Brake lining thicknesses for the Pre-War Jowett.

[Tony Fearn]

What do we collectively know about the reason for two different thicknesses of brake linings for the Pre-war cars?

I've been helping a mate sort the brakes on his 1934 long saloon and we've found that after he'd had the back brakes relined with, I think, commercially available 'new old stock' linings, the rear brake rods (with the butterfly adjuster on them) are now not long enough to enable the butterfly nut to be fully engaged.

This suggests to me that the linings are thicker than the originals, everything else being equal.

Tony.

[ian Howell]

Tony: -

I found a similar situation on my Long Four (You kindly sent me some butterfly nuts!). I made new rods anyway as the previous ones were badly 'necked' at the hook end. (I used the old rear ones to make new front ones - Jowetts would like that!).

Incidentally, the linings had been 'packed out' from the shoes with brass shims between the rivets, I guess to get that l e e e tle bit more wear out of them, possibly during wartime. They were down to the rivets again anyway!

The drums on mine are marked (inside, in chalk) '10 1/16 +20' and I relined the brakes with Ford 20 linings from Beaulieu. All seemed to fit well and the brakes are GOOD!"

I suspect IP would have the answer.

I also think that Bob Jones had something to say on this matter, but that will have been ages ago.

[Tony Fearn]

Hello Ian.

There was another method of moving the linings nearer to the brake drum.

Some of the brake shoes I have in stock had part of a metal hacksaw blade underneath the flat steel bearing plate on the end of the shoe - I suppose that a piece of shim metal would do the same job.

The other end of the shoe which fits on to the circular bearing in the back plate can also be 'padded-out' with a shim around the bearing.

This was probably to compensate for brake lining thickness as you said.

Another problem is that if you buy/have bought brake linings at an autojumble, (I'm talking pre-war) then they could be one of two thicknesses, ( they usually have JOW/**/** written on their undersides) and if you use them to re-line your shoes you need to be wary of the difference in the thicknesses of the linings.

Depending on the brake drums, there might be a need for shims especially if the linings are of the thinner type.

But as I was told many years ago, the brake levers on the vintage and pre-war vehicles need to pull up towards 90 degrees for maximum effort, whereas levers that are already at 90 degrees at rest, and pull a greater angle don't have anywhere like the same efficiency.

Tony.

[Leo Bolter]

Hello Tony and Ian.

The following URL will take you to a contribution I made to a discussion on the LE Velocette Forum . . . it may be of interest.

The method described gets the very best out of mechanical brakes.

http://www.leveloclubforum.org.uk/viewt ... highlight=

Best regards, Leo

[Alastair Gregg]

Hello Leo,

Unless I am doing something really silly (That is very possible). I can't use that forum unless I become a member.

[Leo Bolter]

Sorry everyone . . . my mistake. I should have known there would be problems with access to the LE Velo forum if you weren't a member!
I'll copy the relevant information in the post, to this forum tomorrow.

Leo

[Leo Bolter]

Acknowledgements should go to Nick alias "neddyo" from whom I "stole" the photo and a selected portion of the text that was in his post on the LE Velo Forum

Here's a shot of turning down semi finished brake linings for my Mk3, I gave them .5 mm clearance. I mounted the back plate on a mandrel and replaced the return springs with wire, anxious moments as I waited for the tool bit to dig in, but all went well.I have not tried them on the road but wheeling the bike along they now seem to bite really well.
The people who relined the shoes gave a good tip, if wheels have been respoked the drums should be skimmed as they nearly always go out of shape. Cheers, Nick.
_________________________________________________
My bit . . . .
Hi neddo (and all who are watching this post).

May I add a couple of other tips to your good advice above?

When in the trade, I have used the above excellent technique for many years on every type of motorcycle from road racers and motocross machines to scooters and mopeds . . . it really make a huge difference in improving braking in most cases. Especially along with the other "cunning ploys" to be had (quote from Baldrick!)

Here's a couple of extra "tricks" I have used.

1/ You'll need a absolutely "bog standard" (not modified in any way) and undamaged brake plate to do the turning on. Spin it on the mandrel in the lathe to be certain it's not wobbly and that the shoe mounting points are true with each other. The cam shaft and bush should have no wear as well. There's a possibility that the rear brake retardation can also be improved by using this method of machining its shoes on a front backplate. Perhaps this backplate could be set aside as a jig for future lining turning use.
I marked the shoes so they go back on the brake plate in their "as turned" positions when they are removed. Then I inserted two 0.010" or 0.015" shims between the brake shoe to cam faces before turning the linings to the minimum clearance required to insert them into the drum, without any binding. (shims go between both items 19/20, the brake shoes and 21 (the two slippers), as shown in the diagram below).
The shims were removed when turning was completed of course.
This means that when the brake is applied, the turning of the cam through about the equivalent of 0.010/0.015" is going to cause the maximum area of the linings to make contact with the maximum area of the drum. (nearly the full circumference of the linings, as they were turned)

2/ Also, if the spigot (part 18 ) clearance in the brake plate is increased from standard (by say, 0.020"), perfect centering of all the brake parts in the drum can be achieved. The method is to assemble all the components, put the wheel back in place to the point where the axle nut is about to be tightened. At this stage apply the brake as hard as you can and while holding the brake "on" do the axle nut up to it's normal tightness.

Don't forget to chamfer the leading edges of the brake linings or grabbing or shuddering might occur . . .

Also, there's a wealth of other "hints-n-tips on improving brake performance in section 7, page 17 of the Technical Notes club publication

Skimming of the drum of the assembled and trued wheel, as well as the above tips, should give you the ultimate in braking for the friction area versus weight of the machine (and rider/s!)

Incidentally and personally, I would be more happy when using wire to secure the shoes together, to see a couple of twists with pliers, of the wire joining point than that as shown . . . but then you were going to do that before turning commenced weren't you?

"may your brakes be the only things that cause you to feel retarded!"

Cheers, Leo

[ian Howell]

Just to be clear - the shims were between the shoes and the linings! Not at the end pegs or cams.

When I had relined the shoes, the drums fitted pretty well.

To be sure, I marked the drums with chalk, refitted them and operated the brakes. Then I took the drums off again and looked for 'tell-tales' on the shoes.

A very little fettling was required and I got a good fit on about the second attempt for each drum.

I like the idea of turning them on a lathe but I do not have that option: -

1. My lathe is only 3" centres.

2. I don't have a new backplate as a reference.

Of course I have not yet been able to test them on the flat road or Porlock Hill, but they certainly 'bite' here at home.