1934 RP rear brakes

[morrisminor]

Just got back from a 6 mile run and the back brakes are hot, I'm new to RPs, can they be adjusted ? They don't appear to be binding because the wheels spin freely even when hot ?
Another quick question I've took the cover off the transmission tunnel to grease the torque tube/prop and there's no grease nipple, just a blanking plug.
Thanks guys

[Bob Culver]

Are you jacking the car such that it duplicates the riding condition. There should be some movement availalble on each lever when the cable is plucked. Is the heat just from normal stopping? It is very easy to have a conditon where the front brakes do little in actual on road operation, esp if there is a mix of levers and brake systems (girling and pre) and/or there is movement in the front radius rod ball joint..

[morrisminor]

I jacked it Bob so both wheels were off the ground. 
The fronts were warm but not hot like the rears. When you say cable plucked do you mean brakes on so cable tight , but there should be movement on each lever attached to the drum?

[Reckless Rat]

Sounds like the rear cables are over adjusted, or possibly the camshafts are sticking. You hardly need any tension in the rear cables or they will come on harder tgan the fronts which in an emergency will lock the rear wheels and cause the car to rotate on its axis. The fronts should do the most.

[morrisminor]

Camshafts sticking ? are they the levers that go from the cable and attached to the  drum back plate ?
How do you adjust them,  I'm only used to the girling type on a Ruby

[Reckless Rat]

Yes. There is no adjustment except by shimming. The levers shouls point downwards by the way.

[Martin Prior]

The rear cables on all of our Sevens are adjustable.

As Bruce (Reckless) pointed out, make sure that the levers are pointing downwards (and slightly backwards).  Amazingly, they're incorrectly assembled on perhaps a quarter of the cars that come to us.

[John Cornforth]

Hi

The blanking plug is normal. Just take it out, substitute a nipple and swap back when you are done.

If your wheels spin OK, that suggests the brakes aren't binding. A very light drag is acceptable. The cable run should be such that rear suspension movement hardly alters the cable length, but it's always possible that the run is non standard.  As others have implied, jack the car under the rear axle so that the weight is still on the rear springs and conditions are as close as possible to the on road state.

Prior to Semi Girling, brake adjustment is done on the cables themselves.  There is no front/rear compensation, and in my experience, the front/rear brake balance can be altered quite a bit for only a few turns adjustment of the nut on the front cable yoke near the cross shaft.  So maybe you have too much rearward bias.  One method of checking is to find a gravel surface with no traffic, brake hard, and compare the front and rear skid marks. The best method is to check on a rolling road brake tester if you can find an older testing station with one that is narrow enough.  Some folks don't like the idea of roller testing an A7, but I have had it done many times with no problem. Ideally you are looking for at least 70 kg per wheel when you stand on the pedal.

The front brakes should balance reasonably well side to side due to the pivoting quadrant, which (in theory at least) equalises the cable tension between the two sides.  The rear brake balance side to side can be problematic for A7s of that era, due to the vagaries of the cross shaft design.  Most people aim for best balance at near full braking, and accept that balance will not be perfect for lighter applications.  Again, balance is quite sensitive to rear cable length so I suggest changing it in only 1 or 2 mm steps.

I once resorted to putting the car on axle stands both front and rear, and using a bottle jack and wooden blocks to apply pressure to the brake pedal.  It was possible to feel the turning resistance of each wheel increase as the brakes were progressively applied.  Unfortunately, there was no way I could summon up by hand anything like the 150 ft-lb torque at the wheel needed to simulate full braking, so it was only a basic guide to balance at light application.

[Tony Press]

I jacked it Bob so both wheels were off the ground. 
The fronts were warm but not hot like the rears. When you say cable plucked do you mean brakes on so cable tight , but there should be movement on each lever attached to the drum?

No check the rear cables with the brakes off - there should be some slight slack before the levers pull the shoes onto the drums each side.

[Chris KC]

As Recks observed if the rears are hot and the fronts cool there is something wrong, either the rears are dragging (when the car is standing on its wheels) or the rears are coming on in advance of the fronts (which is a Bad Thing).