Early 1962 E Differential , disc mounting distances

[nandovegni]

Hello everybody. This is my first post.
I’m trying to replace the rear discs and calipers with a newly made specialist vented ones.
To cut a long story short, in the standard E type diff with mounting brackets the distance from the back face of the disc to the outside of the fixing lug is ~42mm* - in my case this distance to be 31mm. See pictures
The new caliper if fitted as is would then interfere with the cage , and would require spacers to the disc making the entire geometry a disaster.

Can anybody help? Was the differential case sooo much different early days?

[Robbiee]

Hi
Welcome
What’s your name and car details please?

Probably not a helpful answer but, Why are you doing this??
Robbie

[nandovegni]

Hi, my name is Ferdinand, and the car is an OTS Feb 1962, LHD.

[abowie]

It's going to be hard for any of us to supply you with measurements because as you know the mounting brackets are just about totally inaccessible on the IRS when it is in the car.

The S1 cars had two iterations of brake discs with C15223 being fitted to earlier IRS and C20326/C26779 being fitted to later IRS. The later discs are thicker. I think the discs have different offsets but I don't have any to hand to compare. The change was sometime in mid 1963.

Looking at the SNGB parts book there are also two different rear brake calipers which change at 850254, 875964, 860023 and 885143. This is around late 1961. I don't know what the differences between the callipers are.

I don't know whether these changes reflect a change in the diff housing casting or not, but certainly the calliper mounting plate is different in the early cars.

I suspect to use your current callipers you're going to have to fabricate yourself custom mounting brackets. This shouldn't be too difficult as you have the diff stripped and so making measurements is easy.

As Robbie alludes to above, unless you're going to seriously circuit race your car fitting brake "upgrades" on the E type is not enormously beneficial. All you'll maybe gain is better heat dissipation and therefore a few more stops before you get brake fade. Your car is probably not going to stop any faster. The original brakes work well as long as they're in good condition.

If you really do want to fit vented discs and bigger callipers to the rear there are certainly companies out there that make stuff that will fit.

Alternatively what many people do is upgrade the fronts to a ventilated disc and 4 pot caliper, then put the 2 1/8" front wheel cylinders on the rear. You need to be mindful of not upsetting your brake bias as if your rear brakes are too good they will lock up before the fronts which is very dangerous coming into a corner.

The other problem you may run into with larger pistons and 4 pot calipers is that the 3/4" master cylinders may not be big enough, requiring changes there as well.

Please update us on your progress.