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MG TD TF 1500 - Brake Adjuster problem

I just reassembled and bled my brakes. New shoes, all six wheel cylinders resleeved/rebuilt by White Post, new hoses, turned drums. Everything is fine except even with the adjusters turned full-up the drums don't quite lock up tight, and of course the pedal is a bit low for my comfort zone, although all works well.

Maybe I should not have had the drums turned. I watched it being done and the mechanic who did it was amazed at how very little had to come off. Maybe it's the cumulative effect of 56 years wear and previous turnings.

I see on Ebay (item 310164325471) that a guy is selling brake shoe "masks" with 1/8" bar stock welded to the bottoms to raise them a bit and put the shoes closer to the drums. Is this a good solution?

What's the preferred way to deal with this problem?

TIA!

Allen
Allen Bachelder

Allen-
Seems to be a lot of this problem about, either all the drums are worn out, or the new shoes are wrong.
Whatever, the problem is that the shoes need to be bigger some way, and adding material to the end is the easiest way to do it. The spacer trick is easier than welding up the shoe end, but neither will correct a mismatch in the shoe/drum radius. That calls for either new drums or thicker linings.

So far as I know, all new shoes originate from Moss - someone there informed me of that a few years ago when I asked why the price was so exorbitant - "because we are the only supplier and because we can."

Mismatched radii is a real problem, in that the designed self servo effect doesn't work correctly if the shoe doesn't contact the drum as it should; and, the shoes will deflect under load leading to a spongy pedal until they wear in to full contact. If your adjusters won't lock the brake now, you are never going to get to that point without running out of adjustment once the nubbles wear off.

The shop manual says the drums started at 9". It states that the adjusters must be backed off all the way to get the drum over new shoes, and I can attest that that was formerly true, when the cars were newer. Of course, it also says that the brakes should be adjusted when the pedal gets to within 1" of the floor before the brakes start working!

I personally have always believed that turning of drums is primarily a marketing scam by the brake industry, and for obsolete and rare parts it just wastes precious metal. Drums rarely need it; the only valid reason is that the drum is out of round or badly scored. Heat checks and deep scoring both call for new drums, since you have to turn them past the -.060 that was formerly the universal standard. All drums should be deglazed for new shoes. Slightly scored drums just need a little more bedding in, and the results are far better than mismatched radii, which requires at least as much bedding before they work correctly. The correct way is to grind oversize lining to the right radius, but environmental concerns have pretty well done away with that practice. Further, the mass of metal available to absorb heat is important and turning just takes off too much. I am known for being picky, and I do not remember the last time I had a drum turned, maybe 30 or 35 years.

A number of years ago, in a discussion of Velvetouch shoes for a Magnette, I gave you the contact for a guy who still did it the old fashioned way, with thicker linings radius ground to match your drums. Don't know where that info is now, the guy was somewhere in WA or OR I think. It's possible that an industrial brake reliner can do it also.

You can approximate the process by gluing sandpaper inside the drum, adjust the shoe to make very light contact, and rotating the drum to grind the lining to size and shape. Then add material to the adjuster or shoe end to get your adjustment back. Modern linings won't have asbestos in them, but wear a dust mask. You will lose some lining life, but how many miles is the car ever going to do? Probably more with brakes than without!

FRM
FR Millmore

Allen - The only place you might need shimmed masks is on the rear brakes and then only if there is some wear on the shoes. The adjuster for front and rear wheels are the same, but on the front brakes, each shoe has its own adjuster and the range of adjustment is about right between a new set of shoes and shoes that have reached their normal wear. On the rear shoes though, the adjuster is operating on both shoes, thus the range of adjustment is only half as far as on a single shoe, so you run out of adjustment before the shoes are worn even half way. If you are experiencing problems with all four wheels, you may have drums that have been turned out beyond specs as Fletcher suggests or possibly the shoes need to be arched to fit the drums. Cheers - Dave
David DuBois

It would be interesting to compare original unworn parts, including the rear shoe abutment, wheel cylinders, masks, and the shoes- as far as the total contacting circumference to the repro or worn new ones. I think it is likely a combination of a little wear everywhere, perhaps new shoes that are a touch short, as well as turning the drums. A couple people here have TD's that had new repro rear drums installed a few years ago, and we had to grind some off of the heal of the shoes to get them to fit. The adjusters have to lock up totally tight, with some more room to adjust- if not they are starting too loose, and with just a little wear you have a big problem and no way to adjust. George
George Butz

O'Connor Classics carried the shimmed masks in the past ($10 per mask, plus shipping).

http://www.oconnorclassics.com

CH Topping & Co. relines brake shoes and I think they may be able to install thicker pads on the rear shoes to close the gap between shoe and drum. (This information needs to be confirmed.) Cost was $15 a pair in 2006, plus shipping, for standard thickness.

http://www.chtopping.com

Larry
Larry Shoer

Thanks, guys!

Fletcher, come to think of it I knew that brake drums rarely, if ever, need turning from my experience with rears on MGBs. Different context here and I got to thinking this was just good maintenance on a 56 year-old car. Fortunately (?) since the drums were already "in surprisingly good shape" VERY little material was removed, but nevertheless, all I did was add to the cumulative problem.

Larry, I'll check with CH Topping about thicker pads for the rear shoes. I have a spare set of shoes I could send them if they do this. Could this not be done on front shoes also? I'll also check into those shimmed masks at O'Connor.

Cheers,
Allen
Allen Bachelder

I debated getting thicker pads, but opted to just have Topper replace the existing pads. Although the old pads (and the replaced pads) required me to crank the adjustment to about 75% of its travel, I was afraid that specifying thicker pads could lead to pads which bound up on installation. In other words, I didn't know how much thicker to specify the new pads and was afraid they may turn out too thick.

Knowing that the shimmed masks were available (I purchased a pair from O'Connor), I'll be able to slip in the replacement shimmed masks in the future if I run out of adjustment travel.

Potentially, you could get thicker pads for the front, as well as the rear. As already mentioned, the two adjustment points on each front wheel mean that you have twice the adjustment range in the front as the rear. Of course, the front brakes do most of the work, so it is true they will wear faster.

Whatever you do, reshoe all front shoes if you do any front shoes and reshoe all rear shoes if you do any rear shoes. Otherwise, you run the risk of unequal performance of the brakes side to side, which presents a safety issue.

Larry
Larry Shoer

Larry,

Thanks for your continuing help. The front shoes on my car look practically new. I did install new rears - both sides, as the old ones did not look so good. Part of my current problem is I can't remember how high or low the pedal was before I did this job. It may not have been any higher than it is now. On my test drive, I did a little hard braking and they pulled evenly.

In my Google search for "mg td Brakes", I found your page on brake rebuilding. Of course it's one of those things I wish I had seen before I did the job, but I did learn it all - sometimes the hard way!

BTW, this all started out when I finished installing seat-belts (as per Horst Schach) and was about to take the car off the jack-stands when I noticed brake fluid leaking from three of the six wheel cylinders. One thing always leads to another...

I did put in a note to CH Topping, and I looked at O'Connor's online catalog only to find no shimmed masks. I did send them a note too. ' Will see what happens.

Cheers,
Allen
Allen Bachelder

All,
I have used a penny on each of the "masks" for many miles with out a problem. Had to grind a bit off so they would fit. 6 cents vs $60 (plus shipping) for the welded ones

SPW
Steve Wincze

Steve,

Would dimes work without the need for grinding? Yeah I know - ten times more expensive... 8^)

Allen
Allen Bachelder

Another method to compensate for the larger diameter of turned brake drums, is to add a shim in between the linings and the shoe.
To determine the thickness of the shim required, measure the diameter of the drum, the thickness is half the dimension above 9”
With this method you don’t lose any lining thickness and the curvature will be correct, however you can only use it for riveted linings.
It easy to cut the shim stock to the right size with tin snips and make the holes with a hole punch. Brass is a good material as it is a better heat conductor.


John
J Scragg

No filing necessary...I just trimmed a penny with a scissors!
Joe Walck

You comment that the pedal travel seemed high. It might be agood idea to go under the car and re-set the pedal adjustment height. This is a oft neglected adjustment which can contribute to the pedal being "low" before the brakes make contact.
colin stafford

Thanks all,

Acting on Larry's advice, I contacted O'Connor and found that they do still have the shimmed masks available. And I contacted SH Topping and found they can reline shoes with thicker material. In part, here is what they wrote to me: "Yes we can, do you know if your lining is 5/32" or 3/16" we can put up to 1/4" then arc to size. There is a segment for Porsche that is .280" but very expensive."

So now, these two solutions are available plus a third: the combination of both if necessary.

Colin,

Yes, I've thought of adjusting the pedal travel, but I'm more concerned right now about my inability to lock the drums with the adjusters. Once I solve that problem, if the pedal is still too low, I will re-set the pedal height adjustment.

Again, many thanks for all your input!

Allen
Allen Bachelder

Allen-
Orig lining is 0.187 = 3/16" I've seen relines that are noticeably thinner.
Seems to me that you need to accurately measure the drums as the first step in all this foorah. That should narrow down the problem and give the correct fix.

FRM
FR Millmore

Fletcher,

Thanks. Precisely, what should the drum measurement be? Exactly 9"?

TIA,
Allen
Allen Bachelder

Allen
I have been using the O'Connor mask shimms and they took care of my problem which was exactly as you describe.
Good luck.


Tim
tw hager

There is a set(6)of masked shims on ebay right now.
David
David Sheward

Don't lose your original adjusters...the O'connor ones work on shoes that are worn down, but won't work on new shoes....I couldn't get the drums over them when i did mine....now i'm waiting for some wear!
gblawson(gordon)

Gordon,

Each case is different. My drums and relined shoes required the original mask be run out almost to its limits of adjustment. This could be the result of previously turned down drums or lining that was just a little less than employed when the TD was new. I've got a pair of shimmed masks ready for when I need to compensate for wear on these relined shoes (and would have installed them if I had them during the rebuild).

In other words, the need for the shimmed mask isn't necessarily an indication that the linings are worn.

I do agree that the original mask should be kept in a safe place for potential future reuse.

Larry
Larry Shoer

Larry,

I think you just established my own course of action. I'll buy the shimmed masks and keep them until my pedal starts moving further down; which may happen fairly soon as I'm presuming my shoes are not bedded in yet. I'll then switch to the shimmed masks and put my originals in my safe deposit box.

I'd get a set of CH Toppings' thicker linings right now, except I don't want to give up my drums for however long that takes. If the shimmed masks don't do it, I suppose I can go for the thicker linings in the winter when the car is off the road anyway.

' Can't believe how folks keep adding to this thread!

Thanks!

Allen
Allen Bachelder

Allen-
The book says 9", and usually they meant exactly what they say. Seems the modern way of stating things in more decimal places was not used in days of yore - wouldn't fit on the abacus.
If you take the shoe and put it in the drum, you can get a pretty good idea of how much difference there is in the lining and shoe radius, which could suggest a course of action. Use sheets of shim stock or paper to fill the gap and then measure the stack.

But, if your weather is like mine this week, forget about it and drive!

FRM
FR Millmore

This thread was discussed between 30/08/2009 and 02/09/2009

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