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Old 07-11-2020, 05:45 PM   #1
Tim Ayers
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Default '40 rear brake question: How snug should the drums be on the shoes?

OK, about to finish up the brakes on my '32 chassis. Front brakes were NOS '42-'48 drums & hubs with '40 backing plates. They were not turned and measured exactly @ 12".

Front installation was a breeze and they turn nicely. All four backing plates have both adjusters set at the starting point according to service manual and Rumbleseat's tips.

Rears brakes are a combination of Bolling Bros. drums on stock '40 hubs. These drums also measured 12" with a drum mic.

Left drum went on without having to sand the shoes but it turns with much more resistance than either front brake does. The left will not free wheel, but the both fronts will.

Right rear drum is super tight. At first, the drum would not slide on. I've been sanding the shoes (original style, riveted to original cores) at the high spots that I can see, but it is slow going.

Question: Once installed, how much drag should new drums have? I like that the shoes are close, but I also don't know what is considered normal drag that will "break in" after an initial drive or are just set too tight and there needs to be more clearance.

If it helps, I am not turned them with a tire on. I am just grabbing the drum and turning it.

Thanks all for any tips or suggestions.

Last edited by Tim Ayers; 07-11-2020 at 05:52 PM.
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Old 07-11-2020, 06:03 PM   #2
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

You say you're just grabbing that rear drum and turning. Is it difficult to turn, or just dragging? I've always set-up shoe brakes with SOME drag, yet NO real difficulty in turning. ALMOST sounds like your fronts MAY be a little loose, which of course means somewhat farther for the pedal to travel before resistance. DD
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Old 07-11-2020, 06:06 PM   #3
Tim Ayers
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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You say you're just grabbing that rear drum and turning. Is it difficult to turn, or just dragging? I've always set-up shoe brakes with SOME drag, yet NO real difficulty in turning. ALMOST sounds like your fronts MAY be a little loose, which of course means somewhat farther for the pedal to travel before resistance. DD
Thanks for the reply Coop,

To be clear, the front drag somewhat.

Left rear is dragging, which I think should be fine. Right rear is hard to turn.
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Old 07-11-2020, 06:10 PM   #4
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Thanks for the reply Coop,

To be clear, the front drag somewhat.

Left rear is dragging, which I think should be fine. Right rear is hard to turn.
Well, I guess CONTINUE sanding. Sounds like the other three are good to go. DD
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Old 07-11-2020, 06:11 PM   #5
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Well, I guess CONTINUE sanding. Sounds like the other three are good to go. DD
Yes.
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Old 07-11-2020, 06:37 PM   #6
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

I agree. Be careful on the initial drive. Stop after a while and put a hand on each wheel and feel for it being over hot. If one is hot, let it cool and drive carefully home. It might be ok after bedding in, but be careful during the first few miles.
This happened with my late model daily. I had one brake too tight and it got so hot it was smoking. I parked it and left it. When I came back it had cooled down and I was able to drive home. I loosened the adjustment a little before setting out again.

I'm not sure, but the lining material these days might be thicker than normal because the suppliers expect the drums to be somewhat oversize. Pure conjecture, but sanding until the drum turns with no more than slight drag does sound like a sensible approach.

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Old 07-11-2020, 07:00 PM   #7
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

On my Bolling Bros rear brakes I rub chalk on the shoes and then adjust the brakes as per the Bolling Bros instructions. I do have a light drag on both rear drums with tires mounted. Test drive and then remove the drums to see chalk wear pattern. You may have to readjust them again as top pin plays a key role.

My Bolling Bros. brake shoes and drums slid on with no problems. Make sure you have adjusted shoes inward so drum will slide on. Also, make sure drum does not rub on lip of backing plate. I had this problem and had to make a spacer.
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Old 07-11-2020, 07:01 PM   #8
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

I should have mentioned, the shoes were arched prior to purchase.

I'm thinking either the drum mic isn't precise enough or the shoes are just too thick. I'll keep going and report back.
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Old 07-11-2020, 07:01 PM   #9
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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On my Bolling Bros rear brakes I rub chalk on the shoes and then adjust the brakes as per the Bolling Bros instructions. I do have a light drag on both rear drums with tires mounted. Test drive and then remove the drums to see chalk wear pattern. You may have to readjust them again as top pin plays a key role.
Interesting. Where did you see those directions? My drums did not come with that.

I did call them and ask if they have found they needed to be cut prior to installation. The gentleman said their machining is generally spot on and they have not found a need to cut the drums with I liked. I was trying to start with 12" (standard, non-cut) brakes.
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Old 07-11-2020, 07:18 PM   #10
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

Tim: I checked the run out on the Bolling Bros. drums at it was .0005 ' at most.
Also, PM me with your email address and I'll send you the copy of the Bolling Bros. instructions I have. it is critical that the top pin adjustment be correct and that the pin be able to slide up and down during adjustment. It took me a couple of practice runs to get the knack.

One more thought. I used my OEM Ford rear wheel bearings as the new repros. are of questionable quality.
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Old 07-11-2020, 07:26 PM   #11
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Tim: I checked the run out on the Bolling Bros. drums at it was .0005 ' at most.
Also, PM me with your email address and I'll send you the copy of the Bolling Bros. instructions I have. it is critical that the top pin adjustment be correct and that the pin be able to slide up and down during adjustment. It took me a couple of practice runs to get the knack.

One more thought. I used my OEM Ford rear wheel bearings as the new repros. are of questionable quality.
OK, will do. Thanks. Yes, agreed. I'm using Ford script rear bearings.
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Old 07-11-2020, 07:46 PM   #12
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

Rule of thumb on drum brakes is .005" clearance between drum and shoe.
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Old 07-11-2020, 09:32 PM   #13
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

I've found that rear brakes must be set somewhat looser than front brakes to allow them to begin a skid at the same time as the fronts begin.
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Old 07-12-2020, 12:22 AM   #14
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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I've found that rear brakes must be set somewhat looser than front brakes to allow them to begin a skid at the same time as the fronts begin.

The most-efficient front to rear brake bias is accomplished through pressure regulation. That's the main reason for the smaller diameter of the rear wheel cylinders. You certainly don't want rear wheel lock-up to occur before the fronts. The most-efficient braking overall occurs just before lock-up, but with the tires still turning. Friction is considerably less with tires sliding. DD
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Old 07-12-2020, 03:07 PM   #15
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

These were Boling brothers drums and backing plate assemblies. At first i could not even get the drums on with the shoes backed right off. Contacted Boling and they admitted that had a bad run of shoes and I could send them back or relieve the shoe where it contacts the wheel cyl. Which is what i did . My hillbilly way of re arching shoes. I noticed the new shoe arch did not quite matc the new drum . A roll of sticky long board sand paper i had on hand solved it easily . Made sure i had the brakes adjusted correctly first. Bolted the drum and wheel back on , a few turns re adjust shoes a few more turns And perfect. Second pic shows poor contact , last pic I was happy.
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Old 07-12-2020, 08:03 PM   #16
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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The most-efficient front to rear brake bias is accomplished through pressure regulation. That's the main reason for the smaller diameter of the rear wheel cylinders. You certainly don't want rear wheel lock-up to occur before the fronts. The most-efficient braking overall occurs just before lock-up, but with the tires still turning. Friction is considerably less with tires sliding. DD

Well shucks, that makes sense, but with my '38 mechanicals, I have to accomplish the pressure differential with adjustments at the shoes. I'll have to look again, but I don't think there is a leverage difference at the cross shaft, so all cables pull equally.
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Old 07-12-2020, 08:53 PM   #17
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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These were Boling brothers drums and backing plate assemblies. At first i could not even get the drums on with the shoes backed right off. Contacted Boling and they admitted that had a bad run of shoes and I could send them back or relieve the shoe where it contacts the wheel cyl. Which is what i did . My hillbilly way of re arching shoes. I noticed the new shoe arch did not quite matc the new drum . A roll of sticky long board sand paper i had on hand solved it easily . Made sure i had the brakes adjusted correctly first. Bolted the drum and wheel back on , a few turns re adjust shoes a few more turns And perfect. Second pic shows poor contact , last pic I was happy.
Thanks for input all.

I walked away from it today (watched my sons play baseball) and I'm going to do two things:

1) Measure the lining thickness on the front compared to the one rear I haven't sanded yet.

2) I don't think it's the same issue with the shoe base since they are OE Ford cores that had the original style riveted linings put on.

3) If all fails, I'll call Richard (EV8 Garage) where I got them to see what he thinks.

I'll get this sorted out.

Last edited by Tim Ayers; 07-12-2020 at 08:58 PM.
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Old 07-12-2020, 09:42 PM   #18
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Well shucks, that makes sense, but with my '38 mechanicals, I have to accomplish the pressure differential with adjustments at the shoes. I'll have to look again, but I don't think there is a leverage difference at the cross shaft, so all cables pull equally.

Yup, and Henry and the boys (mostly the boys) IMPROVED the immediate efficiency by going hydraulic the next year, didn't they! Longevity-wise...the cables never leak or get nasty and rusty inside the cylinders like the juice units. DD
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Old 07-12-2020, 11:54 PM   #19
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Yup, and Henry and the boys (mostly the boys) IMPROVED the immediate efficiency by going hydraulic the next year, didn't they! Longevity-wise...the cables never leak or get nasty and rusty inside the cylinders like the juice units. DD

I have to disagree on the first part. I don't consider Ford's first hydraulics to be an improvement at all. The Hotchkiss brakes were less efficient than were the self energizing cable brakes, and remained inferior until replaced by the Bendix system in 1949. Cables aren't as fussy as hydraulics, but they do stretch, and the wedges wear, so maintenance is still as important as with hydraulics. For the collector though, cables are far superior than any hydraulics of any make or model, due to the self degrading of hydraulics just sitting in the garage.
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Old 07-13-2020, 02:23 AM   #20
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Default Re: '40 rear brake question: How snug should the drums be on the shoes?

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Yup, and Henry and the boys (mostly the boys) IMPROVED the immediate efficiency by going hydraulic the next year, didn't they! Longevity-wise...the cables never leak or get nasty and rusty inside the cylinders like the juice units. DD
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I have to disagree on the first part. I don't consider Ford's first hydraulics to be an improvement at all. The Hotchkiss brakes were less efficient than were the self energizing cable brakes, and remained inferior until replaced by the Bendix system in 1949. Cables aren't as fussy as hydraulics, but they do stretch, and the wedges wear, so maintenance is still as important as with hydraulics. For the collector though, cables are far superior than any hydraulics of any make or model, due to the self degrading of hydraulics just sitting in the garage.

Alan.....Read carefully! By "immediate efficiency", I alluded to the LIKELY attempt to improve front to rear brake bias by differing the size of the front/rear wheel cylinders. Ford obviously felt the need to update the brakes in '39. YOU mentioned that "Hotchkiss" brakes were less-efficient than cable brakes. Sorry to say that I'm just not familiar with the "Hotchkiss" term relative to brakes. Did you mean "Lockheed" brakes?


You also mentioned...."I have to accomplish the pressure differential with adjustments at the shoes." I don't believe that you're actually adjusting 'pressure' with this method. I believe that you are only adjusting the timing of the application of the rear shoes to be slightly later than that of the front shoes.


We own a very stock '37 coupe with the stock brakes, so I do have first-hand experience with that set-up. I agreed with you that the cables don't leak, nor do they sit there and make nasty, rusty fluid over time. My opinion though (and who cares what I think)….when reasonably-maintained, I prefer the hydraulics over the cables, especially with Bendix-types in the front and the Lockheeds in the rear. It's a combination that seems to work pretty well by default for a lot of guys, including my experience. I believe the reason that combination does work so well is that the rear Lockheeds are so marginal to begin with, both because of narrow shoe sizing and the fact that they are NON-self energizing. One thing that any of us should be careful of is oversizing or over-energizing the rear brakes.


With biasing in mind, it would be interesting to find-out whether the Ford cable brakes may have different length levers on the rears in an attempt to modulate the application of those shoes compared with the fronts. That's the only method I can imagine that would differentiate pressures derived from a single mechanical input. DD
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