Rotor Offset Adapter: 6 Bolt Rotor on Centerlock Hub

The wheelset on the Birdy AXS 12 Speed has been upgraded to the awesome looking Suncord 4 Spoke carbon wheelset! The wheelset came with a Centerlock hub that is compatible to Centerlock disc rotors. However, the rotor position is not the standard spacing. Rather, it is offset 5 mm inwards, as first explained on the Ascent Cirrus Elite carbon wheelset post.

I found this very interesting, as it meant that the wheelset is only compatible to Birdy bikes in stock condition. One problem with supplying bikes for Birdy wheelset is the special front hub that is needed, with the inward offset rotor position and clearance needed around the hub flanges to accommodate the folding.

I realized that Suncord has done a clever thing with the design of their hubs. Instead of having dedicated front hubs with different rotor spacings for Birdy and other bikes, they decided to base all the front hub designs on the smaller Birdy rotor spacing. Then, to make it compatible to other bikes, just a 5 mm offset adapter is needed to push out the rotor position to the usual spacing.

That is what I am going to show you today, an interesting adapter which I have not seen before.

Most brake adapters convert Centerlock hubs to make it compatible to 6 bolt rotors. This is a standard conversion which converts a standard Centerlock rotor position to a standard 6 bolt rotor position. Both rotors have the same distance from the hub centreline.

However, the adapter below not only converts a Centerlock hub to fit a 6 bolt rotor, it also moves the rotor position outwards by 5 mm! That is how a Birdy Centerlock hub can be made to fit standard bikes, while using a 6 bolt rotor.

Centerlock spline position on the Suncord wheelset, which is offset 5 mm inwards for Birdy bikes.

Although the special adapter is not included with the Suncord wheelset, it can be purchased from the same seller for a small cost.

At first glance, this looks like a standard Centerlock-to-6 bolt adapter.

However, the adapter is thicker (+5 mm), while the threaded lockring also has longer threads.

Special +5 mm adapter set on top, normal adapter set below that is 5 mm thinner.

Special lockring with longer threads on the left, compared to the standard Centerlock lockring on the right.

If you noticed the wording on the lockrings above, you will see that the special longer lockring states "100 to 110 for 9/12/15 Thru Axle only". That refers to the front hub OLD used on MTB, which used to be 100 mm. However, MTB started having wider front hubs for increased strength, and the OLD was increased to 110 mm, and this standard is called Boost.

In a way, this is the same concept being reused, where older 100 mm MTB front hubs were boosted to 110 mm to be compatible to new Boost MTB suspension forks. The additional 10 mm was added equally to both sides, 5 mm on the left and 5 mm on the right of the hub. This is why the lockring is 5 mm longer, and is exactly what is needed for this special adapter set.

Centerlock to 6 bolt adapters, with the special adapter on the left being 5 mm taller. Specially designed for Birdy front hubs, to make it compatible to standard (non-Birdy) forks.

Standard adapter plus lockring is 29 grams

Special adapter set weighs 40 grams due to more material. However it is just a 11 gram increase which is a small price to pay for universal compatibility.

Here is how a 6 bolt rotor fits onto the special adapter for Centerlock hubs. The lockring will then clamp down on top and secure everything.

When fitted properly, the 6 holes on the rotor should fit fully over the 6 steel pins on the adapter. This  special adapter moves the rotor position 5 mm outwards.

With this special adapter, you can buy a Birdy wheelset, and still be able to retrofit it to a standard bike later on, if you decide to move the wheelset to a different bike.

Birdy AXS: Assembly Completed with Suncord Wheelset

Assembly of the Suncord 4 Spoke carbon wheelset is completed! Let's look at some pictures of the Birdy AXS 12 Speed with the new wheelset.

Unique to Birdy bikes, the front rotor is mounted on the drive side.

The hollow look of the 4 carbon spokes look awesome alongside the front suspension fork.

Using the same SRAM drivetrain, but with a new wheelset.

Lots of empty space visible through the rear wheel.

XTR MT900 rotors used on both the front and rear.

Full bike with Suncord 4 spoke carbon wheelset!

It's a unique hybrid of SRAM drivetrain with Shimano brake components.

Updated bike component specifications! With the weight reduction from the wheelset and rotors, the bike is barely above 9 kg if you exclude the pedals and kickstand (which is the standard way of comparing different bike weights).

At Teck Whye View Playground

Using all black components allow the blue frameset to stand out!

At Villa Verde bridge along Pang Sua PCN

Great weather!

More pictures of the Birdy with new Suncord wheelset

At Villa Verde Park Playground

One of the best pictures in my opinion

Lovely cloudy weather again

After the Suncord wheelset modification, I currently don't have any other modifications planned for the Birdy. It's perfect in terms of performance, appearance and weight, not much room to optimize in any significant way.

Birdy AXS: Suncord Wheelset Installation

The new Suncord 4 Spoke Carbon Wheelset was introduced in the previous blog post, now I will install the new wheelset onto the Birdy AXS 12 speed!

I will be transferring the Panaracer Minits Lite tires from the Ascent Cirrus Elite carbon wheelset over to the new Suncord wheelset. However, new disc brake rotors will be installed as the Suncord wheelset accepts Centerlock rotors instead of 6 bolt rotors.

Suncord rim vs the Ascent Cirrus Elite carbon wheelset, before removing the tire and rotor.

Big difference in appearance! The 4 spoke design makes the traditional spoke design look outdated.

Both use hooked rims, but the Suncord wheelset does not require rim tape as it does not have spoke holes on the rim bed.

Gloss vs matte carbon finish. Suncord rim height is 38 mm vs 45 mm on the Cirrus Elite.

Centrelock hub vs 6 bolt hub.

Tire and inner tube transferred over to the Suncord wheelset! Using the same lightweight TPU inner tube, which has a long 60 mm valve.

Putting on a used XTR MT900 rotor of diameter 160 mm.

Both front and rear rotors are 160 mm diameter. SRAM Force AXS 12 speed cassette installed on the XDR rear hub as well.

 

Suncord front wheel with rotor, tire and inner tube installed weighs 768 grams. Previous setup was 878 grams (+110 grams)

Suncord rear wheel with cassette, rotor, tire and inner tube installed weighs 1214 grams. Previous setup was 1285 grams (+71 grams).

After installing the new Suncord wheelset, I found that the chain is almost touching the rear triangle at Gear 1. There was a bigger gap with the Ascent Cirrus Elite wheelset.

Since there is nearly zero clearance, during movement the chain will scrape against the rear triangle and wear off the paint. Since all components (chain, chain ring, cassette) are the same, the cause has to be due to the Suncord wheelset.

It seems that the cassette is slightly more inboard on the Suncord wheelset, since there is still a noticeable gap between the 10T sprocket to the inside of the dropout.

Adding some spacers in the right places should solve the chain rubbing issue, this is not the first time I have made these kind of adjustments before. In fact I did a lot of adjustments when I was modifying the United Trifold folding bike.

Found some thin spacers for the freehub body. Intention is to place it behind the cassette to push it outwards slightly.

Left spacer is 1 mm thick, right spacer is 1.85 mm thick (the kind you put behind a 11 speed cassette when used on 8/9/10 speed freehub body).

XDR freehub body on the Suncord wheelset.

1 mm spacer placed on the splines, before installing the XDR cassette.

With the cassette installed, the silver 1 mm spacer can be seen sandwiched between the hub and the cassette.

However, adding 1 mm spacer on the cassette did not create enough clearance between the chain and the rear triangle. Since it is not advisable to add more spacers on the freehub body, I decided to add a spacer on the crankset instead.

These are smaller spacers that are designed to be placed on the Shimano crankset spindle of 24 mm diameter. Each spacer is 1 mm thick.

Used one piece of 1 mm spacer on the spindle of the Dura-Ace R9100 crankset. This will push out the chain line by 1 mm.

With both the front and rear chain lines pushed out by 1 mm, there is now additional 1 mm of chain clearance. May not be enough to completely eliminate chain rub, but at least it will minimize the occurrence and impact. 

Suncord 4 spoke wheelset has been installed successfully! Needed additional 1 mm spacers on both the crankset spindle and freehub body to push out the chain line slightly, but otherwise no issue.

Birdy AXS: Suncord 4 Spoke Carbon Wheelset

New wheels for the Birdy AXS 12 speed folding bike! I will be upfront and say that I got these carbon wheels mainly for the looks, and partly for the lower weight. Other than that, I don't really care about the aerodynamics or performance of this wheelset.

Let's jump right into it and let the pictures tell the story!

These carbon wheels are made by Suncord, which is known for making aftermarket components for the Brompton.

These carbon wheels have a unique 4 spoke design! I initially wanted the 5 spoke design but was told it is no longer available and they have moved to 4 spokes for better comfort and lower weight.

Suncord logo splashed across the rim, in a style that reminds me of SRAM.

20" 406 wheel size, same as the Ascent Cirrus Elite carbon wheelset that is currently on the Birdy.

I chose the carbon weave design with a gloss finish, as it would be easier to clean compared to a matte carbon finish.

Due to the 4 arm design, there are no spoke holes on the rim at all. What you see here is the valve hole.

This also means that there is no need for rim tape since there are no spoke holes.

Internal rim width is 18.5 mm, which is slightly narrow but not too narrow like 16 mm.

External rim width is a healthy 26.5 mm.

Rim height is 38 mm, which is a nice balance between visuals and susceptibility to side winds.

The 4 arms blend into a large section in the middle where the hub is. This hub has Centerlock rotor mounting.

There is no traditional hub and hub shell in the middle. Rather, the carbon forms a cavity for the internals of the hub to be inserted and bonded.

Other side of the front wheel showing the "hub".

Rear wheel comes with the XDR driver, but can be swapped for other freehub bodies as well.

Non-drive side of the rear wheel showing the Centerlock splines. Interface between the hub and the carbon parts is interesting.

I believe the carbon rims/spokes are the same for the front and rear wheels, just that the hub components are different.

A glossy top coat makes these carbon wheels look shiny!

Front wheel weighs just 456 grams

Rear wheel is just 593 grams!

Ascent Cirrus Elite Carbon Wheelset (20" 406)

Front Wheel: 560 grams

Rear Wheel: 657 grams

Total: 1217 grams

Suncord 4 Spoke Carbon Wheelset (20" 406)

Front Wheel: 456 grams (104 grams less)

Rear Wheel: 593 grams (64 grams less)

Total: 1049 grams

This Suncord 4 spoke carbon wheelset is more than 160 grams lighter than the Ascent Cirrus Elite, which itself is already pretty lightweight! The only other 20" 406 wheelset that I know of that is lighter, is the Dahon Kinetix Pro wheelset that weighs just 998 grams. Even so, that wheelset has a narrow and shallow rim, as well as being rim brake compatible only, which makes it lighter than disc brake compatible wheels.

At the same time, I also ordered the Shimano HG spline freehub body, just in case I want to put on other cassettes.

Shimano HG spline freehub body, made of titanium to ensure durability while saving weight over a steel version.

Freehub body weighs 91 grams, which is heavier than aluminium ones but lighter than steel.

It uses a hybrid metal spring + magnets to activate the pawls. I first saw this kind of magnetic pawls on the Ascent Zenith Elite wheelset.

For this kind of hybrid pawl and ratchet system, the metal spring provides minimal spring force, to minimize the rolling resistance and energy lost during freewheeling. However, just reducing the spring force from a traditional pawl spring system would cause the drivetrain to slip and skip when you pedal hard, as the weak spring cannot prevent the pawls from slipping out of the ratchet during high torque conditions.

Therefore, the magnets on the pawls are designed to keep the pawls fully engaged in the ratchet, without requiring a high spring force to keep them there. Ideally, this system would maintain the engagement required during high torque conditions, while minimizing the energy lost during freewheeling. Hopefully it helps to reduce the freewheeling sound as well!

In the next few posts I will show the installation of the Suncord 4 spoke carbon wheelset onto the Birdy AXS.