I had previously modified the Cervelo Aspero from a 2x11 speed drivetrain to a 1x11 speed drivetrain. The gear range was reduced, as the largest cassette that is supported by the GRX Di2 rear derailleur RD-RX817 is limited to 42T.
Although the gear range is well suited to a gravel bike, at 24 to 93 gear inches, I have always wanted a lower gear for steep climbs. This was not possible on the GRX 11 speed drivetrain, until I came across some third party options.
Garbaruk makes conversion kits to expand the gear range, through the use of a longer rear derailleur cage and larger cassettes. Merely changing to a longer cage is not enough, as the movement of the guide pulley needs to accommodate larger sprockets as well.
In this comparison between GRX rear derailleurs RX815 and RX817, you will notice that the front single RX817 rear derailleur has an offset guide pulley to match larger sprockets.
For this upgrade, I got the Garbaruk rear derailleur cage and also their own cassette. Although there are other wide range 11 speed cassettes, such as from Sunrace, the Garbaruk version is the lightest.
Garbaruk cassette, lightweight but very pricey!
11 speed cassette with a gigantic 11-50T gear range! Fits on standard freehub bodies.
Packed in a large pizza-sized box, including the lock ring.
Skeletal design for minimum weight!
Lots of machining done to minimize the weight of this cassette, more details below.
Sprocket Sizes: 11-13-15-17-20-24-28-32-36-42-50
From 11-17T, the spacing is common among wide range cassettes. However, there is a large gap from 17T to 20T, and from 20T to 24T. There is usually a 19T and 21T sprocket, instead of a single 20T sprocket. After that, the gear spacing from 24T to 50T is also commonly seen.
Comparing the Garbaruk 11-50T cassette with the XTR M9000 11-40T cassette and Dura-Ace R9100 11-30T cassette.
Weight of 11-50T cassette plus lockring is just 324 grams which is very light for the size!
The XTR 11-40T 11 speed cassette weighs exactly the same at 324 grams, but it is much smaller. Also, the XTR cassette uses 6 titanium sprockets to lower the weight.
Garbaruk lockring looks a bit different.
Aluminium lockring weighs 4 grams which is standard.
Comparing with the XTR lockring.
Same thread length and design, so nothing special here.
The cassette is mostly hollow! The first 10 sprockets are all machined from 1 piece of steel, with plenty of cutouts to save weight.
Only the first and last sprockets have splines to engage the freehub body!
Last sprocket is engraved to show that this is a 11 speed cassette with 50T sprocket.
I assume that a hollow construction such as this would be easy to clean, as any dirt can be flushed through easily.
Chamfers around the black aluminium cutouts, and minimum connection between the steel sprockets.
The 50T sprocket is made of aluminium and screwed onto the rest of the sprockets. It is also available in a variety of colours to suit your preference.
Sand blasted finish on the steel sprockets look good.
Lots of small connecting bridges between the different sprockets. Reminds me of the Campagnolo Ekar 13 speed cassette!
Small chamfers and teeth shape to help shifting performance.
This Garbaruk 11-50T cassette looks really high quality, with the nicely machined parts and well finished design. It is also one of the lightest, if not the lightest, 11 speed 10-50T cassette.
In fact, it is lighter than the 11-42T cassette that it will replace, allowing me to reduce the Cervelo Aspero gravel bike weight and expand the gear range at the same time!
More posts on the Garbaruk rear derailleur cage, as well as the completed upgrade coming soon.
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