Having seen the many advantages of having an Outboard Rear Axle, how easy would it be to Convert the Inboard Rear Axle on an XJS V12 to Outboard, as in any case I may have to drop the Cage on 'The Ice Princess' in order to remove a Broken Rear Bleed Nipple

Or would it be easier to just buy a Complete S/H Outboard Rear Axle and just Swap it over?

Two concerns now come to mind: In the UK a S/H Outboard Rear Axle would come from an XJS 4.0L Six Cylinder Car, so would the Diff Ratio be any different to that fitted to an XJS V12?

Also is the Hand Brake fitting the same or would I have to Fab up a Bracket?

Has anyone done this and do you have any Pics of this Conversion?

 

I stand to be corrected, but I don't think any 5.3 car came with outboard brakes. If so, that means that only 4.0/6.0 cars had outboard brakes, and both had 4 speed transmissions with a 3.54 differential ratio, instead of the 2.88 ratio the 3 speed cars had.

It's certainly possible to swap out the differential from a 2.88 car into the IRS assembly from a late outboard car, just lots of work. The handbrake mechanism is completely different, but Jaguar engineered it so the same cable can be used.

Be aware that there are 2 versions of the outboard IRS brakes on the XJS, the rotors are different sizes and thickness. I don't believe either will accept anything smaller than a 16" wheel. If you have 15" wheels it is possible to mix and match some XJ40 parts such as rotors, hubs and halfshafts, but you will need the unique XJS handbrake mechanism. Some XJ40 brakes are different from the XJS, but I don't believe all.

 

Hi Jagboi

Thanks, these bespoke conversions are never as straightforward as they seem and my XJS 4.0L does have 16 inch Wheels, which I am not mega keen on (but maybe that's just me)

I was initially thinking, that it might be as simple as swapping the drive shafts and hub carriers as I want to keep my 3 Speed Diff Ratio the same

So looks like its maybe not quite so easy as I was first thinking

 

Diff ratio different, handbrake different, car a touch less original. And as the axle has to come out anyway, why bother? An entire axle is the easiest way if you do convert, as the hub fulcrums are not he same either.

 

Other thing is setting up the little drum parking brake inside the disk is a real pain on the outboard cars. So far I have not managed to find the perfect sweet spot of not dragging when released and effective when applied.

 

Hi Greg

May be better to keep what I've got

 

considering how much you intend to drive the car which only you will know, will it be worth all the time and considerable aggravation swapping the axles when if you just 'do' the inboard gubbins and enjoy for a considerable amount of time until it needs doing again.
Mine has inboard brakes, but it is not by any means a daily driver and in 3 years I have not had to touch it and everything seems ok, until I post a thread about being wrapped around a tree on fire

cheers
eddie

 

Hi eddie

I think you are probably right, as its very easy to over-think these things rather than get the Spanners out and then just get stuck in

 

just had mine motd and taxed and actually drove it, good lord wonders will never cease ragged the **** off it

 

That's always been my rationale against doing the conversion.

The outboard brake conversion would've made especially good sense a 20-25-30 years ago when these old Jags were in regular use....and needed brake repairs much more frequently. As it stands we'll spend a couple weekends slogging thru a rear brake overhaul... and then we can forget about for the next 10 years.

Cheers
DD

 

So...what is the advantage of outboard vs. inboard brakes, simply ease of maintenance?

Thanks,

John
1987 XJ-S V12

 

Inboard is supposed to have less unsprung weight. Meaning the wheel maintains better contact with road. Important in racing.

 

OB brakes are easier to service and ventilated rotors are available and easily fitted.

I was going to do the conversion, I had all the parts mostly XJ40, but after talking to a mate who has built many E Type and XJS race cars he told me not to bother. If I want to upgrade the rear brakes put bigger pistons in the rear caliper, and for road use not to bother with ventilated rotors.