Wheelsport Ultegra Di2 2x11 Speed: Part 8 - 451 Wheelset Installation + Ultegra 6800 Brake Calipers

Part 1: Frame Design and Carbon Fork
Part 2: Compatibility Check for Wheelset and Brake Calipers
Part 3: Component Selection
Part 4: Installation Issues and Solutions
Part 5: Final Assembly
Part 6: Accessories and Geometry Comparison
Part 7: Wheelsport Smart 1.0 451 Wheelset + Schwalbe One 451 Tires

Continuing from the previous post where I changed the wheelset from the custom 406 gold coloured wheelset to the Wheelsport Smart 1.0 451 wheelset, it is now time to upgrade to better caliper brakes! That was the primary objective of changing from 406 to 451 wheelset on this Wheelsport Fantasy mini velo. This frame was originally designed for 451 wheels anyway.

By changing to 451 wheels as originally designed, it will allow the use of standard reach caliper brakes, which have better braking power than long reach caliper brakes. Why is this so? It can be explained by using the brake ratio of the caliper brakes.

For caliper brakes or V brakes, the brake ratio is defined as the distance between the pivot and the cable fixing bolt area, divided by the distance between the pivot and the brake pads. The higher the brake ratio, the higher the clamping force applied to the brake pads, and hence a higher braking power. This assumes that all other factors (such as activation force at brake lever) remain the same.

Brake Ratio = Distance from Pivot to Cable Fixing Bolt / Distance from Pivot to Brake Pad

Graphic showing the dimensions for determining brake ratio and hence brake power

The brake ratio of the brakes must be compatible with the brake ratio of the brake levers, in order for optimum braking performance and feel. If there is any mismatch, there will be insufficient or excessive braking power, either of which can be unsafe. To find out more about brake lever and brake caliper compatibility, check out this article for the details.

Measuring the dimensions of the brake calipers will give us some theoretical values regarding the brake ratio. The standard reach brake caliper that I decided to use is the Ultegra 6800 brake calipers, as this would match the Ultegra groupset on the bike perfectly. Comparing the Tektro R559 Extra Long Reach brake calipers to the Ultegra 6800 brake calipers, here are the dimensions.

Tektro R559 Extra Long Reach Brake Caliper
Distance from Pivot to Cable Fixing Bolt: 84mm
Distance from Pivot to Brake Pad: 55mm
Brake Ratio: 84/55 = 1.5

Ultegra 6800 Brake Caliper
Distance from Pivot to Cable Fixing Bolt: 70mm
Distance from Pivot to Brake Pad: 33mm
Brake Ratio: 84/55 = 2.1

From the calculations, the Ultegra brake caliper has a brake ratio of 2.1, which is 40% higher than the brake ratio on the Tektro brake caliper. The longer arm Tektro brake caliper will probably also flex more during hard braking, causing some loss of braking force. Also, the Ultegra brake caliper has a new cam mechanism that improves the braking power. This means that the increase in braking power is likely to be more than 40% when the brakes are changed from Tektro R559 to Ultegra 6800. This is a big jump in performance that can definitely be felt.

That was all theoretical calculations, it is time to upgrade the actual brake calipers to try it out for myself!

Tektro R559 Extra Long Reach brake calipers on the rear of the Wheelsport Fantasy mini velo, with 406 sized Kojak tires.

Tektro R559 on the front fork, with 406 sized Kojak tires. The large gap between the brake caliper and the tire is due to this frame being designed for 451 wheels instead of 406 wheels.

Swapping the brake calipers is straightforward, as there is no need to remove the brake cable from the shifter or outer casing. At the same time, the SwissStop brake pads were also transferred over from the Tektro brakes to the Ultegra brakes. Also, more work is required to change the wheelset, as the cassette also needs to be transferred over from the 406 wheelset to the 451 wheelset. Finally, the most time consuming job is aligning the brake pads nicely with the rims to ensure optimum braking performance and good braking feel.

Ultegra 6800 rear brake caliper

Small clearance with the Schwalbe One 23-451 tires! Not possible to use wider and taller Durano tires (28-451).

Ultegra 6800 front brake caliper

More clearance at the front, and it may be possible to use a wider tire at the front if necessary.

The black and white design of the wheels match well with the matte black frame with white decals

No more gold coloured wheelset or gold bling on the brake calipers. Black, white and silver is the new look

Ultegra Di2 6870 2x11 speed drivetrain, with the new Wheelsport 451 wheels

Other than allowing the use of standard reach brake calipers, the larger wheels will also raise the height of the bike slightly, as the centre of the wheelset is now higher off the ground due to the larger wheel radius. This also increases the BB to ground height, which will improve the pedal clearance when cornering with the bike.

Previously, when this bike was using 406 wheels, the BB to ground height is 267mm. With the new wheelset and tires, the BB to ground height is now 277mm. Comparing to the other bikes that I have:

BB to Ground Height:
Wheelsport Fantasy Ultegra Di2 2x11 Speed (406 wheels, Kojak tires): 267mm
Wheelsport Fantasy Ultegra Di2 2x11 Speed (451 wheels, Schwalbe One tires): 277mm
Dahon MuEX and Dahon Vitesse: 284mm
Merida Scultura 5000: 275mm
Avanti Inc 3: 274mm

This new BB to ground height of 277mm is similar to that of the Merida Scultura 5000 road bike. Not that I had any issues with pedal strike when cornering, but this shows that the original design of the frame is such that it will have the geometry of a road bike when using 451 wheels.

As a recap, this latest modification to change wheelset and brake calipers is to improve the braking performance of the bike, by allowing the use of a standard reach brake caliper that is more powerful. It is not about more speed or lighter weight, but about improving braking performance. In fact, this modification added about 50 grams overall to the bike due to the larger and heavier 451 wheelset, although this increase is partially offset by the lightweight Schwalbe One tires.

During the test ride of this bike, the improvement in braking performance can be felt immediately. Previously, it took quite a bit of effort to pull hard enough on the brake levers to stop the bike quickly. Both brakes needed to be used at the same time to generate sufficient braking power for strong braking.

With the new Ultegra 6800 brakes on the 451 wheelset, the braking power has been increased by quite a lot. It is now possible to apply only one brake to get sufficient braking force. Also, the return springs on the Ultegra 6800 brake calipers are lighter than the Tektro R559, and together with the smoother mechanism, it takes much lesser effort to apply the brakes. Being able to stop quickly and confidently is what I look for in my bikes, and this latest modification has made this possible.

Here is the component list for this Wheelsport Fantasy mini velo after the latest upgrade.

Component list for this mini velo after the latest upgrade

This is still a lightweight mini velo that weighs only 7.9 kg without pedals, which is significantly lower than other mini velos such as the Tyrell FSX (8.6 kg) or Tern Verge X18 (10.4 kg), both of which are small wheeled drop bar bikes.

View of the mini velo with Wheelsport Smart 1.0 451 wheelset, Schwalbe One tires and Ultegra 6800 brake calipers

All ready to go! Very little gold bling left on the bike except at the BB area. The colour theme for this mini velo is now black and white.

With this upgrade, the objective to improve braking performance has been achieved! In the next blog post, I will summarize all the things that I have learnt from building this mini velo, and how I overcame all the challenges and issues that occurred along the way.