fatboy wrote:I have made my audax bike Shimergo and was thinking of going 10 speed. I was wondering if the GRX would do triple since its capacity is close to Sora triple?
No reason why the GRX-400 shouldn't. It's now shifting the same 11-36 10-speed cassette on my tourer but with a 40,20 double. That's as much difference total as almost any triple but without the unnecessary middle-ring / stumbling-block. And it wraps ALL the chain. No 'flottant' combos, not even little and little.
I don't know why Shimano rates this mech at only 41T total (ie chain-wrap) capacity. With 107mm between pulley centres (and the same size pulleys) it actually has a longer cage than 96mm on the Deore XT SGS mech, that's rated 43T. And here it is happily handling 45T on my tourer - as one might expect from those measurements.
GRX doesn't look so useful for 11-speeders however. The 810 mech claim not to handle bigger sprockets than 34T and with only 40T wrap capacity. Of course these may also be underestimates, but since nobody gives me free stuff to test anymore, I can't shed any light upon that.
The 812 mech meanwhile, is strictly for single rings, because it achieves its tempting 42T sprocket capacity by offsetting the guide pulley from the cage pivot - so it moves further down as the cage rotates anti-clockwise, as you shift down the cassette. Accordingly this pulley will bob upwards and NOT clear a sprocket that big, if the cage arbitrarily rotates clockwise instead, as it will if you shift to a smaller ring up front.
So my advice is stick to 10-speed, fit a GRX-400 (also buy a pair of Deore XT sealed-bearing pulleys to upgrade the plain originals when they wear out) and be happy!
GRX is a recycling exercise. There are new chainsets with new chainline, new BCD and new FDs.
These are a 46/30 double effort ('600', though it matches with '400') , with the same assembly but a subtly different outer ring for 11-speed. Then a 48/31 double with hollow crank arms which is '810' level, because the crank arms are lighter.
Then there is a 1x crankset in solid crank arm 600 level, and hollow crank arm 810 level; which has 42t or 40t single ring. Supposedly these are 1x11-speed, but this is nonsense, and they would be just as good (or bad) for 1x10.
The brifters are recycled from R8020/R7020/4720 series, which are largely identical anyway.
The calipers are 100% identical to the same series of 'road' calipers (which are internally identical apart from plastic pistons on the 4720/rx400 rather than ceramic)
The RDs are three:
* RD-RX400 uses the RD-T6000 pulley cage (same part numbers). Since it's a single-sprung pivot, the cog numbers are likely fairly accurate. RD-T6000 and RD-RX400 match here 11-32 to 11-36. The T6000 part has a 47t capacity and RX400 41t, the latter reflects only the fact that there is only one matched chainset, the 46/30 double, which gives (36-11)+(46-30) = 41t, whereas the actual capacity might be something else
* RD-RX812 in fact uses the RD-M8000-GS pulley cage (82mm), and can be modded with the RD-M8000-SGS pulley cage (100mm). RD-M8000-GS was originally sold for 1x11-42t or 11-40t with 36/26 double. RD-M8000-SGS was sold originally for 1x 11x42t or more typically 11-40t with 40/30/22 triple. After the release of new cassettes, they updated these specs (not the actual RDs) such that both GS and SGS were specced for 1x11-46, 2x11-42, and SGS for 3x11-40t.
There are also third party mods for this RD for a 1x 10/11-50t cassettehttps://www.garbaruk.com/rear-derailleu ... speed.html
People also run the RX812 with a 50/34 and 11-34 cassette
* RD-RX810 is a bit different in that it uses 13t pulleys like the new MTB 12-speed stuff, but it's intended for a smallish cassette and compact chainset.
Comparing the 'road' stuff, you have in the same pull ratio:
6800/5800/4700 (11/11/10 speed but with the same pull ratio). These cages are recycled from 6700/6600/5700/5600 using the previous pull ratio. Depending on different specs you might get a 20t front triple (or double) and an 11-32t, or 16t double with 11-34t. The cage is shorter than the RX400 (80mm), but these are obviously more durable in that they lack the clutch mechanism, and are made all from metal, whereas RX400 is substantially plastic.
R8000/R7000 which are similar in construction to the GRX, but without the clutch. The cage is longer than 4700 (100mm). Probably slightly less capacity than RX400.