Stoptechs and poor fitting brake pad backing plates

I first went to Stoptech ST40s in 2014, In 2020 I got a good deal on another complete kit and now run those (the old set was rebuilt, including slide plates and kept as spares. The calipers design is slightly different although obviously they are considered the "same".... This is relevent in a minute.)

Soon after switching to the newer 2020 ST40 kit I noticed the Carbortech pads I run did not fit into the calipers. I actually have to grind the metal down a little on each side so they slide in. This continued with several sets of pads. In 2020/2021 in talking to my competitors, they ALL have the same problem however the group of us are using 3 different brands of pads. I've talked to Carbotech about it and they state they've bought the backing plates from the same source for years and in fact, there are only 2 places in the country that make the plates for all the brake companies.

I pulled out my old ST40's to test fit pads and sure enough, same problem. I re-installed my old slide plates (can't believe I left them in the box) and same problem. I ran those calipers from 2014-2020 always using Carbotech and NEVER had a problem back then.

So.......for those running ST40's, are any of you experiencing this problem?

Very strange, I have run Performance Friction 01/11 pads in mine since 2010 and have never had that issue. Haven’t heard of anyone else having that issue either.
I’d check with Stoptech for the exact diameter of the opening and see if your new ones were machined incorrectly. Stoptech might swap them out for a new set if they were made incorrectly.

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Originally Posted by michaelmosty

Very strange, I have run Performance Friction 01/11 pads in mine since 2010 and have never had that issue. Haven’t heard of anyone else having that issue either.
I’d check with Stoptech for the exact diameter of the opening and see if your new ones were machined incorrectly. Stoptech might swap them out for a new set if they were made incorrectly.

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That's what is weird. I was sent the stoptech spec sheet for sizing of the backing plates and mine measured correctly. (and remember, my old stoptechs no longer fit the newer pads either). Carbotech did tell me they buy backing plates 100's at a time so it's possible they've been using the same batch for a long while. However that doesn't support others having the same problem (K. Lydic is running Performance Friction and having the same problem).

The Wiseman/Sanchez 4th gen had the red powder coated ST40s, and always had issues with pad fitment.

I've got black ST40s, and my hawk pads fall right in. I think you're onto something with it possibly being a lot issue. Maybe 100s are slightly out of tolerance at a time?

Josh

I can't remember if I ran into this on wildwoods or atoptechs, but I distinctly remember a set of carbotechs where the pad material creeped just past the perimeter of the backing plate and I had to grind to fit

I can't remember what pads I run now on my stoptechs but they're not g loc or carbotech, no issues