Thirty years ago, Brembo introduced the rear brake on the left clip-on handlebar. An idea now appreciated by track day enthusiasts.

Can a dramatic accident spark the development of an innovative product available to everyone? We're talking about the Brembo thumb master cylinder, which started as a tailor-made solution for a single rider and has now become a product accessible to all enthusiasts.

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The birth

The Brembo thumb master cylinder was designed by Brembo engineers to compensate for Mick Doohan’s physical limitations. After crashing during the 1992 Dutch GP practice session in the 500cc class, the Australian rider risked amputation of his right leg, which had been crushed in the accident.  

 

His limb was saved thanks to the quick intervention of Dr. Costa, who brought him to Italy. Still not fully recovered, Doohan got back on his Honda NSR 500 to compete in the final two races of the 1992 season, attempting to fend off Wayne Rainey’s comeback. However, his efforts were in vain, as the American rider ultimately overtook him in the standings.

Despite the winter break, in 1993, Doohan continued to struggle with limited mobility in his right foot. Before the accident, he frequently used the rear brake, especially to control his cornering speed. After the crash, he could no longer perform that task with his leg.  

Given his evident difficulty in modulating force with his leg, Brembo engineers designed a custom solution: the rear brake, instead of being operated by the right foot pedal, was controlled by a hand-operated lever on the left side of the handlebar.

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Thanks in part to this innovation, Mick Doohan regained his competitiveness and went on to dominate, winning five consecutive world championships from 1994 to 1998. Many experts still believe that the use of the thumb-operated brake master cylinder played a crucial role in his extraordinary victories.

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Today

Today, the Brembo thumb master cylinder, available in three versions with 11mm, 13mm, or 14mm diameter pistons, is also an upgrade product that can be purchased by all enthusiasts who love riding on the track. It is primarily used to prevent rear-wheel slippage in corners.  

 

In practice, the thumb master cylinder functions as a kind of traction control: it is activated at mid-corner to help riders stay close to the apex, allowing the bike to straighten more quickly.

This solution is particularly appreciated by riders with large feet, as it makes it easier to maintain maximum lean angle in right-hand corners without the risk of the right boot touching the asphalt.  

Additionally, compared to a traditional rear brake, the thumb master cylinder offers superior ergonomics, providing greater sensitivity in modulating braking force with the thumb rather than the tip of the foot.