Chrysler brake system

[VicW]

I started a brake job on my 1937 Chrysler Royal & I found a couple of unique things I want some members input on. First the rear wheel cylinders, the piston diameter is larger on the rear shoe 1-1/4" than on the front shoe 1-1/8" of the rear axle, I think I know the reasoning for this but haven't came across this before. I ordered brake shoes from Andy Bernbaum & they came as 4 identical shoes with full length lining on each shoe (not surprising for that era IMO). When I pulled the drums I found whoever did the last brake job used a set with 1 primary & 1 secondary shoe. I have no Idea who did the last brake work but I plan to use the shoes I have. The steel brake lines quite rusty & I will replace all of them, they show their 83 years of trusty service. I was planning on using the straight steel lines with the spring coil covering but the parts store suggested the newer steel line with a plastic covering. Lastly I seen an article on converting the 1960s era tapered shaft axles from the swedged on drums to the newer style floating brake drums. That conversion involves studs on both hubs so all your doing is freeing the drum to be removed without a puller. Does anyone know if the newer 60s era studded hubs are interchangeable with the older hubs with the threaded wheel bolt holes & drums rivitted to the hub. Thanks in advance for any input on this.....Vic.

[knuckleharley]

5 hours ago, VicW said:

I started a brake job on my 1937 Chrysler Royal & I found a couple of unique things I want some members input on. First the rear wheel cylinders, the piston diameter is larger on the rear shoe 1-1/4" than on the front shoe 1-1/8" of the rear axle, I think I know the reasoning for this but haven't came across this before. I ordered brake shoes from Andy Bernbaum & they came as 4 identical shoes with full length lining on each shoe (not surprising for that era IMO). When I pulled the drums I found whoever did the last brake job used a set with 1 primary & 1 secondary shoe. I have no Idea who did the last brake work but I plan to use the shoes I have. The steel brake lines quite rusty & I will replace all of them, they show their 83 years of trusty service. I was planning on using the straight steel lines with the spring coil covering but the parts store suggested the newer steel line with a plastic covering. Lastly I seen an article on converting the 1960s era tapered shaft axles from the swedged on drums to the newer style floating brake drums. That conversion involves studs on both hubs so all your doing is freeing the drum to be removed without a puller. Does anyone know if the newer 60s era studded hubs are interchangeable with the older hubs with the threaded wheel bolt holes & drums rivitted to the hub. Thanks in advance for any input on this.....Vic.

Can't advise you on the hubs,but I will advise you to go with the copper/nickel brake and gas lines. They never rust,inside or out,and you can bend them with your hands without them kinking.

They are available everywhere.

[kencombs]

2 hours ago, knuckleharley said:

Can't advise you on the hubs,but I will advise you to go with the copper/nickel brake and gas lines. They never rust,inside or out,and you can bend them with your hands without them kinking.

They are available everywhere.

And, they are so much easier to flare.  Agree wholeheartedly with that advice.  

[desoto1939]

I own a 39 Desoto and according my documentation from my 1936-42 Desotomaster parts manual the shes have a primary and a secondary shoe lining. The parts manual shows that the secondary shoe which is the small lining alwasy is mounted on the rear of each wheel.  These are not self energizing shoes so the short on fron and long on the back was done in later years go back to the proper setup.  Also each brake lining should be chamfers at both ends of the lining material so as to make a smoother transition when the brakes are applied.

 

I would not go to the effort of chaning out the drum and studs.  Your car will have the bolt on sytem for each drum and it should have the mounting pin cast into the drums faces.  I have these same drums on my 39 Desoto.  I have a five hole drum puller and it also has the hole for the pin.  I have never had any issues with pulling these drums.  Suggest that every year pull the rear drums and you will never have an issue.  Write to me and I will show you my drum puller.

Note the extra hole on the left side around 11 o clock this is for the mounting pin. If you have studs then this is not needed.  So why chnage and spend the money to convert to studs. Just use a good quality drum puller.

Rich Hartung

Desoto1939@aol.com

 

 

 

 

[keithb7]

I  started a brake job on my 1937 Chrysler Royal & I found a couple of unique things I want some members input on. First the rear wheel cylinders, the piston diameter is larger on the rear shoe 1-1/4" than on the front shoe 1-1/8" of the rear axle, I think I know the reasoning for this but haven't came across this before.  

 

There must be an engineer here who can tell us what exactly is going on. Different sized cylinders will all see equal pressure form the master cylinder. However a larger diameter piston would offer increased pounds of force. For example say 700 pounds PSI of force is exerted from the master cylinder.  700 x 1 ¼ = 875 lbs force on the front shoe. 700 x 1. ⅛ = 787.5 lbs force on the front shoe. My old study book here tells me that by having stepped cylinders, the larger cylinders get more breaking force.  So perhaps n your 37 Chrysler, they wanted the lazy rear brake shoes on the rear wheels,  to be forced into doing a little more work.

We almost always see large cylinders for sure, on the front of the car, compared to the back.

 

I ordered brake shoes from Andy Bernbaum & they came as 4 identical shoes with full length lining on each shoe (not surprising for that era IMO). When I pulled the drums I found whoever did the last brake job used a set with 1 primary & 1 secondary shoe. I have no Idea who did the last brake work but I plan to use the shoes I have.

 

If you got modern reproduction shoes, there won't be any asbestos in them. My understanding is they may not perform as well as the eariler shoes with asbestos.

 

The steel brake lines quite rusty & I will replace all of them, they show their 83 years of trusty service. I was planning on using the straight steel lines with the spring coil covering but the parts store suggested the newer steel line with a plastic covering.

 

Good idea. Replace all brakes lines. Right to the master cylinder as well. I highly recommend the Cal-Van brake line flare tool kit. Seen here. Easy peasy. Professional flares every time. https://www.ebay.com/c/1100195016

 

Lastly I seen an article on converting the 1960s era tapered shaft axles from the swedged on drums to the newer style floating brake drums. That conversion involves studs on both hubs so all your doing is freeing the drum to be removed without a puller. Does anyone know if the newer 60s era studded hubs are interchangeable with the older hubs with the threaded wheel bolt holes & drums rivitted to the hub. Thanks in advance for any input on this.....Vic

 

Personally, I wouldn't bother with this idea either. My puller works well. No complaints. Seen here: https://www.amazon.com/Cal-Van-Tools-94800-Hub-Puller/dp/B0066PU1PM/ref=sr_1_10?dchild=1&keywords=brake+drum+puller&qid=1602196582&sr=8-10

[Sniper]

PSI is PSI.

 

As in pounds per square inch, so a larger diameter wheel cylinder with have more force applied to the shoe with a given input pressure.

having a shoe with smaller area will require more pressure applied to get the same force on the drum.  So it looks like, if I am reading your post correctly, the smaller shoe got the larger wheel cylinder.

 

Why they did that I do not know.

[desoto1939]

Here is a reason why the rear shoes use the short lining compared to having the short lining on the front side of th drum  Bendix style:

 

New message from: gt46tc (7,103)

Brakes are designed with a 60/40 front/rear balance for skid control. That balance is generally achieved with smaller diameter or more narrow rear shoes. Given Mopar cars of the era used the same diameter/width drums front/rear the balance was accomplished with the rear short shoe to the rear. Hard to tell that to the "experts". GT

 

 

Rich Hartung

[Sniper]

17 minutes ago, desoto1939 said:

Here is a reason why the rear shoes use the short lining compared to having the short lining on the front side of th drum  Bendix style:

 

New message from: gt46tc (7,103)

Brakes are designed with a 60/40 front/rear balance for skid control. That balance is generally achieved with smaller diameter or more narrow rear shoes. Given Mopar cars of the era used the same diameter/width drums front/rear the balance was accomplished with the rear short shoe to the rear. Hard to tell that to the "experts". GT

 

 

Rich Hartung

 

lol, that is so bad it's not even wrong.

 

The 60/40 balance mentioned is 60% braking on the front axle brakes vs 40% on the rear axle brakes.

 

The length of the front shoe vs the length of the rear shoe inside the drum has ZERO effect on front to rear axle braking balance.  Whomever wrote that is, to quote him, an "expert".