Cervelo Aspero: Front Single Conversion - Part 1

Ever since I built the Focus Paralane to be my primary road bike, this Cervelo Aspero no longer needs to be a dual purpose road and gravel bike. As such, I have more freedom to change out some of the components, to better suit its new purpose as a pure gravel bike.

One of the differences of the gravel bike from a road bike is the gearing required. On a road bike, you will need a higher gear ratio due to faster speeds on the road, and also closer gear steps if you need to optimize your cadence during group riding.

On a gravel bike, you are usually riding slower, more often on unpaved roads than paved roads, thus the gearing can be lower. Also, there is less group riding on gravel, therefore cadence control is not so important. You can basically pedal at your own preferred cadence and speed, thus bigger gear steps are acceptable.

I considered swapping out the crankset, from the Dura-Ace R9100 50/34T to the GRX RX600 46/30T combination. This will lower the gearing to make it more suitable for gravel riding, while still keeping closer gear steps.

However, I found that the RX600 46/30T crankset is really heavy! As it uses solid crankarms instead of hollow crankarms, it weighs a lot more than the Dura-Ace crankset.

Right side of the RX600 46/30T crankset weighs 536 grams.

Left crankarm weighs 276 grams, excluding the plastic crankarm fixing bolt.

This gives a total crankset weight of 812 grams, which is even heavier than the 105 crankset. In comparison, the Dura-Ace R9100 crankset only weighs 610 grams, which is more than 200 grams lighter. With such a big weight difference, I could not accept this change.

Therefore, I decided to go for a front single drivetrain, which simplifies the drivetrain setup and might reduce a bit of weight at the same time.

As mentioned in the other post on the Focus Paralane, I decided to swap the cranksets between the Focus Paralane and the Cervelo Aspero. The Dura-Ace crankset thus goes onto the Paralane road bike, while the Ultegra crankset and 38T Wolf Tooth chainring will go onto the Aspero gravel bike. This is better as the smaller chainring is suitable for gravel riding. This right side crank arm plus chain ring weighs just 396 grams, a whole lot lesser than the GRX RX600 right side which weighs 536 grams.

Ultegra R8000 crankset with 38T Wolf Tooth chainring. With multi-coloured chainring bolts for decoration.

With a front single crankset, I will need a wide range cassette at the back, in order to get enough gear range. Unlike with the front double drivetrain, there are much lesser restrictions as to what cassette I can use, since there is no front derailleur or total chain capacity to worry about.

In this case, I can use the dedicated GRX Di2 rear derailleur, RD-RX817 which is designed for front single drivetrains. Check out the detailed comparison between the rear derailleurs for front double or front single drivetrains. The RD-RX817 is basically very similar to the Deore XT Di2 MTB rear derailleur.

RD-RX815 for 2x11 speed on the left, RD-RX817 for 1x11 speed on the right.

With the front single crankset and front single specific rear derailleur prepared, the next component we need is a wide ratio cassette. The widest Shimano cassette available is actually a 12 speed MTB cassette, with a range of 10-51T. However, it requires a Microspline freehub, while there is also no 12 speed Di2 system from Shimano.

Therefore, what I need is a 11 speed MTB cassette. I can choose between the ratios 11-40T, 11-42T, and 11-46T. I have used the 11-40T cassette on the Bike Friday Haul-A-Day cargo bike, and the 11-46T cassette on the Polygon Cozmic MTB.

A wide ratio is nice, but a huge gear step jump is still not preferred. The 11-46T cassette has a wide gear range but also a big gear step from the 37T to the 46T. I did not like this, which is why I decided to use a smaller 11-42T cassette now instead. The low gear difference between a 11-40T and 11-42T cassette is small at just about 5% difference.

11-42T cassette can be found on the SLX CS-M7000 cassette.

It has one large aluminium spider, with the rest being full spline sprockets. The Deore XT version has two aluminium spiders for lower weight.

7 sided aluminium spider joins up the 3 largest sprockets.

3 largest gears are 32T, 37T, and 42T.

A spider spacer is used to help support the sprocket during sideways bending loads.

This 11-42T cassette weighs 478 grams, which is not lightweight. 

Although weight is saved from the removal of one chainring and front derailleur, it is added back by the use of a wide ratio cassette. I don't expect to save much weight by converting from front double to front single drivetrain, let's check out the weight comparison later. This SLX cassette is much heavier compared to the Sunrace 11-36T cassette, the Ultegra 11-34T cassette, or the Dura-Ace 11-30T cassette.

Finally, with the removal of the front derailleur, the front derailleur mount on the frame can be removed as well. It is not necessary, but since the replacement cover is available, I decided to change it. This cover was provided with the frameset.

Cover with front derailleur mounting on the left, blank cover on the right. The screws used are the same.

Used the blank grommet to replace the previous grommet which has a hole for the front derailleur Di2 wire.

Blank cover and rubber grommet installed! Now it becomes 1x ready. See how it looked like previously.

Here is the first part of the front single conversion, where I have gathered all the parts, ready for bike modification. To be continued!