Friday, July 23, 2021

Focus Paralane: Wide Gear Range with Sunrace RX1 Cassette

After I installed the Wolf Tooth Roadlink DM onto the Dura-Ace rear derailleur, the capability of the rear derailleur has theoretically increased. It should now be able to work on larger cassettes, beyond the recommended 30T largest sprocket.

I plan to install the Sunrace RX1 11-36T cassette onto the Focus Paralane, to increase the gear range for better climbing. This cassette comes from the Cervelo Aspero gravel bike, where I used it for gravel riding.

The previous cassette is 11-32T, which is good but I still need one more lower gear for steeper slopes. For 11 speeds, I believe this is the widest cassette that I can go, before the gear steps get too big for comfortable road riding. Remember, this Focus Paralane will also be my primary road bike, as I have installed all my best road bike components on it.

With the rear derailleur modified, the next step is to install this 11-36T cassette and see if it all works well together.

To recap, this 11-36T cassette from Sunrace weighs 351 grams. Not so lightweight, but still acceptable.

A 1.85 mm spacer is needed behind this cassette, as I will be using it on a 11 speed freehub body.

The red coloured lock ring and cassette spiders are the trademark of Sunrace cassettes.

Sunrace cassette installed on the Ascent Zenith Elite carbon wheelset! This wheelset and tires are probably one of the fastest available.

Here is how it looks at the lowest gear, with the rear derailleur fully stretched.

I purposely used a slightly shorter chain to provide higher chain tension, which will reduce chain slap when in the smaller sprockets. In this case, the rear derailleur cage is not over-stretched, so it is OK.

B-tension of the rear derailleur is adjusted to minimize the distance between the guide pulley and the 36T sprocket.

Still plenty of bolt length available on the B-tension screw, as this Roadlink can actually support up to 11-42T cassettes.

Chain position set in the middle of the cassette.

I used a cable tie to fix the Di2 wire to the Roadlink, so that there is no stray wire that can catch on objects.

With this Wolf Tooth Roadlink DM, the Dura-Ace rear derailleur can be used on the 11-36T cassette.

A front single drivetrain provides a clean setup and works for me, as long as you choose your gear ratio and gear range carefully.

After extensive testing, I am happy to report that this wider range 11-36T cassette works well for me. I get to keep all the high gears for relatively fast road riding, and yet I gain one additional low gear for climbing steeper slopes. I lose the 14T that was on the 11-32T cassette, but the jump from 15T to 13T is not an issue.

New gear range with 11-36T cassette

Shifting across all gears is good, except for the most outward gear, which is when I shift from the 12T to the 11T sprocket. For this shift, if I maintain high chain tension while shifting, it will not shift smoothly outwards to the 11T. Instead, the chain will remain on the 12T sprocket, while the rear derailleur has already moved to the 11T position. This leads to chain rubbing sound, until I perform the shift again.

To solve this, I need to reduce the chain tension by pedaling softly for a split second, during this outward shift. This will allow the chain to shift outwards from the 12T to the 11T smoothly with no delay. Most likely this issue is due to the larger distance between the rear derailleur guide pulley and the 11T sprocket, as the whole rear derailleur has been moved downwards due to the Roadlink.

I expect that this problem will become more severe if an even larger cassette is used, such as 11-40T or 11-42T cassette. Therefore, if there is a need for a larger cassette, just change to a MTB or gravel rear derailleur instead, like the Deore XT or GRX versions.

Other than this issue, there are no other shifting problems with this cassette and rear derailleur. Seems that this Roadlink is actually pretty useful and not just a gimmick.

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