HS rim brakes are a closed hydraulic system, so storing a bike on its rear wheel, transporting it in a horizontal position or turning the bike upside down has no adverse effect on the function of the hydraulic components, provided that they are correctly bled & filled.
If the open hydraulic system of a disc brake is perfectly filled and bled, storing the bike on its rear wheel, transporting it in a horizontal position or turning the bike upside down will have no adverse effects. However, since the perfect filling level cannot be seen from the outside, it should always be assumed that there may be residual air in the system.
If there is residual air in the hydraulic system, e.g. after the brake cable has been shortened or the brake has been insufficiently filled or bled, the residual air from the expansion reservoir can enter the brake system circuit either through vibrations or if the bike is positioned on its side or upside down. When the brake is then actuated, the result can be a spongy or completely missing bite point – and in extreme cases, total brake failure.
This is why MAGURA highly recommends that bikes with open hydraulic disc brake systems are placed in an upright position during maintenance & repair tasks, storage and transport. Alternatively, if the running wheel is mounted or the MAGURA transportation retainer is used, you can shut off the expansion reservoir by actuating the lever, thus preventing expansion reservoir air from entering the system. Use an elastic band to hold the lever blade in a pulled-on position. Due to the permanent actuation of the lever, the piston overruns the inflow to the expansion reservoir, thus closing the system. This allows the bicycle to be individually positioned for transport or storage.
For more information on our braking systems, please refer to the relevant user manuals.