Couple of Quick Questions About Shimano GRX...

[XXtwindad]

I want to go 2x on my new build.

1) I thought they had an 11-36 cassette, but I don't see it advertised.
2) Is the RX812 (max low 42 tooth) compatible with a 2X? If not, which derailleur do I run a 40t cassette with?

Thanks.

[eddief]

I think 36 tooth 11 cassette available from SRAM, not Shimano.

Watch this guy do 11-40.

https://www.youtube.com/watch?v=wNeYYM9_aeM

I want to go 2x on my new build.

1) I thought they had an 11-36 cassette, but I don't see it advertised.
2) Is the RX812 (max low 42 tooth) compatible with a 2X? If not, which derailleur do I run a 40t cassette with?

Thanks.

[Clean39T]

I want to go 2x on my new build.

1) I thought they had an 11-36 cassette, but I don't see it advertised.
2) Is the RX812 (max low 42 tooth) compatible with a 2X? If not, which derailleur do I run a 40t cassette with?

Thanks.

I'm putting 11-36 w GRX 2x Di2 RD on my Ellis mated to 31/48 up front - will report back if it seems like there's capacity to go to 40. I can't imagine climbing anything that requires a 31/40 low gear though......can barely imagine anything I need a 31/36 for.....but it seems worth trying.

[eddief]

interested to hear results.

I'm putting 11-36 w GRX 2x Di2 RD on my Ellis mated to 31/48 up front - will report back if it seems like there's capacity to go to 40. I can't imagine climbing anything that requires a 31/40 low gear though......can barely imagine anything I need a 31/36 for.....but it seems worth trying.

[XXtwindad]

I think 36 tooth 11 cassette available from SRAM, not Shimano.

Watch this guy do 11-40.

https://www.youtube.com/watch?v=wNeYYM9_aeM

Exactly what I was looking for. Thanks.

[XXtwindad]

I'm putting 11-36 w GRX 2x Di2 RD on my Ellis mated to 31/48 up front - will report back if it seems like there's capacity to go to 40. I can't imagine climbing anything that requires a 31/40 low gear though......can barely imagine anything I need a 31/36 for.....but it seems worth trying.

Should've specified. Mechanical shifting. Also, we have 15% grade "gravel" here in the Bay Area. More than happy to have any "bail out" gear short of a motor.*


* not that there's anything wrong with that :)

[prototoast]

I can't imagine climbing anything that requires a 31/40 low gear though......can barely imagine anything I need a 31/36 for.....but it seems worth trying.

Come visit this neck of the woods some time and you'll see. The fire roads around here are steep and long. I usually opt for my rigid mtb just because I have 32/50 gearing on that. With my 36t cassette in my gravel bike, I'm walking a lot more segments.

[Clean39T]

Should've specified. Mechanical shifting. Also, we have 15% grade "gravel" here in the Bay Area. More than happy to have any "bail out" gear short of a motor.*





* not that there's anything wrong with that :)Sorry, didn't mean to sound judgy -- would love to come ride w y'all down there...

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[HTupolev]

I want to go 2x on my new build.

1) I thought they had an 11-36 cassette, but I don't see it advertised.
Not for GRX.

The chain wrap ratings that Shimano supplies for their derailleurs are usually pretty accurate. Many people choose to exceed them, but doing so *does* result in bad behaviors in one or both cross-chained areas of the drivetrain.

Max cog capacity is more complicated.
The max cog that Shimano lists for a given rear derailleur is usually the largest cog in the largest cassette that they ship in a group with that derailleur. The biggest cassette that Shimano offers in a 2x GRX800 configuration is 11-34, so that's the max cog that they list for the RD-GRX810.
Obviously you can often get a rear derailleur to clear a bigger cog, by manipulating the b-pivot screw or - if that's not enough - by using a hanger extension like a Road Link. Sometimes this can cause balkier shifting in the smaller cogs, but usually everything works out fine outside of extreme cases.
An 11-34 cassette paired to the 48-31 chainring option is already at the nominal wrap limits of the RD-RX810 derailleur, which is probably a big part of why Shimano doesn't permit a wider cassette in their specs. Plenty of people are using drivetrains that exceed those specs, though. If you do it, just choose your chain length carefully and be aware of what parts of your gearing range your drivetrain exhibits poor behaviors.

2) Is the RX812 (max low 42 tooth) compatible with a 2X?
The RD-RX812 is specifically designed for 1x applications.

This is most visible in the design of the pulley cage. When you shift to a bigger cog, the pulley cage has to let out chain, and it rotates counterclockwise (when viewed from the drive side of the bike).
On the RX812, there is a large distance from the cage pivot to the jockey wheel, so this counterclockwise rotation has the effect of lowering the jockey wheel away from the cassette. This is reasonable behavior, because you just shifted onto a bigger cog which needs the jockey wheel to be lower!
However, front shifts also affect rotation of the pulley cage. If you were to use an RX812 derailleur in a 2x drivetrain, shifting from the small ring to the big ring would also cause the jockey wheel to move away from the cogs, which can result in balkier shifting.
Obviously you don't want front shifts to affect rear shifting. Derailleurs that are designed for multi-chainring drivetrains usually avoid the issue by using a smaller distance between the cage pivot and the jockey wheel. In the case of the RX810, the cage pivot is actually concentric with the jockey wheel, so cage rotation does not affect the position of the jockey wheel at all.

Also, although the RX812 is designed to clear a bigger cog than the RX810, it actually has less chain wrap because it's not intended to wrap chain from front shifts. The RX810 is the longer-cage model.

So, definitely use the RX810 in a multi-chainring drivetrain.

I can't imagine climbing anything that requires a 31/40 low gear though......can barely imagine anything I need a 31/36 for.....
All depends on the regional terrain. There's one forest road near me that slices an extremely sharp path up a foothill, averaging 15% over a two-mile stretch. That's a bit extreme: most climbs will have half-mile or 1-mile stretches at 12% or so, but even then, I end up spending a lot of time in my 19" gear.

[joosttx]

Sram PG-1170 11x36 is what you want and compatible with Shimano 11 speed free bodies.

I have on lightly used that I would let go for $40.00 PP. https://forums.thepaceline.net/showthread.php?p=2635332&posted=1#post2635332

[Hindmost]

* not that there's anything wrong with that :)

Where are we in that picture? Wildcat canyon?

[XXtwindad]

Where are we in that picture? Wildcat canyon?

Bingo :)

I would actually use my MTB for much of Wildcat. I was trying to find pics of the Canyon Trail in Redwood Regional Park, which is the connector trail. I would use my gravel bike on that, and man, is that a steep sucker...

[R3awak3n]

I thought you were going to ask... is GRX really that ugly? which I was going to say, yes, yes it is :banana:

[weaponsgrade]

I'm running an RX800 RD, which was the precursor to GRX, 11-40 cassette, and 2x, 31/48. The RD is super stretched out in the big-big combo, but otherwise works great.

[charliedid]

I want to go 2x on my new build.

1) I thought they had an 11-36 cassette, but I don't see it advertised.
2) Is the RX812 (max low 42 tooth) compatible with a 2X? If not, which derailleur do I run a 40t cassette with?

Thanks.

GRX 10 spd advertised 11-36

I have not tried it but I am 93.5% certain 11 spd will run an 11-36

[John H.]

The GRX 812 will work great with a double- At least it will with 34-50 chainrings. Not sure about the 31-46 or whatever.

I have been using an 817 (DI2 version of the 812) with a 34-50 double and 11-40 cassette.
One of my cohorts uses the same derailleur with a 34-50 and an 11-42 cassette.

I live and ride in the same area as yourself (SF Bay area). So I ride the same steeper grades as yourself.
I am also pretty finicky about shifting performance- I would not use a setup that was a compromise.
I find the longer cage GRX derailleurs to work flawlessly with a double and a wide range cassette.

Before the GRX was available, we were using Ultegra RX- those were a compromise. The derailleur was not as robust and you had to dial the tension of the clutch way down to get it to shift well.
GRX exhibits none of that behavior. Install like a normal derailleur and go.

[Clean39T]

I thought you were going to ask... is GRX really that ugly? which I was going to say, yes, yes it is :banana:You're not wrong. A little piece of me died today when installing a GRX RD on my Rock Lobster.....but it really is the right tool for the job..

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[R3awak3n]

You're not wrong. A little piece of me died today when installing a GRX RD on my Rock Lobster.....but it really is the right tool for the job..

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I am sure, and I have heard from EVERYONE that has it, that it is excellent and function over style but man, why did they have to make those levers so damn ugly

[DRZRM]

Can't you use any Shimano 11 road lever with a GRX RD?

I am sure, and I have heard from EVERYONE that has it, that it is excellent and over style but man, why did they have to make those levers so damn ugly

[Clean39T]

I am sure, and I have heard from EVERYONE that has it, that it is excellent and function over style but man, why did they have to make those levers so damn uglyI'm using mech R8000 w the Lobster, but trying the Di2 GRX on my Ellis.. Those are less bulky at least.

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[R3awak3n]

Can't you use any Shimano 11 road lever with a GRX RD?

but then why use GRX at all really?

I'm using mech R8000 w the Lobster, but trying the Di2 GRX on my Ellis.. Those are less bulky at least.

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nice, yeah if I ever would do GRX would definitely be DI2... but I think I would go AXS over it every time, big fan of sram wireless, has been great on 2 of my bikes

[XXtwindad]

I'm running an RX800 RD, which was the precursor to GRX, 11-40 cassette, and 2x, 31/48. The RD is super stretched out in the big-big combo, but otherwise works great.

This sounds great. Ultimately, really not sure what the big hullabaloo is about with this group, especially if you want to go mechanical. Looks like the crank is the only thing I'd be interested in.

[charliedid]

The GRX 812 will work great with a double- At least it will with 34-50 chainrings. Not sure about the 31-46 or whatever.

I have been using an 817 (DI2 version of the 812) with a 34-50 double and 11-40 cassette.
One of my cohorts uses the same derailleur with a 34-50 and an 11-42 cassette.

I live and ride in the same area as yourself (SF Bay area). So I ride the same steeper grades as yourself.
I am also pretty finicky about shifting performance- I would not use a setup that was a compromise.
I find the longer cage GRX derailleurs to work flawlessly with a double and a wide range cassette.

Before the GRX was available, we were using Ultegra RX- those were a compromise. The derailleur was not as robust and you had to dial the tension of the clutch way down to get it to shift well.
GRX exhibits none of that behavior. Install like a normal derailleur and go.

This is good to hear.

[charliedid]

[QUOTE=R3awak3n;2635407]but then why use GRX at all really?

I know, sometimes I look through all the GRX stuff and think.....okay Shimano designed a new crankset.

It makes sense from a marketing perspective when developing the whole all-road/gravel category. Bikes, components, accessories, clothing etc. Soon to have gravel water bottles and saddles.

I'm okay with it.

[weisan]

If I may interject...

For gravel riding, personally I have found that it's better to have a triple crankset in front than to rely on bigger sprockets in the back...they are simply not big enough for me. I need all the help I can get up the hill....

For road, no problem, I will do 11-34 every day any day.

[saab2000]

For those who think GRX is ugly I offer this. I don't actually find it all that ugly and the levers are quite comfortable.

This is a new Zanconato and I've only recently gotten it built up. I still need to shorten the steerer but I'm playing with different options with spacers.

The levers are actually quite comfortable. It's a full GRX Di2 groupset with an 11-34 cassette.

https://live.staticflickr.com/65535/49174652393_923c4b6a44_c.jpg

[zap]

Saab. Your Zanc looks very nice. Enjoy the rides.

[Clean39T]

Saab. Your Zanc looks very nice. Enjoy the rides.+1 - GRX is utilitarian, but there's a beauty in that too...

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[R3awak3n]

For those who think GRX is ugly I offer this. I don't actually find it all that ugly and the levers are quite comfortable.

This is a new Zanconato and I've only recently gotten it built up. I still need to shorten the steerer but I'm playing with different options with spacers.

The levers are actually quite comfortable. It's a full GRX Di2 groupset with an 11-34 cassette.

https://live.staticflickr.com/65535/49174652393_923c4b6a44_c.jpg

sorry, ugly (but crank and RD I like) but thats a super nice bike. Would ride.

[Kirk007]

I guess ugly is in the eye of the beholder. Me, I smile everytime I shift it and think wow, 1000x better performance and better looking than SRAM Force 1 hydro.

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[R3awak3n]

I guess ugly is in the eye of the beholder. Me, I smile everytime I shift it and think wow, 1000x better performance and better looking than SRAM Force 1 hydro.

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Yes I agree. The sram is ugly as well. Does shift well for me, has not been a problem. I guess I just never had a problem shifting wither either of the 3 groups, they all work well so was never blown away by how a specific brand shifts. I do like e shifting. I also do like campy thumb button but as far as the chain moving from one cog to the other, they all work great and the same to me

[Gummee]

Yes I agree. The sram is ugly as well. Does shift well for me, has not been a problem. I guess I just never had a problem shifting wither either of the 3 groups, they all work well so was never blown away by how a specific brand shifts. I do like e shifting. I also do like campy thumb button but as far as the chain moving from one cog to the other, they all work great and the same to me

IME it isn't the rear shifting that's been SRAM's Achilles' heel, it's their brakes. ...and front derailleurs. Hence the 1x they're pushing.

I get to bleed some SRAM brakes on Tues. Oh BOY! can't effing wait!
M

[Pinned]

nice, yeah if I ever would do GRX would definitely be DI2... but I think I would go AXS over it every time, big fan of sram wireless, has been great on 2 of my bikes

SRAM's big advantage on a gravel bike is the ability to run the Eagle cassettes. The 10-50 is awesome and Shimano made a huge mistake by not offering a gear combo lower than 40t front w/ 11-42 rear - it's just not that low for how capable the bikes have become.

That said, the GRX brakes and ergonomics are far and away the best on the market. The updated pivot location for the lever blade is awesome and 1 finger braking from the hoods is pretty incredible.

[Clancy]

That said, the GRX brakes and ergonomics are far and away the best on the market. The updated pivot location for the lever blade is awesome and 1 finger braking from the hoods is pretty incredible.

I’ve own Ducati’s and currently have a BMW R1200R and I will tell you the brakes on my GRX feel like the brakes on my motorcycles. I was blown away. I also have a hydro Red 22 set-up, no comparison.

[Hindmost]

...1 finger braking from the hoods is pretty incredible...

I'm having a hard time picturing how this works.

[R3awak3n]

SRAM's big advantage on a gravel bike is the ability to run the Eagle cassettes. The 10-50 is awesome and Shimano made a huge mistake by not offering a gear combo lower than 40t front w/ 11-42 rear - it's just not that low for how capable the bikes have become.

That said, the GRX brakes and ergonomics are far and away the best on the market. The updated pivot location for the lever blade is awesome and 1 finger braking from the hoods is pretty incredible.

interested to try it.

As far as the gearing. I agree but also agree that sram missed out in not having any gears lower than 10-50T. They are both not thinking properly lol, they should offer something like 46T which I think is a nice in btw. I think 11-42 is now low enough and 11 is too big if the ride has a lot of pavement and you have a 40T in the front. I think this will all get rectified when GRX will go 12 speed, 10T small ring, more gear options, ect.

[Kirk007]

Sunrace 10-50 12 spd cassette on 11 speed Shimano hub and you get the range, Grx and can keep your wheels without needing yet another freehub.

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[R3awak3n]

IME it isn't the rear shifting that's been SRAM's Achilles' heel, it's their brakes. ...and front derailleurs. Hence the 1x they're pushing.

I get to bleed some SRAM brakes on Tues. Oh BOY! can't effing wait!
M

I just bleed sram not long ago, went well, was pretty easy actually. Having 2 sets of sram hydro, both etap and force the braking is great. I say similar to my old shimano but I preferes the campy I had. I felt campy had better initial bite, I really like campy hydros, they were excellent. That said, sram hydros are fine and work great