Shimano GRX 48-31T, 46-30T - RX810, RX600, RX400

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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fourfa
Posts: 26
Joined: Mon Sep 26, 2011 3:04 am

by fourfa

tomh79 wrote:
Mon May 13, 2019 10:18 am
fourfa wrote:
Mon May 13, 2019 6:55 am
I've been riding this very happily with DA 9120 shifters, DA 9100 FD, Ultegra RX800 RD, FSA SL-K 46/30 crank (630g). 11-36 on my 650B x 47 gravel wheels, 11-32 on my 700C x 28 road wheels. Shifting is great. No experience with GRX yet, but I imagine it has to be the same or better?
How do you like that FSA crank? Also thinking about buying it...Easton wouuld be best I suppose but so expensive. 48/30 combo with 11-36 would be awesome. Wondering if it would work - since Shimano will release a 31/48 - if they could make it work with the new FD...they probably would have released a 30/48...
Love it. Not cheap of course, but the occasional 20% coupon at the full-retail sites reduces the sting a little, and honestly it's decent value for the weight. Two things to think about: most MTBers riding carbon cranks off-road want some sort of hard plastic boot on the crank ends, and I haven't found one that fits. How much that matters to you, depends on how hard you shred. I'm primarily a roadie with some fire roads, so I'm ok with it. Second, it comes with some plastic film to protect the arms and this is rather short-lived. I had to peel one off, about to do the other, and replace with something tougher, stickier, and with more coverage.

(If you're tempted to play with the rings like I am, I'll just note it's cheaper to buy the 48/32 crank and replace the 32 with a 30, than to buy the 46/30 crank and replace the 46 with a 48. Just sayin)

tomh79
Posts: 106
Joined: Thu Dec 27, 2018 9:50 pm

by tomh79

Thanks a lot! In the German review I posted the only flaw they found was "variing chainring stiffness" - probably meaning there are stiffer chainrings or the rings aren’t equally stiff?! did you notice anything?
Easton (670g total) would set me back about 620 EUR with BB, FSA (727g total) about 335 EUR and Rotor Vegast (716g total) about 370 EUR.

Actually, did you play around with 30/48? got it working?
Last edited by tomh79 on Mon May 13, 2019 9:57 pm, edited 1 time in total.

by Weenie


fourfa
Posts: 26
Joined: Mon Sep 26, 2011 3:04 am

by fourfa

I weighed my SLK crankset with 46/30, with spindle, no pedals no BB, at 630g. Not sure where 727g comes from?

I'm not sure what varying chainring stiffness could refer to. The flat spline-mount construction can't be as laterally stiff as the thick oversized Shimano chainsets, but FWIW I can't tell any difference with the FSA on my stiff carbon gravel bike vs the Ultegra 6800 crankset on my flexy titanium roadbike.

Haven't gotten the 48T ring in yet to play with, but I can report back when I do.

tomh79
Posts: 106
Joined: Thu Dec 27, 2018 9:50 pm

by tomh79

fourfa wrote:
Mon May 13, 2019 7:33 pm
I weighed my SLK crankset with 46/30, with spindle, no pedals no BB, at 630g. Not sure where 727g comes from?

Sorry, the weights above are incl BB (90g BSA FSA).
fourfa wrote:
Mon May 13, 2019 7:33 pm
Haven't gotten the 48T ring in yet to play with, but I can report back when I do.

That would be great!

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onemanpeloton
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Location: Edinburgh, UK

by onemanpeloton

Can anyone advise how well the RX812 (the 1x version) rear mech would work with an 11-32 cassette?

I'd like to use a 42t cassette when gravel riding and a 32t cassette when racing cyclocross. Will the mech handle this change as long as I have the correct chain length for each set up?
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ooo
Posts: 814
Joined: Sat May 21, 2016 12:59 pm

by ooo

RX812 looks like XT rear mech. I have both XT di2 rear mech and ultegra di2 rear mech, and for 1x 11-32 I prefer to use ultegra

Di2 1x setup weight is ok (with ST-R8070 shifters),
but for mechanical shifting shimano will be heavier comparing to sram cx1,
left "1x" lever is actually 2x lever with pads removed (saving just 50-60 grams) >230g (vs 119g sram cx1 left lever)
ST-R9120-R + ST-R9170-L + RD-RX812 - this 1x combo may have have better weight, not sure how comfortable it is

Image Image
'

ChiZ01
Posts: 315
Joined: Wed Jan 01, 2014 6:20 pm

by ChiZ01

that lever is for dropper post

MichaelB
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Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

It's a pity the GRX Levers weren't available sooner, so ended up going for R7020 levers to replace the munted RS505's on my Slate.

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Noctiluxx
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Location: Southern California

by Noctiluxx

I'm interested in the RX 810 2X (48-31) crankset to replace the current Ultegra 8000 on my 2019 Giant Revolt gravel bike. I assume it should be no issue?
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TonyM
Posts: 3263
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

Noctiluxx wrote:I'm interested in the RX 810 2X (48-31) crankset to replace the current Ultegra 8000 on my 2019 Giant Revolt gravel bike. I assume it should be no issue?
You will need the GRX front derailleur also (Shimano moved the chainline a bit)

ooo
Posts: 814
Joined: Sat May 21, 2016 12:59 pm

by ooo

weight info update:

373 pair - ST-RX815 (some websites reported 565g before, but that was mechanical shift sti weight)
286 - RD-RX815 (-2g)
318 - RD-RX817 (-4g)
135 - FD-RX815 (+4g)

286/284 - ST-RX810 (R/L) 2x11 (-5g)
307/306 - ST-RX600 (R/L) 2x11
307/306 - ST-RX400 (R/L) 2x10

222 - BL-RX810-L
227 - BL-RX600-L
263 - BL-RX810-LA
81.9 - BL-RX812

255 - RD-RX810 (-4g)
267 - RD-RX812 (-3g)
303 - RD-RX400
96 - FD-RX810 (+2g)
96 - FD-RX400 (+1g)
'

fourfa
Posts: 26
Joined: Mon Sep 26, 2011 3:04 am

by fourfa

tomh79 wrote:
Mon May 13, 2019 5:32 pm
Thanks a lot! In the German review I posted the only flaw they found was "variing chainring stiffness" - probably meaning there are stiffer chainrings or the rings aren’t equally stiff?! did you notice anything?
Easton (670g total) would set me back about 620 EUR with BB, FSA (727g total) about 335 EUR and Rotor Vegast (716g total) about 370 EUR.

Actually, did you play around with 30/48? got it working?
Topping this; finally got around to it after some months. Easy swap to pull the 46/30, install the 48, install the 30 to the 48. The tool is more than it should be ($30 retail). The 4 shift ramps are in the same place, same design, very little difference between them.

I'm using the DA 9100 front derailleur (with 9120 shifters), can't speak to any other. I found when setting it up originally with 46/30, there was a pretty wide band of adjustment where shifting worked OK, and a little narrower range where it worked great. With the 48/30, it's noticeably narrower and took a few iterations on the stand before it would shift reliably. I made sure to set the outer cage just about as low as it will go - the spec is 1-3mm gap to the large chainring teeth, so I set it for 1mm. On the road (did a 40mi mixed ride today) it shifts just fine when spinning easy. Under minor load, it will sometimes skip on two ramps (half a rotation) before catching on the third. I'm not planning to try it out of the saddle, ever (something that worked surprisingly well on my straight Ultegra 6800 roadie).

Downshifts are (unsurprisingly) excellent, though I did add a chain catcher at the same time after a mechanical in the moondust of Catalina Island a couple weeks ago (had to swap spindle spacers when the FD mech and limit screws packed full of dust, got an OK field repair done, except kept dropping/jamming chain after)

Overall the front shifting is better than my first 3-4 generations of road bikes, but to be sure not as good as a modern all-Shimano setup. It's nice to have a stiffer top gear again though. I think I'm going to be a big fan of the 48/30 - 11/36 setup.

PS - sorry, WW - forgot to weigh the big rings while they were both off.

tomh79
Posts: 106
Joined: Thu Dec 27, 2018 9:50 pm

by tomh79

Thanks! So you think a 105 r7000 FD could shift 30/48 or 31/48 (GRX) as well? I think I'm buying the 31/48 GRX crank but not sure if I really have to buy de derailleur as well...

weiwentg
Posts: 206
Joined: Mon Feb 09, 2004 8:16 pm

by weiwentg

TonyM wrote:
Sat Jun 01, 2019 3:33 pm
Noctiluxx wrote:I'm interested in the RX 810 2X (48-31) crankset to replace the current Ultegra 8000 on my 2019 Giant Revolt gravel bike. I assume it should be no issue?
You will need the GRX front derailleur also (Shimano moved the chainline a bit)
Shimano's official literature should say that the GRX crankset has to go with the GRX FD. Shimano did move the GRX chainline outwards by 2.5mm.

The thing is, 2.5mm is potentially within the range of adjustment for road FDs. On this thread on the Paceline forum, one person reported using the GRX crankset with a 6870 (i.e. Di2 FD), one person said they have the GRX crank with a 6700 (!) FD, and one other guy is using the disc version of the Rotor Aldhu crankset, which has the chainline moved by 2.5mm like GRX, with a CX-70 FD (Ultegra level CX derailleur, 10s era).

I might be interested in swapping in that GRX crankset if I can adjust my FD low enough. It's a braze on mount. I'm not sure there's enough space for a 46t chainring, but there may be for a 48.

fourfa
Posts: 26
Joined: Mon Sep 26, 2011 3:04 am

by fourfa

If you run out of room in your FD braze-on, there are adaptors for juniors racing (which has strict limits on how tall gearing can be) to accomodate smaller chainrings:

http://wickwerks.com/products/fit-link-adapter/

by Weenie


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