ahultin

I am looking at this groupset for a new co-motion steelhead that one of my stokers just ordered . The main advantage is the native support for up to a 42 tooth cassette. What I cant seem to locate is what post mount brake would be the best to use (flat mount is not yet an option for the steelhead). Does anyone know, Would the new xt 2 or 4 piston post mount brakes work ?

OneIsAllYouNeed

The GRX rear derailleurs aren't much different from other current offerings from Shimano and SRAM. They have a 1X version (with limited chainwrap) for 42T cogs or a 2X version for 34T cogs. The Shimano RD-M8000 (plus WolfTooth Tanpan) and SRAM GX (plus WolfTooth Roadlink) remain much better derailleurs for wide range drivetrains.

To the original question -- yes, you can mix Shimano road hydraulic levers with Shimano MTB hydraulic brakes and vice versa.

ahultin

Thank you! I completely missed the reduced chain wrap in the specs and thought it was just a long cage and short cage version.

Chris_W

I'm also interested in the new GRX group and had noticed the two derailleurs offered. Does anyone know if the "1x" version of the GRX derailleur really is limited to use on single chainrings, like SRAM's 1x derailleurs are? I'm running a 40 or 42 tooth cassette PLUS a double chainring to get the gear range that I want without any excessive gaps between ratios. Shimano MTB or any SRAM derailleurs are not options because I'm using Di2 and the FD needs to have a braze-on mount.

So, should I go with the GRX derailleur that officially gets low enough to clear the 42-tooth cog, or go with the version that is officially listed for double chainrings and hope that it can drop down low enough? Chain wrap capacity isn't so important since the Di2 sensibly blocks access to the small-small gear combos anyway. Thanks.

Darth Lefty 

I think that you are going to see longer cages for these derailleurs just like we used to with the 10 speed MTB derailleurs.

sch

If Shimano is true to form, the GRX group stuff probably won't be available on the retail side until late fall,
maybe even early next spring. I got all hot and bothered about the Ultegra 8000, announced in April-May but
could not find any for sale on the web til Jan-feb of the following year. Ditto with the following year 105
7000 group. Annoyingly, a few months ago I finished re-uping a 2001 frame to a 7000 group but had to
use an FSA chainset to get the desired 48-32 at a reasonable price. Now GRX comes out with such......... Maybe in 3-4 yrs, when
the FSA gets long in the tooth and worn..... At least Shimano is finally making sub/sub compact CW sets.
By that time the 46/30 might be more attractive.

Chris_W

Regarding availability, at least some of the GRX cranks are already available - I received two 46-30 cranks in June that I ordered from the local importer as soon as they were announced back in April. Availability for the mechanical derailleurs is listed as July/August and the Di2 versions for September. I have a bunch of parts back-ordered to go on various bikes, so we'll see when they all arrive. Many bike brands have gravel bikes with full GRX groups listed in their 2020 lineups that should be available this fall/autumn.

BTW, the standard Ultegra Di2 front derailleur works perfectly on the new 46-30 cranks, despite the chainline being slightly wider than the derailleur was designed for and the teeth of the big ring being slightly lower. Making the necessary adjustments was no problem on two separate bikes that both have braze-on FD mounts.

sch

That is interesting but I note you are in Switzerland. Just quoting my experience with the 8000 and then 7000 series Shimano groupsets
availability in the US and applying to the GRX. OTOH Shimano has pretty much cutoff European sourced sales to the US, at least the
3-4 UK outlets that had 105 to Di2 groupos for somewhat less than US pricing until ~6-8 months ago. The year the Ultegra 8000 Di2 was
announced ( in April) a friend getting a custom bike built had to wait to December to finally get his Di2 hydraulic shifters in that groupset.
Manufacturers get stuff a lot sooner than the retail channels. I would really have liked to have the GRX on my rebuild but it is too late.

A bit of google shows that Jensen in US has 46-30 GRX cranks in stock.... (...appropriate curse words...)!

cherz

did you find an answer to your question yet ?

Tom M

This is from Redkite Prayer (https://redkiteprayer.com/2020/05/shimano-grx/):The entire review is worth a read.
Tom

Chris_W

I've setup the GRX 2x rear derailleur that's officially rated up to a 34 tooth cassette on a couple of bikes with a 40 tooth cassette without any problems - the upper cog can be adjusted low enough to clear the big cog and it stays close enough to the small cogs to give pretty crisp shifting. Maybe it won't work on some bikes with extra short derailleur hangers, but in general it should be OK. I haven't tried it with a 42-tooth cassette because the 30-40 combo is sufficient for me even when riding in Switzerlad.

bikeinxs

I put the Di2 GRX group on a single bike last fall and I really like it. Unfortunately our tandem was all built up before GRX became available. Having said that, I'm not sure I'd be happy with a 48 tooth big ring on the tandem and it turns out we can run an 11-42 cassette with our Ultegra rear derailleur. It all depends on the geometry of your derailleur hangar.

Also, GRX chainrings use a different bolt pattern. Not sure they would work with any current tandem cranksets.

tandem rider

I had Di2 Ultegra with 50-34 on front and 11-34 cassette (11 speed), fall 2018 before GRX. I wanted Di2 and it was the lowest gearing I could get on a new tandem. With a team age of 138, it was geared too high for steep hills in southern Indiana. On flats with wind or in rolling hills the front derailleur was frequently shifting between chainrings. Last July, my wife and I took the tandem to Tandems East. They replaced the cranksets with an FSA triple and Di2, XTR derailleurs to change our gearing to 52-39-30 and 11 speed with up to 11-42 Sram cassette. We chose the 11-36 which is enough gearing for us and keeps the jumps closer together. The FSA crankset also reduced the q-factor. Tandems East used our original shifter, battery, and had the original Di2 "brains" reprogramed to work. We choice to have the XTR Di2 "brain" put on as it is easier for me to use. It briefly shows what gear I am in, the charge left in the battery, and if in manual, semi-synchro or synchro shifting. The cost, and trip from Indy to New Jersey were well worth it, we are much happier with this crankset, and gearing.