Installing & Adjusting GRX FD-RX810?
 

Hello,

I have a relatively new gravel bike with this FD. I thought that I had it adjusted correctly. However, this is a 4-position lever and the cable was slack in the L-trim position which didn't seem right.

Then I tried to follow the instructions in the Dealer Manual for installing the cable and everything went to hell in a hand basket. Page 16 #1 tells you to put the lever in what I believe is the lowest (L-trim) position.

Next they tell you to use the L limit screw to set the outside of the cage even with the outside of the big ring. So so the lever is set to L--trim yet they want the cable tightened with the cage fixed most of the way to the big ring? This doesn't seem right. The only thing that makes any sense is the adjustment barrel tab in contact with the input link.

Missing details:
1. The cable attachment pantograph moves up and down. Which position should it be in when tightening the cable?
2. Should the cable adjustment screw be in / out / or somewhere in the middle?

Can any of you help me figure this out or recommend a better way to do this. I think that the Shimano document lost a LOT in the translation from Japanese to English!

Thanks,
Steve

I found this site helpful when installing and adjusting my R8000 front derailleur

From the website: "Whilst this article features a Shimano 105 front derailleur, the adjustment process is the same for all mechanical front derailleurs from the following Shimano group sets;

• Shimano Dura-Ace – R9100 front derailleur (FD-R9100)
• Shimano Ultegra – R8000 front derailleur (FD-R8000)
• Shimano 105 – R7000 front derailleur (FD-R7000)
• Shimano GRX – front derailleur (FD-RX810, FD-RX400)"

Thanks for the link. However it doesn't really address initial setup of the FD Which is where most of my problem lies. It just says that if the cable is too tight loosen it and if too loose just tighten it. Duh! It is not easy to do this in small increments with a "fuzzy" inner cable.

Reading the comments the author mentioned that the initial cable setting interacts with the "H" limit screw. Now that is about as non-intuitive as you can get! So the H limit has to be set correctly before the cable is tightened. This is TOTALLY missing from the Shimano Dealer Manual... and likely most of my problem.

Luckily the author covers this in a separate article on FD installation that can be found here:
https://cycling-obsession.com/instal...nt-derailleur/

When you attach a new cable you have to reset at least the cable tension and "H" limit screw and then set trhe "L" screw to position the outside of the cage with the outside of the big ring teeth.

I'll try to have another go at this tomorrow in the daylight.

I’ve always set the F low limit when the chain is in the small ring and in the largest cog. Set to just not hitting the chain. Ditto high, chain on big ring, smallest cog.

Is this on a GRX crankset? Other cranks can cause issue due to chainline and chainring spacing.

The crankset has no bearing on this issue, and yes we all know the GRX crankset is slightly different to accommodate wider tires.

How do you know? Shimano's wide chainring spacing makes the current mechanical indexing lose the low trim position when used an normally spaced cranks. Seen that many times.

As I recall, GRX uses a b-bracket that puts the rings further away from the b-bracket and can cause issues if you don’t use a GRX F derailer. As the OP describes this as a new bike, with a GRX F derailer, the assumption is all the components should match and he’s just having adjustment issues.

I ran into first this on Specialized bikes that had Shimano 11 speed shifting with a Praxis crank. And the spacing difference between narrower Praxis and the Shimano crank the shifter was designed for meant that setting the stops properly caused the low trim to do nothing. Since those bikes came with a mix of parts from Specialized, seems reasonable the OP's bike might too.

And then Shimano will tell you that a road derailleur won't work on the 47.5 GRX chainline due to the way the derailleur swings.

Cable slack in the innermost L-trim position is just fine. The L-trim position of the FD is defined by the low limit screw, not by shift cable tension. In other words, the cable must be slack enough when the smaller STI lever is in the L-trim position for the FD to rest against the lower limit screw.

Among the 2x11 Shimano mechanical FDs I have installed and setup, the newer models (FD-R7000 and FD-RX810) swing further for a given length of cable pull compared to an older model (FD-5800). On the older FD, the shift cable attaches to the end of a lever arm extending away from the parallelogram, whereas on the newer FDs, the shift cable attaches directly to the parallelogram. Who cares about some cable slack in L-trim as long as you have sufficient cable tension to consistently shift well onto the Top position?

I also have this problem on my old Cannondale Synapse, which has FSA rings on Cannondale SI spider and cranks with a BB30A bottom bracket. Shifting improved slightly with 105 rings but L-trim still does nothing.

Interesting data point... To answer Kontact The crank is a Shimano FC-RX810-2 crankset. However, I have changed the rings from 48/31 to 46/30 from the 600 series crank for better lower gearing. I don't think that this is the issue.

Did you lower the derailleur after you installed the smaller rings? Did you realign the tail angle?

Yes, on both counts.

I got a chance to work on this today and I think that I got everything sorted out.

One thing to note is that you can but don't necessarily need to set the high limit screw per the referenced article. However, if you do set it its main function is to hold the plate that contains the cable attachment down against the FD. You can accomplish the same thing by pulling the cable straight out with a little downward bias when you tighten the cable clamp screw.

One thing that I try to do when adjusting the limit screws is to aim for not needing to use the trim positions. So far I have been pretty successful.

Thanks for everyone's input!

maybe unrelated - but the 810 48t ring and 600 46t ring are / do mount slightly different (I believe *** see below)

I purchased a 46t ring to install on my 810 crank and compared the rings - can’t recall the exact difference (senior moment) but it was enough to convince me to stop the swap from 48t to 46t

the one thing I do recall was related to look / appearance - the 810 ring appeared to be a better quality ring … maybe better material … ? … machined instead of stamped ? …

I also struggled with the GRX FD setup initially … the GRX FD Shimano doc appears to be thorough - but at the time grew impatient with the doc and then just winged it … eventually got it to shift fairly well … it’s a bit clunky but shifts up and down reliably and the trim positions work etc

other thing I struggled with initially was the cable routing - which is unique … sorta / kinda …

*** I believe the 46t ring I purchased is for a 10 speed crank

So it is spaced differently.

possibly and probably

but note even the difference in the 2 x11 chainrings / mounting

2x11 600 crank (top pic) - 2x11 810 crank (bottom pic)

can’t recall if the chainring fasteners are the same - had that info at one point but was unable to locate


https://cimg4.ibsrv.net/gimg/bikefor...536985edb.jpeg
https://cimg5.ibsrv.net/gimg/bikefor...37f94eb7a.jpeg

Well, I didn't find any spacing differences and didn't even have to tweak the FD. The recent incident occurred because I tried to fix something that wasn't broken!

The 46/30 rings (from a 600 crankset) will mount correctly on the 810 cranks. The only issue I had was that the chain catcher pin had to be shortened. Shimano put 2 scribe (cut) marks on the pin so these same rings must be used elsewhere.

I think you have quickly realized why turning to these forums for advice is an effort of futility. The usual armchair experts quickly weigh in with opinions without any real experience or practical common sense. For example; I have this bird which has webbed feet, a bill and makes a quacking sound. Responses would start with, you sure it’s not Albatross, how about a Loon, I have seen Penguins that fit that description!

Hope your problem is fixed and good luck.

So the pin was pushing on the back of the crank arm and the ring was no longer true?

Correct.

Was that hard to see as you hand pedaled the bike and observed the shifting? Or was it covered up by the chain and then you were looking at the small ring after the shift, so you never looked right at the chainring?

Edit Late to game, see issue fixed this may be helpful for others
I followed the manual for Ultegra R8000 front derailler and it worked well.
it should be noted this is not intuitive or exaclty like previous setups certainly different than 105 5800 set up

This was obvious during the ring mounting process. Zero clearance between the pin and the crank arm.