Post mount or IS disc mount, does it matter?

Wanting to buy some Exotic Carbon 29er rigid forks, post mount or IS mount, does it matter which? Ta

post mount would be lighter and stronger (in theory, but no one ever had a problem with IS), but most importantly the thread is in the fork! damage the thread and youve ruined the fork (or frame).

also with PM, its easier to ruin the thread, as the hole generally isnt straight through, it goes INTO the leg, magnesium? and therefore has a max depth.
A friend of mine put a bolt slightly too long into his fork and pulled the thread out of a brand new pair of 36s.

To be clear, weight as a priority, go PM.
fear you MAY be a bit hamfisted, IS.
I would choose IS anyday, having said that both ends of my bike are now PM. seems to be thats the way things are going. as i have bigger rotors then the standard, i was super careful fitting the adaptor, with plenty of threadlock, i intend to never take it off again. If i knacker the thread in the adaptor its much less of an issue obviously.

Post as it’s more common these days.
You can adapt between the 2 if needed but it generally increases the rotor size.

Thanks Olly, that’s what I’m thinking, better going with IS.

I prefer IS to post mount due to the thread reasons mentioned. But I prefer my brakes to be post mount. that way you get maximum safety from ruining frame or fork and lots of easy adjustment. IS to IS is a pain.

It sounds like it is a preference thing then really!

Post mount is a better system IMO. Simpler, lighter, neater. As long as you’re not totally hamfisted, they’re fine.

I’ve always worried about the potential to strip threads in soft (suspension) fork lowers but it doesn’t seem to be a huge risk. Presumably the carbon forks will have a metal insert for the threads so they ought to be more robust than soft magnesium sus fork lowers.

It is a preference but if you go IS and the brake is PM (more than likely these days) you will end up stepping up a rotor size unless you can find the zero step one that is made from unicorn horns 🙂 Not much of an issue if you are going to step up anyway.

if you think about the load being applied to the fork, PM is clearly better, and therefore they can take reinforcing off the leg and save weight.
If your sensible, and careful, you wont have a problem, but you never know.
My pref is IS on the fork, and then PM “slidey” on the caliper. i think you would struggle to find proper IS calipers these days.

Thanks for the advice guys, I’ve hit the button and gone for IS 29er forks in 3k weave from Carbon Cycles. The PM version was only available in white and £20 extra, the only other option was UD carbon with PM but I want to see the carbon weave in the forks! 😀 Also I’m changing some bits over from an older bike, I’m using the discs so I’ve already got the IS mount for the caliper! Thanks again.

I prefer IS to post mount due to the thread reasons mentioned. But I prefer my brakes to be post mount. that way you get maximum safety from ruining frame or fork and lots of easy adjustment. IS to IS is a pain.

I agree, I’m still using a pair of IS Shimano Callipers on My HT, but recently changed from and IS to PM fork, considered getting new brakes, but instead wound up with a PM-IS +20 mount and a slightly bigger front rotor… Next brakes will have to be PM (does anyone event do IS Callipers any more?)…

It always seemed eminently sensible to have IS mounts and PM callipers IMO, Fork and frame manufacturers only had to produce one type of mounting, Brake suppliers only had to make one sort of calliper, but all sorts of rotor sizes and set-ups are accommodated simply through switching adaptors. Yes you can space and adapt a PM direct mountings for a bigger or smaller sized rotor but most fundamentally with IS you eliminated any need to tap a hole in the frame or fork…

Its all well and good dismissing thread stripping, gorillas as Ham-fisted but there will always be a proportion of people prone to such things, why design products to ensure their cack-handedness results in damage to the most expensive components on the bike rather than a £8 adaptor?

It’s basically irrelevant in use, with a couple of exceptions… If it means you’re using no brake adaptors (ie usually 160mm rotors) then it’s obviously lighter, one less component. If you strip or crossthread PM you’ll regret it more than IS. And unsung benefit of IS, you can take the brake off and refit without having to readjust/realign.

Yeah the forces are a little different but do you think it makes a real world difference? Am skeptic.