Front Derailleur Adjustments after Crank Swap

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amngwlvs
Posts: 144
Joined: Fri Apr 20, 2018 2:45 pm
Location: Barrie, Ontario

by amngwlvs

Hoping the WW can help me with this one...

I recently changed the RS500 crankset (50/34) on my 2015 Giant Propel to a set of Ultegra R8000 (52/36). I took the bike (my spare/backup/trainer bike) for a 35km ride to test everything out and it rode ok but was having chain rub issues when in the 52 tooth ring. I played with the barrel adjuster during the ride to try to quiet it down but it didn't solve the problem so I threw it on the bike stand when I got home to look into it further.

I realized the derailleur needed to be moved up to allow more clearance for the chain to get onto the new bigger ring and got to work. Adjusted the derailleur up, reset the limit screws (to what seems to be correct based on YouTube), adjusted the cable tension and it seems to be pretty good save the big ring/bottom two cogs on the casette combo. I'm still getting rubbing on the outboard side of the front derailleur but I can't adjust the derailleur out more or I get rub on the inside of the crankarm.

What am I missing here?
2018 Giant TCR Advanced Pro 0 Disc
2015 Giant Propel Advanced 2
2013 Trek 520

by Weenie


CrankyCarbon
Posts: 44
Joined: Tue Aug 13, 2019 1:15 pm

by CrankyCarbon

When you were adjusting it up you also probably inadvertantly changed the angle of the deraileur where the back part is sticking outwards more and rubbing against the crankarm.
Last edited by CrankyCarbon on Fri Sep 13, 2019 4:48 pm, edited 1 time in total.

amngwlvs
Posts: 144
Joined: Fri Apr 20, 2018 2:45 pm
Location: Barrie, Ontario

by amngwlvs

I was pretty cautious to make sure the derailleur was aligned with the chainrings but that is certainly a possibilty. I'll have to double check tonight to see if it's the front or back part of the derailleur that is rubbing. Thanks for the input!
2018 Giant TCR Advanced Pro 0 Disc
2015 Giant Propel Advanced 2
2013 Trek 520

amngwlvs
Posts: 144
Joined: Fri Apr 20, 2018 2:45 pm
Location: Barrie, Ontario

by amngwlvs

Hmm, reading some troubleshooting ideas on Park Tools site, is it possible that because I didn't adjust the height of the mech after switching to the 52 tooth that when shifting to the big ring I bent the front derailleur causing it to bulge and rub on the inside of the crank? That could be another possibility I would think.
2018 Giant TCR Advanced Pro 0 Disc
2015 Giant Propel Advanced 2
2013 Trek 520

alcatraz
Posts: 2208
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

1. No play in the crank/chainrings/fd mount tab on the bike frame.
2. Slacken the cable/disconnect.
3. Adjust low limit screw so that outer plate of cage is over big ring.
4. Loosen clamp and align the outer plate parallel. Look from above. Place a flat object against the big ring and see that it floats at same distance from fd cage all the way. Fd height should be 1-3mm over the teeth, check full rotation.
5. Tighten clamp. Double check. If your fd has an fd support bolt, ensure it just touches the pad/fd mount behind. (r7000/r8000/r9100/9070)
6. Slacken low/high limit screw. Attach cable. Shift to the toughest gear. Adjust cable tension so there is a clearance to the chain by 0.5-1mm. Turn the crank to ensure clearance for a full rotation. Set high limit so it just starts to move cage.
7. Shift to easiest gear. Set low limit so you have a clearance of 0.5-1mm for a full rotation. Listen for noise.
8. Test ride. It could work on the stand and work crap on the road. Only way is to test it properly.

by Weenie


amngwlvs
Posts: 144
Joined: Fri Apr 20, 2018 2:45 pm
Location: Barrie, Ontario

by amngwlvs

alcatraz wrote:
Sat Sep 14, 2019 3:11 am
1. No play in the crank/chainrings/fd mount tab on the bike frame.
2. Slacken the cable/disconnect.
3. Adjust low limit screw so that outer plate of cage is over big ring.
4. Loosen clamp and align the outer plate parallel. Look from above. Place a flat object against the big ring and see that it floats at same distance from fd cage all the way. Fd height should be 1-3mm over the teeth, check full rotation.
5. Tighten clamp. Double check. If your fd has an fd support bolt, ensure it just touches the pad/fd mount behind. (r7000/r8000/r9100/9070)
6. Slacken low/high limit screw. Attach cable. Shift to the toughest gear. Adjust cable tension so there is a clearance to the chain by 0.5-1mm. Turn the crank to ensure clearance for a full rotation. Set high limit so it just starts to move cage.
7. Shift to easiest gear. Set low limit so you have a clearance of 0.5-1mm for a full rotation. Listen for noise.
8. Test ride. It could work on the stand and work crap on the road. Only way is to test it properly.
Thanks for such a detailed reply! Having checked over the weekend, to my untrained eye, the FD doesn't seem bent so I'll try the above list in order to see if I have more success. I'll report back. Thanks again!
2018 Giant TCR Advanced Pro 0 Disc
2015 Giant Propel Advanced 2
2013 Trek 520

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