Brake rotor adapter confusion

mike_kelly · Apr 23, 2022

So I got a new fork. The old fork and the new fork have different post mount profiles. One has a longer post on the bottom and one has a longer post on the upper. I am confused because the forks are brake caliper neutral. So why are the posts not standardized?
Anywho the original fork had what I assume were 160-180 pm/pm adapters because it came with 180 rotors and I assume all forks are designed standard for 160 spacing stock so they can support 160mm rotors. So not sure what to do about the orientation of the adapters on the different post fork mounts. Because if you put the adapters in upside down it rotates the calipers around the rotor.
SO does it not matter what the orientation of the calipers are as long as the brake pads sit lined up with the outer rotor strip? Then some adapters have arrows indicating up but they would be oriented entirely different on the two different forks.

Hope I explained this well enough for you to answer.

Cheers

Dharmabum · Apr 23, 2022

I would check the specs for the new fork- a lot of new models are set up for 180mm standard.

keen · Apr 23, 2022

Definitely need to find out what size rotor direct post mounts. I have 2 forks in my stable and the long travel has 180mm minimum, 160mm on the short travel. The easiest adapter route is to use the same brand as your brakes. Run arrows in correct direction.

006_007 · Apr 23, 2022

Depending on the make and model of your fork it might be 180pm and no adaptor needed. But we don't know what the fork is so can't really advise you ......

mike_kelly · Apr 23, 2022

Unfortunately it is a no name fork with no specs but it is the only one made period for my bike. Requires 135mm spacing.
So no thoughts why one fork has long studs on the top and the other long studs on the bottom?
I suppose I could measure the length of the posts and compare it to a known 160mm fork.

Jayem · Apr 23, 2022

mike_kelly said:
Unfortunately it is a no name fork with no specs but it is the only one made period for my bike. Requires 135mm spacing.
So no thoughts why one fork has long studs on the top and the other long studs on the bottom?
I suppose I could measure the length of the posts and compare it to a known 160mm fork.

Realize that a brake caliper can be anywhere around that 160mm circumference. Fork and adapter A do not have to place it in the exact same spot as fork and adapter B. It doesn’t matter as long as the caliper is at the right radius. This is one reason why it’s advisable to always get an adapter that’s the same name as your brake, because each company does place the caliper a little different and that can cause minor spacing issues. But it sounds like you have some kind of bizarre bike/fork that doesn’t adhere to standards? Post mounts are either 160, 180 and some are coming with 200/8” for heavier duty applications. Except for strict XC stuff on an XC bike, a 160mm rotor usually doesn’t make a lot of sense.

mike_kelly · Apr 23, 2022

"It doesn’t matter as long as the caliper is at the right radius" Ok that would account for the different shaped adapters placing the calipers at different angles. I don't think there is such a thing as standards these days. I wish there were. So I guess I will get a couple of different 160-203 adapters and choose the one that aligns best with the rotor.
Thanks

Brake rotor adapter confusion

mike_kelly

Dharmabum

keen

006_007

mike_kelly

Jayem

mike_kelly

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