mfgillia

After taking a few decades off from cycling, a few months ago I purchased a new gravel bike, a much loved Ribble CGR SL, and started riding again mostly on paved, relatively flat bike paths. As my fitness improved, I noticed I spend the majority of my time on the 3-4 smallest cogs and yearn for a bit higher gearing especially during workouts focused on maintaining increasingly higher watts over longer durations.

Checking out Shimano's website I see I can swap the front chainring from 40 tooth to 42 tooth but that doesn't seem like too much of an increase to make a meaningful difference. So was wondering if anyone has experience successfully using a 44 tooth chainring with this groupset on the stock SLX M7000 11-42 tooth cassette? - Much thanks for the help.

rosefarts

I ran a 44x11-46 setup on SRAM before I switched everything out for 10 tooth dreams.

It worked fine once I got chain long enough.

Why wouldn’t it also work with shimano? Especially considering that you’re only looking to run 11-42.

Just gotta make sure the chain is long enough.

mfgillia

Yep, moving most of the gears down one tooth ending in 10 would probably be ideal for me based on where I'm riding these days. Not sure if that's possible either though.

Badger6

I'm running a RX817 with a 10-42 cassette and a 46T chain ring. It has the same cage as a the RX812 (mechanical).

That said, because the 1x RDs are designed for 1x operation, they will work with whatever size chainring you run, as long as you get the chain sized properly (as stated above). Using a 10-42 cassette however, is not within the stated specification either derailleur, but it works just fine, it is only one additional tooth in terms of capacity.

trailangel

Huh?

ETA: I see Sram calls some of theirs 1x and 2x, but Shimano does not.

How would the bike know?

Badger6

It's your drivetrain that will know.

RD capacity will be limiting factor. The "2x" RDs in the GRX line have a 40T capacity, with max cog at 34T...a decidedly 2x specification. The "1x" RD has a capacity of 31T (I run mine with 32T), and a max cog size of 42T. Please note, when I say "max" I am reiterating the Shimano published spec. The RDs can be made to work a little outside of these published spec's.

mfgillia

Oh - awesome! So in theory I should be able to run a 10-42 cassette with a 42T or 44T chain ring without too much difficulty. What's the 10-42 cassette you're using? Shimano doesn't appear to make one.

mfgillia

Much thanks for the info - I'm now seriously considering trying a 42 or 44 tooth front chain ring with a 10-42 cassette per Badger6's feedback.

Badger6

Not in theory, in practice. It definitely works.

SRAM XG1175. It rides on an XDR Driver with a 1.85mm spacer behind it for the correct spacing on the driver, since it is a MTB cassette on a road driver (my wheels are DT Swiss, so I just pulled off the Shimano Hyperglibe, aka HG, driver, and slipped the SRAM XDR driver on). It required me to do nothing to the setup otherwise. The RD is more than capable of wrapping of the "extra" tooth of range.

msu2001la

I'm running a 1x 44t front ring with a GRX810 rear derailleur. I'm using an 11-34 out back.

Should be no problem with GRX600.

mfgillia

Much thanks - based on your info I was putting together a shopping list for the SRAM cassette, Shimano spacer, Hunt XDR adaptor and then started searching around for the 42 or 44 tooth front chainring and ran into the Wolf Tooth GRX chainring options. So now thinking I'll first try just replacing the front chainring with their GRX 44 or 46 tooth chainring and then see how that goes.

mfgillia

I could see eventually going down a similar path and changing the cassette from 11-42 to 11-34 too if I end up sticking with riding mostly on flat paved roads. Which cassette are you using with the GRX810 rear derailleur?

msu2001la

I have a few that I use. The 11-34 is a Shimano Ultegra, and I also use 11-32 which is a SRAM Force cassette. Now that I think about it, I only use the 11-32 with the 44T ring, and I don't think I've ever tried the 11-34 with that one. I don't see why it would be a problem, but I'm not sure about chain length.

I also run a 40T ring during fall/winter/cyclocross. I swap to the 44t for summer when I'm riding more road and faster gravel. I don't have to change the chain length when swapping between the 40T and 44T rings. I think the GRX 810 rear derailleur is limited to 34T max cassette size, otherwise I'd probably just run the 44T year round and use something like an 11-42 cassette when I needed more range.

mfgillia

Oh, I see. So your GRX rear derailleur is different than mine (RD-RX812) and guessing was intended for 2x setups. So just to double check... do you foresee any issues running a 44 tooth front chain ring with my existing 11-42 cassette and rear derailleur? The 44 is technically two teeth higher than the stated limited but as Badger6 pointed out Shimano tends to be conservative and many have successfully exceeded the specs without experiencing additional problems.

Badger6

The size of the front chainring on a 1x setup is a non factor. Total drivetrain capacity is determined by the difference between the largest and smallest cog on the cassette and the difference between the chainrings (which is exactly 0 teeth on a 1x). The GRD RD812 is spec'd for 31t of capacity, and as I stated above, is no different than any other Shimano RD, it is spec'd conservatively. In theory that RD was designed to work with 11-40 (29t) and 11-42 cassettes (31t). However, exceeding the capacity by 1t is doable, which allows running the SRAM 10-42 cassettes that ride on an XD driver, and I can attest that it works in the real world on real gravel. Again, because you are running a 1x system, you can run any size chain ring you want to run, because there is no additional capacity to be "wrapped" by the RD.

In a 2x system this becomes a factor. For instance, the GRX RD810 has a maximum total capacity of 40t, and a specified ability to be able to wrap 17t of front tooth difference (leaving 23 teeth for the cassette, and is the difference of the non-series Shimano 11-34 cassette). Again, on that RD, I've seen folks run a SRAM 11-36 cassette (HG spline) thus shortening the low end a bit, but with a 46/30 chainset gives a total capacity of 41t, and with a 48/31 chainset a total capacity of 42t. In both instances, the only thing that effectively needs to be done, is turn the B-screw in a few turns to clear the larger low cog, assuming the chain is properly sized big/big.

mfgillia

Thanks! That's pretty much precisely what I couldn't figure out and understand well from researching online - i.e., calculating drive train capacity on a 1x setup and how/if the front chain ring affects the capacity. So in my case capacity isn't affected by the size of the front chainring. If I keep with a 11-42 cassette for now and add a 44 or even 46 tooth front chainring then I'm still within specs. Later if I switch to the SRAM 10-42 cassette then that's only an additional tooth so its fine but will require that spacer and XDR hub adaptor otherwise should be good to go.

Badger6

Precisely!

mfgillia

I wanted to thank you for all your help. I did go ahead and get that 46 tooth chainring replacing the 40. Had to get a new chain too but otherwise worked out perfectly. Didn't require any adjustments to the rear derailleur and seems to actually shift a bit smoother than using the stock chainring and chain for some reason. Much thanks!

Badger6

Welcome the big ring 1x world, mfgillia. "We get there faster!"

msu2001la

The differences between the RX RD-RX810 and RD-RX812 are a bit confusing. My understanding is:

RD-RX810 = 1x or 2x and works with road cassettes up to 11-34T. The max gap between 2x front chain rings is 17T.
RD-RX812 = 1x only and works with MTB cassettes up to 11-42T.

Both have clutches in the RD that can be switched on/off. (And for the record, I just leave mine on all the time)

The stated limits by Shimano are for the rear cassette, not the front chainring size.

Badger6

Yes, in a 1x.

2x RDs will have three "limits": max/min large (low) sprocket, Total capacity and front chainset capacity.