Adding washers/spacers to disc mounts

Have seen a few times where people have added washers/spacers between the caliper & adaptor

Would like to know why, purely out of curiosity 😕

Cheers

Would like to know why, purely out of curiosity

Not all frames are made equal

running a 205 disc on a 200 adaptor.

I have a old inbred with about 8 washers as i think it needs a special adaptor but it works fine with the washers

Sometimes a frame is welded up a little out and the brakes rub.

My Transition TransAM needs a couple of spacers to make sure that the brake disc doesn’t catch the inside edge of the caliper, but that’s because the frame is slotted for singlespeed so gets used with the wheel in a variety of positions.

Some brake/frame combinations require shimming. Unless permanently rubbing brakes is your thang.

On IS mounts, shimming is often needed to align the caliper with the rotor.
On post mounts they are not necessary unless you are using Avids (BB7 certainly) which incorporate convex/concave spaces to help with pad alignment.

when adapters are 200 and discs 203, not all 203 rotors are 203mm, not all “Standard” frame mounts are “Standard”

This all goes for post mount if it’s IS then it’s just lining it up.

Some caliper/rotor combinations don’t quite match in size, so moving the caliper slightly so all the pad contacts the rotor.

Or maybe they fitted it wrong!!

So…and excuse me for being a bit thick here…if I had a 180 PM-PM adaptor and I wanted to try a 203 rotor all I would need to do is add some washers between the caliper (Elixir) and the adaptor to space it outwards until the caliper was aligned over the braking surface of the rotor?

^I can see bolts shearing and faces bleeding^

Get the correct(ish) sized adaptor 🙂

No as the PM adapter moves it up rather than out. Shimming is more for a few mm

Bolts are okay for fine tuning and tweaking. A couple of mm max.

I have a spacer on one of mine because the bolt hits the rotor if not, way easier than getting a new bolt 😉

I am convinced I am linked telepathicaly to the STW forum as I was just about to post on a very similar topic.
I have a set of SLX brakes that have been on 2 frames with no problems but when transfered to a new frame, using the same wheel and disc, made the wheel almost impossible to turn. The innermost pad was dragging on the disc despite the caliper being at the limit of the mounting slots and the piston fully retracted. I had to mount a couple of quite thick spacers between the frame bracket and the adaptor to get the disc central between the pads. They now seem to work better on the new frame than the old!
As somebody said, all frames are not created equal.

Some hubs also put the disc in a slightly different plane, so shimming is needed to push the caliper over a bit so the disc sits central between the pads.

That’s on IS anyway. For Post Mount it may be using a 180mm adapter for a 183mm disc to push the caliper out a bit so it doesn’t rub on the outer edge of the disc.