Hi, I'm looking to find out if the rear brakes from an X308 will bolt up to the hubs on an XJ40?

Thanks

 

I believe even some XJ40 brake fitments change over the range, so why not check the part numbers against your vin?

https://parts.jaguarlandroverclassic.com/

Larry

 

Checking part numbers will only tell me if they are the same as stock, not whether they would bolt on?

It would appear the brake shoes and disk/drum depth was the same from the early XJ40 all the way to the end of line X308, so the disk should fit and the handbrake work. What I'm less clear on is the calipers and whether they have the same mounting bolt pattern to the hub

 

late 1993/94 XJ40 used the newer X300 rear suspension platform that was carried into the X308 , so most if not all these parts are interchangeable,

i would not expect earlier pre 1993 XJ40 parts to be as compatible as the lower wishbone and hub carrier and damper/spring setup was different to the X300 and X308 ( and the late XJ40 )

BB

 

I have a late model XJS with outboard rear brakes so solid discs and single piston calipers. Im lead to believe these are the same as the XJ40 including the hubs and hub dimensions.

I have since fitted X308 vented discs and calipers and they are a direct bolt on, although you will need the backplate or if not, cut the lip off the inside of the backing plate to it doesnt foul on the inside of the thicker disc. The inner handbrake drum parts are the same.

Having said all this, Im in the process of looking at early x350 calipers which have an integrated handbrake mechanism in them so I have dispense with the drum in hat handbrake.

 

That's very useful, thank you very much!

So to cut to the chase, I'm actually looking to to the reverse. I have an X308 XJR and I want to run 15 inch wheels and drag radials, so I'm looking for a bolt on brake conversion. It would appear that the hub geometry is common and the difference is in the caliper carriers and the handbrake is common too which is perfect.

Can I ask if you recall what your disk diameter is? I believe XJ40s had two types and the calipers for one are far more common than the other.

Thanks!

 

The original discs were solid before I went to vented. I'll measure them up but 270mm seems to ring a bell.

I have seen a conversion which uses XJ40 front discs on the rear. They are:

Option1 - This uses a four pot caliper and handbrake in conjunction with an XJ40 290mm vented front rotor, mounted on the rear hub. The caliper is mounted on a specially produced mounting plate which bolts onto the old mountings for the hub handbrake backplate. This will fit in 16" wheels -

Option 2 - This uses a 325mm two part rotor and the same four pot caliper and handbrake assembly. In this case the caliper mounts onto the original caliper mountings. This kit requires 17" wheels and the use of an oversize front brake kit to maintain braking balance. Photo attached of the rear axle with this kit installed.

This doesnt answer the issue of a 15 inch wheel though

One thing i found was that fitting 15inch wheels on the with X308 calipers didnt work as the caliper is too big to fit inside the wheel. This setup has the 305mm vented discs.

I suspect its possible to fit 15 inch wheels if you used a solid disc and the smaller caliper, but thats just a guess.

I started a post looking at an X350 rear caliper to see if this could be mounted to an X300 hub. I dont know the answer to that but it would open up the possibility to use that caliper (possibly) and the x350 2.7tdi disc which is 275mmm i think. The only problem I think is that that PCD is different.

Nothing is ever simple...but then it wouldnt be fun if it was.

 

Bold section is what I'm hoping, some XJ40s came on 15s so it should work.

I know the 15s wont fit over the X308 brakes, I have these at the moment.

It does sound like the XJ40 rears will bolt up to my X308 hubs and should then fit inside a 15" rim.

If you could possibly measure your disks that would be great, then I just need to find an XJ40 owner who wants an upgrade to swap with...

 

I think we are both being a bit daft here and I should have re-read my original response!

I had solid, outboard discs on 15inch wheels with small single pot calipers. It was only going to X300 vented discs that they needed 16 inch wheels.

So my original discs were 278mm. The part number is JLM12429. Its the calipers you will also need as they will fit in the 15inch wheel. It'll ne pre 1990 calipers, which I think are Teves. The x300 back plate should be ok for XJ40 parts, its the XJ40 back plate that needs to be changed for X300 parts.

Hope that helps.

 

Yep, and the X300 and C308 parts are the same, with a 305mm vented disk and you managed to bold that disk and caliper to the XJS hub carrier, so it stands to reason I should be able to bolt the solid 278mm disks and corresponding caliper to the X308 and then have clearance for the smaller wheels.

The pre 1990 stuff is very rare now and also popular for a brake conversion on some old Hillman I'm lead to believe, but there was also a later 295mm solid disk. I guess if the caliper bolt spacing and the drum assembly were common from early XJ40 to X308 they will also be the same on the late Xj40, just need to confirm if 15" wheels fit as the later bits will be easier to find.