1934 RP rear brakes

[Robin Oldfield]

I should know the answer to this, but on coupled brakes why is brake balancing always done with the footbrake (piece of wood if you are acting alone) and not the handbrake?

[David Stepney]

I have always balanced the brakes with the handbrake. I've had no problems so far. In fact, having only recently (3 weeks ago) relined the brakes, I managed to shoot the Motoring Dog off the back seat of the RP yesterday during a sharp 'anchor up' to avoid colliding with a marauding Audi on a single track lane.

[Martin Prior]

Like David, I have always set up the brake on our (coupled) cars using just the handbrake.

I set the front brakes to "just scuffing" with the handbrake on by one click, and the rear brakes on two.

["Slack Alice" Simon]

Just to point out something that is known to most of us but may not be known by MorrisMinor :

You can get brake cables where one end is a fixed connection, and the other runs through a pinch bolt set in a forked end.

Releasing the pinch bolt allows you to adjust the braking by slightly shortening or lengthening the cable.

This can be a bit of a fiddle, and on my car I have had to grind bits off the forked end to allow it free movement, because it catches on the operating lever on the cross shaft.

[AustinWood]

Rolling road brake testers flatter the front brakes. On the roller there is no effect from the momentum of the car when it is motion.
Momentum causes the front axle to move back and slacken the cables.

[David Stepney]

Rolling road brake testers flatter the front brakes. On the roller there is no effect from the momentum of the car when it is motion.
Momentum causes the front axle to move back and slacken the cables.

The effect is reduced considerably if the front suspension including the radius arm pivot point on the chassis are all is good condition. And one can compensate for the residual effect by carefully setting up the brakes.

[John Cornforth]

Austinwood raises an interesting point (apologies to morrisminor if I am drifting off topic)

When the brakes are applied, there is a small amount of twist in the front axle and bend in the radius arms due to the torque reaction and this has the effect of slackening the brake cables.  This was probably true even for cars when they left the factory. If certain components have wear, the whole axle can also move backwards fractionally as the cable tension takes up any clearance.

When the front brakes are tested on a rolling road, these two effects are still present, so the front brake effort reading is true.  When the back brakes are tested, any backward front axle movement due to wear will still be present. However, the front torque reaction/axle twist is now absent so the front cables are tighter than they would be on the road.   Due to the lack of any front/rear compensation mechanism, the tighter front cables tend to result in looser rear cables. The rear brake effort reading will therefore be a little less than true.  So I agree that in effect the front readings are flattered.

With the introduction of semi-girling brakes on the ARR Ruby, the radius arms and their axle attachments were strengthened to better resist axle twist.  Also, a swinging arm compensator was fitted to the cross shaft, so the front and rear cable tensions are immune to cable movement and forced to be equal.

As far as I am aware (happy to be corrected), the lengths of the various levers in the semi-girling sytem are the same for front and rear, and the brakes are the same, so the braking effort is equal front and rear and can't be changed by cable adjustment.  Considering that the Ruby is front heavy, and even more so under braking, there must be a risk of the rear brakes locking under slippery conditions if applied too enthusiastically.

[Bob Culver]

Hi Robin and more
On the all cable semi girling 1936/7 models the front rear balance is determined by the beam and this is checked with the pedal applied. Operation alters when handbrake used. Earlier systems and left to right rear balance can be checked however applied. Care necessary esp with original cables that adequate thread engaged. (With girling brakes minor adj an be made by setting one adjuster back a flat or two and maintaining the difference.) For earlier cars retrofitted and with no balance beam the adj as recommended above applies, with the brake applied either way.
It gets confusing on cars with mixed systems and/or mixed lever lengths. Altered cable runs can also cause brake operation to vary with load and on bumps.