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TR owners sometimes neglect their back brakes only maintaining them when the handbrake won't adjust up.

When I built my long door TR2 about the only consumable item I reused were the rear brake shoes. They looked to have a lot of meat left but as it turned out I needed to have them on full adjustment. Even then they weren't quite there. I suspect the shoes were aftermarket and not quite right.

The brakes were very good, the local Triumph man said they were the best he had seen on a drum braked Triumph. But I wasn't happy so I had a new set of oversized shoes made up. I fitted them yesterday, after much filing to get them to shape, and took the car for a brief test drive this morning.

The brakes are absolutely superb, nearly as good as the C250 Merc.

Lesson is to keep your rear brakes up to scratch, they aren't just there for the handbrake. They add a lot to stopping power and brake balance.

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Hi John,

did you measure the inside diameter of your drums?

Are the old and close to be worn? Have they anytime been on a lathe to get a smooth surface? 

There is a max diameter to be allowed.

In the case of a too large inside diameter oversized shoes make sense,

best is some more meat and to grind them down to the exact diameter of the drum.

This grinding machines are no longer common, there was one very well known producer of them - but I forgot it....

Only this way the self forcing effect of a drum brake works to its full ammount.

Easier is to fit standard shoes and new drums.

If you lay the shoes in the drum you see what happens:

does they shape of shoe and drum fit perfect, or does the shoe move like a beam of a seasaw?

I guess you are far over this point to do this experiment....

Ciao, Marco

 

Edited by Z320
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Thanks Marco. I measured the drums and I can't remember the detail but they weren't seriously oversize. The car has only done about 70,000 miles from new (only used from 1954 until 1965) but it was raced for all that time.

The new oversized shoes, once filed down to fit the drum, don't have much more meat than the old ones but fit snugly at the bottom of the adjustment. 

I suspect the old shoes were the problem.

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Hi John,

I remember there is not so much difference between the new diameter and worn.

If your drums are original parts please keep in mind to have a closer look on them the next time.

Shure you agree with me: on a TR with about 70,000 miles front brake discs have been changed 1 or 2 times since new - why not the drums?

On my old drums I found no indication for the max. diameter, on the one I remember there is someting stamped on.

But sorry me, I'm to lazzy to put one of the wheels of.

Ciao, Marco

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35 minutes ago, Z320 said:

Hi John,

I remember there is not so much difference between the new diameter and worn.

If your drums are original parts please keep in mind to have a closer look on them the next time.

Shure you agree with me: on a TR with about 70,000 miles front brake discs have been changed 1 or 2 times since new - why not the drums?

On my old drums I found no indication for the max. diameter, on the one I remember there is someting stamped on.

But sorry me, I'm to lazzy to put one of the wheels of.

Ciao, Marco

Thanks Marco. Drums aren't the same as discs. Drums should last for 100s of thousands of miles if adjusted right.

The disc pads are nearly always in contact with the disc and the swept area is smaller. The drum shoes are held off the drums by springs until the brakes are applied and have a larger swept area spreading the load.

 

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Hi John,

I'm a bit late in on this discussion but I'll add my twopennerth anyway.Some time ago when restoring my J2X Allard I took my brake shoes (12" which are the same as Jag C/XK120) into my Lockheed factors for relining.It was a comfort that the guy behind the counter knew exactly what they were.They duly relined the shoes but I immediately had the same problem as you did, i.e/ shoe material too thick.I rang them up and asked what the problem might be and they told me that they routinely fit .060" oversize linings in that particular application, but to return them with the brake drums and they would sort the issue out whilst I waited.The shoes were fitted to a brake shoe linisher which duly reduced the material from the areas they considered to be too high after having offered up to the drums and I refitted them with no further problem, but the adjusters were on the lowest settings for the initial bedding in and for some time afterwards..They have been superb for the last 14 years with only the usual basic maintenance.

Roger M-E

 

 

 

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42 minutes ago, John McCormack said:

Thanks Marco. Drums aren't the same as discs. Drums should last for 100s of thousands of miles if adjusted right.

On my TR4A the front discs do the main job (the pads not always in contact with them),

after 115,000 miles on the clock (if correct) the original drums have been worn.

You have a TR2 with 4 brake drums?

70,000 miles and raced?

Origianal drums?

Obersize brake shoes?

Just my thoughts.....

 

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1 hour ago, Z320 said:

On my TR4A the front discs do the main job (the pads not always in contact with them),

after 115,000 miles on the clock (if correct) the original drums have been worn.

You have a TR2 with 4 brake drums?

70,000 miles and raced?

Origianal drums?

Obersize brake shoes?

Just my thoughts.....

 

Thanks Marco for your thoughts. Your points are well made.

The car came with heaps of spares including 3 sets of front and rear drums and shoes. Some of the drums were rusted out and others had hard spots on them (probably used for racing as the heat build up causes the hard spots) so I picked the best pair. I didn't make a note of the drum size when I selected them but they were only a few thou, probably less than 10, oversize from the 9" they should be. 

I then had them checked by a local brake specialist who do a lot of classics and honed to ensure they were round.

The old shoes had about 3/16" left on them so I thought they would be OK for awhile but when fitted were already on the max adjustment. I used them for a year or so because the brakes were OK. 

When I got  the new shoes they were way way too big. I took a lot off over 5 hours of filing, trial fitting, filing etc. They now they have about 1/4" thickness the same as stock shoes. The brakes are now on the bottom of the adjustment cam. I wasted my money and time getting oversized ones made.

I am confident the problem was the old shoes. I assumed they were OK and I really should have bought new ones when I bought new front ones. Don't know why I didn't. 

All is good.

 

 

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