I want to convert my mechanical disk brakes to hydraulic. I don't know what size calipers to get. I plan on using the same rotors.

  • 2
    There is no such thing as different sized calipers, so I'm not sure what you are asking. What make/model of mechanical brakes do you have now? Commented Jan 3, 2019 at 0:32
  • All you need to do is duplicate the mounting format (postmount / flat mount / IS mount) Theres some good info here bicycles.stackexchange.com/questions/44161
    – Criggie
    Commented Jan 3, 2019 at 10:30
  • Oh i didnt know...im not sire what brakes is on it now im not home at the moment but they are cheep brakes...i got the bike off of ebay. Commented Jan 3, 2019 at 12:47
  • And let's not forget that hydraulic brakes require different type of brake levers, different type of cables (hydraulic line), and matching hydraulic fluid in most of the cases. Commented Jan 3, 2019 at 21:29

2 Answers 2


Worth reading, not a dup - What is the difference between I.S., post, and flat mount disc brake mounting standards? -

The calipers are (mostly) standard mounting, its the mounts that determine the size of the disk used. Therefore you can 'just' (that infamous trivializing adjective) buy a new set of brakes, bolt them on and start riding.

When buying, you can buy prebleed brakes ready to bolt on with hoses attached. This is easy but the hose length is usually a bit too long - however no bleeding is required. Its possible, in theory and if done with care, to shorten the hoses without needing a bleed the brakes afterward.

If you go with pre bleed brakes, be sure to get the correct 'handedness' of the levers. Different countries have the brakes on different side, the front brake will have a shorter hose and rear brake a longer hose.

  • 1
    Paragraph two, can we change it to “it’s the mounts that determine the size of disk used” or something like that?
    – Swifty
    Commented Jan 3, 2019 at 9:25
  • @Swift - Good suggestion-done.
    – mattnz
    Commented Jan 3, 2019 at 20:12

I just changed mine over on my Sondors fat ebike. I used calipers from Juintech M-1s from Bolton ebikes ( used to be called Velomobile shop) No cable change as it has self-contained hydraulic calipers. Easy 20 minute fix. It was ~$150 USD. Stop nice.

  • Thanks for posting but I'm not sure how this answers the question. What calipers should the asker use? Commented Feb 1, 2019 at 12:32
  • I think this answer condenses to "just change the brake subsystem for the same thing but hydraulic." OP seems to be making this upgrade harder than it has to be. Self-contained hydraulics come pre-bled and its little more than unbolt old levers/calipers and bolt on new ones.
    – Criggie
    Commented Feb 1, 2019 at 23:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.