Derailleur and chain length

[jannmayer]

I'm replacing the Shimano 105 derailleur on my road bike with a GRX. It's a 2x11 with 11-34 cassette. The GRX cage is longer than the 105 cage. Will I need a longer chain? The chain length calculators I've seen don't factor that in, but it seems like the chain would have a longer path with a longer cage...

[Tijoe]

I see you use the same name in MTBR as on this forum.    Double questions, you should get a good answer on one of the forums.    Your MTBR  thread will probably have 50 responses by the end of the day tomorrow, and start drifing off-topic after the first 5 to 10 replies. 

Regarding your question,  If I change components and put on a new chain, I often make the chain 2 or 3 links longer as a starting point.  Shift it through the gears and see how far the cage travels.  If it isn't tensioned as much as the old derailleur, I will remove a link until it shifts smoothly across the range of gears.  Remember to adjust the limit/tension screw first before removing any links.

[jannmayer]

Yes, I figure I'm 25% more likely to get a good answer if I post in two places!


I will start with a few extra links. The GRX derailleur should be able to take up a lot of slack, so it might not be too critical (I'm running a 2x11 with an 11-46 cassette on my gravel bike, same rear derailleur.)

[jonathanf2]

I just recently swapped a long cage GRX400 RD for a mid-cage Ultegra RX800 rear derailleur on my gravel bike. No need to change chain length as long cassette and chainrings are the same.