Rusty Driver
Posts: 195
Joined: Mon Sep 04, 2017 6:22 pm
Re: 1948 KB5 Railway Express
Does it mean that someone went to great lengths to swap out all the hydrovac parts and install a "standard" braking system, anything is possible in 70 years. The hydrovac appears to have been an option on the KB5 and I have enclosed a photo of one that is found on my brother's spare KB5 chassis. I could have added it, but felt it was not needed since the truck will only be for show, act as an advertising billboard, and sit most of the time. If needed, then it could be added in the future.
The addition of the check valve was done by myself and the lines are all new and also cut/flared/joined by me as you see it. So that is not anything factory, just an add-on I thought might pan out to be a good idea.
I honestly am not sure how it will stop, but road speeds are not going to be high, maybe 45 MPH, as it does not have overdrive, just the 4 gears and reverse. Being a truck driver, I know how to also use gearing to slow down as I am sure you do.
I am not sure IF these rear wheel cylinders are indeed the "mountain brakes?" The KB5, according to the Manual show the standard rear wheel cylinders as 1 3/8" x 11/16". The Manual also lists the "Special Wheel Cylinders" as the same 1 3/8" x 11/16" BUT the "Increased Capacity" brake shoes are listed as 15" x 4" x 3/8" and 15" drums. So is this a misprint if the "Standard" and "Special" rear wheel cylinders for the K-5 are the same? According to the Service Manual, and looking at the K-6 brakes, it seems that the "Increased Capacity" rear shoe is the same as the optional "Increased Capacity" rear shoe/drum for the K-5. Shouldn't the larger rear wheel cylinders also be part of the "Increased Capacity" brake shoe option?
So for arguments sake, lets say the "Mountain Brakes" were the optional 15" x 4" x 3/8" shoes and 15" drums. If you look at the rear wheel cylinder sizes, the K-5 uses the 1/3/8" x 11/16" and the "Special Wheel Cylinders" are listed exactly the same as 1 3/8" x 11/16". Then looking at the K-6 with the same optional brake shoes/drum (the "Increased Capacity") uses a larger rear wheel cylinder size of 1 1/2" x 3/4". The K-6 also uses a larger 1 1/2" bore Master Cylinder according to the Manual.
IF the photos of the rear brakes for the K4 - K11 Hydraulic brakes are correct, they all show the same style of rear wheel cylinders with the only difference being that there appears to be 2 different bore sizes, 1 3/8" x 11/16" versus 1 1/2" x 3/4".
With all that said, it is my guess that the "Mountain Brakes" on a K-5 would be the use of the larger 15" shoes/drums, and possibly the larger rear wheel cylinders.
Again, if the original rear cast brake shoes are correct for my truck and the rear axle has not been swapped out, from what I seem to come up with, and according to the Service Manual, it seems my KB5 has the "Standard" 14 1/8" x 3" x 3/8" shoes and the 14 1/8" drums and not the "Increased Capacity" or "Mountain Brakes."
I am open to comment if you can clarify any of this - just this 1 time. LOL