Minoura Japan – M20-D

he M20-D is an M-series model, specially designed for the very popular Mini-Velo bikes. The frame has been altered to suit all possible wheel sizes in the 18 and 20” sizing, as well as 17x1.1/4”.

The M20's frame design was built for strength and stability. It uses large 38mm steel tubing for the U-shape, which is durable enough to supply 100% support, for riders up to 120 kg in weight. The U-shape is supported by 29mm legs, which fold slightly outwards for a very stable platform. The legs also fold flat for best possible storage.

Minoura’s Magnetic “Eddy Current” benefits:

• Quiet operation
• Constant power output
• Controllable resistance

We at Minoura have been the pioneers of magnetic resistance indoor trainers. In the 80’s, there were only two ways to generate resistance; Wind fan and Roller pressure.
The Fan type was very noisy, but with a reasonably exponential power curve, up to a certain speed, at which it would stop giving resistance.
The Roller pressure type had very fast wear and very unreliable resistance.


The Minoura patented system was a major breakthrough in regards to a quiet and smooth resistance system.
The basic principles of the “Eddy Current System” are simple. There are two magnets opposing each other, and an alloy disc is located between the magnets. The magnets pull or push each other, depending on their position versus each other. The alloy rotor between the magnets cut the magnetic fields, thus creating resistance. This is a very reliable resistance method, which does not alter the resistance when heating up during exercise.
Later resistance developments such as simple magnetic and fluid based systems still find it hard to cope with heat built-up in the resistance units, causing large variations in resistance. That is why Minoura has continued with the proven “Eddy Current” system.

The current versions of this unit have a similar design, but more refined and tuned for optimum performance.

All M-series models feature a convenient quick release type hub clamping system, allowing you to engage/release the bike very quickly. By moving the special lever up/down, the right side coupling slides in/out, fixing/releasing the wheel from the frame. This is a great time saver in setting up time, before/after your workout. After you secure the bicycle, you tighten the resistance unit against the tyre itself with a dial-knob.

The Fluid system was originally developed by CycleOps. Its mechanism is quite simple.
A turbine with fins spins in a fluid, inside a chamber. This system generates resistance with the fan blades turning inside the fluid.

The problems start with a Fluid system needing a fully sealed housing to avoid fluid leakage. Secondly a fully sealed chamber causes additional problems with expansion of fluid/air when warming up, changing the characteristics of resistance badly. Continuous repeating of the heat built-up will cause sealing issues and the fluid will start to breakdown and change characteristics even more. Therefore a reliable resistance and troublesome usage for many years, is never possible with fluid.

Trainers are traditionally used by riders wanting to build up muscles and increasing cardio. There are however also riders that are more worried about doing a little exercise, purely for a little cardio workout. For these riders it is more important to have a smooth quiet operation and easy operation and the M20-D model is perfect for this.

• Mag resistance unit may become HOT while workout. Do NOT touch it during and at least for 15 minutes after finishing session.
• The rear wheel spins very fast and will cause serious injury if touch them. Keep children and pets away from trainer while using.
• The maximum load of M20-D is 120 kgs including bike weight.
• The couplings fit the supplied quick release skewer only. You cannot use your own skewer on Minoura trainer. You must replace the skewer before use.
• Hub nut type bike should have fitting problem. The inner diameter on coupling is larger than the standard hub nut so we cannot guarantee the stability. Replace the left side coupling to the optional special one.
• Any bike with internal transmission type hub cannot be used.
• M20-D does NOT have the Foot-Step. It's the normal knob bolt style.
• M20-D is NOT compatible with Watt-Master.

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