Forum menu
Can anyone enlighten me as to the pro's / cons of changing my rear brake set up to a post mount as opposed to it's current IS set up?
Background: I'm considering getting some tweaks / alterations done on my HT inc some swinging dropouts fitted. I've got the choice between a IS set up or Post Mount set up. I run a Rohloff so hence the tweak towards swinging dropouts...amongst other things.
Is one set up better than the other given that I can easily acquire an adaptor if I want to run a bigger disk? Is it simply aesthetics or is there some performance improvement?
Post mount is a sounder solution to fastening a caliper onto your frame as there is much less shear force on the bolts. But I doubt anyone has ever sheared a bolt on a properly fitted IS mount caliper so it's probably irrelevant.
It's easier to adjust caliper alignment with post mount brakes as the caliper bolt holes are slotted.
There a re probably other reasons too.
Oh, and fashion.
IS is better because it keeps the threads in the caliper so if you strip them its cheep to fix, once aligned they never shift unless you bend the frame and alignment can be perfect on a faced frame and the correct shims.
Post is better as it's quicker to set up if it works, otherwise it can be a faff getting it spot on as small adjustments are difficult to make, just keep repeating the procedure until it ends up centered rather than fine tuning with tiny shims, it's also lighter on modern brake as it wont need and adapter (assuming you get them welded on at the right height for your brakes). In theory it's stiffer as the bolts can't flex, but that's more relavent to motorbikes weighing a quater of a ton for bike+rider.