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sunroof
Samba Member
Joined: October 06, 2006
Posts: 2067
Location: Winnipeg
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 Posted: Fri Nov 07, 2025 1:58 pm Post subject: Re: Field find 1954 Canadian custom |
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Sure, the shoes and drums will get hot and lose efficiency, but it sounds like you had worse than that?
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It is not that they lose efficiency it is that the drums expand and get larger in diameter. This means that the shoes must travel farther to contact the drums resulting in the brake pedal migrating to the floor. Along with boiling any water out of the brake fluid causing what little brakes you have left to go even softer. Of course I have fresh brake fluid in the system so there is little or no water to boil.
As hot as my brakes got, the pedal remained high and firm, they just made a terrible stink.
Don
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sunroof
Samba Member
Joined: October 06, 2006
Posts: 2067
Location: Winnipeg
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| Posted: Sat Nov 08, 2025 6:56 am Post subject: Re: Field find 1954 Canadian custom |
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OK this will be wrapped and put aside just in case I sell the car and the new owner wants it
It fits! Phew!
It looks like this is going to work
Don
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Zwitterkafer
Samba Member
Joined: November 17, 2007
Posts: 1017
Location: Lanark County, Ontario, Canada
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| Posted: Sat Nov 08, 2025 11:21 am Post subject: Re: Field find 1954 Canadian custom |
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[quote="sunroof"]
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It is not that they lose efficiency it is that the drums expand and get larger in diameter. This means that the shoes must travel farther to contact the drums resulting in the brake pedal migrating to the floor. Along with boiling any water out of the brake fluid causing what little brakes you have left to go even softer. Of course I have fresh brake fluid in the system so there is little or no water to boil.Don |
Well, as drum temperatures rise, the coefficient of friction falls, and you get "brake fade" manifesting as a hard pedal with less effect. Quality linings are paramount.
Engineers know how much cast iron expands when heated and take this into account when designing brake systems. Below is an estimate of how much a 230mm cast iron drum expands when overheated by 600 deg F (!).
CTE = thermal expansion coefficient (cast iron) 12 x 10^-6 m/m deg C
delta T = 600 deg F = 315 deg C.
L =dimension of cast iron
delta L = CTE x L x delta T
delta L = (12 x 10^-6 m/m deg C) x (.23 m) x 315 deg C
delta L = 0.0008694 m
delta L = 0.8694 mm
Yes, that affects pedal travel, but would it fall all the way to the floor? Pumping the pedal (assuming compensation port, check valve, free play all good) would not help?
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sunroof
Samba Member
Joined: October 06, 2006
Posts: 2067
Location: Winnipeg
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| Posted: Sun Nov 09, 2025 7:39 am Post subject: Re: Field find 1954 Canadian custom |
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Interesting!
As I careened down the mountain side I did not experience brake fade or the pedal softening just a terrible smell. The drums definitely saw some heat tho.
I wonder if the kind of amazing performance of the brakes during that descent have to do with modern alloys used in the drums and modern materials in the shoes.
So in my other car club there are a bunch of guys that started racing in the 1950s, mostly TR3s and MGAs. They have been telling me for decades that over heated brakes will make the pedal migrate to the floor because of the expansion of the drums. I am going to have to ask them again about that, perhaps I misunderstood.
On another note... I had a 1981 Honda Silverwing with a front disc brake that my Dad bought new and sold to me. What a turd of a bike. Anyways, it was severely underbraked and if I clamped down on the binders too hard the brakes would just fade away. It was super hard to bring to a stop in any emergency situation. I didn't realize how really bad it was until I drove my buddies 1981 Kawasaki KZ1000, now that bike had brakes!
Back to the job at hand.
I used these tools to do the brake swap
Don
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sunroof
Samba Member
Joined: October 06, 2006
Posts: 2067
Location: Winnipeg
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| Posted: Mon Nov 10, 2025 4:26 pm Post subject: Re: Field find 1954 Canadian custom |
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All buttoned up and on the ground. That went off without a hitch.
On another note...I was going through some stuff looking for something the other day and came across this
This is what took the car off the road in 1977. Rod bearing #1 burned right up.
Don
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