I might have only gone and solved the Handbrake issue!

[Darren C]

Like most of you, each year I have to adjust my Delorean Handbrake just before the MOT, so that it just scrapes through and for a few weeks afterwards its ok but progressively looses efficiency over the year.
This year with MOT looming I decided to overhaul the handbrake once and for all and came across a worrying engineering issue that may just be why our Delorean handbrakes are so in effective.

Firstly I removed the hand brake and stripped the complete assembly down, opening the casing to reveal the self adjuster. This was thoroughly taken apart cleaned and greased and re assembled. The handbrake cables were disconnected from the brackets and oiled to ensure they weren’t snagging in the sheath’s and replaced.

The return forks (that spring apart to keep the pads clear of the disc when not in use) were checked to ensure they were still strong enough to hold the pads out of contact to stop them dragging on the disc and refitted.

New handbrake pads were purchased and installed. (The old ones hardly looked worn, but I thought as good measure I’d replace them once and for all to get a better handbrake.

Everything was refitted to the car and with the cables still disconnected, the slot head adjusting screw was tightened until the pads dragged and backed off so that the slot in the head of the adjuster was vertical to take the split pin.
The recommendation is 5 thousands of an inch clearance between pad and disc. Not always easy to achieve with the need to get the screw slot vertical for the split pin, but better the pads to be just clear than binding. Split pin back in, the cables were then attached. Adustment MUST be done this way around so that when cables are adjusted they only take up cable slack and not pull on the lever. If this is done the opposite way around the handbrake arm can pull hard up to the top suspension arm and foul it before pulling the pads on.
It is also critical to take the slack up on the cables equally on each side until they just pull the pads and drag on the disc; then back them off ½ turn on the cable adjusting nuts so the disc spins free. The reason that they must be adjusted equally each side is that under the handbrake lever is a vertical bracket with a pivot in the centre. One cable fits the top, the other in the bottom. The lever pulls from the middle so the bracket needs to be vertical as it pulls otherwise it will cant over and one cable can come disconnected. Also if adjusted with the plate vertical it pulls equally on each handbrake rather than on one and when that’s tight starts pulling the other. This is what causes handbrake imbalance (along with miss adjustment of the slot screw adjuster on the calliper arms)
Ok, all still following me?…..

Now this is where it gets interesting.

Having rebuilt and adjusted the handbrake by the book, I drove to the MOT and it FAILED spectacularly!

The efficiency was so poor it hardly registered?
The handbrake was lever was rock solid after 3 – 4 clicks, but the floor rollers at the MOT station simply overwhelmed the handbrake.
How could a total overhaul make it worse than it has ever been?
Maybe the pads needed bedding in a little?
I spoke to the MOT tester and decided to go for a drive around the village (slowly) with the handbrake on 1 click and light on, on the dash and back to the test station.
In the rollers again and guess what, NO better!

I reluctantly took the car home and not one to be beaten, decided once and for all to find out what the inherent problem is with a Delorean handbrake.

I checked the mechanism, cable and lever, all were fine. Not one to be defeated by an engineering issue I took the handbrake apart again.

Then EUREKA I found the problem that I suspect is affecting most of us.

On inspecting my BRAND NEW handbrake pads I was astounded to see one corner crushed and crumbling.


This had been caused by very high pressure focused on a very tiny area. What was going on?

I took my old pads, out of the bin in my garage (the ones that didn’t look too bad) and cleaned them with some acetone on a rag to reveal a similar fault.



The pads weren’t mating to the disc properly.
These old pads were in the car when I shipped it back from California back in 2006, so have never bedded in, despite 8 years of use and 8 yearly adjustments!
But why not?
What’s going on here?

Now in my time restoring pre-war cars, when ever you replaced the brake linings (you had to rivet them on, they never came in a box ready to fit in the old days) they needed cutting before use. This ensured that they were a perfect match for the inside of your drum. Here’s a rotating tool that clamped on the hub with a cutter that you spun by hand and wound in a few thou at a time to cut the lining.



So I took a look at the Delorean Handbrake calliper and made several observations:

The handbrake works in a PINCER operation, with both arms that hold the pads hinging on two pivot pins/bolts. These are at a FIXED distance “A”
By pulling on the handbrake lever the arms close until the pads make contact with the disc at dimension “B”



This is TAPERED and NOT PARALLEL.

New pads are square and parallel, the result of fitting new pads is that ONLY the corners of the pad make contact with the disc.
This is WHY NEW PADS have a POOR EFFICIENCY.

To make matters worse the CORRECT adjustment of the handbrake means that the pads DO NOT drag or meet contact until the handbrake is applied when the car is stationary so would if used correctly NEVER bed in properly!
With such a poor surface area contact its no wonder there is little friction and efficiency.

So to make a Delorean handbrake work properly you cannot drive around with your handbrake on the match the pad angle to the disc (wear them in) without cooking the pads or blueing and warping the discs, not to mention melting the grease out of your wheel bearings.
The only solution is to “fit” the pad in the old fashioned “fitter” type way with a file, & marking blue.
Its amazing how much of an angle is required to get a proper fit and full pad surface contact.





Now since this is NOT something I would recommend the average DIY Delorean owner should do. It’s not easy.
It really is up to our Delorean PARTS SUPPLIERS to re-manufacture pads to the correct angle.
Until then, I have thought how it could be done easier, so here’s a simple solution.
For new or existing pads.

1. Take out the split pin and wind out the slot head adjuster screw about 6 turns (Don’t take it all the way out, you’ll need to dismantle the whole box section lever and self adjuster to get it back in as the internal spring ratchet and pawl will miss-align the threaded hole)
2. Take off the M6 Nylock holding the Handbrake cable into the arm.
3. Remove the lock tabs and take out the two pivot/pin bolts
4. Remove the return fork and put back the pins.
5. The arms holding the pads should now be free to move in and out.
6. Obtain some 40 or 60 grit adhesive sanding discs and cut them to stick on your brake disc.
7. Gently squeezing the arms to contact the pads with the disc, rotate the disc to and fro to sand down the pads to the correct angle.
8. DO NOT sand down further than 75% of the pad face. This means the pad will taper, and at the thickest part of the pad it should still be the same thickness as new/or before in the case of a used pad. In this way you’ll get more life out of the pad.
9. Once done, remove adhesive sanding discs and clean off any glue residue completely.
10. Replace the return forks and new lock tabs.
11. Adjust the slot head screw adjuster until the pads bite the disc and back off ½ turn to get the split pin in.
12. Adjust cable as stated at start of this thread.

Over the life of the pad the pincer movement of the arms should wear the pad evenly increasing the angle until fully worn out. (Providing you’re self adjuster is working)

So did it work?

Well I took the car back to the MOT station today and the efficiency was TWICE what it had EVER been since owning the car!

I can’t believe no one else has ever spotted this fatal engineering flaw?

[Chris Williams]

Brilliant! As some one who has to do this in the next few weeks for the MOT, I will give it a try. After replacing the radiator & Condensor :roll:
Chris

[Starglider]

Good work, I aggree it's surprising that (apparently) none of the vendors noticed this.

[Darren C]

Cheers Chris,

I'd be interested to know what pad contact you have? You can take the outer pads out easy as the small M5 nut is straight in front of you when you take the wheel off. You dont need to take it all the way off as the pads are on Tee slots so just loosen and slide up and out.
A top tip for the inner pad removal is to take out the two pivot pins (leave the cable connected) slide the pincer arms out of location and flip the whole lot over. With cable connected pull on mechanism it will open and you can just get a socket on the inner M5 nut to loosen and remove inner pad. No need to take cable off, or remove split pins and drift box mechanism pin out to get at the M5 nut.
Believe me I did this a few times which is a right pain before finding out you can get at the pad nut this easy way.

[Darren C]

Starglider Wrote:Good work, I aggree it's surprising that (apparently) none of the vendors noticed this.

Now funny you should say that.....

I have Dunlop calipers on my vintage Ferrari they have the same handbrake assembly.
Dunlop designed this caliper and handbrake!
Girling bought them out a few years later.
Guess what,
If you can ever get your hands on a NOS 1958 Dunlop handbrake pad set they are TAPERED.

It's just a case of someone in the very early sixties making square pads who did not understand engineering, and the error getting replicated over and over.

[Chris Williams]

Quote:Cheers Chris,

I'd be interested to know what pad contact you have? You can take the outer pads out easy as the small M5 nut is straight in front of you when you take the wheel off. You dont need to take it all the way off as the pads are on Tee slots so just loosen and slide up and out.

Ohh yes, lots of experience of getting these pads in and out :roll: However as the pads have only been in for a year and failed to work at all after about a week I doubt there are much diffferent to yours. However I will post up the pics when I get around to them.
Chris
And why are your calipers so clean and shiny, thats just not right :wink:

[Darren C]

Also forgot to mention a most important check.

Have you got your handbrake pads in the RIGHT WAY AROUND?

If you carefully look at this Girling exploded picture below, you need the widest/tallest part of the pad at the end where the pivot pins are. It is possible to put the left hand side pad in the right arm and visa versa.



What way around are your pads? Don't just copy what a previous owner/garage did!

PS, My callipers are dirty Chris, they’ve done 67000 miles, what’s your excuse!
:lol:

[Chris P]

Fascinating stuff.
Most of the DeLoreans I've owned have had rubbish handbrakes. Luckily my current one is great, but if it does start to fail I now know how to fix it properly. Thanks.

[Darren C]

The Plot Thickens while the pads thin!

Following something Nick T said yesterday in passing, I have been thinking about the handbrake pads all night. (Yes I know, I know, it’s my engineering OCD and there’s no cure)
The handbrake works in a “Pincer” movement, my old pads and my brand new pads were being pinched at one end giving little surface contact and therefore poor efficiency.
Now how about this for a fast ball……what if, just what if, the old and new handbrake pads were too thin straight out of the box?
I got up at dawn this morning and took the rear wheels of the car dismantled the handbrake assembly and took out the pads again Opening up the Pincer arms using the return fork action and the slotted screw, I carefully measured with verniers and feeler gauges until I knew when the arms were open to give a parallel pad mounting face with the disc. This is where they would have to rest with FULL surface contact of the pad if the pad was parallel and not tapered (as I have had to do to get surface contact)
14.2mm give or take. (Some further testing required)
So if you could get a pad straight out of the box to fit a Delorean handbrake that was “matched” to the mechanism it would need to be 14.2mm thick.
This is the best engineering solution. Filing, sanding and fettling the pads to suit as I have had to do is not really acceptable.
So with this in mind I decided to investigate a little further….
I am fortunate (or unfortunate, which ever way you look at it) to own 3 cars that use the very same Calliper and handbrake mechanism. Over the years I have collected spares and replacement callipers and pads. After an hour in my various sheds, drawers and cupboards I found several pads.

Now take a look at this….



Two NEW unused handbrake pads. Left is a Makland (I had the box), the right hand one I cannot identify but suspect its genuine Aston.

The left is 13.3mm thick
The right is 14.0 mm thick

Ok, now alarm bells started to ring in my head.

So I investigated further and here is the result of this morning’s investigation on various manufacturers of pads for the Delorean Handbrake.

Sizes from NEW

GDB1640 marketed by TRW. 13.3mm thick
PA482 Lucas & Brake Engineering. 13.3mm thick
151-2008 Ween. 13.3mm thick
6116401 Girling. 13.3mm thick
LP553 Delphi. 13.5mm thick
FDB822 Ferodo. 13.5mm thick
P36004 Brembo. 13.8mm thick
37828 ABS. 13.8mm thick
BP250 Quinton Hazel. 13.8mm thick

A range from 13.3mm to 13.8mm, that’s 0.5mm. Not much you would think? WRONG!
When fitted in a Pincer movement handbrake with a parallel arm position giving an ideal 14.2mm pad size you need to wear down almost 1mm (in a taper) off a 13.8mm pad to get full surface contact. With a 13.3mm pad you need to wear almost 2mm (in a taper) off the pad to achieve a full surface contact. Unfortunately the new pads I fitted were 13.3mm to start with so you can see the problem at the beginning of this thread.

So if you’re in the market for new handbrake pads AVOID anything below 13.8mm!

Now, if only I could track down which supplier that 14mm pad came from.

[Rissy]

...I hate to say it without receiving a flurry of "yeah, yeah"'s from people, but the whole observation of the pincer movement and requirement for angled pads is not brand new information. I've been on to the garage and people in the club for years about this. I think Richard Hutchison might remember us talking about this issue when buying new pads and talking about how it's such a crap design and how you're actually in a worse off position getting new pads than what you are with old ones... (I think I even remember discussing this in an earlier thread somewhere on the forum too...?)

I've got a mixture of old and new pads on LEX all in an attempt to get the best and most surface area of pad(s) to hold flush against the discs. It's a nightmare. Talk about making it up as you go along with what odds and ends you can... I've even tried using angled washers and home made spacers to try and get brand new pads to be permanently angled from the start so that when they meet with the disc, the angle is eliminated as the disc is gripped. This worked to a fashion, but also tended to put undue stress on the pads and they'd eventually fall apart.

I've found also that at least on one side, my pads don't even grip along the front edge in a uniform attack. It actually comes in one one corner only! I've discussed all of this issue with the garage I take the car to and they appreciate that I need some severe bedding in of the pads before they will make a flush connection with the discs. My garage suggest it, but never offered to help, but I've tried taking the pads out and wearing them down with rough wet and dry paper but it's just such a long exhausting job to do that I soon lose interest. I've destroyed more than one pad trying to use machinery to help me do it. On more than one occasion the pad material has come completely away from the metal facia, meaning i've then had to crack out the Araldite to reattach it again.

As you say, simply driving around, even up and down the country as I do with LEX, with the handbrake on a click or so to try and bed in the pads is useless.

I completely disassembled the caliper assembly for the handbrake component and greased everything and checked to make sure everything was fully lubed and free moving a coupe of years ago. Every year my mate Kevin and I go through the annual assessment of the angle of attack and space between disc and pad process and adjust until as perfect as we can manage (meaning Kev (who's a big guy) cannot move either wheel or push the car at all with the handbrake on). Still, every year, i fail my MOT, all be it by a bit less every year than the previous year, meaning it IS improving all the time but it's an awfully slow process with the mileage I put on the car every year.

I don't know where others get their pads from but here's the link to where I've had at least two sets over the years from (They don't specify dimensions unfortunately). I do still have at least two pads untouched, never used, brand new in the box which I could measure, but that wont be until I'm next with the car (and my boxes of bits) at the end of April (according to my current plans)

Anyway, link:

http://britishparts.co.uk/products/7749 ... ke-JLM1514

[Chris Williams]

Though little help, I measured a spare set I have and they to come in at 13.3mm :roll: Think they may have been the TRW ones but cant swear to it.
Chris

[Darren C]

To further my quest to get to the bottom of all this, I forgot to mention brake disc thickness.
As previously stated the pads are sensitive to thickness, so this can be compounded by wear on the brake disc.
I measured and cross referenced my other cars that have the same handbrake and ALL have a factory disc thickness when new of ½” or 12.7mm.
A new rear Delorean brake disc should be 12.5-12.7mm so this ties in with the calliper requirements.
My discs are quite new at 12.5mm thick, so my calculated 14.2mm ideal pad size is correct.
However the minimum Delorean rear brake disc thickness is 11mm before its recommended to change.
This is a full 1.7mm wear that in effect compounds the handbrake pad thickness issue I discovered above. So for example if you have a rear disc near minimum the 14.2mm ideal pad size would require tapering to mate the disc by 0.85mm. (Half of the 1.7mm wear on the disc).
So lets say you bought a new set of pads that were 13.3mm; then you’d need to taper the pads by over twice that to get full face pad contact.

THIS IS WHAT I THINK IS THE MAIN PROBLEM WITH DELOREAN HANDBRAKES.

It’s a combination of WEAR on the rear disc and UNDERSIZE pads. (Subject to correct adjustment and no other defects in the linkages)

The only solution is to buy the thickest pads available (13.8mm, until someone makes thicker ones) and make sure your discs are not worn, then bed them in as described at the end of my very first post to get a good surface contact.

Take your time, be patient, don’t be ham fisted and there’s no way you’ll break the lining of the pad from the base unless you’ve bought absolutely rubbish pads!

Edited upon Darren's request.

[Rissy]

Darren.

Please don't call me a muppet and go to that extreme with the picture.

I DO NOT APPRECIATE IT! I'd thank you to remove it, or this forum will be losing another member. There is no need for personal insults.

Now i'm not saying that what i've tried was ever perfect, but I was illustrating the extremes I've gone to, to try and over come the design issue you claim to have discovered (even though it's been discussed on more than one occasion between myself and others quite a few years ago)

I can assure you that Araldite has been more than effective on holding the pad to the metal facia. It's a stronger bond than what was there before (which might be as a result as you've suggested that the pads might be crap).

The shims, yes, I'll admit I didn't like trying, but I only did it the once as an experiment and never drove more than round the block a couple of times just to try it out. As you said, all it did was stress out the minute (too small for the job) M5 bolt and I removed the shims again.

What you have to remember though is that it is a handbrake pad only. It never engages on to the disc when it's moving. It's only to hold the disc still, which mine does no problem on very steep hills. It just doesn't stand up to the test in the MOT.

[Darren C]

Rissy,

It's satire, and not meant to really offend you, just an expression of my opinion on your post, with a playful friendly putdown.
I do not claim to have discovered a "design issue". Nothing of the sort. We all know how it works. What I have done is analyse the condition and highlight and explain (in detail) what is wrong and how to resolve it.
Granted, others have noticed the angle of the pads, but no-one has posted an informative and detailed resolution.
Yes we all understand the occasional nature of Delorean usage and the
in-frequent use of the handbrake to hold the car when parked. But unfortunately we need the car to meet the MOT regulations and have become complacent with the "Delorean handbrakes are Sh*t" attitude when in fact the problem can be resolved.
I have these exact same calipers and handbrakes on my other cars, and they work well. So they should work well in the Delorean.
The fact of the matter is that most owners have simply given up.

[Chris Williams]

I think sometimes (and I include myself in this) people skim read and/or dont realise that (as in your csae) you were trying various methods to try and fix it. Indeed even re reading it it's not completely clear but I read it as you were trying things out.

ANYWAY back on topic, as i wrote mine are not working at all, despite getting them to be OK'ish prior to the cars last MOT thay have no effect whatsoever at the moment. I did try to refurb them when I fitted new calipers last year, but something was missing/broken (cant remember what now) so was planning on sending them to Ward's for a proper refurb with new pads. Be interesting to see what they send them out with.
viewtopic.php?f=11&t=4979
Chris