I bought a used mountain bike and it does not have a caliper or a brake lever for the front. How can I go about finding out what will work on this bike and where is a good place to buy online?

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  • When replacing the brake pads (or in this case the whole calliper) it would be a good idea to clean the rotor before re-bedding in the rotors/brakepads. Commented Jul 29, 2020 at 5:32
  • @Superman.Lopez good point - OP should also check rotor for thickness too - it looks okay in photo but still worth checking.
    – Criggie
    Commented Jul 29, 2020 at 8:49

1 Answer 1


The disc rotor size is 160mm as engraved on the rotor (160mm is a common size rotor).

The mount type for the disc brake calliper is Post Mount (which should be 74 mm spacing between the mounts, center-to-center), which is the most common standard for mountain bikes.

You can purchase a single Post Mount calliper and matching lever, separately or as a set. My understanding is that 160mm is the standard size to be used without an adapter, meaning only larger rotors would require an adapter. The selected calliper for purchase should have a specification that confirms it is compatible with 160mm rotors.

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    bicycles.stackexchange.com/a/44210/42015 see this answer for a full overview of disc brake standards. Commented Jul 29, 2020 at 5:19
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    "160mm is the standard size to be used without an adapter" — this is generally true for MTB forks in the 100 - 140 mm travel range (trail use). Forks with larger travel values are likely to accept 180 mm rotors without an adapter. For example, I just checked that single-crown Fox 38 enduro fork with 160 -180 mm travel range accepts 180 mm rotors as the smallest size. Commented Jul 29, 2020 at 7:25
  • Front and rear rotor don't have to be the same size. Commented Jul 29, 2020 at 11:19
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    @Paul the site doesn't do recommendations. Look on a major bike parts site that ships to your relevant locale. There are many :-) or do your LBS a solid and buy one there. Look for mineral oil based callipers with the correct brake handle orientation (left or right) for you. Shimano(Deore) or SRAM(Level) are good but other brands work well too, again online reviews will give you relevant signals as to $$/quality tradeoffs. Commented Jul 29, 2020 at 14:31
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    One can purchase pre-bled brake lever and caliper having the pads in place at a variety of online sites. For instance check eBay or Amazon and you'll see the kind of selection you have. Pre-bled means the caliper and lever come to you hooked together and the oil is filled. One literally puts the lever on the handle the caliper on the fork, securing the brake hose to the designated spot on the fork, check the function and go ride.
    – Jeff
    Commented Jul 29, 2020 at 23:18

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