40 SLX Cassette on Ultegra R8000 / RX

[cbdcaffie]

Based on the findings of a guy that posted his video on Youtube, it gave me the confidence to change the short cage Ultegra derailleur to a long cage RX version on my Cannondale Slate, and slap on a 40 SLX cassette.

The maximum cassette size stipulated by Shimano for Ultegra is a 34 (Ultegra).

I desperately needed this conversion to work - the standard cassette that came with the bike was a 28 which combined with 52/36 chain rings offered many ratios, but none favourable for the type of climbing and distance which I have in mind. My local gravel route has many 20% plus gradients.

Thankfully the conversion seems to be a success, with no issues when changing up and down through the cassette under any circumstances. The setup also works perfectly under load.

The biggest surprise perhaps is that the chain length required still allows me to run small/small and big/big combinations. Time will tell if any flaws show when the setup is worn, but honestly its hard to see why it shouldn't wear and function normally.

My only alternative to this would have been a full groupset change to Sram Force which would have been monumentally expensive, and would not have given me the best of both worlds in terms of ratios - I ride on the road quite a bit with the bike.

 

Hopefully this post helps out those either stuck with a Shimano setup on their gravel bike, or those looking for more ratios on their current Ultegra / 105 setup. I would be cautious though, I think that this setup may be sensitive to chain stay length - This is only 405mm on my large Slate. 

 

Here is a link to the video for reference - 

 

I can post pics if anyone wants to see the finished product - It looks quite OEM

 

[Schnavel]

Just realised that we are discussing mechanical and not di2 so my original comment was invalid.

 

Any idea if a XT or XTR derailleur would have worked? Or does it have a different pull ratio to a road shifter?

[lechatnoir]

Thanks for this! It's far simpler to spin fast and go slowly up a monster climb than grind up painfully. and still go slowly...

 

I'm still working on upgrading my legs, but this will be a good option too.

 

FWIW, I've looked into the Goatlink-thingy that extends the hanger, but will have a crack at the cassette on its own first

[cbdcaffie]

Just realised that we are discussing mechanical and not di2 so my original comment was invalid.

 

Any idea if a XT or XTR derailleur would have worked? Or does it have a different pull ratio to a road shifter?

 

Unfortunately it has a different pull ratio.

[cbdcaffie]

Thanks for this! It's far simpler to spin fast and go slowly up a monster climb than grind up painfully. and still go slowly...

 

I'm still working on upgrading my legs, but this will be a good option too.

 

FWIW, I've looked into the Goatlink-thingy that extends the hanger, but will have a crack at the cassette on its own first

 

I looked into the aftermarket Roadlink, but part of me felt that this was a hack. I was intent on finding an off-the-shelf solution.

[Martin PJ]

I have used a Chinese version of a goat link on a couple of bikes, it is very cheap (like 2 dollars) and works well to give you a bit more space between cassette and derailleur.

The Ultegra Rx is a must if you ever ride in muddy rainy races. At Berg 100 this year I saw gravel bikes having to stop and wash their chains in puddles with their normal derailleurs, chain suck was so bad.

[PeterF]

I looked into the aftermarket Roadlink, but part of me felt that this was a hack. I was intent on finding an off-the-shelf solution.

Running a MTB cassette with a road derailleur is also a hack, the Roadlink just relieves the stress off the derailleur.

[cbdcaffie]

Running a MTB cassette with a road derailleur is also a hack, the Roadlink just relieves the stress off the derailleur.

 

Yes, indeed. Not sure about the stress on the derailleur, but an aftermarket appendage didn't appeal to me.

Time will tell if my setup works in the long term.

[cbdcaffie]

Happy to report to those interested that I have now run this setup on my Slate for over 1,000km with no issues whatsoever and no signs of any sort of unusual wear.

 

The setup works perfectly on 11 through to 40 on both 36 and 52 chain rings. If you were tentative about such an upgrade, I say fear not. The only thing that I stress is that you consider chainstay length.