nellborg
I'm having a new frame built this winter and I plan to put GRX 11 speed mechanical on it.  Mechanical because the Ultegra on my other bike works so incredibly well - except for the front derailleur occasionally.  

In two 100+ mile rainy, wet gravel events this past season, I had mud and sand caked underneath my BB where my Ultegra front derailleur cable runs, and in both of these events, my left shifter was rendered useless.  I had to reach down alongside the downtube and yank on the cable to get it to shift, and that hardly even worked.  

So, for my new custom frame, I'm thinking that I'd like to use a top pull front derailleur.  But, I don't see one listed on Shimano's website for GRX.  Does anyone know what would be compatible?  XT or XTR?  Something else?
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owly
GRX discussions that I've read seem to mention the offset/outboard? front derailleur position. Can't suggest an option but you may require the use of an assymetric clamp to get your derailleur in the right position over the rings.
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Thijsvanderwal
Indeed the GRX chain line is 3mm further out so you will need to adjust your front rings accordingly, either via spacers (if your axle is long enough) or with a complete new crankset. Indeed there is no GRX top pull derailleur available, you could potentially go for XR/XTR but I’m not sure these are supported by road shifters. They will also have the 3mm offset plus they might not be able to support the 16T difference in compact chain ring sets.
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brando
If you are building a custom frame, can you have it made for full-length housing?The most recent shimano front derailleurs include a housing stop, so you'll be fully protected up to the derailleur this way.

outercasing.jpg 
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nellborg
Full length housing sounds like a great idea - I wasn't sure if that would work.  So, on the diagram, it looks like the housing runs all the way to the derailleur...and the cable would be entirely enclosed from the brifter to the derailleur stop.  I'll bet the builder could figure out a way to keep the cable controlled and looking good against the downtube.  

I found some info on the Shimano CX70 top pull front derailleur that's made for cyclocross.  It's probably the wrong chainline for the GRX crank, and so I'd probably have to get a different crank, and the CX70 might not be compatible with 11sp... - and then I'm immediately over my head as to how to make it all work, so I'll try the GRX with full length housing.  Thanks.

It does seem odd to me that Shimano didn't make a top pull GRX front derailleur too, though.  Gravel can be sort of like cx with all the muck that collects under the BB.
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Nebo
If you search Google for speen umlenker you will find a German company that makes front derailleur adapters to convert bottom pull to top pull. No mention of GRX but send them an e-mail. I am using on on s Sram Rival FD. It works very well. Much better than the  pulley I used before.
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nellborg
The speen umlenker looks interesting.  Very simple design.  Thanks.
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owly
Another possible option is to use a Carbon Ti X-Pull along with a Dura Ace braze-on style front derailleur. This would probably be an experiment though to see if it works.  

Again I'm thinking you may need to use an assymetric clamp. 

I was using the X-Pull with Sram Red and it worked very well. However for me the cage length really was too long in combo with the small rings I was running. 

They aren't made anymore though and it took me ages to track one down for sale in a shop.
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clarksonxc
nellborg wrote:
Full length housing sounds like a great idea - I wasn't sure if that would work.  So, on the diagram, it looks like the housing runs all the way to the derailleur...and the cable would be entirely enclosed from the brifter to the derailleur stop.  I'll bet the builder could figure out a way to keep the cable controlled and looking good against the downtube.  

I found some info on the Shimano CX70 top pull front derailleur that's made for cyclocross.  It's probably the wrong chainline for the GRX crank, and so I'd probably have to get a different crank, and the CX70 might not be compatible with 11sp... - and then I'm immediately over my head as to how to make it all work, so I'll try the GRX with full length housing.  Thanks.

It does seem odd to me that Shimano didn't make a top pull GRX front derailleur too, though.  Gravel can be sort of like cx with all the muck that collects under the BB.


I can confirm that the CX70 does indeed work with the 11sp pull ratio.  So using a 6800 lever would be no problem.  The chainline issue for GRX would still be an issue, but you could avoid that by using a road style Shimano crank.  If you're OK with the road size chainrings, of course.
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nellborg
Thanks for the info.  There seems to be a few choices when I thought there were none - full length housing, top pull CX70 with road style crank (like FSA, I would imagine), or that speen umlenker. 
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pkram
brando wrote:
If you are building a custom frame, can you have it made for full-length housing?The most recent shimano front derailleurs include a housing stop, so you'll be fully protected up to the derailleur this way.




This is a great suggestion, I just build up my bike with GRX and wasn’t aware this was possible (just checked my manual and it is included).  I think the next time I redo the shifting cables (front and rear) I will do full outer cabling for both!
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