Currently in the process of buying a set of post mount disc brakes, the new ones will be coming without the mounting posts

This’ll be the first time I’ve done something like this and it dawned on me that I know very little regarding which mounts work with what

New brakes (hopefully) will be TRP Spyres, I currently have a set of Shimano M365 brakes, will the posts for these work with the TRP’s or will I have to source some others?!

How do I know which ones to buy or which ones will be right, someone educate a post mount noob…

They should work with the same rotors.

Like most standards, it’s not very standard so there’s the odd bit of wierdness. Just remember to re-use the conical washers on top of the caliper if the addapters need them (if theres only one set of long bolts going through the caliper/addapter/fork so they don’t end perpendicular to the face of the adapter).

Aren’t the posts of post mount not already on the frame/forks? If the the frame or forks have the older International Standard (IS) mounting then you need an IS to post adaptor.

without the mounting posts

Yeah, what are these mounting posts of which you speak? The mounts are on the frame, so if you’re buying post mount brakes and have a IS mount (wasn’t that what they were called?), you’ll need an adapter – loads available on ebay cheap as chips.

(eg. https://www.ebay.co.uk/itm/223486704139 – but depending on your rotor size)

If you’re replacing post-mount brakes with post-mount brakes, they should just bolt on. However, there are some oddities with adapters and stuff so it is possible that you will need a new adapter. Best to just try them first and see. If you have any problems, take photos and post them on this thread and people should be able to point you in the direction of the adapter you need.

Thanks for all the comments so far

My lack of definitely knowing what’s called what probably isn’t helping,

For clarification

These are what I should have coming…

This is what I currently have…

Will the new ones fit and work onto the frame as is or will I need something like this…

Without having the new bits in my hand currently it’s a bit difficult to tell how / if it’d work, is there any way of knowing if it’s correct once screwed on or not or whether I’ll need new rotors or to add brackets or anything similar

Many thanks again all

They will bolt straight on BUT have you swapped hydraulic brakes for cable operated?

They should bolt straight on – you’ll need that adapter you’ve highlighted in red if your rotors are too big for the calipers when bolted straight on. You’ll know cos the wheel won’t turn 🙂
Make sure the pads line up with the braking surface of the rotors too – might need some washers to space it out a few mm

BUT have you swapped hydraulic brakes for cable operated?

I wasn’t going to comment on this matter 😀

I’m not aware of any post-mount brakes that use adaptors for anything other than changing rotor size. That is, you can swap calipers between bikes just fine and you’ll only need different adaptors if you’re also changing rotors.

Has the whole Shimano metric 200mm vs SRAM imperial 203mm thing gone away now?

@steel4real @desperatebicycle a valid point, seems absurd right?! it’s all in the name of experimentation, if I may draw your attention(s) to a thread I started earlier in the week

Drop bar levers and brakes question…

So from what I understand, with the proviso I’m keeping the current rotors, largely, it SHOULD be a straight swap pending braking surface alignment

Ah, so you’re attempting to use road brake/STI levers on the cable brakes… never tried that. I did go from centre pull brakes to v-brakes on a gravel bike once. That was ..hmm ok.

I’m not aware of any post-mount brakes that use adaptors for anything other than changing rotor size.

Problem is that calipers can sometimes foul the mounts so you can run into weird compatibility issues.

Err, aren’t road brifters a lower cable pull than MTB standard? Certainly that used to be the case.

Just be careful, yeah.

@superficial thanks for the heads up, appreciate the input. The guy I’m buying the callipers from has mentioned he used them with STI levers with no issues so I figure it’s worth a go, worst case, it doesn’t work and I go back to the proverbial drawing board, just got to hope they fit on the bike without too much faff…

@thols2 excuse my ignorance but how do you mean?

Different calipers are different shapes. Usually you can fit any caliper to any frame/fork/adapter, the bolt holes and general geometry are the same. However, in some cases, you might find that calipers from one manufacturer won’t fit adapters from another. It’s also possible that some calipers won’t fit some frames. You just need to try and see.

Makes sense, as you say, all o can do is try and see what happens