Rear brakes

[Alice]

Will someone please jog my memory to assist in re-re-restoration of "Minnie". Is the correct location of the rear brake / backing plates such that the cam is behind the axle, with the lever pointing down?

[Jpallis001]

Hi - I am in the process of putting my rear brakes back together at the moment. The backplates that I removed from the axel had the cam positioned behind the axel. I did wonder why the cam on the front brakes operates in front of the axel while that on the rear was positioned behind the axel. I had to drill out the bolts that held the back plates to the axel, so was fairly confident that they had been fitted with the cam aft for a long time.

Some associated discussions at:
http://www.vintageminor.co.uk/Forum1/ph ... 8326#p8326
http://www.vintageminor.co.uk/Forum1/ph ... &start=225

John

[Ian Grace]

Hi John,

Well, that sounds correct to me, if I understand you. At the back, the cams are to the rear and the brake shoe fixed fulcrum pins are forward of the axle. And at the front, it is the other way around - with the cams forward of the axle. The original SV Minor front brake cables ran forward from the brake cross-shaft, around pulleys that were attached to brackets on the chassis about a foot behind the front axle, then out at about 45 degrees to the outboard pulleys mounted on the top of the kingpins and then forward again to the lever. The only exception to this was the early OHC Minors that had the inboard pulleys mounted on a pin on the axle beam just outboard of the front spring. (In fact the fifth hole for this pin was never deleted and can still confuse the SV Minor owner occasionally!) And the outboard pulley was mounted under the kingpin so that the cable then turned backwards to the cam lever behind the axle.

Does this make sense?

Ian

[Alice]

OK, we agree that the cam is aft of the axle. I'll add here that the "wisdom" behind lever location on many cable systems is that when there is road spring "wind-up" under braking the rotation of the axle causes the brake cables to be pulled harder. Ask any A7 man about the front brakes, which back off under braking with the original design! This idea then suggests that aft of the axle is correct, as long as the lever points down, which was part of my original question.

[Ian Grace]

Barry,

Apologies - I read John's post but missed yours above it!

Also, nice to see someone from 'down under' on the forum.

[Alice]

OOPS! My first question arose because I thought there was going to be a hell of an angle of the cable from the rear crossmember to the cam lever. Have just been studying the situation when I noticed that there would be a conflict between the brake cable/lever area and the shock absorber lower mounting (on the bracket under the rear spring). This led to realisation that lovingly rebuilt springs had these brackets on the wrong sides. OOPS,The joys of rebuilding from memories! Cursed having to dismantle springs to fix problem, then had brainwave that it only needed for springs to swap sides and all's well. NOT QUITE! I have assembled springs so that the heads of the bolts through the rebound clips are on the outside, and these bolts have square section under the head, which meant filing a square hole on that side of the clip. Swapping sides puts the bolt heads on the inside. So I do have to dismantle and change the brackets after all.
In the words of a comic song from about 50 years ago, "life gets tejus don't it".

[Jpallis001]

Thanks Barry, I had not thought of the spring 'wind-up' bit, it would explain things. It might go someway to explain a problem that I think Kartik was having with his brakes? If the brakes were over-adjusted, and there was a lot of movement in the rear springs, once the brakes were applied axel movement would result in the brakes being applied even more? and not released until the axel un-winds?

John

[Alice]

Hi again fellas,
I was about to post an urgent call for a definite answer when, while having lunch, I trawled idly through the forum and lo and behold found a thread dating back to May 2009 which covers the topic and seems to answer my question. To the rear and pointing down!