Better climbing on a road bike with changed bigger cassette and smaller crank?

Question

Looking for the advice of professionals. Maybe common question from a dummy cyclist, but…

Problem: I have an endurance Trek Domane SL6 2023 bike Shimano Ultegra groupset with crank 50/34t, and cassette 11/34t. Excellent bike but I would prefer easier climbing.

Goal: easier climbing, better with mixed terrain. I am okay with reducing max speed as I rarely use it. It kind making endurance more gravel.

Thoughts: want to change either crank or cassette or both.

I have:

• Wolftooth Roadlink DM
• Shimano Ultegra RX rear derailleur
• Shimano Deore XT CS-M8000 Cassette 11-speed 11/40t
• Shamano GRX FC-RX600 2x11-speed Crank 46/30. I understand I can change to Shimano Deore XT CS-M8000 Cassette 11-speed 11/40t using Wolftooth Roadlink DM.

Questions: 1. Can I change crankset from 50/34t to 46/30... the same 16t capacity… 2. Can I change both the cassette and crank? 3. Should I change to RX derailleur? It seems RX adds more “stability” to the chain

Concerns

1. Will my Shimano Ulterga shifter and front derailleur work with a smaller Shimano GRX crank?
2. Should I make my chain shorter?

Thank you!

Answer 1

If you go to 46/30, to keep good performance you should change the FD to FD-RX810, which is compatible with your current left shifter. Could it be limped along with 46/30 without changing it, maybe, but it will be far from optimal. The answer to whether you can do it is not universal between frames because it depends on whether there's room to get it as low as you want before the tail end interferes with the chainstay, which in turn depends on the BB drop and chainstay thickness and how its bends are done. Even if you can do it, there will tend to be a big gap between the cage and the big ring due to the mismatch of the intended contour, which can lead to issues with chain drop especially if the shift is rougher than ideal.

Going to 11-40t while keeping it a double isn't really practical. You'll be blowing way past the total capacity of the RD, which is the same between RD-R8000-GS and RD-RX800-GS. Cheating the total capacity a little is one thing, but you'll likely wind up with unusable combinations that you don't want to be unusable if you do this. If you really had to change the back along with going to 46-30, you might try cheating the capacity with what you have just a little and going to 11-36, likely skipping the Roadlink (if doing so works).

RD-RX800-GS has a clutch and that's the only difference with what you have. If all you're trying to accomplish is lower gearing, it won't do anything for you.

Answer 2

You would want a sub-compact crank. I think that under a recent question on this site the lack of interest of Shimano for subcompact cranks was discussed. But I cannot find the question now. The exception is the gravel GRX line. However, it is not compatible with the rest of the road Ultegra components. The chain line is different, the chainrings are farther from the frame. Also, the front derailleur must get lower. It might work, but the shifting would be compromised, but it may also not work at all.

There are road third-party subcompact cranks available (SRAM, FSA,...). They may require a different bottom bracket, but it is not a problem to just buy an appropriate one.

You can also change only a cassette and keep the rest. In that case stick to what your Ultegra rear derailleur allows. Normally, 34 is the largest allowed size but Shimano is very conservative and with some play with the B screw one can often get a larger one working.

Changing to an RX rear derailleur is not impossible, but would make more sense if you also changed the crankset and the front derailleur to GRX. The RX rear derailleur for 2x cranksets is limited to the same 34t cassettes as is Ultegra. The RX812 version allows larger cassettes, but has lower total capacity and is intended for 1x cranksets.

Fortunately, the Ultegra shifters, if using disc brakes, are compatible with the GRX ones. To be sure, check the compatibility chart.

Regarding the chain: yes, buy a new chain for any new crankset (not strictly necessary, but better) you get and adjust the length according to the usual methods.

Answer 3

Your Ultegra shifters will work. As Vladimir points out, GRX chainrings are further outboard (by 2.5 mm). I'm not sure if this makes a difference in practice. I've got 46/30 on one of my bikes, and a glitch that I've found is that a Shimano road front derailleur's sideplates have contouring that will rub on the chain when I'm in top gear (which is admittedly not very often) because it's designed for a big ring that's at least 50t.

Whenever you're replacing a cassette or chainring, you should get a new chain.

If you change to an 11-40 cassette in back, you'll need a rear derailleur that has 45t of capacity. That's a lot. I believe your RX derailleur has 39t of capacity. The Roadlink doesn't increase total capacity, it just moves the derailleur lower to accommodate a bigger sprocket.

The RX derailleur is clutched, which maintains chain tension when riding over rough surfaces, but shouldn't really make a difference if you're staying on the road.

Answer 4

So, finally, I am cycling outdoors and have a feedback

Tested option of Wolftooth Roadlink DM + Shimano Deore XT CS-M8000 Cassette 11-speed 11/40t

It is really an excellent option to start with. I would highly recommend it to non-professional not-young randonneuring riders who look for comfortable long-distance riding with easier climbing in geographies with flat terrain or <8% hills. Pros: relatively inexpensive, superb shifting quality, significant improvement in climbing. 8% was good, and 6% - was easy. Cons: 10% incline continued to be a challenge, but of course, it was much easier.

I still consider changing a crankset to Shimano GRX FC-RX600 2x11-speed Crank 46/30 and FD to SHIMANO GRX FD-RX810 Front Derailleur 2x11-speed. based on the compatibility chart it is possible.

I thought about using Shimano GRX FC-RX810-2 Crankset 2x11-speed - 48/31 Teeth. But I am not sure if it is compatible with my Praxis, T47 threaded, internal bearing bottom bracket.

I understand that max speed potential will decrease but I never pedal faster than 30 -35 km/h, I think the combination of 46Front and 11Rear and its 40 km/h potential is a good option.

Answer 5

thank you very much. very clear.

based on the answers I think the optimal decision would be to change the cassette, using Roadlink DM ad the chain as well. Just found out that Shimano recommends adding a 1.85mm sprocket spacer. At least this is the cheapest reversible option approx. 100$

I will have to change the FD, Crankset and this will be an additional $150. Changing to GRX might be an option but at a later stage. Yes FD is in the lowest position which might limit the experiments :)

Answer 6

ok, changed the crankset as well. now have 30-46 and 11-40 Happy, nothing to add! 45 km/h is my max pedaling speed but I don't need more. Climbing became easier and I like it! all in all, a good decision for me!