I might have only gone and solved the Handbrake issue!

[Darren C]

Thanks Chris,

Looking at one of my very first pictures in this thread of the new pad being crushed at its very edge due to uneven contact with the disc, I'd edge bets that this is what has happened here. The edge point crushing crumbled the pad and eventually broke it apart and sheared it off the backing plate.

More to follow from this weekends continued investigation....

[Darren C]

This weekend I continued my investigation into the Delorean Handbrake.

I had an idea about the cable and wanted to check it out.
When pulling the handbrake lever after making all adjustments, after 4 clicks its like hitting a brick wall there seemed to be no more to give in the way of pull without excessive force which as explained earlier is what bends the bracket under the lever.
So with handbrake firmly on I took a measurement from centre of the pin in the lever to the rear of the locknut at the hub bracket. Roughly 91mm (90.8mm)



Inside the handbrake cable at the end by the calliper is a concealed spring. It’s under the rubber dust bellows.

Internal spring



I needed to check that this spring was not becoming “coil bound” under operation. This is when a spring is compressed so that all its coils meet and no more compression can occur. I wanted to check that this wasn’t happening when you pulled on the handbrake lever, as if the spring became coil bound you would not get any more movement of the cable, lever or handbrake, while it is possible that there was more “pull” to be had in the mechanism of the calliper. (Basically locking the cable before the handbrake got chance to grip firmly).
Since the cable and spring sit under a rubber bellows I didn’t want to cut it off just to see as it would ruin the dust cover. So to get an accurate measurement I took the cables off the car and compressed them against my vice.

Max compression



This gave about 75.5mm max compression to make the spring coil bound. So in reality at 91mm full pull when fitted to the car, the cables have 15mm to give before they would lock solid.

This is good to know as if you have miss-adjusted the handbrake pincer slot headed screw or got very worn pads, you can check that the cable is not pulling to a point near 75mm, otherwise your going to bend your lever and cable brackets.

As the threaded part of the cable sheath end runs inside the spring, this 75.5mm is a constant size. So it NEVER changes regardless of how far you move the two cable locknuts.
This theory of coil bound cable springs can be dismissed as causing poor handbrake performance unless you have miss-adjusted slot head screws and/or worn pads.

Next I decided to see if any mechanical force is lost at the calliper cable bracket. Like before at the lever I set up my DTI at zero



Then applied the handbrake with reasonable force and got a10 thousandth of an inch deflection.



Combine this with the 5 thou at the lever it gives a maximum 15 thousandth of an inch “loss”. Not really enough to cause concern. I can therefore rule this out as a cause of poor performance.

Going back to what I mentioned earlier; I’d noticed a slight dish in the bracket below the lever, but proved with my DTI that this was not causing a problem. This did however play on my OCD mind.
So for the benefit of those who may discover their plates badly bent, I have made the following solution.

New 3mm thick steel Re-enforcing plate



Seam welded all around its edge to the existing bracket, then file dressed, so as to make it look original.





If you look closely at the cable holes you can see the new and old metal end plates and that it’s much thicker than the original.

I fitted it back in the car this evening and have lost the 5 thousandth of a inch flex, not enough to improve the handbrake, but just for my OCD sanity.
:wink:

[JohnC]

Very interesting (even to me... ) . My car had it's MOT earlier in the month, it too was reported as having one of the pads missing.

For those of us who don't service our own cars, for whatever reason, is there the option for some enterprising person to earn a some extra cash...

I'm perhaps missing something obvious you mechanically minded people undersand, but since one DeLorean's brakes should be like another, there may be a market for someone to create a template and grind some new pads (of the optimum commerical thickness) to the angle suggested ready for use... ?

JohnC

PS, I agree with the others, that's all looking very shiny Darren.

[Chris Williams]

Quote:it too was reported as having one of the pads missing.

Interesting, I wonder if thats just coinsidence or the pads are not such good quality now, seems odd, thats me, you and rissy all with pads failing.
Chris

[andyd]

When I replaced mine (just cos I was rebuilding the calipers anyway), the friction material also came away when I removed the handbrake pads...

a

[Darren C]

The odds are increasing with every report of the friction material coming away from the backing plate, that this is not just a 1 off occurrence.
As I noted in my very first post the uneven pad contact and localised point load, started to crumble the edge of my brand new pad within a 1 mile drive to the MOT and back. Had it gone un-noticed I'm sure it would have progressed to the majority of the pad coming away from the backing plate.

I'd strongly recommend everyone checks their handbrake pads. (Even you John) All you have to do is take the rear wheels off and you can see them easily.
For those of you more mechanically minded, I'd take them out and have a good look at wear pattern and any point load stress cracking.
Prevention is always better than cure :wink:

[Chris Williams]

Just got these back from Wards and thought for info I would post up a picture and pad thickness. Anyway the pads mesure in at 13.6mm
[ATTACHMENT NOT FOUND]

[Darren C]

The gold zinc plate looks nice Chris.
13.6mm pads will give a better less angled contact than the 13.3mm ones, but I place a wager with you that once you fit them you'l still have less than 40% face contact of the pad to disc straight off.
Refit the arms but leave off the cable, squeeze/push the arms to meet disc with pad and shine in a torch to take a look at the face contact pad to disc and let us know what you have.
Regards
Darren
PS. I have a new lever tool I'm making almost finished that bolts on to the hub using two wheel nuts and allows you to easily rotate the disc to check or bed in the new pads.
Much easier than trying to grasp the disc or lever between the wheel studs when setting up your handbrake clearances!

[Chris Williams]

Quote:PS. I have a new lever tool I'm making almost finished that bolts on to the hub using two wheel nuts and allows you to easily rotate the disc to check or bed in the new pads.

So no chance of having it made and delivered for the morning then? :wink:
Will take a picture of them installed ,the discs have less than 2000 miles on them so are nearly as new, none the less I will install as you suggest with sanding them down. Spent today installing Ed's new radiator, Harveys's condensor and DPI's fan kit.

[Chris Williams]

OK, to add my 2pth to this. As you can see from the picture below I have re-installed the newly refurbed calipers. However I don't seem to have so much as an issue as Darren/Rissy have had with tapering the pads, as you can see the pads measuring 13.6mm fit reasonably well less than a 2mm gap (actually between 0.5 and 2mm at worst) on the pads. Now the odd bit is these are on virtually brand new discs that mesure in at 12mm thickness.
I have done as Darren suggested with the rubbing down method (actually easier than it sounds) and these are now tapered to fit. despite my best efforts at adjusting the handbrake cables I cant get them perfect. As there very close to the end of the threads I suspect the cables may be overstretched but they do hold the car on a hill so that's a plus point! I will when time allows I think remove the bracket for reinforcing and probably change the cables as well but hopefully they should be good enough for an MOT next week.
[ATTACHMENT NOT FOUND]
Chris

[Darren C]

Chris Williams Wrote:the pads measuring 13.6mm fit reasonably well less than a 2mm gap (actually between 0.5 and 2mm at worst) on the pads. Now the odd bit is these are on virtually brand new discs that mesure in at 12mm thickness.

Great Chris, that confirms exactly what I found at the end of Page 1 of this thread. A 13.3mm pad needs to taper about 2mm at most so your 13.6mm pad being between 0.5mm and 2mm at worst confirms my theory on the pads not having good contact even with new discs.

Have you adjusted the ratchet mechanism in the arm to take up play before connecting your cables Chris? Even stretched used cables can work better with all play taken up in the lever self adjuster first. (just a thought)

[SpudMurphy]

it's a shame that this thread petered out and of course that the original picture hosting no longer allows us to view all the great visual info on the thread , as !a picture speaks a 1000 words).

I was wondering - is there any chance for previous contributors to repost the pictures please? I'd be interested to know whether further progress was made?

I'm interested,because my car is up on blocks with one rear brake/handbrake mechanism on the car and the other one in my box of bits !!!

[Guinney1971]

I'll message DarrenC who's the original poster and see if he can update the photos - some of us
have migrated to Flikr due to issues with Photobucket.

[Darren C]

Hmmm, 

Somethings going on with Photofucket at the moment??? 

I can see all the pictures in this thread on my work PC without any "patch" ?

This is the same on some other Forums where, over the years I've posted pictures?

No idea whats going on, but for now it seems to be working again.

Can anyone else see the images now?

[Chris P]

Amazingly, I can now view the pictures ! Ive tried numerous times in the past with no success.