New front drum brakes binding in reverse

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scottonthefen

scottonthefen

Well-Known Member
Posts
532
Location
England
I fit new wheel brake cylinders all round on my 88" 2A about three years ago. I fit new master cylinders and pipes and bled the system to a good pedal about a year ago. First test drives have been the last couple of weeks. Good pedal, good brakes, but terrible brake binding in reverse. Tracked it down to the front two wheels, couldn't turn either one backwards by hand even with the adjusters right off.

Removed the drums today to find the pistons on both front cylinders acting very strange. On the back wheels when I checked they all had a nice stiff action and a good strong push-out when you pull the shoes away a little. You could push each side back in with your finger and you would only move the piston you were pushing. But on the front, they all seemed very unresponsive, and if you pushed one piston back in the piston on the other side would move out too.

I've read if you fit new cylinders and don't use them for a while (it's been 3 years in my case) this can happen because sat around not being used is no good for them. Would you agree with that? They're the correct cylinders, front SWB, RH and LH, Lockheed, and I've got a good brake pedal (well I did have until I started playing about with the pistons on these two by hand today..).

(All the springs are fit correctly, red between post on back of leading shoe, under cam, back to brake plate post. Black between holes in lower leading and trailing shoes.)
 
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Have to admit I am wondering now if I'm imagining the front cylinders are suspect when I might just need to take a little more off the top edge of the trailing shoes on the front? :| My theory about the cylinders doesn't really explain how the trailing shoe would be catching the drum..
 
Ok Rob that's good to know.

I'm sure I've got all my shoes and springs correct. The leading shoe has a post on its back for the red spring which passes back under the adjuster cam to a post on the back plate. The black spring connects the two shoes, lower down, just above the anchor plate. The anchor plates are all screwed to the trialing shoes as they should be. And they're all 10" drums and shoes.
 
@boguing - I don't actually know that my back cylinders don't do that, when I checked those before the front ones it was a cursory look because they weren't grabbing in any way. I took the drums off, eyeballed the springs were right, checked the pistons creeped out and weren't seized if I pulled each shoe away in turn and put the drums back on. I think the rears are ok. And I'm starting to think the fronts are ok now.. but why do they grab in reverse? I don't know. Maybe it's normal until they're worn in a bit? This is my first land rover so I wouldn't know if it's to be expected.
 
Do both front wheels resist being turned backwards? What are the drums like, they can go out of true slightly and cause all sorts of bother. You could try putting chalk on the shoes to see where the drum is catching. I would try taking a bit off the back and front edges of the shoes with a file or summat before you start stripping anything. When I did mine, I had to give the drums a few good whacks with a mallet to get everything to settle.

Col
 
The drums were new three years back and not been used much like the rest of it. I didnt think to check them. I could try moving the drum to a rear wheel where there's no catching and see if the problem follows it. That's a good idea. Also the chalk will show me better where it's catching on the shoe so I can have another go with the file sander. Two good ideas there cheers col. (and yes both front wheels grab when turned backwards, not just rubbing, adjusters right off and can't budge em by hand..)
 
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Your brakes grabbing in reverse is the "self servo effect" top edge of shoe is catching drum and drum is applying the brake.
Chamfer the top edge of trailing shoe more to reduce the effect.
You said you have the lower clamp [magnifing glass shape] fitted which shoe has the bolts in?
 
If the binding is constant then look at chamfering. but if it's at one position as you turn the wheel then two possibilities:- clean the seating area of the hub/drum so that it's definitely on square. Makes a huge difference. The one you don't want is that the drums were badly machined - two regular suppliers no longer sell new drums because they were getting almost all returned.
 
Check those damn spring one last time. Put plenty of red grease into the gap between the cylinder and piston and under the boot. Check the shoes again and adjusters, I wasted weeks on a worn adjuster. Chamfer the trailing edges - leading when you are going in reverse, and put a small chamfer ou the outer edge of each shoe, when new they can catch the drum edge. If its been stading a lot you may have some corrosion on the drum catching the shoes, this will wear off once it gets driven. A few really hard stops often help.
 
Right, I've managed an hour and she hardly noticed I was gone. Chocolate brownies baking when I got back in anorl. ;-)

- I checked the rear cylinder pistons do push each other out when pressed like the front ones do and they do, so they're alright.
- The springs are definitely hooked up right and they were all new when I fit them.
- All the anchor plates are screwed into the trailing shoes.
- The problem does not follow the drums. I moved a front drum to the rear axle and the problem did not follow it. When I brought it back to the front axle I had to push the shoes in to get the drum back on and then the bigger front cylinder pushed the trailing shoe straight back out again against the drum and I couldn't turn it backwards again.
- The front cylinders are bigger than the rear, as I think they should be, so when I push the trailing shoe in at the piston and see it push back further and faster under pressure that's expected because it's a bigger piston right? At the rear there's much less push-out like that.. but this is definitely what's pushing the trailing shoe against the drum even at rest.

Why are front wheel cylinders handed? Is it just for where the flexi hoses join them (mine's a 2A the flexis go straight to the cylinders)? My flexi hoses are going into the rear port of the front wheel cylinders. Are they handed because one of the pistons pushes out harder, and I've got the 'front' piston pushing the trailing shoe out too hard?

If I don't have the cylinders on the wrong sides.. Next job is to file some more off the top of a trailing shoe to see if I can get that to make a difference, but what I've took off already (a 15mm slope) is about the same as I took off at the rear..

I will be packing bits with red hydraulic grease all round when the drums are ready to go back on.
 
There may be a good reason that you have different sized cylinders, but I'm not familiar enough with them to know properly ...

May be a grown up can help ?

Edited to add : it's not the 10" or 11" mix up ?

Tis 40 years since I did 2A brakes so I is foggy ......
 
Have you actually drove it in reverse or just checking by hand?
15mm is a good chamfer The cylinder has a spring which pushes both shoes out leading shoe is held off by the red top spring pulling it to the adjuster. Trailing shoe is relying on bottom spring to pull it back , by design the shoe needs to be close to the drum to get efficient braking.
TRW make brake cylinders some of there 1st manufactured ones had a stronger spring in the cylinder which caused an issue. They sorted that issue out.
You said your cylinders where Delphi have not heard of issue with these.
 
Yes, driven in reverse it grabs like a bastard, and I can't push it back in the garage by hand anymore. Which is a bloody good point.. I've been pushing it in and out the garage by hand for three years with all these new brake parts fitted. Then soon as I had those first couple of test drives.. I've got this problem.. pretty suspicious.

Anyway I dug the parts I ordered out of my email.. two axle sets of 10" shoes, Delphi cylinders, rear/front/RH/LH.

STC2796DKIT Axle Set of Brake Shoes - 10" 2 GBP28.28 GBP56.56

243296D Lockheed Delphi Wheel 1 GBP15.00 GBP15.00
Cylinder S1, S2a & S3

243297D Lockheed Delphi Wheel 1 GBP15.00 GBP15.00
Cylinder S1, S2A & S3

243302D Lockheed Delphi Wheel 1 GBP15.00 GBP15.00
Cylinder S1, S2A & S3

243303D Lockheed Delphi Wheel 1 GBP15.00 GBP15.00
Cylinder S1, S2A & S3

And 4x 10" drums: FRONT/REAR BRAKE DRUM BR 0636
FRONT/REAR BRAKE DRUM 10 INCH SUITABLE FOR SERIES 2A WITH SMALL STUDS VEHICLES
 
Long shot, but worth checking the free play on the brake pedal rod. If this is not enough the brakes stick on, perhaps yours is right on the cusp?
 
There's a nice bit of free play on the pedal, don't think it's that.

Seems to be boiling down to this: on the rear, when I pull the trailing shoe back, the black spring can overcome the piston and pull the shoe back in.. just. On the front, the piston is stronger than the black spring and is pushing the shoe out into the drum.
 
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