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I've set my girlfriend's bike up with 9-speed Shimano MTB shifters and road derailleurs. Specifically, the shifters are Deore SL-M590 (3 x 9 speed), the front derailleur is Tiagra FD-4600 (2 speed) and the rear derailleur is Sora RD-3500.

The rear setup works fine, but the front is very difficult to shift up - you have to push very hard and through the full travel of the lever. This is quite difficult if you have small hands. Is there anything I can do to make it easier? I wondered if there was a compatibility issue between the 3 speed shifter and the 2 speed derailleur.

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  • I assume you’ve increased cable tension (using the barrel adjuster) as far as possible already? Otherwise a lot of lever travel is “wasted” on pulling in slack. Does the bike have two or three chainrings?
    – Michael
    Commented Nov 14, 2022 at 12:40
  • Yes I’ve done that. Bike has two chainrings and I’ve set the shifter up to use the lower two positions. The H screw on the derailleur prevents you trying to shift into the (nonexistent) third gear Commented Nov 14, 2022 at 22:51
  • Mayyyybe it would actually be worth a try to go the other direction: Make the cable slack enough to use all 3 shift positions and use the middle one similar to the “trim“ position on 2 speed derailleur shifters?
    – Michael
    Commented Nov 15, 2022 at 8:07

2 Answers 2

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RD-3500 is a "road" 9-speed derailleur. Shimano "road" derailleurs up to 10 speeds (exception: GRX, Tiagra 4700, 10-speed) used the same cable pull ratio that "MTB" derailleurs used up to 9 speed. Thus, the rear shifting is matched.

However, the front shifting isn't matched. "road triple" and "MTB" front derailleurs don't have the same amount of cable pull. Thus, it's impossible to get shifting right. With a double setup (2 chainrings) having too much chain pull in the shifting lever would be correctable (just set the limit stops right), and even very little too little pull might be tolerable too. But with a triple setup, you need exactly the correct amount of chain pull per setup.

Your options are to:

  1. Find a "MTB" front derailleur
  2. (Maybe this could work, not sure) Configure the system such that the smallest chainring is never used and you only use the middle and big rings, by setting the limit stop screw to prevent small ring from being used. Then you maybe could have tolerable shifting between those two rings.

So it isn't "double" vs "triple". It's "road" vs "MTB". But anyway, I would recommend a real "triple" front derailleur since the "double" front derailleurs don't work as well with "triple" chainring systems.

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  • I wasn't clear - the FD is two speed and my current setup is what you describe in option 2. I guess an alternative is also to find a 2 speed road shifter like Sora. Commented Nov 13, 2022 at 19:42
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On my mum's bike, we used an old friction shifter for the left hand. It saves alot of bother and two rings are easy -- up for high ratio and down for low ratio. Tiagra flat bar shifters exist and would work or you can get a mtb or city (nexave etc) front derailleur to work with your flatbar shifter. It has to be able to clear your big ring but the touring/trekking options (XT, Deore, Deore LX) can usually handle 50t depending on seattube angle (despite being rated for 48).

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