Sunday, October 3, 2021

United Trifold: Brake System Upgrade

The stock brake system that comes with the United Trifold is not very good. It does not brake well, even when you apply a lot of force to the brake lever.

A bicycle braking system consists of many components. Brake lever, outer casing, inner cable, brake caliper, brake pad and the rim. Each one of these components must function optimally, to enable a smooth braking operation and strong braking effect.

Based on my plan, all the components will be changed.

Brake Lever: Change to Shimano SL-R780
Outer Casing and Inner Cable: Change to Shimano outer casing and inner cable
Brake Caliper: Change to Shimano brake caliper if possible
Brake Pad: Use the Shimano brake pad that comes with the brake caliper

The challenging part is changing the brake caliper, all the other changes should be no issue. This is because the stock Tektro brake caliper is a long arm type, to allow the mudguards and wide tires (37-349) to fit inside. The reach is measured to be about 70 mm, which is very long.

Standard Shimano road brake calipers have a reach of around 51 mm, which is way too short. Even with a brake pad extender, it only adds 10 mm which is still insufficient.

Previously I have experimented with different brake calipers on the mini velos and folding bikes, you can read about it here.

From all the prior experience, I know that the best braking performance can be achieved if you can use standard reach Shimano brake calipers, instead of resorting to long reach brake calipers or other adapters.

Stock Tektro brake caliper, which has a long reach to encompass the mudguards and wide tires.

My idea is to use the Elosix brake adapter for the front brake, like how I did many years ago. No idea for the rear brake yet.

The brake adapter does not fit well, as it sticks out too much from the fork and interferes with the tire.

Part of the reason that the brake adapter sticks out so much is due to the internal profile of the fork, where there are internal protrusions that prevents the adapter from resting properly.

Another reason is that the slot on the brake adapter is rather short, limiting its range of positions.

Old Elosix brake adapter on top, new one below. Note the longer slot on the new brake adapter.

New brake adapter on the right has a thinner wall at the larger diameter, where the brake caliper will be fixed to.

On the other hand, the new brake adapter on the right has a thicker wall at the smaller diameter, where it locks to the fork.

Even with the longer slot on the new brake adapter, I cannot push up the brake adapter all the way.

Time for some DIY, to grind a longer slot on the brake adapter, so that the brake adapter can be tucked into the fork as high as possible.

With a longer slot on the brake adapter, it can now go all the way up into the fork.

This is the new brake adapter, secured to the fork at its highest position for tire clearance.

The brake adapter is secured to the fork using the internal nut, and double secured with the external nut.

With the tire installed, there is enough clearance. Mudguards definitely have to be removed, as I already planned.

Here is the Shimano 105 BR-R7000 brake caliper, of the same generation as the Dura-Ace R9100 and Ultegra R8000 brake calipers.

Unfortunately, the 105 brake caliper is unable to fit, as it will interfere with the tire. The brake caliper is only designed for tires with maximum width of 28 mm, so the 35 mm width of the Schwalbe One tires is just too much. Previously on the Dahon Boardwalk, the brake calipers were able to fit over the 35 mm wide Kojak, only because the brake mounting point was a bit higher up.

In this case, the Elosix brake adapter puts the brake caliper too far down, and there is no way to reduce the amount of extension. Therefore, the Elosix brake adapter does not work for this bike, for me to install a standard Shimano brake caliper. In this case, I have to use the stock Tektro brake caliper, but I can still use new brake pads.

Separately, I got Ultegra caliper brake pads, so that I can replace the stock brake pads on the Tektro brake calipers. The stock brake pads are really bad, as they are very hard and not grippy at all. It goes right into the bin, no need to keep for future use.

Shimano Ultegra brake shoe set, with the brake pad holder and brake pads.

Each set of brake pads weigh 36 grams.

Each set of Tektro brake caliper weighs 173 grams, without brake pads.

I thought that the brake pads would be a straight swap, but it turned out to be a nasty surprise instead. Apparently the brake pads do not fit into the brake calipers directly.

The nut of the Shimano brake pad does not fit into the slot of the Tektro brake caliper.

Outer diameter of the nut on the Shimano brake pad is 6.4 mm.

Slot width on the Tektro brake caliper is only 6.1 mm.

I was surprised at this finding, as I always thought the slot width was a standard width. However, I realized that the stock Tektro brake pads are one-piece type, with the bolt molded into the brake pad. The bolt has an M6 thread, which means an external diameter of around 6 mm. That was why the Tektro slot width is 6.1 mm, to prevent too much free play with the M6 thread.

However, the Shimano brake pad uses a M5 bolt and nut, and thus the external diameter of 6.4 mm on the nut is just to ensure sufficient wall thickness on the nut. The slot width thus needs to be wider to fit the nut.

In this case, the width difference is only about 0.3 mm, so it is safe and not too difficult to widen the slot width on the Tektro brake caliper. Using a hand file, it will take quite some time. I used an electric grinder and it was done quite easily.

Grinding off some material from the slot of the Tektro brake caliper, so as to fit in Shimano brake pads.

Now it fits!

Since I have removed the brake calipers from the frame, this is the best chance to condition the brake calipers, so that they move as smoothly as possible. After all, I don't have any other solution to change the brake calipers.

The Tektro brake calipers does not operate smoothly, as there is quite a lot of friction in the pivots and joints. I added some grease to the sliding areas, and oil to the pivots. After conditioning it, the brake calipers are able to operate more efficiently. This ensures that more of your hand input force goes to press the brake pad against the rim, instead of working against friction.

Front Tektro brake caliper with Ultegra brake pads weigh 207 grams.

Rear Tektro brake caliper with Ultegra brake pads weigh 209 grams.

Ultimately, I was not able to change the brake caliper, but I was able to improve the efficiency of the Tektro brake caliper by applying grease and oil to the moving areas. The brake pads were changed to Ultegra brake pads, which should be better than the stock brake pads.

Whether all these improvements are able to provide a good braking performance will be confirmed after the whole bike is set up.

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