P2 brake balance assembly

RobHomewood
Posts: 219
Joined: Tue Oct 22, 2013 8:04 pm

P2 brake balance assembly

Post by RobHomewood » Sun Jul 19, 2020 2:17 pm

I'm looking for some advice/help on my brakes. My '39 14 has the Girling rod brake system and I was looking to improve the effectiveness of the brakes. There was a lot of play in the set-up and I know it needs some play but at times I have had my foot to the floor when braking not that hard. The brakes aren't bad generally but I want to reduce the ineffective travel before they activate. I have checked the shoes and they are in good condition and didnt need much adjustment so I looked at the front balance assembly as it is called and this was wobbling about on the mounting. It was fairly easy to tighten up the mounting castle nut a flat or two (without locking it tight) and this took a lot of the play so I was going to do the same on the rear balance assembly. I found however that instead of the mounting being bolted in place it appears to be a sliding piston into the mounting on which there is no means of tightening up. The result is that the whole assembly moves foward when the brake is initially applied until the piston reaches its stop. I am thinking this means the rear brakes will be less effective. Can anyone tell me whether the mounting piston is meant to be unrestrained and how best to take up at least some of the free play? Having read the manual several times it goes into great detail on setting the rods up initially but does not mention this piston or adjusting the mountings of the balance assemblies at all. I can only think that I have to adjust the long rod leading to the rear assembly but am nervous of that because the manual gives warnings against tinkering. Any help would be appreciated
Rob

User avatar
luli
Posts: 447
Joined: Sat Jun 04, 2011 6:49 am
Contact:

Re: P2 brake balance assembly

Post by luli » Sun Jul 19, 2020 10:15 pm

You can get excellent brakes if you follow by the letter the instructions in the WSM. Having 4 leaf springs the axles move back and forth while driving therefor the need for those pistons. Make sure that all clevis pins, forks etc. are in good shape and replace as necessary. Remember that the "mechanical wheel cylinders" need to be floating on the back plates, and well lubricated. See more here: https://wp.me/pXLKy-2tJ here https://wp.me/pXLKy-1pg here https://wp.me/pXLKy-3An here for under the car photos:https://wp.me/pXLKy-3Zh . https://wp.me/pXLKy-2B1
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

GOY189
Posts: 487
Joined: Sun Oct 19, 2008 5:08 pm

Re: P2 brake balance assembly

Post by GOY189 » Mon Jul 20, 2020 9:42 am

Its also a good idea to strip the expanders and see how much lost movement is due to wear in the eye of the brake rod and the dowel that locates the rod to the expander piston. The dowels are a standard engineering spare.

Mike

RobHomewood
Posts: 219
Joined: Tue Oct 22, 2013 8:04 pm

Re: P2 brake balance assembly

Post by RobHomewood » Mon Jul 20, 2020 11:11 pm

Thanks Luli and Mike
Mike: is it mainly the pin which wears or the fork or both equally? There is quite a lot of movement in the joints but not necessarily affecting the operational direction. And do you know the thread details etc for replacment forks? The parts book seems to say 5/16" for the fork ends and 5/16" for the pins but doesn't give the thread type and size onto the rod.
Luli: I am going around again checking the expander plates and the first one looked OK - well lubed and quite clean sliding faces. I had forgotten what a pain it is getting the shoes back on and ran out of time and energy after one wheel!
Rob

User avatar
luli
Posts: 447
Joined: Sat Jun 04, 2011 6:49 am
Contact:

Re: P2 brake balance assembly

Post by luli » Tue Jul 21, 2020 6:55 am

The thread is BSF. The rule is iron=BSF, Aluminum=BSW.
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

RobHomewood
Posts: 219
Joined: Tue Oct 22, 2013 8:04 pm

Re: P2 brake balance assembly

Post by RobHomewood » Tue Jul 21, 2020 6:17 pm

Thanks again Luli. You are showing up my inexperience!
I did the other rear wheel today which was also in fair condition except that the flat washers were missing from the expander bolts on the backplate. Now replaced.
But I did see that whilst I was working away (with all the rods still connected together) the balance mechanism piston had come right out of its shaft and the balance mechanism was hanging free. Easy enough to put back into place but surely that's not right? I also registered then that when replaced, the travel on the piston allows the balance mechanism to impact the front of the fuel tank which again I am not happy about. Am I missing some control here?
A short test run showed the brakes no better than before as far as I could feel, by the way.
regards
Rob

TonyG
Posts: 192
Joined: Mon Sep 07, 2015 4:38 pm

Re: P2 brake balance assembly

Post by TonyG » Tue Jul 21, 2020 9:34 pm

Rob,

If I understand your posts correctly, the brake rod to the rear is pushing to operate the swivel for the rear cross rods and, in doing so, pushing the balance piston out into the front of the tank? This is wrong. The brake rod should be pulling towards the axle when you operate the brake. I can only think that the main rod is connected upside down and that the front brakes are also working the other way. Or I may have misunderstood the problem.

You are always welcome to look at my cars- no idea where you are- or I can take pictures if that would help?

Let me know, but I do think this might be the problem.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

RobHomewood
Posts: 219
Joined: Tue Oct 22, 2013 8:04 pm

Re: P2 brake balance assembly

Post by RobHomewood » Tue Jul 21, 2020 11:27 pm

Hi Tony
I probably didnt explain it very well because I am still trying to get my head around the operation of the balance mechanism etc. The rear balance mechanism is mounted on the rear of the rear axle via a piston which slides forward and back into the mounting. When the brakes are operated the main rod pulls the lower lever forward which pulls the piston into the bore (ie the whole assembly moves forward) before the lever arm starts to turn. When the brakes are let off the balance mechanism tends to move backwards on the piston and there is nothing to stop the piston coming right out of the bore except that in normal operation I think the upper part of the balance mechanism generally impacts on the front of the fuel tank before the piston leaves the bore. I think it only came out totally maybe because I was wriggling the rod to the offside wheel. But I am surprised if that is how random it is meant to be. Sorry I cant get a picture to load but it doesnt explain very much anyway.
I would love to look at your cars but I am remaining in semi isolation for now and anyway I am in the far south west a long way from most other Rover owners,
Rob

User avatar
luli
Posts: 447
Joined: Sat Jun 04, 2011 6:49 am
Contact:

Re: P2 brake balance assembly

Post by luli » Wed Jul 22, 2020 6:36 am

Please note that adjusting the rods lengths should be done only when the car is on four wheels and leveled. Practically that means that you can do it only if the car is on a proper ramp or you have a pit. If the angles are right and the piston is makes the rods to rub the axle you can take the balance a bit backwards by using washers.
https://lulisml.files.wordpress.com/201 ... jpg?w=1024
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

TonyG
Posts: 192
Joined: Mon Sep 07, 2015 4:38 pm

Re: P2 brake balance assembly

Post by TonyG » Wed Jul 22, 2020 7:25 am

Rob,

Well that's a relief, my apologies for the misunderstanding. That said and hoping I've got it clear now, the rear balancer should be sitting close to the axel in its swivel when the brakes are not operated. If yours is pushing out far enough to hit the tank when the pedal is released then there must be a problem further forward in the system.
The swivel/piston device is there to provide lateral and vertical movement of the axel without compromising the brake operation so most of the time the piston will be located fully into its housing.
The braking system is really very simple and easy to set up when you have just the chassis and axels to look at. However, with the body in place and laying on the floor it all becomes more complicated as you cannot see the whole operation at the same time.
I suggest that you start at the foot pedal and spend time getting to grips with how it operates and also how the handbrake works the back wheels only- the main rod slides with a rubber dust cover over it.
Once you know that everything forward is correctly aligned, move backwards and adjust the main rods to achieve the proper location of the balancer at the rear. You will probably require a helper to press the brake pedal while you watch what happens.
I assume you have always had this brake problem? If not, some work must have been done to upset the adjustments.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

Post Reply