Replacing my front disk brake pads and noticed there is a rounded notch in the rear edge of the the metal backing–on both the new and current pads. On the theory that everything has a purpose, can somebody tell me what the purpose of that notch is...and should it go up or down, since it's off-center?

The position of the pads is defined by the pins. Both pads are the same. The springs stop the pins and pads rattling. The centre "loop" rests on the pad. All pads I have seen have been roughly rectangular with straight edges on 3 sides including where the "loop" rests. I've not seen any notches but I did find these.
https://www.ebay.co.uk/itm/303829897119?hash=item46bdac4f9f:g:aUgAAOSw1Ylf7Jcf

Almost sorry I started this discussion since it seems to be going in circles. But, not much happening in this space recently, so maybe we can keep this going just for giggles. To that end, since I'm never able to remember how to post photos, or links to photos, on this forum, I've posted a photo on my web site:

https://soeast.com/2021/07/01/1800-front-pad/

Perhaps this can ensure we're all talking about the same thing. This is a just-taken shot of a gen-u-ine, super-fine, top-of-the-vine Volvo replacement pad, taken from the gen-u-ine, etc. Volvo packaging I have in my spares. The arrow points to the mystery notch I'm referring to.

As mentioned, the pads I'm replacing have these notches (think they were aftermarket), the Centric ceramics I just installed have them, and these Volvo pads have them. So, back to the original question: Why are they there?

Link doesn't work for me. I can get to your website by clipping it but can't find the photo.

Link doesn't work for me. I can get to your website by clipping it but can't find the photo.

Sorry, mate. Seems to work for others. Tried to send it to your email address associated with this forum, but it bounced back. I changed the characterization of the photo so you should be able to access it through my web site now: soeast.com >archive >other. Third item down.

Yes an old email address is in my profile but it won't allow me to change it to my current one. Comments welcome on that.

Thanks, that worked for me. I've not noticed that notch. The Mintex racing pads (sports) linked here have it, a bit larger in fact, but it's not on the standard pads for the twin circuit cars. Not on the standard or sport pads for the single circuit cars. No idea of the significance of it. Note that the twin circuit callipers are 4 puck and the single circuit are 3 puck.

https://www.classicvolvoparts.co.uk/parts.asp?carID=2&cID=32&scID=174&page=B_Front_Brakes_P1800_with_Twin_Circuit

https://www.classicvolvoparts.co.uk/parts.asp?carID=2&cID=32&scID=173&page=A_Front_Brakes_P1800_1961_to_1968_Single_Circuit

The notched backing plates might be because I think they are also used on Jaguar callipers. They might have something that uses the notch.

Guys;

...as Derek suggests, maybe that notch has a function on one of the other cars which use the caliper, but I don't recall seeing ever noticing that notch before, and I've seen plenty of pads in my day...both OE Volvo, and alternate manufacturers...and yes, the three-piston calipers are indeed used on some Jaguars.

I propose the notch could also be for purposes of lightening...!

Cheers

Imaginative reasons for the notch:

1.) It’s somehow used to assist in measuring pad wear, like without removing wheel.
2.) On some fancier cars it has something to do with a wear warning.

Thanks, that worked for me. I've not noticed that notch. The Mintex racing pads (sports) linked here have it, a bit larger in fact, but it's not on the standard pads for the twin circuit cars. Not on the standard or sport pads for the single circuit cars. No idea of the significance of it. Note that the twin circuit callipers are 4 puck and the single circuit are 3 puck.

https://www.classicvolvoparts.co.uk/parts.asp?carID=2&cID=32&scID=174&page=B_Front_Brakes_P1800_with_Twin_Circuit

https://www.classicvolvoparts.co.uk/parts.asp?carID=2&cID=32&scID=173&page=A_Front_Brakes_P1800_1961_to_1968_Single_Circuit

The notched backing plates might be because I think they are also used on Jaguar callipers. They might have something that uses the notch.

We stock new Volvo OE brake pads for the 4 piston Girling calipers and they have that little notch.

I'm going to guess the notch is used to locate the metal backing plate during the brake pad bonding process.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Been a while since I worked on those. Does one end of the anti-rattle spring rest in that indent?

Obviously you had an oops.

I always look the new parts over carefully when I get them. then look over the old parts while you are taking them out.

Compare for similarity and install the same.

People have the same issue with brake shoes - different lengths, front or rear shoe?

Not sure what you mean by "Oops." I've done dozens of pad changes on these types of Girling calipers, even rebuilt the calipers themselves. Never had any trouble...although the Centric ceramic pads I just installed were a bit of a tight squeeze. But all the pads I've ever seen, of any manufacture, including Volvo's, have this notch.

They don't have anything to do with the anti-rattle springs as they are too far offset from the center of backing plates edge. And they're oriented so that one notch is always up and one is always down.

Again, they must be there for a reason, one that has nothing to do with any of the many Volvos I've had and re-braked. Just curious if anyone knew why?