I have GRX800 on my Trek Checkpoint and can confirm that a 36 works fine. I recently used the bike a lot on gravel roads and no issues with shifting. 40 seems like it would be too large but I've never tried it.

It will work. Might need a goat link.

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Suffer Well.

Lots of people exceed spec on the RD-RX400 and RD-RX810. 11-36 will likely be no problem, chain resize and b-limit adjustment should let it work fine. 11-40 or 11-42 are common changes, but depending on the bike you may also need a hanger extender like a Roadlink DM, and you should expect the drivetrain to get pretty slack toward the small-small region.

It still works beautifully with an 11-40 cassette. 11-42 gets a little sloppy at the 11 to 13 shift. A Roadlink makes that 11-13 even worse and I wouldn't recommend it. But I will sell you one quite cheap if you think you need it.

31-34 gives you ration of 0.91.
I've yet to encounter a gravel climb where this is insufficient as a bail out gear and I've dome some serious AF gravel rides.
Why trade tight gearing and shift performance for a rarely used gear?
It's like riding knobby MTB tires when .05% of the course has some rooted muddy single track when the rest is hardpacked roads.
Choose your bike and components based on the most common use case, not the outlier use case.

If you plan to add the weight of bikepacking gear, then I could see the use for lower gearing.

There's a lot of variance in riders and riding. Someone whose gradients are 18% steeper or whose legs are 18% weaker could have just as much use for a 31-40 as you have for a 31-34. I have a .75 ratio on my gravel bike and use it extensively, and most people I ride gravel with are in a similar boat.

+1

I had 30-34 on my gravel bike and was constantly wishing for 2 more gears. Never once did I think, "man I wish I had smaller steps between shifts." In fact, I often wished I had larger steps so that I wouldn't need to shift as frenetically.

Now I use my XC MTB for climbing long, steep gravel roads, and I've been thankful many times for my 34-50. :)

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At 90 rpm, you are going 8.5 km/h with a .75 ratio.
Are you better off to walk your bike through those sections?

Yeah, today had me facing a 15+% grade at 4500 feet above the elevation where I live and train.
Was trying to hang on, cranked out 400+w for 6 minutes before I caved and bailed with my HR at 198.

I'll be very happy to have the extra gear or two.

I can verify this works, just installed an shifts perfectly on the stand. Will test it put tomorrow

I can't imagine walking tough sections will make anyone a better cyclist.

Neither will spinning.

If I'm trying to go fast, no. 8.5kph is an extremely fast pace to "walk" a bicycle up steep mountainous gradients. As long as the gearing and technicality makes pedaling practicable, it's nearly always more performant than walking, even when cycling speeds get much lower than 8.5kph.

I also think that walking a bike uphill for extended periods can get uncomfortable on the core.

OP: "Can I install a bigger cassette on my gravel bike?"

Slowtwitch: "I won't answer your question but don't bother with that, you can just walk your bike up the steep hills instead"

Yup, did this recently. I have a 48/33 up front and a 11-40 in the back. It requires a little more fine adjustment then the 11-34 or 11-36 but I had it dialed after a couple rides. I'd say go for it.

To those saying you don't need those gears...come to SLC and ride with me :D I use every bit of that range on a regular basis.

I'm curious to hear your explanation here?
If I can ride up a hill and dictate my own output, i.e. hit my target watts at a given cadence, from my experience that is what makes someone a better cyclist.

Walking up the hill certainly won't make me a better cyclist and "spinning" up it (which was never part of the discussion mind you) will certainly have more impact on bike fitness and skill then walking ever would.


Curious to see examples of those who have gotten faster on the bike by walking their bike instead of riding.

Hahaha, sounds about right

Install a road link and you can run a really big cassette on a GRX 2X set-up. That's what I am running on my Checkpoint, as some of the Epic gravel climbs here have long pitches over 15% with several 20% or more ramps. Big Gears = Big fun.

Did you have to swap to a longer chain? I using an 11-36 with my GRX and it works great. Would love to go to a 40 though.

I did, but I always use a new chain with a new cassette or chainring.

Depending on how generous you were sizing your chain for 11-36, you may well need to go to a larger chain, especially with a 4t jump, rather than just a 2t larger cassette.

Too small a chain risks ripping your RD off in the big-big combination - an expensive mistake. Yeah, you shouldn't be using that gear combo, but hey, ALL of us lose track of what gear we are in at some stage.

Perhaps buy a new chain, but see how it goes with the old one. Put it in the big ring on the work stand, but a smaller cog, and gradually work your way onto the larger cogs. If you get to the 2nd last cog, and the RD is already stretched all the way forward with little slack left, then you will need to fit the new chain. If there is sufficient slack to shift into the 40t, all good, and you can keep the new chain as a spare until the old one is worn out.

I just finished installing an 11-40 and new, longer chain on my GRX810. Works like a charm. Looking forward to having some extra gearing on my Colorado trip next month.

I didn’t bother comparing the length of the new chain vs old, but it was cheap and easy to install a new one. Great thread - definitely benefited from this one.

Now I’m going to see if I can fit the 11-40 cassette on my wife’s 105 long cage Domane.

Shimano XT 11-40 cassette?

SRAM 11-36 ?