Upgrading to a larger front brake rotor on the CCS

[Reid]

Our bikes have oversized matching 180mm Tektro rotors. Most other bikes have 160mm front/rear rotors. There is a small but growing demand for larger brake rotors on bikes that can benefit from greater brake torque. Likewise, there is some recognition that bikes can benefit from unequal brake rotors, larger in the front, smaller in the rear.

I have ordered from Niagara Cycle Works through Amazon a larger Tektro rotor and matching disc adaptor .

The larger 203mm rotor on the front will increase stopping power from high speed in particular.

The basic physics are found, for instance, here. These excerpts from the car brake article apply just the same to our bikes:

When the vehicle decelerates, mass or load is transferred from the rear tires to the fronts. The amount of load transfer is determined by the height of the vehicle's center of gravity, the length of the wheelbase and the rate of deceleration. Anti-dive geometry does not materially effect the amount of load transferred - only the geometric results of the transfer. Second, when a tire locks under braking, braking capacity is greatly reduced but lateral capacity virtually disappears. Therefore, when the front tires lock before the rears, steering control is lost and the car continues straight ahead - but this "under steer" is a stable condition and steering control can be regained by reducing the pedal pressure. If, however, the rear tires lock first, the result is instantaneous "over steer" - the car wants to spin. This is an unstable condition from which it is more difficult to recover, especially when entering a corner.

3) Only increasing the effective radius of the disc, the caliper piston area, the line pressure, or the coefficient of friction can increase brake torque. Increasing the pad area will decrease pad wear and improve the fade characteristics of the pads but it will not increase the brake torque.

Lock-up of either bike wheel is pretty dangerous. But with the equal sized brakes the CCS (and most all bikes) come with, if the rider braking at high speed or on a downhill grade does not consciously and carefully apportion rear brake lever grip to front brake lever grip, the rear wheel will lock up long, long before the front. In fact, I find it very hard (impossible, actually) to lock up my front CCS wheel on dry pavement at high speed, but very easy to skid the rear.

By going to the larger front rotor, the dynamic braking of the bike will improve.

Later, I may decide to reduce the rear rotor diameter to 160mm, in order to further improve the match of maximum usable braking torques of the respective wheels, to the actual traction available to them when a fast stop is made, when forward weight transfer and resultant rear wheel skid make clear that identical front/rear brakes are not ideal.

 

[hurricane56]

nice Upgrade. I did a similar upgrade on my HF1000, but used a Shimano RT86 rotor. The Tektro ones work, but I’ve noticed the Shimano rotors have more resistance to bending due to the aluminum core. Definitely a worthwhile upgrade.

 

[Reid]

Shimano RT86 rotor

Hey, that is really interesting, the black aluminum core must act as a heat radiator!

How would you characterize the difference in haul-it-down-fast, brake power over stock; by what percentage of improvement, if any?

 

[hurricane56]

Yes, that's how Shimano describes the aluminum core, plus they look extra cool. I would say with the larger rotor, I feel there is a noticeable increase in stopping power, maybe 10% at most. However, the main difference is the ability to modulate the brake power after the initial application of the brakes. It's like having more resolution to how you can feather the braking.

My original plan with the HF1000 was to upgrade the stock Tektro brakes to Magura MT5e brakes that I retrofitted onto my Haibike Trekking. When I converted that bike from two piston to four piston, it felt like you could easily lift up the rear end of the bike with panniers and gear under a panic stop. That would have made a lot more braking power with the four pistons, but I didn't want to hack and splice the stock Juiced Bike wiring harness.

I do agree that 203mm rotor on the rear is more of a cool looking feature than something you can actually use. In theory, it would dissipate heat by having more surface area, but for anything other than a downhill mountain bike, probably money down the drain. A 180mm is more than enough stopping power to lock up the rear wheel under heavy braking.

 

[Reid]

Cool! I don't use the brake inhibitors, they have been disconnected, so no worries there.

With what you say, I am sure going to upgrade the front to a four piston caliper and the matching lever. I guess I'll go with Tektro? Have no hills here, it's just for that rare need for a straight line stop, to avoid a collision.

 

[hurricane56]

I looked into a four piston Tektro and the particular model might be an OE part currently. The dorado brakes that come with most Juiced Bike models don’t use a banjo bolt connector, which limits your options.

If you’re not using brake inhibitors, I highly recommend Magura MT5.

 

[Reid]

Thanks! Sure seems to be the ticket. Hundred bucks as shown, pre-bled long hose that can be cut shorter:

Magura MT5 ready to mount

The MT5 and MT7 are the two models that sit in Magura’s range of gravity brakes, with a special edition Danny MacAskillversion of the MT7 available too. The MT5 is basically a cheaper version of the MT7 but both brakes use a four pot calliper and run on Magura’s low viscosity mineral called Royal Blood and share very similar characteristics and feel. Built in their German factory, both models have a very well engineered look and feel, with plenty of the brand’s motorcycle braking tech and thinking in their design.

‘It almost feels like your fingers are on the discs, so sensitive is the feeling. Simply superb’​

The MT7 really is the one to go for if funds allow but we really do love everything about both these brakes. Primarily it’s the sensory stuff that this Magura brake is simply so good at. There’s a super sensitive connectivity between lever and disc, which no other brake manufacturer offers quite like.

The materials feel right, the lever shape is spot on and stiffness/flex is excellent too. As we’ve found with heavy e-mtb’s the power delivery is consistent, precise and reliable. It’s all you need in a brake on a downhill bike or e-bike.


Read more at https://dirtmountainbike.com/bike-reviews/brakes-gears/magura-mt57-brakes.html#qv8lVtOD0qB2rBzO.99

 

[hurricane56]

That’s the one. The cool thing about Magura is they have different levers you can change out and the magnet retention on the brake pads is very well designed.

 

[Dunbar]

I tried to upgrade to a 203mm front rotor about a year ago on my original Cross Current. I didn’t realize that there were two different adapters available for Tektro Dorados. I ordered the wrong one on eBay and it wouldn’t work due to having different caliper spacing. At the time Tektro was sold out of the proper spaced adapter (you want the Tektro Auriga 203mm adapter BTW) so I gave up on my upgrade plans.