Packard Forum Index » V-8 (1955-56)

The Brake Parts List is here.https://www.packardinfo.com/xoops/html/downloads/partslist5556/01_Brake.pdf

Auto Parts guy asked if my rear wheel cylinders were 1" or 1 1/16". I have a 1956 Clipper Sedan Deluxe. If I read correctly, my model number is 5640, meaning I have a 1 1/16" bore.

I feel pretty confident in telling the guy this, but he has to order them in, so I don't want to have egg all over my face for making a newbie mistake. Am I right that they are 1 1/16"?

Thanks.

Correct.

Good deal, Owen. Thanks. I'm getting more comfortable finding my way around. For a while, I've been thinking "5622," but I figured out where I was going wrong.

Thanks again.

Parts interchange lists are handy, but when the answer to your question is right in the printed orignal Packard specifications (in the Service Counselors), best to go to a primary source.

Wait just a minute, now.

While the 1-1/16" size certainly matches what's shown in Section XXI - Specifications of the 1955-56 Shop Manual (as well as "Mechanical Specifications and Adjustments" provided in SC Vol. 29, No 13), there's a bit more to this story.

Take a look at the 1955-56 Service Index Brakes section, which shows a relevant topic regarding "Rear Brakes" in STB 56T-24. Although we do not yet have copy of that bulletin on file, here, I can tell you that it recommends use of 1" diameter rear wheel cylinders - same as used on 55-56 Senior cars. This information is reiterated in SSB No. 344, along with other checks and amended adjustment procedures, plus improved rear drums.

However, DO NOT go and simply order 1" wheel cylinders. These measures should ONLY be applied to those vehicles that exhibit a problem of premature wear and grabbing of rear brakes. It does NOT mean that ALL Clipper (and Executive) models had the problem.

So, BEFORE you order anything, I recommend you measure what's on your car.

I don't think any of the cars will have "premature" wear after 56 years of service.

I have STB 56T-24 and will scan and post a copy tomorrow. It is a follow-up to 56T-22. Essentially, 56T-24 advises to install the 1 inch cylinders if you have both premature lining wear AND severe brake grab on moderate to heavy application.

Well, I already ordered the 1 1/16". Hopefully, that's what I have in there. I haven't driven the car a whole lot to be able to judge anything other than the brakes seemed okay, given that they are not power brakes and the car is pretty darn heavy.

The good news is that even if I needed to switch, these wheel cylinders are about the cheapest parts I'll ever be buying for this car. They were barely over $10 a piece.

STB 56 T24

Attach file:

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Thanks for providing that copy.

Interesting that the bulletin number is handwritten (same as the photocopy that I inspected) - likely due to the hectic times that followed the shutdown of Detroit operations. The paper trail is rather curious over the relative timeline; for example:

56T-22 is dated July 12, 1956, and is signed as usual
56T-23 is dated July 20, 1956, and signed as usual
56T-25 is undated and lacking signature
56T-26 is dated November 20, 1956, but lacking signature

So, this bulletin, dated October 19, 1956, is rightfully noted and should be considered as 56T-24.

Getting back to nuts-and-bolts, SSB No. 344, in addition to advising of an improved type of rear drum for this problem, reiterates the recommendation of smaller diameter rear wheel cylinders. Given the additional steps provided in that bulletin to address the complaint, it seems that the brake shoes were not fully seated against the anchor pin, following pedal release.

Of course, that condition could result in dragging, which in turn, leads to premature wear of the linings. Given the self-energizing design, I can see how that could also lead to grabbing.

The idea behind using a smaller diameter cylinder must have been to provide improved shoe release and seating (vis-a-vis nominal residual line pressure) by increasing the relative effect of the return spring. Apparently it was easier to fine tune cylinder size than mess around with springs.

While there's no need to follow those recommendations if the vehicle does not exhibit such problems, this is good info to have on file.