Wednesday, August 21, 2019

Bike Friday HaD: Wheelset and Brake Caliper Installation

Previously, I had prepared the Ascent Bikes custom wheelset, tires, and the Deore XT brake calipers, to be ready for the Bike Friday Haul-A-Day frameset. Once the brake rotors and 11 speed cassette have been installed, the wheelset will be complete!

Let us now install the complete wheelset onto the frameset, hopefully there will not be any major issues.

This was the initial setup, with the 180 mm brake rotors. 

11-40T 11 speed cassette, roughly the same size as the 180 mm brake rotors.

Rear brake mounting is the post mount type, which matches nicely with almost all brake calipers. For a 180 mm brake rotor, an adapter (160 to 180 mm post mount type) is needed (not shown).

The front fork brake mount is the IS type, which means that an adapter to convert it to the post mount type is needed. As the IS mounting tab on the steel front fork is thin, the original bolt length for the adapter is too long. I added a nut as a spacer, so that the bolt does not stick out at the end and hit the rotor.

With the brake adapter mounted on the front fork! This brake adapter is for use with 180 mm brake rotors at the front.

Trying on the other side of the brake adapter, by fixing it to the brake caliper first, instead of the front fork.

However, there is a big problem! The brake rotor will interfere with the brake caliper, when I try to mount it. This is the closest I can put the brake caliper as it is already touching the brake rotor.

After double checking the brake adapter specifications, I am sure that it is correct, as that adapter is for mounting the front brake caliper to use with 180 mm brake rotors. Somehow it just does not fit...

Upon searching online, I found that this issue has been highlighted before. The brake mount of the Bike Friday front fork is actually not of standard design! To mount a 160 mm brake rotor, a 180 mm adapter is actually needed. In other words, if I want to mount a 180 mm brake rotor, I need to upsize to a 203 mm brake adapter!

This is really weird, and is just one of the few designs on the Bike Friday frame that is not of standard specifications. I am not sure what is the rationale behind this, but it means that the components that I have prepared will not fit.

I can either change to a larger adapter (203 mm type), to use with the 180 mm rotor, or downsize the rotor to 160 mm, so that I can use the 180 mm adapter that I already have.

As previously calculated, downsizing from 180 mm to 160 mm brake rotors will mean a 12.5% decrease in brake power. I think it is acceptable, because overall, the brake power is still very good, due to the smaller wheels and also the 4 piston hydraulic disc brakes.

Therefore, I decided to downsize the rotors to 160 mm for both front and rear. This means that I can use the existing 180 mm brake adapter for the front brakes, while there is no need for an adapter for the rear brakes.

Wheelset with 160 mm diameter Ultegra RT800 brake rotors.

Gives a different look compared to the RT99 brake rotors which look more aggressive.

Now it fits! Using a 180 mm adapter, to match the front brake caliper to the IS type mount with a 160 mm brake rotor.

Even so, an additional spacer of about 1.5 mm is needed to push the brake caliper outwards slightly, to avoid touching the brake rotor.

Front brakes installed!

Testing the fitting of the rear brake caliper.

Without spacers, the brake rotor will touch the edge of the brake caliper.

Added about 3 mm of spacers to avoid interference between the brake rotor and the brake caliper.

Rear brake installed! Both front and rear brakes are using 160 mm brake rotors.

Routing of the hydraulic brake hose, following the main frame, to the left chain stay, then to the rear brake caliper.

If you had noticed, you will see that on this frame, the hydraulic brake hose routing is all external. It does not even run through the holders on the frame, but outside the holders.

This is because the brakes were prepared separately, before installing onto the bike fully bled. I took measurements with the brake levers and brake calipers in the actual position, and cut the hose to the correct length.

Then, off the bike, the brake lever and brake caliper were connected, and bled with the hydraulic mineral oil. Once done, it means that the brakes are ready to be installed onto the bike. This also means that I cannot run the hose through the holders on the bike.

Although it does not look as neat, I prefer it this way as I can bleed the brakes properly off the bike, without having to handle the bike with the brake components already mounted on it. In the future, if I ever need to change the brake system, I can remove the entire brake system (brake lever + hose + brake caliper) without disconnecting the hose anywhere.

Once the wheels and brake system have been installed, the bike is almost ready to go on a test ride! The drivetrain goes on without any problems.

Up till now, the trickiest problem was solving the front brake adapter issue, due to the non-standard specifications of the front brake mount.

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