$ 617.00
Master Cylinder

Racetorx Thumb brake

Made from T6 billet aluminium, Hard anodised in either silver or black, Hardware including pivot pins and pushrods are made from Ti 6Al-4V Titanium. The thumbscrew provides a detent ball for precision and a 13mm Brembo master cylinder for reliability and perfect thumb pressure with the thumb lever providing a knurled finish for grip. Handlebar fitment is the standard 22mm which 95% of bars are and in the coming months, other mounting options will come available. This wonderful kit provides 4 points of movement to give the best position to suit you! Comes complete with our GP reservoir tube kit in a colour of your choice. To complete the kit you can either go directly to your rear calliper or you can have the rear foot master cylinder in conjunction. You can order specific lengths of braided lines from either Venhill or Goodridge. If you decide to have the rear foot pedal usable in conjunction you'll need to fit a "Junction Valve" to your rear master cylinder which feeds into the reservoir port. This is a very simple layout and we are happy to assist where we can.


  • 11mm Master cylinder for single cylinder 125cc-500cc motorcycles (supermoto, motocross, trails & road)
  • 13mm Master cylinder for 2, 3 & 4 cylinder 500cc - 1400cc motorcycles (Road, track, superbike and adventure)

The Racetorx Thumb Brake has additional thumb paddles for personal preference, This is listed in the drop-down menu. You can also purchase the paddles separately here - https://racetorx.co.uk/product/rtx302/

when using your foot in a road/race boot or a motocross boot you can not gauge pressure, with your thumb you can gauge the pressure through the paddle, this means more control breaking in a corner on a race track, angle of the bike in the air on a motocross track, on a trails bike in a technical route and even wheelie control on a stunt bike. 

We use www.Venhill.co.uk for our braided lines. If you know the length required please inform us and we can update out (Venhille braided line list) order it in directly and update the website so you can order all parts from us as a bulk kit. This is - www.racetorx.co.uk/product/venhill

A lot of people ask What is a thumb Brake?

It’s a left thumb-operated rear brake, Thumb brakes are a great addition to any motorcycle, especially on a race track. The thumb brake provides more control simultaneously when braking and leaning into corners. They are also great to help with wheelie control and stunt riding.

Thumb brakes are great additions for any motorcycle from a 300bhp MotoGP bike to a 50bhp 450cc Supermoto or a Motorcross bike and trails for technical routes.

The Australian 500cc world champion legend “Michael Doohan“ was the start of the thumb brake when he seriously injured his right leg so switched to a handlebar-mounted thumb-operated brake. Doohan then in the 90’s won several championship races with the use of the thumb brake, It has been a benefit ever since, other racers noticed the benefits of the thumb brake and now it's one of the most used aftermarket rear braking kits on the market.

Some questions that are commonly asked-
Q: Can you run in-line with ABS?
A: Yes, you can keep the ABS intact

Q: Can you run directly to your rear caliper?
A: Yes, you can remove the foot brake pedal and master cylinder completely and feed a new braided brake line direct from the thumb brake master cylinder to the rear caliper.

Q: Can you run the thumb brake in line with the rear foot pedal?
A: Yes you can, the rear master cylinder would require a Racetorx junction valve " https://racetorx.co.uk/product/rtx450 ", there are only 5 variants to suit the master cylinder you have, here is a link to the Racetorx junction valves https://racetorx.co.uk/product/rtx450 these are quite universal to Brembo, Nissin and non branded units.

Q: How do you build the kit?
A1: If you want to fit the Thumb brake direct to the caliper, (NON-ABS models) Remove the rear foot brake pedal and master cylinder and remove the braided line (be sure to keep the brake fluid clear from the bike as much as possible, also when removing the surplus parts clean any residue spilled)
Fit the thumb brake and feed a pipe or cable up to 10mm thick in the routing location you want, this would be from the thumb brake master cylinder port down to the rear caliper routing under the top yoke, under the tank and down the right side of the bike. This is so you can work out the length of braided line you require.

A2: If you want to fit the thumb brake in conjunction with your rear foot brake, (This includes ABS models) Remove the reservoir on your foot master cylinder, some will be a screw-in adapter, some with a teardrop adapter with a small M4 bolt, others will be a plastic adapter pressed into a donut-like rubber, these just pull out with a good tug and wiggle (don’t be shy). Clean brake fluid that will spill out and in the area the junction valve locates, then fit the correct “junction valve” to suit the master cylinder. Racetorx so far does the Cylinder type that screws into the built-in reservoir and the Teardrop type.
Fit the thumb brake and feed a pipe or cable up to 10mm thick in the routing location you want, this would be from the thumb brake master cylinder port down to the rear foot master cylinder routing under the top yoke, under the tank and down the right side of the bike. This is so you can work out the length of braided line you require.

Any questions feel free to get in touch. Enjoy.

Bike Fitment-

These are a universal kit for the majority of motorcycles, Road bikes, race bikes, adventure bikes and even motocross bikes.

We have the most adjustable thumb brake on the market and even then our kit on some bikes can touch fairings, tanks or frames, This being said with the adjustability you can work around it nicely most of the time.

Motorcycles with Handle bars have the most clearance whereas if using clip-ons you can have some challenges, the Ducati V4 Penagale has no room and the fairing would need some modding, Ducati V2 Penagale is similar with more clearance but still touches at full lock.

Adventure bikes. motocross bikes and streetfighter bikes all have clearance.

The list would be endless but to give some idea of bike styles which our kits are fitted to so far-

  • Ducati V2 (David Shoubridge) WSBK
  • Ducati V" & Ducati V4 (moto Rapido) BSB
  • CBR1000 (Michael Dunlop) IOM TT
  • Kawasaki zx10 (FS3 BSB)
  • Aprilia RS660
  • KTM super duke 1290
  • Yamaha Tenere 700 & World raid
  • Yamaha MT10
  • Yamaha YZF 250
  • Yamaha YZF450 & WR450
  • KTM 690 SMCR
  • KTM250 2 stroke
  • KTM 300 EXC
  • Yamaha R1M
  • BMW M1000 (Tas BMW BSB)
  • Honda CRF450
  • Honda SP2

Again this is not a list of the bikes i will only fit but a list of bikes that our kits are fitted to plus many more.

The Latest BSB Thumb paddles are now available. working with the team's Moto Rapido, FS3, and SyneticBMW we now have 2 new thumb paddles that are suited to the BSB riders. 

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