Packard Forum Index » V-8 (1955-56)

G'day Mates, I'm in need of some expert advice. Some routine maintenance repacking the front wheel bearings on my '56 Patrician has grown into new bearings and reco'd wheel cylinders. Everything is ready for reassembly but I've noticed a couple of problems with the brake springs & shoes. You can see in the attached photo that, according to the service manual, the springs are reversed with the yellow to the primary shoe - easily fixed. However, even though the parts book allocates the same number for both shoes, they are not the same. The primary shoe has a lining length of 9 3/4" and the secondary 12 5/8". Also, the diagram in the parts book (#14) implies the secondary shoe has a shorter lining. Which lining is correct for each shoe? Hope you can help. Kind regards, John (can't get photo to load so hopefully description will do)

Can't address your particular brakes (though I do have a 56 Packard), but typically the rear shoe, the secondary shoe, has the longer lining because it does more work. Often with OEM shoes it also had a different lining material with a different coefficient of friction, though this distinction is pretty much disregarded today. The front (primary) shoe, with the shorter lining, is intended to engage the drum first - this happens because it typically (but not always) has the weaker return spring, thus allowing the front shoe to engage first. As the front shoe contacts the drum, it attempts to turn with the drum in the direction of wheel rotation, and thus "cams" or jams the rear shoe into the drum, kind of a mechanical advantage to increase braking force.

Hope this helps, it not the whole story.

Thanks for the info Owen. On rechecking the diagrams and photo's in the service manual and parts book, there's no indication of whether they are right or left hand side. I've assumed I was looking at the LHS brake assembly but, based on your description, it is obviously the RHS. Accordingly, I'm headed out into the shed to reassemble everything that way, apart from the springs which were reversed at some stage in the dim distant past (orange to primary). Then to be on the safe side, it's start all over again down the back end. Cheers, John

Glad to have been of help. I wouldn't get too wrapped up over the weaker return spring on the primary shoe, I believe that was not the exclusive case in all years and models, and I know some modern replacement kits use the same spring for each. But for sure set the shoes into the right respective positions.

I know 54 and 55 Clippers use that same primary and secondary return spring.

JP -

What Owen describes is a self-energizing drum brake. However, do not confuse that with self-adjusting brakes. Your Packard is equipped with drum brakes that are self-energizing (in forward motion), but they have to be manually adjusted, periodically.

Not sure how they do it abroad, but here in the states, brake shoes/linings are not sold not individually, but in sets, per axle - that is, enough to service a pair of wheels on the same axle. Be sure to follow Owen's orientation of shorter and longer lining.

I've seen where installing return springs incorrectly has caused problems with brakes locking up, though.

I have been sent, however, brake lining kits for my 55-56 Senior Packards that included return springs which were NOT colored as original (yellow and orange), but was told the lighter color spring was for the primary (leading) shoe and the darker, for the secondary (trailing) shoe.

The 55-56 Clippers, however, used same return spring for primary and secondary - colored blue, IIRC.

Thanks for the info Brian. I can report that everything is now reassembled completely in accordance with Owen's instructions. When I initially disassembled the brakes I noticed the secondary shoes had marginally more meat on them than the primaries so, as the shoes are the same, I was going to reverse them to get more wear out of the set. That is until I noticed the different length linings and then I started to wonder if the way they were set up was correct. I couldn't find anything specific to explain that, hence my inquiry to you learned gentlemen. By the way, these linings were originally fitted in the US (the car came from California). Out here in good old Oz we wouldn't be able to buy complete matching sets off the shelf, we would get a new set made up by a brake specialist using the old ones as templates. Thanks to you both once again, you've been very helpful. Cheers, John

As Owen indicates above leading shoe and secondary shoe MIGHT have different material for linings. This can be the reason for different spring tensions. Look at sections XXI of the repair manual under brakes and material used.

HOWEVER, REPLACEMNT shoes may or may not be of different material. The materail and differences between primary and secondary shoes can vary from supplier to supplier. Also as Owen indicates the spring tension therefore may not be critical.

It's a crap shoot as to whether or not lining material varies and whether or not the spring tension between front and rear spring is an issue or not.

The short lining shoe goes to the front. Long lining shoe to the rear. THis is typical of all brakes i have seen across a wide variety of manufactueres and years. Springs are a crap shoot as to which spring goes where (relative to REPLACEMENT SHOES) and we need somekind of controlled rigorous test facilities to determine that.

***** Some (but not all) REPLACEMNT shoes have primary and secondary linings the same length. ******

The Short/long lining issue and the spring tension issue was what the factory did to FINE TUNE the brake system using KNOWN lining material.

50 years later we are using parts of different materials that may even vary from year to year or supplier to supplier. So the factory fine tuning for spring tension may not hold for us now.

Just put the short shoe to the front. Long shoe to the rear
and guess at the 2wo springs the best u can or according to Owens instruction/explanation above. If the replacment shoes u have are all the same lining length then front or rear shoe doesn't matter. IT will be just fine.

In some cases of linings all the same length then look at the lining material to see if there is conspicuous difference in the color of the lining or some other visual affect. In that case u will have to determine from supplier documentation that came with the shoes as which is front or rear shoe. I do not ever recall seeing shoes with all same length linings haveing any conspicuous variation in lining material nor any instructions that ever came with shoes to indicate any difference.

Clarification: My above explanation is not Packard specific but tends to hold across a wide variety of drum brakes and across a wide variety of years and across a wide variety of manufacturers or the partts and car models.

One point about drum brakes not mentioned by anyone so far is that, at least in the old days, the shoes were "arced", i.e., lining material was removed by a specialized machine to match the ID radius of the wheel drum. This is particularly important if the drum and has been "turned", i.e., the ID radius is larger than OEM. The purpose of this procedure is to assure uniform contact between the shoe lining and the drum inner surface. If this procedure is NOT done, then brake efficiency WILL suffer if the two radii are different.

Craig