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The Service Letters says that the brakes shoes are marked with "S" (Secondary) and "P" (Primary) and shall be assembled in a definite location. I can not see any difference at all between these to type of shoes! Is it right? The service letter mention that there are different types of brake lining and the "S" and "P" brake shoes. Do somebody know the reason for that? Today I think we will have the same type of lining on both shoes?

Dear 2740:

The markings are there but may be very hard to find or obliterated. The primary is the shoe with a shorter lining and goes in front of the actuator when looking in the direction of rotation. Or the bottom shoe in the case of your car.

However, for your car there may not be a visual difference between the shoes. If the linings are replaced and all have the same friction code then it doesn't matter. If the friction codes are different, take the shoes to a place that does brake work or call Fort Wayne Clutch and ask them which code is for the primary. Ditto if there are different color shoes.

Also Packard used a narrower lining on the left front.

Hope this helps.

Tim's completely on target. On my 34 the primary and secondary shoes are marked on the metal surface of the shoe itself, a large stamped "S" or "P" within a circle although that's only useful information if the corresponding lining material is on that shoe. When I relined my 34 some 40 years back I used the same lining material on both primary and secondary shoes but installed them correctly, shorter lining on the Primary (leading) shoe, and narrower linings on the front left. The brakes on these cars are just outstanding though it's a bit of fussy work to get them properly equalized after a reline.

Thanks to both of you. It was interesting to know about the different length of the brake lining as well as the different materials. I didn`t recognize that the lenght of the brake linings were different when I removed the old worn linings. I suppose that the engineers by Packard worked hard to adjust on all parameters on the braking system to get the mechanical brakes to have the same perfomance as the hydraulic brakes from the competitors. I did also learn that the return springs on the "S" and "P" brake shoes do have different pulls (75lbs and 100lbs). Dave, you are right, even following the service guideline to adjust the brakes, it is still a huge work to do to get the brakes properly equalized after relining. After a week of small drivings each day, with testing the brakes and small adjustments on the brakes I`m close to get the brake equalized.

Somewhere in the literature there is a blurb about having brakes equalized at an authorized Bendix service outlet.

What they had in those days was a drive on dyno that had gauges at each wheel. With the wheels turning the adjusters were equalized.

There used to be an old timer who had one of those machines in his backyard and supplemented his retirement that way.

Three comments. First, with self-energizing brakes and two different strength shoe return springs, the weaker spring always goes on the primary shoe so that this shoe contacts the drum first and then transfers it's force to the rear shoe.

As to adjusting, there is an easy way to get very close the first time after a reline without a road test. After following the full adjustment procedure in the Service Letters, put all 4 wheels up on jackstands. Apply the parking brake (which actuates all 4 wheel brakes) partially (a few clicks) so some drag is felt on all 4 wheels. Then just using your arms to rotate the tires against the drag, adjust each wheel individually until you have the desired result (front left should have ever so slightly less drag). There was a special tool for this which essentially gripped the tire firmly and the tire was rotated with a torque wrench on the fixture so you could actually measure quantitative and relative forces. In this case you're essentially doing the same thing just using your arms and sense of feel to rotate and feel the relative braking force at each wheel.

Third, some of Packard's competitors did not have hydraulic brakes in 1934, and some did not for even longer. Hydraulic brakes were still viewed by some with concern, and Packard and several of their competitors stayed with mechanical brakes for several years. For Packard it was hydraulic in the juniors and mechanical in the seniors. The mechanical brake system was very much more costly. Lincoln stayed with mechanicals for how long? 1938? I don't recall, did Pierce-Arrow ever went to hydraulics?

Personally, I'm a real fan of these Bendix 14" mechanical brakes, they have tremendous braking power, the variable power boost is a neat and useful feature, and for a car that has annual lay-up time, never a concern about wheel and master cylinders, hoses, bleeding, flushing, water corrosion in the lines and cylinders, etc. You could conceivably loose brakes at one wheel if a cable broke, but it's a practical impossibility to loose your all brakes.