Cervelo Aspero: GRX Hydraulic Di2 Shifters

My Cervelo Aspero was initially built as a dual use bike, where I can switch between road or gravel usage, just by swapping the wheelset. As such, the drivetrain was selected to suit both road and gravel riding. I was using a front double drivetrain, with a 50/34T crankset for range, and different cassettes for road and gravel riding.

Up front at the cockpit, I used a road hydraulic shifter, as I usually go for road rides without gloves, so the smaller and smoother Dura-Ace ST-R9170 shifters are more comfortable. Besides, most of the Dura-Ace drivetrain was ported over from the previous Canyon Endurace bike. However, for off-road riding, these road shifters are not as ideal as the hood is small, and thus the hand does not have such a good grip over rough terrain. Many times, if I hold the hoods of the shifter, the hands will tend to bounce off the shifter as it is not secure enough.

Recently, I have converted the Cervelo Aspero to a full-time gravel bike, with a front single drivetrain and more dedicated gravel components. As such, I don't have to make a compromise between road and gravel riding, of which there are different requirements.

Other than the drivetrain, I decided to change the shifters as well. As mentioned earlier, the Dura-Ace ST-R9170 road shifters are good for road riding, but not so ideal for off-road gravel riding. There is a dedicated GRX Di2 shifter, which is designed specifically for gravel riding. That is what I am going to use on this gravel bike, and here is a detailed look at why this GRX shifter is different.

GRX Di2 components!

GRX ST-RX815, which is the Di2 version of the GRX hydraulic shifters.

It comes with the SM-BH90 hose and other small parts which you need to make your braking system complete.

In a separate post, I will compare the GRX shifter side by side with the road shifter. Now I will show the details of this GRX ST-RX815 shifter from every angle.

GRX logo is clearly printed on the lever member. The shaping of the levers are quite different from the road shifters.

Outline is very different, with a very pronounced hood, and a flat surface for the fingers to hold during braking.

Not the most pretty looking shape, I did find it quite weird when I first saw the shape.

There are tall and strong embossed ribs on the rubber cover. The longitudinal ribs on the outside prevent your hand from sliding outwards.

The diagonal ribs on the inside prevent your hand from sliding forward. After riding, I found that the rib design is really effective!

The additional Di2 button is now located at the side of the hood as indicated by the textured surface. It is activated by pressing it with the side of the thumb.

I like the new location of the additional Di2 button, as I can press it without taking my entire thumb off the shifter, unlike on the road shifters, where it is located on top. This means a shorter activation time, and also more secure holding of the shifter when the button is being operated.

There is a clear curvature on the lever, which is designed for your index finger when holding the hoods.

The hoods are tall with a vertical rear surface, which means your hands will remain secure on the hoods even when riding over rough terrain. This is one of the main advantages of this GRX shifter over the road shifters.

The index finger will rest on the curvature of the lever during braking, which makes it easy and ergonomic for one-finger braking.

Previously, on the road shifters, one-finger braking from the hoods are not effective, as it is difficult to get enough leverage to generate sufficient braking power. However, the GRX shifters has changed that, and enabled one-finger braking operation from the hoods! How is this possible?

The pivot location of the GRX brake lever has changed, to be higher than the road shifter. This increases the leverage of the finger on the brake lever, which allows effective one-finger braking.

Simple graphic showing the different brake pivots of the road and GRX shifter, and also the hood shape. 

With the finger further away from the axis on the GRX shifters, it is possible to use one-finger braking. Also, since the pivot is now located higher up, the swing of the lever is different. As such, the lever shape and other dimensions had to be changed, compared to the road shifters. This will be shown in more detail in a separate comparison post. This is another advantage of the GRX shifter over the road shifters, in terms of braking ergonomics from the hoods.

Each of the GRX shifters weigh 190 grams, giving a total weight of 380 grams per pair.

Dura-Ace ST-R9170: 320 grams per pair

Ultegra ST-R8070: 365 grams per pair

GRX ST-RX815: 380 grams per pair

These GRX shifters are Ultegra-grade, with aluminium levers instead of carbon fibre on the Dura-Ace shifters. This is perfectly fine with me, especially for off-road components. The weight is similar to that of the Ultegra shifters, just slightly heavier. The weight of this GRX shifter is no issue to me, given how many benefits it has over road shifters, for gravel riding.

This can be considered the second generation of road hydraulic shifters from Shimano, and has been greatly improved from the first generation in terms of size and weight.

Rubber cover material is TPS, which has been proven to be durable and weather resistant. Not so stretch resistant though, from my experience of loose rubber covers.

Bleeding port is located at the top, in the middle of the shifter, similar to the road shifters.

Di2 ports are located at the side, in a rather compact manner.

Here you can see the high pivot location, and the servo wave cam located below. Also, note the additional Di2 button located at the top, on the side of the hood.

Other side of the shifter, with the rubber cover pulled back.

Here is the servo wave cam, which increases the brake ratio throughout the braking stroke, increasing brake power when the brake pads are contacting the rotors.

The lever reach can be adjusted from the top with a Size 2 Allen Key.

The free stroke can also be adjusted from the side, near the top of the hoods. I always set it to the minimum free stroke, for quicker brake engagement.

From what I see so far, these new GRX shifters will suit the Cervelo Aspero gravel bike really well. With the tall hoods and strong ribs for secure grip, one-finger braking for scrubbing speed while on the hoods, well-shaped levers for ergonomic braking, and servo wave for powerful braking performance, I can't wait to see how it improves my gravel riding experience over the current road shifters!