Dan_Lorenze
Member
Very nice Dan.............
Disc brake upgrade
- Thread starter 3pinr
- Start date
Nice! I should keep the brembo caliper that you have now. Upgrade to a bigger caliper is nice, but dangerous! I have known a boy, with a big brembo caliper, those one they use on a ducati. He had to brake suddenly and he went over head. A 2 cylinder caliper on a dax is more then enough!
MSZ
Moderator
For this bike, I'm going to keep the 2 pot caliper. As long as you match the correct master cylinder to the caliper, modulation isn't an issue going with a larger caliper. The problem lies when people match the wrong master to the wrong caliper and by doing so, you can do stoppies with your pinky with hardly any pressure.
On my ZB I'll be using a 4 pot brembo, the same as stock on a ducati with the correct master cylinder.
And for what it's worth, the 2 pot opposing caliper on my CT is actually a Ducati rear caliper and will handle the braking duties just fine.
The only reason to go bigger is purely for the bling factor and little else, but when building restomods, sometimes it's fun to put fashion and function together all in one ridiculuous small package just for because we can.
I am a firm believer in outfitting disc brakes and good suspension on these bikes when you are travelling in excess of 60-70mph. Lots of times people don't factor this in when going with big engines and make them extremely unsafe at speeds. While I can't speak for others, a panic stop with the stock CT70 brakes at high speeds isn't my idea of a good time
Any disc brake is better then the best drum brake setup.
The stock drum brakes are adequate up to about 50mph, marginal at 55mph and dangerous at 60mph+. Rider skill is still a major component. I could easily do a one-finger stoppie with the stock twin-piston 220mm rotor Nice disc brake on either of my Daxes. It's never been an issue. 98% of my riding is on the road and speaking from experience, braking overkill is preferable to any stock brake setup. When my wife travels with me, what was overkill for rider alone becomes excellent braking capability. To be sure, the bike could still execute a stoppie. But the first time some brain donor pulls out in front of you while rolling along at 60mph having world class brakes transcends concepts like "overkill" and "bling factor".
These bikes were probably never intended to reach the speeds at which we cruise long distances, even for short blasts. Add the combined weight of an adult rider + passenger and you have the total moving mass of a much larger bike (sans passenger) and the attendant momentum with it. Fitting brakes from a larger bike with similar momentum is nothing more than sound engineering In other words, the OEM drum brakes cannot be reasonably expect to cut it. A skilled rider should have little or no problem modulating braking application. Overkill trumps inadequacy. No amount of rider skill can stop a bike with inadequate brakes. 60mph+ is the realm of "real bikes", not children's toys.
These bikes were probably never intended to reach the speeds at which we cruise long distances, even for short blasts. Add the combined weight of an adult rider + passenger and you have the total moving mass of a much larger bike (sans passenger) and the attendant momentum with it. Fitting brakes from a larger bike with similar momentum is nothing more than sound engineering In other words, the OEM drum brakes cannot be reasonably expect to cut it. A skilled rider should have little or no problem modulating braking application. Overkill trumps inadequacy. No amount of rider skill can stop a bike with inadequate brakes. 60mph+ is the realm of "real bikes", not children's toys.
MSZ
Moderator
the brembo kit as I have pictured? I'm having the brackets made for use on NSR50 forks tha can be mounted to any CT70 with aftermarket triple clamps on any year CT70. However, the parts are not cheap. Drop me a note and I'll fill you in.
I hope you don’t mind if I chime in here.
The function of brakes is to change the kinetic energy in a rotating wheel into heat via friction. This reduces the energy in the wheel, slowing it down, and the main factors in play are materials, swept area, and clamping force.
As with all engineering, it’s a balancing act. The wheel only offers control as long as it rotates, so stoppies are bad (unless you’re a stunt rider with no need to stop for safety). An ideal brake would offer massive amounts of friction short of lock-up. The problem is that all components have a maximum amount of heat they can tolerate. The perfect example of this is drum brakes: although they offer the greatest amount of swept area for a given size, their poor ventilation turns them into ovens. So, as you might expect from the theory, they provide superior braking initially, and rapidly fade as heat builds.
Disc brakes provide incredible ventilation, which allows for sustained use. However, with a single piston caliper, the amount of swept area is not very great compared to a drum brake. The piston diameter is limited to roughly the height of the “ring” on the disc where the pads ride, (although in practice it is usually less). That means that if the pads are 1 inch tall, the piston can only exert force on a 1 inch by 1 inch area. How far that extends to the disc depends on how thick and stiff the pad backing plates are, but pads are usually only about 1.5 - 2 times as wide as they are tall.
So the most practical way to add swept area (to increase the amount of available friction) is by adding pistons to the caliper, which allows you to make longer pads. That is why racing brakes will use six-piston calipers. Increasing the swept area allows you to absorb more energy from the wheel without locking it up. The key (as racerx and Pony Express clearly state) is to match the master cylinder so that the driver can modulate the friction effectively. Virtually any disc brake can lock up a wheel, but then you’ve made the friction point the tire contact patch where you have no control (and which was never engineered for that).
Of course there are lots of other reasons for using disc brakes, and there are materials available (such as carbon fiber-based pads) that bring drum brakes into viability for various applications. Maybe some other time.
Cheers!
John
The function of brakes is to change the kinetic energy in a rotating wheel into heat via friction. This reduces the energy in the wheel, slowing it down, and the main factors in play are materials, swept area, and clamping force.
As with all engineering, it’s a balancing act. The wheel only offers control as long as it rotates, so stoppies are bad (unless you’re a stunt rider with no need to stop for safety). An ideal brake would offer massive amounts of friction short of lock-up. The problem is that all components have a maximum amount of heat they can tolerate. The perfect example of this is drum brakes: although they offer the greatest amount of swept area for a given size, their poor ventilation turns them into ovens. So, as you might expect from the theory, they provide superior braking initially, and rapidly fade as heat builds.
Disc brakes provide incredible ventilation, which allows for sustained use. However, with a single piston caliper, the amount of swept area is not very great compared to a drum brake. The piston diameter is limited to roughly the height of the “ring” on the disc where the pads ride, (although in practice it is usually less). That means that if the pads are 1 inch tall, the piston can only exert force on a 1 inch by 1 inch area. How far that extends to the disc depends on how thick and stiff the pad backing plates are, but pads are usually only about 1.5 - 2 times as wide as they are tall.
So the most practical way to add swept area (to increase the amount of available friction) is by adding pistons to the caliper, which allows you to make longer pads. That is why racing brakes will use six-piston calipers. Increasing the swept area allows you to absorb more energy from the wheel without locking it up. The key (as racerx and Pony Express clearly state) is to match the master cylinder so that the driver can modulate the friction effectively. Virtually any disc brake can lock up a wheel, but then you’ve made the friction point the tire contact patch where you have no control (and which was never engineered for that).
Of course there are lots of other reasons for using disc brakes, and there are materials available (such as carbon fiber-based pads) that bring drum brakes into viability for various applications. Maybe some other time.
Cheers!
John