Wednesday, March 29, 2017

Avanti Inc 3: Bushnell Eccentric BB Comparison

The recent upgrade done on the Avanti Inc 3 was a major change, where the drivetrain was changed to an electronic shifting, Alfine 11 Di2 version. Also, the controls and brakes were changed to a drop bar set up with road hydraulic disc brakes.

It was a good change as the drop bar set up makes it easier to cycle faster, as compared to on a flat handlebar bike. The road hydraulic disc brakes also works well, especially when riding this bike in the rain. It is my version of a road hydraulic disc road bike, that is also an all-weather commuting bike.

However, changing to a drop bar set up also means that the cycling geometry and fit is different from before. I noticed that the pedaling stance seems rather wide, as compared to my other bikes. In other words, the Q-Factor of this bike is wider than my other bikes, such as the Merida Scultura 5000 road bike and the Wheelsport Fantasy mini velo.

Q Factor on a bicycle

This is due to the Deore crankset, which was designed for a triple chain ring. As such the Q factor of this MTB crankset is wider than road cranksets. There are two reasons why I had to use a MTB crankset on this bike.

1) I wanted to use a 42T Gates front sprocket, which is only available in 4 arm, 104mm BCD. This restricted my choice of crank arms to MTB types.
2) The eccentric BB that came with the bike has a 73mm width, which does not allow the installation of road cranksets (68mm BB width required).

When using the flat handlebar setup, this wider Q factor was not an issue for me, as it rides more like a MTB that a road bike. However, after using a drop bar setup, this wider Q factor becomes more obvious. The ride feeling is quite strange and a little uncomfortable when the narrower drop bars are paired with the wide Q factor crankset.

I did some research and found that this Deore crankset has a Q factor of about 182mm, while a road crankset has a Q factor of less than 150mm. This is a huge 30+mm difference in Q factor that will definitely be felt. Reducing the Q factor will make this Avanti Inc 3 ride more like a road bike instead of a MTB.

In order to use a road crankset, I had to overcome the two limiting factors as explained earlier. First, to use a road crankset, I need to change the BB width from 73mm to 68mm. This requires the eccentric BB to be changed.

Secondly, the Gates front sprocket that is available for road cranksets are only available in 5 arm, 130mm BCD. The smallest sprocket available with this specification is 46T, which is larger than the 42T that I currently have. This means that the gear ratio will be changed again.

Stock Gear Ratio: 50T / 24T = 2.08
1st Mod Gear Ratio: 42T / 24T = 1.75
2nd Mod Gear Ratio: 42T / 28T = 1.5
Proposed Gear Ratio: 46T / 28T = 1.64

Once I change the front sprocket to 46T, together with the 28T Alfine Di2 rear sprocket, the gear ratio will be 1.64, which should be fine for my usage.

First of all, I need a new eccentric BB. The Bushnell eccentric BB seems to be the best eccentric BB available on the market, which I why I decided to get it to replace the stock eccentric BB on the bike. However, there were some issues with the order...

I ordered the Featherweight version, which has cutouts to reduce weight. However, they sent the normal (Retro) version without cutouts.

Credit to them, once I notified them of the error, they immediately sent out a Featherweight version of the eccentric BB. Which is why I ended up with two Bushnell eccentric BB. Might as well make a comparison then.

Featherweight version on left with many cutouts, normal (Retro) version on the right.

This Bushnell eccentric BB works differently from my stock eccentric BB. The Bushnell design has two wedges that will push open the two "wings" on the BB, expanding the diameter of the eccentric BB. This design applies a symmetrical load and should distribute the stresses better within the frame.

Strictly speaking, both orders were actually wrong as I ordered a black coloured, featherweight version. Instead, I got a black, retro version and a silver, featherweight version. However, I will just make do with what I have as they have already sent over another eccentric BB at no extra cost to me.

Available in silver or black

Featherweight version on left has cutouts at non-essential areas to reduce weight

Featherweight version is 154 grams

Normal (Retro) version at 211 grams. 57 grams heavier.

Now I have a choice to make. Should I use the silver coloured featherweight version, or the black normal version? It is a choice between weight and appearance.

In the end I decided that the weight difference was insignificant compared to the whole bike weight. The black version would look better as it will blend in well with the black coloured frame.

Black, normal version of the Bushnell eccentric BB will be used

Let's do a detailed comparison of the Bushnell eccentric BB vs the original eccentric BB. Weight, working principle and dimensions will be compared below.

Original eccentric BB. Uses a wedge on one side, similar to old school type quill stems. Also has cutouts to reduce weight.

Good weight of 177 grams, lighter than the Bushnell normal version

Side view

Top view. See the different wedge mechanisms.

Original eccentric BB disassembled.

Bushnell eccentric BB. More parts in this design.

One other thing to take note is that the frame needs to be compatible with the Bushnell eccentric BB. The important dimensions are the internal diameter of the frame BB shell, and the overall width of the BB shell.

BB shell internal diameter on the frame is about 55mm

Width is about 66.6mm

Original eccentric BB outer diameter, fits into the 55mm BB shell nicely.

Width of original eccentric BB. 66mm at area that contacts BB shell.

About 73mm wide at the area that the BB screws into. This is the dimension that limited my choice of cranksets to MTB type.

The Bushnell eccentric BB is designed for 53.8-54mm internal diameter BB shells, so the BB shell on the Avanti Inc 3 is too big. Luckily they also provide shims to allow usage of 55mm or 57mm BB shells.

Bushnell eccentric BB outer diameter, too small to fit securely into the 55mm BB shell.

Shim of about 0.5mm thickness is used, to reduce the internal diameter of the 55mm BB shell to 54mm

Bushnell eccentric BB, also about 66mm at area that fits into frame BB shell

About 68mm wide at the area where the bottom bracket cups screw into. This allows the use of road cranksets.

The main objective of this modification is to change the BB width from 73mm to 68mm, so that I can use a road crankset. Next, we will need to use a suitable road crankset, and also get a new front sprocket. Since the sprocket size has changed, a new Gates belt is also required...

Tuesday, March 21, 2017

Wheelsport Fantasy Mini Velo: Full Dura-Ace 9000 Groupset

After the Merida Scultura 5000 road bike has been fitted with a full Ultegra 6870 Di2 groupset, it is this bike's turn to get a full groupset too. The Wheelsport Fantasy mini velo currently has a 1x11 speed setup with a mix of Ultegra 6800 and Dura-Ace 9000 parts. 

Before: Mix of mechanical Dura-Ace and Ultegra components

The right shifter, rear derailleur, cassette and brake calipers are Dura-Ace 9000, while the left shifter and crankset are Ultegra. To make a full Dura-Ace groupset, the crankset, brake calipers and left shifter will be changed to Dura-Ace.

Before swapping the components, I wondered how the crankset would look if the Ultegra crank arm is changed to the Dura-Ace crankset.

Before: Ultegra crankarm with Wolf Tooth chain ring and gold chain ring bolts. Looks very good!

Trying to visualize the Dura-Ace crankarm on the Wolf Tooth chain ring...

It actually looks pretty good! The silver on the crankarm actually matches with the silver on the rims and rear derailleur.

Instead of gold coloured chain ring bolts, I will use black chain ring bolts to let the Dura-Ace groupset stand out.

Length of 8.5mm for the chain ring bolts is just right, as the Wolf Tooth chain ring is thicker than normal flat chain rings.

Ta-da! Dura-Ace 9000 crank arm with Wolf Tooth chain ring and black chain ring bolts. Looks good too!

Close up view of the interface between the crank arm and the chain ring

Weighs exactly 400 grams. 25 grams lighter than the Ultegra equivalent.

While reinstalling the chain onto the drivetrain after replacing the crankset, I found that the original 11 speed chain had a few rusty links and did not move smoothly. Therefore, I had to replace the chain too.

Dura-Ace grade 11 speed chain for maximum rust resistance. Also common use with 11 speed XTR.

Dura-Ace 9000 crank arm with Wolf Tooth chain ring installed

Left side Dura-Ace 9000 crank arm

Using the KMC 11 speed MissingLink

11 speed cassette is also Dura-Ace CS-9000, 11-25T

Full Dura-Ace 9000 drivetrain! Silver and black goes well together.

With the drivetrain settled, the next component to change would be the left side shifter. The left side shifter was a modified Ultegra 6800 left side shifter, with the internal shifting mechanism removed to save weight. As this is a 1x11 speed setup, the left side shifter only acts as a brake lever, no shifting function is required.

Nevertheless, to complete the full Dura-Ace 9000 groupset look, I decided to put on the Dura-Ace left side shifter too, even though the shifting function will not be used.

Dura-Ace 9000 left side shifter, 184 grams.

Modified Ultegra 6800 left side shifter, with internal shifting mechanism removed.

Shiny Dura-Ace 9000 left side shifter installed. The superior grade of gloss finishing is obvious when compared to Ultegra.

Matching pair of Dura-Ace road shifters. I took the chance to replace the Lizard Skins bar tape which were starting to peel off after a few years of use.

The final component to change to Dura-Ace would be the brake calipers. By swapping the brake calipers with the ones on the Merida road bike, both bikes will have a complete groupset.

Dura-Ace 9000 brake calipers

Lightweight and powerful brake calipers

Full mechanical Dura-Ace 9000 groupset on the Wheelsport Fantasy mini velo!

Black and silver surface treatment on all the Dura-Ace components match nicely with the black and silver colours of the wheelset, and the black and white design of the other components.

This mini velo is still a lightweight mini velo, since it has all the lightweight Dura-Ace components. The final weight of the Dura-Ace mini velo is just under 7.3kg (excluding pedals).

Final specifications of the Wheelsport Fantasy 1x11 speed mini velo with full Dura-Ace groupset

Wednesday, March 15, 2017

Merida Scultura 5000: Full Ultegra Di2 6870 Groupset

On two of my bikes, the Wheelsport Fantasy mini velo and the Merida Scultura 5000 road bike, there is a mix of Ultegra and Dura-Ace components. This is mainly due to me getting these parts at different times, and trying out different setups, which is why there is no complete groupset on these bikes.

I decided to switch the components on these bikes, so that I can get a full groupset on each of these bikes. The function would be similar, but the appearance would be more consistent and coherent.

Starting with the Merida Scultura 5000 road bike, the current setup is mainly Ultegra 6870 Di2, with Dura-Ace brake calipers and Dura-Ace crankset. Since the Ultegra Di2 system will remain on this bike, I would bring over the Ultegra crankset and brake calipers which are currently on the Wheelsport mini velo, so that this Merida road bike has a full Ultegra groupset.

Before switching the components: All Ultegra except for crankset and brake calipers, which are Dura-Ace.

The Ultegra 6800 crankset, where only the crankarms are used on the 1x11 speed Wheelsport mini velo

52/36T Ultegra crankset installed on the Merida road bike. I would have preferred the 50/34T crankset, but I had already sold that crankset.

Full Ultegra 6800/6870 drivetrain! Looks better with components from the same series.

Dura-Ace brake calipers are also changed to Ultegra. Quite a straightforward swap.

The brake pads had to be adjusted, but otherwise the swap is easy. Performance is almost equivalent to Dura-Ace.

Full Ultegra groupset on the Merida Scultura 5000! 

Full specifications of Merida Scultura 5000 with full Ultegra 6800 groupset

I think that I have finally settled on a good setup for the Merida road bike, with a full Ultegra 6870 Di2 groupset. Having experimented with a mechanical Dura-Ace 9000 groupset on this bike, I still prefer to have the Ultegra Di2 groupset.

This also means that all the Dura-Ace 9000 components will be going onto the Wheelsport Fantasy mini velo, but that is a story for another day.