[Closed] what is the difference between post mount an I.S mount for calipers?

Post mount is two bolt holes that bolt into the fork parrallel to the wheel. IS mount is two bolt holes where the bolts go at 90 degrees to the wheel (which is what I suspect your J2s are).

If this is in reference to the Shimano calipers, if you're unsure get the IS ones because they come with an adaptor to swap between IS and post mount.

another way to tell, if the frame/fork has a smooth hole passing through then it's IS, if you can see a thread, it's post mount.

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Post mount, the bolts screw into the fork from the back of the fork.

IS, the bolts screw into the brake caliper from the side of the fork.

clubber wins!

clubber wins!

And I've wee'd in your shoes...

thanks for the help!!!

i always remember it as Post mount has Posts