P2 brake balance assembly

RobHomewood
Posts: 219
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Re: P2 brake balance assembly

Post by RobHomewood » Tue Aug 04, 2020 11:07 pm

Thank you Luli but surely the handbrake lever is rigidly fixed to the handbrake shaft with the relay rigidly fixed at the other end operating directly on the rear brake rod without any involvement of the compression tube, which is forward of this? I am still struggling to understand its intended function. I think I can understand the swinging arm under the footbrake pedal which will swing over in the event of a catastrophic failure at the front end or rear eg a rod snaps etc and retains braking capacity to the remaining half of the system through the footbrake but I still cannot get my head around what part the compression shaft plays in this. To me it feels like the movement in the compression shaft is undermining the braking effort of the foot brake pedal. I cannot find any definitive description on the web of such a system either so all work has stopped for now!
regards
Rob
PS I would really appreciate any help on whether the handbrake lever position is adjustable as noted before

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luli
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Re: P2 brake balance assembly

Post by luli » Wed Aug 05, 2020 8:49 pm

The compression tube is activated by the pedal only, not the other way around. If you look under the car, you will see a rod going down from the hand brake lever to the cross shaft . (see picture in the link https://wp.me/pXLKy-1pg) It ends with one or two 5/16 BSF nuts, they are used to adjust the handbrake lever free travel.
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TonyG
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Re: P2 brake balance assembly

Post by TonyG » Wed Aug 05, 2020 11:27 pm

Rob,

Firstly, I'd suggest you get a couple of sets of axle stands so you can raise your car off the ground on all four corners to obtain safe and easy access to the braking system.

As Luli said, ignore the handbrake for now and leave it in the off position. You can address it's operation once the foot brake is working correctly.

The 'compression' tube is a bit of a red herring since it doesn't compress. The foot brake should push the rods to all the brakes evenly so that the slightest pressure will move all the transverse brake rods at the same time. There should be no slack to take up in the compression tube. However, once the foot brake is working on all four corners, the handbrake will operate the rear wheels only because the compression tube can slide backwards under it's operation. If the compression tube were a solid rod the handbrake would operate both front and rear wheels, which we don't want. So, think of the compression tube as an expansion tube and it makes a bit more sense.

I hope that helps a bit? So frustrating that you are so far away or I'd happily pop round and lend a hand! Get the car jacked up and easy access and if you are still puzzled by it all perhaps I could talk you through it on the phone, while looking at my car?

Let me know.

Tony.
Tony Gilbert

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

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luli
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Re: P2 brake balance assembly

Post by luli » Thu Aug 06, 2020 7:00 am

I am even further away... but have recalled that Rover gave a way of adjusting some of the brakes mechanism from above. Remove the back seat. The floor under it is removable and gives you good access to the adjusters and some of the forks and pins. The same of the floor in front of the front seats. see pictures here https://wp.me/pXLKy-282 , and here https://wp.me/pXLKy-28V

And remember, if you use stands to have them under the axles, not the chassis so that the springs stay stretched.

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RobHomewood
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Re: P2 brake balance assembly

Post by RobHomewood » Thu Aug 06, 2020 11:51 pm

Thanks for your support Luli and Tony
I have the front end up on ramps (compensating for the sloping floor) but the rear wheels are on the floor to keep the springs etc in the right mode. However I had to jack up the rear today anyway as I found a flat tyre and that certainly helped with the access. As you say I could put axle stands under the axle rather than the chassis in future.
I think I am beginning to understand the system. I have the various levers adjusted as near to the right attitude as I can make them and tightened up the handbrake even further. I did a tentative road test and soon found the handbrake still did not work. I know the front brakes are working (because at least one skidded) but suspect that the rear ones are not activating at all (hence no handbrake). I need to find a way of testing the rear brakes only and I guess that may be by disconnecting the front rod or backing the shoes right off. I need to think about this some more.
By the way the instructions are to ensure the compression rod moves freely. It moves OK and I can feel pressure as if there is a piston inside rather than just a spring. Is that what is meant? I see it has no rubber bellows over the joint.
Rob

TonyG
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Re: P2 brake balance assembly

Post by TonyG » Fri Aug 07, 2020 9:15 am

Rob,

I think disconnecting the front brakes or slackening the adjusters is a bad idea as this would leave you without brakes if the rears don’t work! Also it is always the fronts that do most of the stopping on any car, hence manufacturers putting discs on the front and not the back for many years, so your car won’t stop very well even with the rears working well.

Easy to test the rear brakes alone though; simply use the handbrake and not the foot brake.

As I said before, the expansion/compression tube is placed between the foot pedal lever and the hand brake lever in the run of rods so that it can expand when the hand brake is applied, thereby preventing operation of the front brakes by the hand brake. This is it’s only function. So, with handbrake off, the tube must sit hard up against it’s stop - I.e fully compressed - so that the pressure from the pedal is solid through to the rear brake swivel unit and any small pressure on the pedal will move the transverse brake rods front and back.

Get that bit working first and then look at the hand brake operation. All it does is interrupt the foot brake rod and operate the rod to the rear with the tube forward of it expanding so the front brakes don’t operate.

The bellows on the expansion joint are only to keep the dirt out but a good dose of grease will ensure it doesn’t rust up and I doubt you use the car enough for this to be a problem.

I’ve been laying on the garage floor with a torch looking at the brake rods running front to back under the driver. Without getting under the car and looking from the side it is possible to see the linkages and I can just about reach in and press the foot pedal by hand to see the rod movement. With hand brake off this is only small, about half an inch. Once hand brake is applied, it’s possible to move the foot pedal up and down so that about half an inch of the expansion rod is apparent.

Hope this helps. If you have an iPhone we could do a face time call and I can look at your brakes remotely and I can show you how mine work. Send me a private message if you want to set something up- or just have a call to discuss. I don’t use my land line number only my mobile.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
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Discovery Sport

RobHomewood
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Re: P2 brake balance assembly

Post by RobHomewood » Fri Aug 07, 2020 5:18 pm

Hi Tony. Thanks for your thoughts. I had worked out that disconnecting the front brakes wouldnt work anyway! I got distracted today by replacing the front No1 compensator with another I found in my spares but this didnt improve things noticeably because the play is in the bush in the mounting which allows the bottom of the drop shaft to sway by about 1/4". Mike Couldry says he can rebush these but I was a bit wary of taking the mounting plate off the car because I wasnt sure whether there could be movement in axle or spring. The mounting doubles as the top plate clamping the axle to the spring and I need to reassure myself it will be safe to dismantle it whilst underneath. Maybe in the end it will turn out that this amount of free play is not so detrimental as it looks.
My compression rod is definitely not up against the stop when at rest with nearly 1" of inner showing. I am trying to work out whether it would be better to shorten the rear rod(s) or the one from the front compensator whilst trying to maintain the angles of the levers.
Maybe tomorrow
regards
Rob

TonyG
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Re: P2 brake balance assembly

Post by TonyG » Sat Aug 08, 2020 12:13 am

Rob,

I’ve just re-read the whole thread here and I believe everything points to a problem with the rear brakes, given that you can lock up a front brake and yet the handbrake is useless and the rear compensator is clonking against the tank. Plus the expansion tube is not compressing fully at the pedal end.

If you look at the last of the pictures I sent it is of the brake rod that goes to the rear compensator where it connects to the lever joining the main rod from the hand brake/foot brake. I think you should try to shorten this brake rod to the rear compensator. Access is from under the rear seat behind the driver.

With hand brake off, shorten this rod so that the compensator sits firmly against it’s location hole in the rear axle and also so the main rod is pushed forward to take up any slack in the compression tube at the pedal end. Do not adjust it so much that the swivel at the rear pulls the transverse brake rods though.

Once this is done I think you will find the rear brakes operate effectively and the compensator swivel unit no longer hits the tank when the pedal is released. Then try the handbrake. It should emulate the foot brake movement of the rear brake rods but, if you feel that the lever travel is too great, you can adjust the rod from the hand brake lever going down to the operating mechanism below as Luli described.

Having got all four brakes operating as they should, you can turn your attention to excess play in the various swivels and Clevis pins. I found it was possible to weld up the holes in the rod yokes and re-drill to fit new clevis pins. The compensator swivels are more challenging and you may need to get the front one re-bushed as you described in last post. The front one is the most crucial as excessive play here will make it hard to balance the front brakes to achieve straight ahead braking.

The key thing is not to get sidetracked from the main issue you have, which is hard when there are a number of bits that are less than perfect. However, once the rear brakes and hand brake are all working you can start to address the other areas of wear.

The front compensator mounting plate can be removed from the top of the spring without issue, even with the car up on axle stands as the weight of the car is pushing down on the spring and therefore onto the top of the axle so removing the four bolts and plate above the spring won’t result in anything coming adrift. However, you will not be able to drive the car or move it about with the offside leaf spring unbolted from the axle.

Hope that helps.

Tony.
Tony Gilbert

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

RobHomewood
Posts: 219
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Re: P2 brake balance assembly

Post by RobHomewood » Sat Aug 08, 2020 5:46 pm

Sage words Tony thanks
I pressed on a bit today only slightly delayed by fitting the missing bellows on the compression shaft which arrived today - super fast delivery from Mike Couldry. Having refitted that I then shortened the rearmost rod by between 1/2" and 1" - I didnt measure exactly how much. This amount just started to visibly put tension on the rear cross rods and achieved a partial result at least. The handbrake is working now but not enough to hold the car on a hill and I believe the rear brakes are therefore working in some form. The handbrake has limited travel (one notch maybe 2 using both hands) The front is slightly out of balance now with the offside wheel locking up and also a tug to the left (and a nose dip) when braking sharply. I suspect I may have slightly shortened the offside rod when I refitted the expander housing (took it right off to clean the faces). Hopefully I am now in a position where I can chase down these elements by small adjustments.
Fingers crossed
Rob

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

Re: P2 brake balance assembly

Post by TonyG » Sun Aug 09, 2020 8:41 am

Rob,

Well done it sounds like you are getting there and, by the time you have sorted all the little bits, you will be quite the braking expert!

I’m wondering why your handbrake isn’t holding very well though. 1-2 notches is rather tight; I’d have expected 3-4. However, the brakes should have been on hard and holding well. Have you had the rear drums off to check the linings are in good shape and that there are no oil leaks? The rear axle oil seals can fail resulting in oil getting on to the drums. Or maybe just rust etc that needs cleaning out. The key thing is to get the brakes, front and back, adjusted correctly before tackling the linkages and rods so that you don’t mis lead yourself. It’s also important that the adjustment of the rods doesn’t result in any tension being applied to the the transverse rods and the brakes themselves or you could end up with one or more brakes in a state of partial operation, which isn’t good at all.

Anyway, good luck and let us know how you get on.

Tony.
Tony Gilbert

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

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