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In several discussions on this and on other boards many Bobber owners posted their unhappiness about the weak performance of the Bobber´s front brake. So it's time to bring some light into darkness:
The wooden feel at the brake lever and the weak deceleration combined with very high lever force are clearly caused by the bad hydraulic transmission ratio between the master cylinder piston (diameter 14 mm) and the original Nissin 2pot caliper pistons (diameter 27 mm each). This gives us a ratio of 1145/154 = 7.4, while the ideal ratio for a single disc motorcycle front brake layout would be 13.5 in order to get a sensitiv 2 finger brake! This is, what we want, not for our comfort, but for safety reasons! Ok, some comfort doesn't hurt!:grin2:
At this Point I must mention, that Triumph uses the same 14 mm master cylinder for their dual disc layouts, which doubles the hydraulic ratio due to the doubled caliper piston area!
Plan A:
Why not swap the master cylinder to a Motocross bike 11mm master cylinder for a few bucks (ebay)? This would bring the hydraulic ratio up to 12 clean and easy! Bad idea! Our Hightech-Bobber is equipped with "Throttle by wire"! Last but not least, the ABS system could be harmed somehow by the higher pressure in the system. And just to be honest: I don't like the imagination to ride the heavy Bobber with a Crossbike brake!
Plan B:
Let's put a bigger caliper onto the fork. Bad idea! Unfortunately there isn't enough space for a bigger caliper between the brake disc and the flat angled spokes of the big 19" wheel! No matter, let us grab one of this Honda CB 1000 or VFR 800 Nissin 3pots on ebay, link the originally rear brake acted center piston to the others, and there we go! Not at all: The Nissin 3pot has two 22mm pistons and one 25mm piston, giving us a hydraulic ratio of just 8.1! This isn't worth the money. And again to be honest: The modified 3pot with its two bleeding valves and two brake hose fittings isn't a beauty!
So what else could we try? Now, some guys were not afraid to spend the money, and installed Behringer or Pretech 6pot calipers on their bikes, after they had swapped the disc to a fat 340mm floating disc. They had a little improvement, yes indeed, because the total piston area of the 6pots was slightly larger. But again, it was by far not worth the money!
But 2018 things are changing! God had an insight and let Brembo design a brandnew, ultra slim 4pot caliper for Supermoto bikes, expensive, but with really fat 34mm pistons! And God let some Bobber specialists in Italy make a front brake upgrade kit for the Bobber with this caliper and a 340mm fully floating disc! Plug and Play!
Look at that:
https://www.freespiritsparts.com/en...onneville-t100-front-brake-caliper-4-pot.html
This setup brings the hydraulic ratio up to 11.8! Just by this the lever force would drop to 62%, but the caliper clamps 4 seperate double sintered brake pads onto a 340mm disc! So there is no doubt, that this setup will boost the braking performance of my Bobber to the desired level regarding safety, sensitivity, power and comfort!
You guys must be strong now, but sad to say the first kit built is sold already! Guess to whom!:grin2:
Stay tuned!
The wooden feel at the brake lever and the weak deceleration combined with very high lever force are clearly caused by the bad hydraulic transmission ratio between the master cylinder piston (diameter 14 mm) and the original Nissin 2pot caliper pistons (diameter 27 mm each). This gives us a ratio of 1145/154 = 7.4, while the ideal ratio for a single disc motorcycle front brake layout would be 13.5 in order to get a sensitiv 2 finger brake! This is, what we want, not for our comfort, but for safety reasons! Ok, some comfort doesn't hurt!:grin2:
At this Point I must mention, that Triumph uses the same 14 mm master cylinder for their dual disc layouts, which doubles the hydraulic ratio due to the doubled caliper piston area!
Plan A:
Why not swap the master cylinder to a Motocross bike 11mm master cylinder for a few bucks (ebay)? This would bring the hydraulic ratio up to 12 clean and easy! Bad idea! Our Hightech-Bobber is equipped with "Throttle by wire"! Last but not least, the ABS system could be harmed somehow by the higher pressure in the system. And just to be honest: I don't like the imagination to ride the heavy Bobber with a Crossbike brake!
Plan B:
Let's put a bigger caliper onto the fork. Bad idea! Unfortunately there isn't enough space for a bigger caliper between the brake disc and the flat angled spokes of the big 19" wheel! No matter, let us grab one of this Honda CB 1000 or VFR 800 Nissin 3pots on ebay, link the originally rear brake acted center piston to the others, and there we go! Not at all: The Nissin 3pot has two 22mm pistons and one 25mm piston, giving us a hydraulic ratio of just 8.1! This isn't worth the money. And again to be honest: The modified 3pot with its two bleeding valves and two brake hose fittings isn't a beauty!
So what else could we try? Now, some guys were not afraid to spend the money, and installed Behringer or Pretech 6pot calipers on their bikes, after they had swapped the disc to a fat 340mm floating disc. They had a little improvement, yes indeed, because the total piston area of the 6pots was slightly larger. But again, it was by far not worth the money!
But 2018 things are changing! God had an insight and let Brembo design a brandnew, ultra slim 4pot caliper for Supermoto bikes, expensive, but with really fat 34mm pistons! And God let some Bobber specialists in Italy make a front brake upgrade kit for the Bobber with this caliper and a 340mm fully floating disc! Plug and Play!
Look at that:
https://www.freespiritsparts.com/en...onneville-t100-front-brake-caliper-4-pot.html
This setup brings the hydraulic ratio up to 11.8! Just by this the lever force would drop to 62%, but the caliper clamps 4 seperate double sintered brake pads onto a 340mm disc! So there is no doubt, that this setup will boost the braking performance of my Bobber to the desired level regarding safety, sensitivity, power and comfort!
You guys must be strong now, but sad to say the first kit built is sold already! Guess to whom!:grin2:
Stay tuned!