Why directional instructions on disc pads ?

[Wayne M.]

Here's an eBay set; 2 pads have arrow pointing one direction, the other two point in the opposite direction, so that each caliper can have its two pads rubbing on a forward rotating disc.

Is this only for R & R of the same pads ? I can't see any difference in the new pads.

[Timothy B.]

Re: Why directional instructions on disc pads ?

Wayne,

I could not begin to tell you why the directional arrows except maybe a bevel on one end of the pad..

[Patrick H.]

Re: Why directional instructions on disc pads ?

Wayne,

I could not begin to tell you why the directional arrows except maybe a bevel on one end of the pad..

My thought as well.

[Michael M.]

Re: Why directional instructions on disc pads ?

Never seen it before. Can't see why it's necessary.

[Steven B.]

Re: Why directional instructions on disc pads ?

Wayne, decades ago when I was a production manager in a brake and clutch facility we supplied our own brand plus Delco, Raybestos, and others. On the D-8's and others we did not inlcude arrows in the markings. For some very SPECIAL RUNS we did when we ran experimental grinds with tapers but these were NEVER used in production from our facility. I see these are riveted pads, not attached with adhesive. Do you know the manufacturer?

Steve

[Edward J.]

Re: Why directional instructions on disc pads ?

Wayne, I believe the the reasoning with the directional arrows is that this would minimize brake noise, I know that here in my auto shop we have used Napa's version of this style pads. They use a inboard and out board pads . The friction material must be molded to the pad to indicate the best use for nosie reduction.

[Wayne M.]

Re: Why directional instructions on disc pads ?

..... we ran experimental grinds with tapers but these were NEVER used in production from our facility. I see these are riveted pads, not attached with adhesive. Do you know the manufacturer? ...

Steve -- the eBay set of 4 backsides I showed were Delco 5452513. Below are thumbnails of 2 sets of D8's I have. On the left is what I believe is a more recent replacement (# 2621609) for the #5452513 (on the right). The latter has asbestos fibers. Notice the 2621609 is shorter by a bit, although backing plate is same. Also I believe the '513' might have been replaced by the '609, as the earlier one no longer prices out in my 1980 master price list.

Notice the Delco symbol on the head of the rivet. Also, the Delco (?) number suffix is different for each of these boxes; 171-178 vs 171-110.

The eBay set was 8 pads (2 boxes, for complete car); sold for $208.

On the early one with the directional arrow, notice that the Delco 601FF is on the 2nd line of print. This is probably the friction material code, as the '609' is Delco is imprinted (on the edge) Delco 107FF, and the J56 metallics have a Delco (903FF) edge imprint.

[Steven B.]

Re: Why directional instructions on disc pads ?

Good pics Wayne. I have some D8's manufactured in '76. I will dig them out and see if they have the arrows. I also have some single pin semi-metallic pads from the same era and they are FF's. They had a slight taper on each end so they could be installed as inner or outer, not a unidirectional pad. We also used to grind pads with a slight taper on each end to prevent probelms bedding in and "fraying" of the friction material on the ends. The FF is the compound code, you are correct. FF was pretty good back in the J-56 days--it was the ultimate in asbestos based compound performance. In the mid '70's most semi tractors and trailers only had FE's.

From an SAE Table:

Official D.O.T. Edge Code	Coefficient of Friction (C.F.) @ 250 F and @ 600 F	Comments
EE	0.25 to 0.35 both temps	0-25% fade at 600 F possible
FE	0.25 to 0.35 @ 250 F 0.35 to 0.45 @ 600 F	2% to 44% fade at 600 F possible
FF	0.35 to 0.45 both temps	0-22% fade at 600 F possible
GG	0.45 to 0.55	Very Rare
HH	0.55 to 0.65	Carbon/Carbon only. O.K. up to 3000 F where it glows

Notes: These edge codes are located on the edge of the friction material of every brake pad by government regulation, along with some other codes. The first letter is a grading of the C.F. at 250 F and the second letter is a grading of the material at 600 F. Each letter grade can actually have quite a range of C.F. But a difference in the letter grade from medium to hot temperature could be an indicator of fade. The letters can be in any order. Therefore FE pads fade when hot, and EF pads would not grab when cold.. Also, you should know that Steel on Steel has a C.F. of 0.25!! So EE pads have only marginally more torque than no pads at all! Therefore FF pads are usually considered the minimum for a high-performance pad.

Steve