jonathanf2

I'm currently running full GRX 400/600 10 speed on my gravel bike. I've read either derailleurs should be able to shift GRX 10/11 speed STI shifters (though not advertised). I've been looking at maybe swapping out my GRX400 RD to the more beefier GRX810 RD. Would there be any performance or durability advantages making the swap or should I just stick with the GRX400 RD from a practicality standpoint? Thanks for any suggestions!

jfranci3

Just the 100gr. I don't think there's a cable pull / shifter compatibility issue. If you're doing 1x the 812 would be the better buy all the way.

This leads me to believe the RX800 series won't work here.
https://brainybiker.com/can-an-11-sp...e-and-shifter/

jonathanf2

From this previous thread I read, it seems current 10 speed GRX/Tiagra has 11 speed cable pull:
https://www.bikeforums.net/bicycle-m...-cassette.html

So in theory shouldn't the 11 speed stuff work fine on the 10 speed shifters/cassette?

HTupolev

Yes. Shimano's original 10-speed road groupsets used the same rear derailleur actuation as 8/9-speed. But starting with Tiagra 4700 in 2015, new Shimano 10-speed road uses the same rear derailleur actuation as 11-speed road. The 10-speed cassette spacing has remained constant.

The RD-RX400 is roughly the same part as the RD-RX810 but at a lower quality tier, with the primary consequence being higher weight. One of my friends has a gravel bike with a 2x11 drivetrain that was originally set up with an RD-R7000-GS. When it got damaged, he replaced it with an RD-RX400, and the new part indexes on the 11-speed drivetrain just fine.

jfranci3

It's not clear whether the GRX 400 is using the MTB or road cable pull in my mind. I thought the GRX800 long cage was a MTB part.

Looks like the GRX400 is Tiagra 4700+ compatible, so you're OK then https://productinfo.shimano.com/#/co...-454&cid=C-453


https://bike.bikegremlin.com/1278/bi...compatibility/

This agrees with what was said above.


I don't think getting the 800 would change your life - it's got slightly nicer jockey wheels I think the GRX400 should be able to reach 11sp, so it doesn't prevent your from going 11sp in the future. You can't use the 812 RD for the wider range 2x, so no reason to go there.

jonathanf2

I wouldn't mind cutting a bit more RD weight going with the GRX810 RD and the derailleur appears to be more heavy duty. Since I'm running 2x, I have no plans to go with the GRX812. So far I'm okay with 10 speed, since indexing the cassette is much more forgiving and quality chains are a bit cheaper. The only thing I don't like about 10 speed is finding lightweight cassettes. It seems 11 speed has more cassette options in this regard especially going aftermarket, but then again GRX400 10 speed STI are a bit more affordable.

jfranci3

it's not more or less heavy duty. The RX400 has a steel cage, which requires less material. If you look at the parts diagram... basically the same thing otherwise. The main unit is probably the same aside from the paint.
https://dassets.shimano.com/content/...RX810-4589.pdf
https://dassets.shimano.com/content/...RX400-4576.pdf

I think a lot of the look has to do with the angle they shot it at, which was not an accident. The more expensive one is in the 11t cog, while the cheaper one looks bigger in the 34t position.

GRX800 on bike
https://images.immediate.co.uk/produ...-5-4f7fbd4.jpg

400 on bike - to my eye, it looks like just the cage (steel), pulleys, 'beauty plate', paint, and pivot bolt finishes are different. The pivots, mech, and springs look the same. The pulleys perform the same, the 800 ones will just last longer and they're $11.
https://images.immediate.co.uk/produ...18-b3803cc.jpg

msu2001la

Shimano's website shows the GRX 400 as 303g, and the GRX 810 as 255g.

48g difference.

The GRX 810 retails for $120. I can't imagine there's any tangible difference in performance between these two parts beyond weight.

jonathanf2

I have another question. My GRX 400 rd can do 11-36t in-spec, while the GRX 810 does 11-34t. I'm currently running my GRX 400 rd with a GoatLink and a Sunrace 11-40t 10 speed. In this particular case, am I better off sticking with the GRX 400? Thanks!

HTupolev

I think that the difference in compatibility spec between the two derailleurs is a consequence of product lineup more than any actual design differences. I know several people running RD-RX810 on multi-ring setups with cassettes 11-40 or wider and getting reasonable drivetrain behavior. I doubt that the upgrade would create problems, although at the same time, I also doubt you'd see much benefit outside of a ~50g reduction.

Racing Dan

Cant say if it will make a worthwhile difference replacing the RD, but one difference to Shimano RDs is the pulley wheels tend to be somewhat nicer in the better models. That is a ceramic bushing in the guide wheel and a ball bearing in the tension wheel vs. metal and plastic bushings in the cheaper models. I recently replaced my worn out Tiagra pulleys with some 10s Ultegra level wheels and shifting did improve a bit.

jonathanf2

Just a quick update. I decided to swap out my GRX 400 RD for a 105 R7000 rear derailleur which I had laying around. Shift indexing works perfectly on my GRX 400 shifters, GRX 46:30t crankset and 10 speed 11-36t cassette + chain. I had to remove 2 links on the chain, but everything works. I cut 100g with the swap, but lost the clutch mechanism. I'll see how it works with this setup. I usually do road, dirt climbing and bumpy downhills. So I'll see if I miss the clutch or not. Though sometimes I forget to engage it, so maybe not!