Different manufacturers, different disc sizes and various brake mounts - the range is huge. We'll help you keep track of the disc confusion.
Everything you need to know: Below we show you the common standards for brake mounts and disc sizes - in tables 1 - 3 you will find all possible combinations of the two. There is also a guide to perfectly adjusted brakes.
Postmount on the rise
For the 2008 season, the majority of fork manufacturers are saying goodbye to the once common IS brake mounts (international standard from 2000) and opting for the Postmount standard, which Manitou introduced years ago on its own initiative. While the brake calliper on IS mounts has to be painstakingly spaced out with washers, post mount installation is achieved by simply sliding the brake calliper over two slotted holes (hole spacing 74 millimetres). Fox, Rock Shox, Magura, Marzocchi and of course Manitou usually use a 6-inch PM standard. However, there are now also some long-travel forks such as Magura's "Wotan" or the "Totem" from Rock Shox with an 8-inch post mount. Normally, cross-country forks through to enduro forks are fitted with 6-inch post mounts. The brake calliper therefore fits on a 160 mm disc without an adapter; adapters are available for 180 and 203 mm discs. On long-stroke freeride and downhill forks, 8-inch postmount mounts are used. The brake calliper fits a 203-millimetre disc without an adapter.
With adapters to the desired combination
Postmount brake callipers can easily be fitted to forks with an international standard using adapters. Conversely, this only works with a larger disc. So if you fit an adapter for IS brake callipers to your 6-inch post mount fork, you have to ride with a disc at least 180 millimetres in size. There are additional special solutions for downhillers. For example, the Fox "40" with its own IS 8-inch standard, or Rock Shox with a special mount on the "Boxxer".
DOT or mineral oil
The market for disc brakes is also very diverse. Some manufacturers (such as Shimano and Magura) rely on mineral oil, while other brake suppliers use DOT brake fluid as a medium. There are advantages and disadvantages for both sides. Regardless of which brake you choose or have already chosen, there are a few things you need to bear in mind: A brake may only be operated with the fluid intended for it. This means either DOT or mineral oil. A mix-up would damage all seals and lead to total failure. Brake fluid is toxic and should be disposed of as hazardous waste. Unlike mineral oil, it must not be mixed with used oil for disposal, but must be disposed of separately at a recycling centre. You can also dispose of mineral oil there.
Disc selection
Under the corresponding disc size, select the standard on your fork and the standard of your brake calliper. In the centre you can see whether you need an adapter.
PM= Postmount brake mount, IS= International Standard brake mount, Boxxer= Special brake mount on Rock-Shox-Boxxer fork, Fox 40 IS 8"= International Standard for 8-inch discs, only on Fox 40 fork.
Fork mount
Three brake mounts currently dominate the fork market, with the IS mount on the left disappearing more and more. PM 6" and PM 8" differ only in the different distance to the wheel axle and therefore the disc size that can be ridden without an adapter.
Brake fluid
The brake fluid serves as a medium to transfer the pressure from the master piston of the lever to the slave piston on the calliper. DOT brake fluid is subject to greater wear and absorbs moisture over time. Bubbles can form in very hot conditions, which can lead to brake failure. Regular replacement also flushes abrasive particles out of the system. The abbreviation "DOT" stands for the American "Department Of Transportation", which categorises brake fluid into three groups: DOT 3, 4 and 5. Boiling point and viscosity are decisive for the categorisation. DOT 3 and 4 stand for conventional brake fluids based on polyglycol ether, while DOT 5 has a silicone base. As there are now also conventional brake fluids that meet the requirements of DOT 5, they are labelled DOT 5.1 (formerly DOT 4 plus). The two types are not compatible with each other. To avoid confusion, silicone-based brake fluids are coloured blue and glycol ether-based brake fluids are coloured yellow. The boiling points are DOT 3: 205° C, DOT 4: 230° C, DOT 5.1: 260° C, mineral oil: 190° C. As DOT binds water, an annual change is advisable.
DOT vs. mineral oil
Both elements have their advantages and disadvantages. However, the majority of brake manufacturers favour DOT. This is due to the higher boiling point. DOT is also "harder" under pressure. DOT seals also have a long service life and constant properties over a wide temperature range. The easier handling (non-toxic, does not attack paint or skin) and the low maintenance requirements (does not absorb water and hardly ages) speak in favour of mineral oil.
Which manufacturer uses what?
- AVID Juicy 3, Code: DOT 4; Juicy 5, 7, Ultimate, Carbon: DOT 5.1
- FORMULA DOT 4
- HAYES DOT 4
- HOPE DOT 4
- MAGURA Mineral oil
- SHIMANO Mineral oil
