkin.   And so on.

All you need is a bunch of spare time...

     Thread Starter
 

10/30/2011 6:24 pm  #4


Re: Narrowest Jag rearend

As it happens I already have that info.  The half shafts cage and wishbones are a little on the light side because these numbers are for a narrowed unit.

108 differential
26 cage and mounts
35 calipers and discs
51 wishbones
49 drive shaft and alloy hubs
18 shocks
9 spindles bolts and washers
7 trailing arms


If it isn't broken..... modify it anyway!!!!
http://dazecars.com/dazed/JagArmssignature.jpg
 

10/31/2011 10:39 am  #5


Re: Narrowest Jag rearend

25+ lb a side for those lower arms?   Wow.   

Of course, I chucked my set of cast-iron MN12 Thunderbird lower arms in the recycling bin before weighing them, so I don't know how heavy they are...they didn't seem 9lb heavier than the aluminum Lincoln arms, though.

Everything else is about what I'd expect.  The cradle is a little lighter than I'd have thought.

Some numbers for the Mk VIII stuff, this is just the moving bits (all my diff carriers are in pieces and the one semi-intact subframe is still at the welder) :

Hub carrier with hub and bearing: 12lb each

Axle shaft with CVs and inner/outer drivers: 22lb each

Lower control arm: 16.5lb each including the little steel dogbone toe-control link.

Upper control arm: 4.5lb each

Last edited by JEM (10/31/2011 10:44 am)

     Thread Starter
 

11/01/2011 8:02 am  #6


Re: Narrowest Jag rearend

so what do you estimate the over all weight of yours will be??


If it isn't broken..... modify it anyway!!!!
http://dazecars.com/dazed/JagArmssignature.jpg
 

11/01/2011 9:48 am  #7


Re: Narrowest Jag rearend

Hi everybody,

I don't know what JEM is planing to do and why he might need the weights for the parts but my guess is that he is planing to install IRS into a smaller car !?!?!?

I didn't get the funds or time to do it but had the idea of transplanting the whole front suspension of a heavy front wheel drive car to the rear of another car less the steering parts. That means that you end up with the struds, spindles and halfshafts. You build the lower control arms, strud mounts and trailing arms around a suitable differential.  You end up with a easy to build, full travel adjustable IRS.  Maybe a big Diesel Van spindle donor caould also be positioned behind a V8 powered Dana44 or even a 9"!!

Just dreaming.................
Mustsed


Nothing is impossible, some just cost more!
 

11/01/2011 9:50 am  #8


Re: Narrowest Jag rearend

Daze wrote:

so what do you estimate the over all weight of yours will be??

Complete with subframe?  Around 380lb, maybe a bit more once I sort out the brake setup.   Maybe a bit under 100lb net increase over the 9in axle,  leaf springs, and 10x2.5in drums, but probably half the unsprung weight.

'Net wisdom puts the complete MN12 Thunderbird rear subframe assembly at a bit over 400lb, and the Mark VIII (aluminum LCAs vs cast iron, aluminum pumpkin vs cast iron, airbags vs steel springs) assembly at 350lb. 

Mine should end up somewhere in between.  Aluminum LCAs, iron pumpkin, coilovers, the Explorer cover and mounts probably add 10lb too.

When one looks at the rear end of an E39 BMW with its hydroformed aluminum-tube subframe that probably weighs 25lb, the collection of aluminum links that totals probably 15lb per side, the aluminum-body shocks, etc...you tend to think some engineer at BMW probably had a 100kg weight target for the whole thing...

Last edited by JEM (11/01/2011 10:01 am)

     Thread Starter
 

11/01/2011 12:52 pm  #9


Re: Narrowest Jag rearend

JEM so what are you working on now.  what might be getting a narrow Jag unit??

Also I missed your question question in your initial post. 

JEM wrote:

How different are the inner LCA pivots on the XJ40/X300/X308 setups?

On the newer Jag units the LCAs mount to the support structure rather than directly to the differential so the design is quite a bit different.


If it isn't broken..... modify it anyway!!!!
http://dazecars.com/dazed/JagArmssignature.jpg
 

11/01/2011 3:45 pm  #10


Re: Narrowest Jag rearend

Daze wrote:

JEM so what are you working on now.  what might be getting a narrow Jag unit??

The MN12/FN10 assembly is going in the '64 Country Sedan, as noted elsewhere. 

I have a Mk1 Cortina GT in the queue, it's fractionally narrower even than an MGB, though the MGB track width could work.    It's really just dreaming at this point - that car's more than likely going to end up with something close to a stock rear suspension, stick axle on something resembling stock GT rear leafsprings and upper trailing arms though possibly something else (Corolla?  7.5in Ford?  late Camaro 7.5in 10-bolt?) for an axle. 

The plan for that car is really to keep it as simiple as possible, though the powertrain agenda has shifted toward a 2-liter Zetec, maybe a Duratec though I've already got a core black-top Zetec in hand.  Looking for about 250HP turboed.

Last edited by JEM (11/01/2011 3:47 pm)

     Thread Starter
 

11/01/2011 4:09 pm  #11


Re: Narrowest Jag rearend

so when do we get to see pix from the MN12/FN10 project???


If it isn't broken..... modify it anyway!!!!
http://dazecars.com/dazed/JagArmssignature.jpg
 

11/01/2011 6:08 pm  #12


Re: Narrowest Jag rearend

Daze wrote:

so when do we get to see pix from the MN12/FN10 project???

Should have subframe back from the welder late this week.  Assembled and back under the car this weekend.

     Thread Starter
 

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