Shimano GRX subcompact crankset and FD upgrade report
#1
Bike Fun Fanatic
Thread Starter
Join Date: Jun 2007
Location: Portland, OR
Posts: 650
Bikes: 2020 Trek Checkpoint ALR5, 2012 Surly Disc Trucker
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 16 Times
in
7 Posts
Shimano GRX subcompact crankset and FD upgrade report
I knew within the first few rides that I was going to want to switch to a subcompact crank on my 2020 Trek Checkpoint ALR5, which comes stock with a 105 R7000 drivetrain and compact 50/34 crank. I've got a BB86.5 bottom bracket that I didn't want to fiddle with, so I waited for the new GRX components to become available.
BikeTiresDirect had my desired GRX 600 46/30 crank in 172.5mm available, as well as the (braze-on) GRX 810 front derailleur, so I jumped almost as soon as they arrived in stock and installed them last night on my bike (with a Dura-Ace FD braze-on to clamp-on adapter).
After my first commuting ride this morning, I can say so far so good! The lower gearing makes the big ring my primary ring most of the time now, and I only removed 1 link from the chain rather than 2 to make sure I didn't go too far when shortening the chain, since I'm likely to end up cross-chained in the big-big combo every so often.
I believe the GRX crank has a slightly wider q-factor than the 105, and I may now have enough room to reinstall my Wahoo cadence sensor on the back of the (non-drive) crank. Previously, that wasn't an option due to the tight clearance with the chainstay. However, one thing that surprised me is the ultra-narrow clearance between the chain and the drive-side crank when in the big chainring/smallest cog combo. There's barely a mm there, and I could no longer use one of those plastic protective boots that you can get for the tips of your crankset. This is no doubt due to the fact that the GRX crank and FD move your chainline outward 2.5mm.
Here's the final result:
If you're looking to do this upgrade, I found these YouTube videos to be very clear and helpful when it comes to crank replacement and setting up the new FD:
How to Remove & Install Shimano Cranks:
Shimano 105 R7000 Braze On Front Derailleur Fitting Guide:
Now go forth and climb great things!
BikeTiresDirect had my desired GRX 600 46/30 crank in 172.5mm available, as well as the (braze-on) GRX 810 front derailleur, so I jumped almost as soon as they arrived in stock and installed them last night on my bike (with a Dura-Ace FD braze-on to clamp-on adapter).
After my first commuting ride this morning, I can say so far so good! The lower gearing makes the big ring my primary ring most of the time now, and I only removed 1 link from the chain rather than 2 to make sure I didn't go too far when shortening the chain, since I'm likely to end up cross-chained in the big-big combo every so often.
I believe the GRX crank has a slightly wider q-factor than the 105, and I may now have enough room to reinstall my Wahoo cadence sensor on the back of the (non-drive) crank. Previously, that wasn't an option due to the tight clearance with the chainstay. However, one thing that surprised me is the ultra-narrow clearance between the chain and the drive-side crank when in the big chainring/smallest cog combo. There's barely a mm there, and I could no longer use one of those plastic protective boots that you can get for the tips of your crankset. This is no doubt due to the fact that the GRX crank and FD move your chainline outward 2.5mm.
Here's the final result:
If you're looking to do this upgrade, I found these YouTube videos to be very clear and helpful when it comes to crank replacement and setting up the new FD:
How to Remove & Install Shimano Cranks:
Now go forth and climb great things!
Last edited by zpl; 08-16-19 at 01:19 PM.
Likes For zpl:
#2
Expired Member
Join Date: Jun 2007
Location: TN
Posts: 11,507
Mentioned: 37 Post(s)
Tagged: 0 Thread(s)
Quoted: 3657 Post(s)
Liked 5,393 Times
in
2,738 Posts
Good report, thanks!
#3
- Soli Deo Gloria -
Join Date: Aug 2015
Location: Northwest Georgia
Posts: 14,779
Bikes: 2018 Rodriguez Custom Fixed Gear, 2017 Niner RLT 9 RDO, 2015 Bianchi Pista, 2002 Fuji Robaix
Mentioned: 235 Post(s)
Tagged: 0 Thread(s)
Quoted: 6844 Post(s)
Liked 736 Times
in
469 Posts
Agreed. Great post.
This is the first I've heard about anyone swapping cranks and FD from Shimano road to Shimano gravel. Congratulations.
The doily is a nice counterpoint to the gravel cranks too. Kudos on the photography.
-Tim-
This is the first I've heard about anyone swapping cranks and FD from Shimano road to Shimano gravel. Congratulations.
The doily is a nice counterpoint to the gravel cranks too. Kudos on the photography.
-Tim-
#4
Senior Member
Join Date: May 2003
Location: Mountain Brook. AL
Posts: 4,002
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 303 Post(s)
Likes: 0
Liked 136 Times
in
104 Posts
Thanks for the followup. I wish I had known about the GRX cranks when I redid my 2001 Ultegra triple 9spd to an 11 spd subcompact about 10 months ago.
Only 48/32 crank I could find under $200 was the FSA. GRX would have been a better and significantly cheaper choice.
Only 48/32 crank I could find under $200 was the FSA. GRX would have been a better and significantly cheaper choice.
#5
Senior Member
Don’t kick yourself - grx was only announced a few months back and the components are just now trickling in. This thread is the first real-world report I know of someone getting their hands on grx.
#7
Senior Member
It's been so long since I looked it up, I can't remember if the instructions come with the chain or the rear derailleur, but I typically wrap the (new) chain around the biggest cog on the cassette and the biggest chain ring and then add two links. That way, if you inadvertently shift into the "big-big" combination, your chain is long enough to handle it.
Mike
Mike
#8
Senior Member
Join Date: Feb 2017
Location: Northern Shenandoah Valley
Posts: 4,139
Bikes: More bikes than riders
Mentioned: 36 Post(s)
Tagged: 0 Thread(s)
Quoted: 1443 Post(s)
Liked 759 Times
in
568 Posts
In sizing a chain, I generally start with the small-small combination, and ensure I don't have any derailleur cage drag, and size to that. In doing so, you'll almost certainly have plenty of chain for the big-big combination. This seems to result in a little less chain tension (compared to a shorter chain) and my drivetrains tend to run a little smoother/quieter this way.
The approach Mike shared above will give you the shortest chain your drivetrain can handle. The approach I shared above will give you the longest chain your drivetrain can handle. Either one will work.
The approach Mike shared above will give you the shortest chain your drivetrain can handle. The approach I shared above will give you the longest chain your drivetrain can handle. Either one will work.
#9
Senior Member
Join Date: Sep 2017
Posts: 7,851
Mentioned: 38 Post(s)
Tagged: 0 Thread(s)
Quoted: 6944 Post(s)
Liked 10,944 Times
in
4,677 Posts
Another data point: switched out a Shimano 50-34 crankset for a GRX Ultegra 48-31 model, and had to remove the Ultegra 8050 di2 FD and replace it with the GRX equivalent. The Crankset and FD are both offset, and apparently the new crankset wouldn't work properly with the old FD.
No problem running the 48-31 with an 11/34 cassette in an 8050 Ultegra RX RD, though, even though the setup exceeds it's max capacity by one tooth.
No problem running the 48-31 with an 11/34 cassette in an 8050 Ultegra RX RD, though, even though the setup exceeds it's max capacity by one tooth.
#10
Senior Member
Following thread. I just did a lot of research into the GRX line but pulled back at the last minute for now. Just to much to swap from my exiting glob based on a traditional Shimano 2x10 setup with the original road pull ratios (Tiagra 4600 and similar). I would have had to do the whole GRX line of brifters, FD, RD, and cranks. I still got my 46/30 but did it just with chainring swap and some chain links. Maybe later..
Last edited by u235; 09-12-19 at 12:38 PM.
#11
Mother Nature's Son
Join Date: Mar 2016
Location: Sussex County, Delaware
Posts: 3,107
Bikes: 2014 Orbea Avant MD30, 2004 Airborne Zeppelin TI, 2003 Lemond Poprad, 2001 Lemond Tourmalet, 2014? Soma Smoothie
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 852 Post(s)
Liked 1,433 Times
in
815 Posts
Following thread. I just did a lot of research into the GRX line but pulled back at the last minute for now. Just to much to swap from my exiting glob based on a traditional Shimano 2x10 setup with the original road pull ratios (Tiagra 4600 and similar). I would have had to do the whole GRX line of brifters, FD, RD, and cranks. I still got my 46/30 but did it just with chainring swap and some chain links. Maybe later..
Likes For delbiker1:
#12
Senior Member
#13
Mother Nature's Son
Join Date: Mar 2016
Location: Sussex County, Delaware
Posts: 3,107
Bikes: 2014 Orbea Avant MD30, 2004 Airborne Zeppelin TI, 2003 Lemond Poprad, 2001 Lemond Tourmalet, 2014? Soma Smoothie
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 852 Post(s)
Liked 1,433 Times
in
815 Posts
I am a little confused. How do you mount 120/90 BCD rings on a crank that is 110 BCD? Are you saying your Omega crank is 120/90 BCD?
#14
Senior Member
Specific to the rings:
Full Speed Ahead FSA Pro Road Bicycle Chainring - 120x46T (30T Compatible) Black N11 WA068-370-0047003050
Full Speed Ahead FSA Omega Steel Road Bicycle Chainring - 90x30T Black N11 WB025-370-0050021140
FSA also has another 120 46 tooth ring that has a different shape made specifically to be paired with a 36 inner ring.
The cranks are FSA Omega Compact that came with 50/34 (just took them off last week). There is a FSA Omega Adventure crankset that comes with the 46/30. Same cranks as the Compact but with the above rings instead. I am using a CX70 FD and it works perfect.
Last edited by u235; 09-12-19 at 08:07 PM.
#15
Mother Nature's Son
Join Date: Mar 2016
Location: Sussex County, Delaware
Posts: 3,107
Bikes: 2014 Orbea Avant MD30, 2004 Airborne Zeppelin TI, 2003 Lemond Poprad, 2001 Lemond Tourmalet, 2014? Soma Smoothie
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 852 Post(s)
Liked 1,433 Times
in
815 Posts
Thanks for the info, I did not know FSA Omega were available with 120 BCD. One of the reasons I like BikeForums, info to be learned from others experience.
I thought all Omega were 120. I know mine are. The Gossamer series is 110.
Specific to the rings:
Full Speed Ahead FSA Pro Road Bicycle Chainring - 120x46T (30T Compatible) Black N11 WA068-370-0047003050
Full Speed Ahead FSA Omega Steel Road Bicycle Chainring - 90x30T Black N11 WB025-370-0050021140
FSA also has another 120 46 tooth ring that has a different shape made specifically to be paired with a 36 inner ring.
The cranks are FSA Omega Compact that came with 50/34 (just took them off last week). There is a FSA Omega Adventure crankset that comes with the 46/30. Same cranks as the Compact but with the above rings instead. I am using a CX70 FD and it works perfect.
Specific to the rings:
Full Speed Ahead FSA Pro Road Bicycle Chainring - 120x46T (30T Compatible) Black N11 WA068-370-0047003050
Full Speed Ahead FSA Omega Steel Road Bicycle Chainring - 90x30T Black N11 WB025-370-0050021140
FSA also has another 120 46 tooth ring that has a different shape made specifically to be paired with a 36 inner ring.
The cranks are FSA Omega Compact that came with 50/34 (just took them off last week). There is a FSA Omega Adventure crankset that comes with the 46/30. Same cranks as the Compact but with the above rings instead. I am using a CX70 FD and it works perfect.