E type series 1 rear discs

ochryfoel · Post by **ochryfoel** » Sat Dec 21, 2013 8:49 pm

Hi, I'm reassembling the rear suspension/diff/brakes of my 3.8 June 1963 coupe. I have noticed that the new 3/8 discs seem way too thin. The handbrake pads are at an angle and the heels by the pivot bearings don't touch the disc, and the lost movement in the normal calliper pads seems to indicating they will only be half worn when the pad carrier hits the stops. I see the 1964 4.2 had 1/2 inch 12 mm thick discs and am wondering if I should be fitting these.
I have had the car since 1970 and often noticed I had to change pads every 5k miles!. Thicker discs will fit in the callipers ok and will give me more miles,
Any advice/ experience would be appreciated before I put it all back together.
Cheers Peter

andrewh · Post by **andrewh** » Sat Dec 21, 2013 9:15 pm

Hi there. Welcome to the forum and whist I am not the best to help you with this question I want o say well do e for owning you car since 1970. Awesome performance I am sure someone will offer you advice on this as I am not that familiar with the different set ups between models.

38E · Post by **38E** » Sun Dec 22, 2013 2:08 am

I'm pretty sure that 3.8 rear discs are 3/8" thick.

kingzetts · Post by **kingzetts** » Sun Dec 22, 2013 10:08 am

What you're describing sounds normal to me. The handbrake pads when new are cut on a chamfer and the rear edges never get anywhere near the disc surface.

If you fit thicker discs you'll probably not get new main pads to fit between the caliper pistons and the disc.

When you say you had to change pads every 5000 miles do you mean main pads or handbrake pads? If the latter then something is wrong - unless you routinely use the handbrake to stop the car, as opposed to simply as a parking brake, the handbrake pads should last for donkey's years.

ochryfoel · Post by **ochryfoel** » Sun Dec 22, 2013 11:09 am

kingzetts wrote:What you're describing sounds normal to me. The handbrake pads when new are cut on a chamfer and the rear edges never get anywhere near the disc surface.

If you fit thicker discs you'll probably not get new main pads to fit between the caliper pistons and the disc.

When you say you had to change pads every 5000 miles do you mean main pads or handbrake pads? If the latter then something is wrong - unless you routinely use the handbrake to stop the car, as opposed to simply as a parking brake, the handbrake pads should last for donkey's years.

Hi thanks for replies,
With main pads in and fully retracted there is a gap to the disc of 4 mm each side, so pad to pad is 15 mm. The hand brake pads trailing edges are 13 mm apart. The new handbrake pads I have are parallel and not chamfered.
It was the main pads I replaced often, but they were only 1/2 worn when the pad carriers hit the stop.
I wonder what was fitted in 1976 when I had replacement callipers all round.
I suppose what I need to know , is a 12 mm disc the same as a 3/8 one except for the thickness and will just bolt in?
I have the diff on the bench right now and am building up with new (1998) discs and refurb callipers etc. so now is the time to get this sorted. I was hoping to get some guidance before buying some 12 mm discs and trying them. M&C Wilkinson talk about 12mm discs being part of an upgrade for 3.8's, but they are all on holiday now!
Cheers Peter

kingzetts · Post by **kingzetts** » Sun Dec 22, 2013 1:42 pm

If you've got a 4mm gap each side between new pads and the disc then there's something not quite right. On my Dec '62 3.8 there's only just room to slide new pads in with the pistons fully retracted. It could be that you've got later calipers as you suspect.

You could do with someone measuring up genuine 3.8 calipers to compare to yours - you certainly want to sort this before you build up the IRS. Unfortunately my IRS is in the car and inaccessible or I'd do some measuring for you.

PeterCrespin · Post by **PeterCrespin** » Sun Dec 22, 2013 3:27 pm

Clive's right, the car would have had 3/8" discs originally.

The only way I could understand your symptoms was if someone had messed about and fitted the wrong calipers somehow, but I assumed that since you'd owned the car since 1970 that was very unlikely. Now that you say you got someone to renew calipers all round I think that may be part of the issue.

All new pads are flat not chamfered, unless one refers to the corner cut off the handbrake pads to follow the disc circumference as a 'chamfer'. The mechanisms are adjustable so pads can always be set up flat to the disc initially, though they can then wear a taper in use if not looked after.

Pete

neil4444 · Post by **neil4444** » Sun Dec 22, 2013 4:45 pm

Hi Peter,

Photos of my 3.8 with 3/8" discs.

I can't get a measure in to get correct inner dimension of the carrier however it looks like I have approx 3mm from each side of the disc to the inner face of the carrier. This would suggest approximate inner measurement of 15.5mm (9.5+3+3). With a 1/2" disc this would give you 1.75mm clearance either side. I know at the flange of the disc I have about 1mm clearance. I therefore think it would be impossible to install a 1/2" disc in a 3.8 calliper. My assumption from your comments is that everything on your car has been swapped to a 4.2 set up. My one thought is that you may have 3.8 handbrake calipers on a 4.2 brake carrier which could explain the issue of the handbrake pads not meeting the disc.

Regards,

Neil

neil4444 · Post by **neil4444** » Sun Dec 22, 2013 4:46 pm

btw, I think you can tell which type handbrake carriers you have by size of the pad rebate as they were different for 3.8 vs 4.2

Dave K · Post by **Dave K** » Sun Dec 22, 2013 6:04 pm

About 10 years ago when I rebuilt my IRS I can recall a similar problem to yours with the handbrake pads I bought from a stall at Stoneleigh.
To get them anywhere near the discs I had to remove them and file them to fit. I'm sure that if Angus and Pete plus a few others had archived emails from that period then they would also recall the problem.

The pads I bought were perfectly flat all over but they should be slightly angled so they fit square to the discs from new. I bought a new set from SNGB a few years ago and they were the right ones.
There is more to this story but it's so long ago I just can't remember it all. It goes something like there are two types of the same handbrake pads available and both will fit the S1 E-Type but only one set is right.

Dave

ochryfoel · Post by **ochryfoel** » Sun Dec 22, 2013 8:38 pm

Thanks for all the info and Neil for pics.
You may have it there maybe 4.2 calipers. I do remember giving the car to the jag main dealer asking them to sort out the brakes as they were terrible.
The caliper bridge where the main pad retainer is fastened measures is 1/2 inch thick, and your calipers seem narrower.
I see some 12 mm discs cheap on eBay so I"ll try some, sell them on if won't fit. I,ll get on with the head while I wait for the post, oh and better spend some time with the family.
Thanks for your help chaps I,ll report back when I have tried the discs,
And seasons greetings
Cheers
Peter

neil4444 · Post by **neil4444** » Sun Dec 22, 2013 8:45 pm

Hi Peter,

Yes, I think that confirms it. The bridge where pad retainer fixes is 3/8" on mine. I remember I got sent the wrong retainers initially which were the 1/2" ones for the 4.2.

Regards,

Neil

abowie · Post by **abowie** » Sun Dec 22, 2013 9:54 pm

There are 2 different types of handbrake pads, one thinner than the other.

ochryfoel · Post by **ochryfoel** » Mon Dec 23, 2013 9:51 pm

Hi folks,
I did some more digging and reading all my e type books. In my 1991 copy of "6 cylinder restoration and originality guide" by Prof Haddock, page22 he says about June 1963 from 87944/1 , 879460/1, 888694/5, 850721/2, 861184/5, 879493/4, 888705/6, and 888672/3 for cars with 3.54:1 , 3.07:1 and 3.31:1 rear ends ,
the rear discs were increased to 1/2 inch, and were mounted on adapter brackets not direct on the diff. Ipso facto mine should indeed have 1/2 discs, and I guess it's been on 3/8 inch ones since I had it. No wonder the handbrake was poor and wore out main pads so quick.
The 4.2 was introduced and used these brakes.
Thanks for all your help, so we now know 3.8 e type rear discs can be both sizes.
Cheers
Peter

ochryfoel · Post by **ochryfoel** » Thu Jan 02, 2014 11:22 am

Hi folks,
12mm discs arrived and now fitted, perfect. All slack removed, handbrake pads now parallel , main pads slide in and out with about 1 mm clearance.
Anyone else out there with same- perhaps not aware? Check calliper web is the same thickness as the disc.
Another interesting difference is the length of the rear suspension inner fulcrum bearing tube, books say 3.8 has long ones, mine has short!
Cheers
Peter.

Andrew20 · Post by **Andrew20** » Mon Oct 19, 2020 8:15 pm

Hi Pete,

I’m in the similar position to you!
I have a 1964 series 1 3.8

Can you please tell me the part number for 12mm thick disc, to suit the 3.8

All information appreciated

Cheers
Andrew

Post by **mgcjag** » Mon Oct 19, 2020 8:43 pm

Hi Andrew...give SNGB a call....and check with one of their tech sales guys....Steve

Andrew20 · Post by **Andrew20** » Tue Oct 20, 2020 7:46 am

Hi Steve, thanks for your support
Cheers
Andrew

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