Originally Posted by
SoSmellyAir
I have a related question: Does either crank arm need to be removed to install different chain rings? Or can the crank be left in place? There is a bike I want but it only comes with 52/36 while I would rather use 50/34.
IMO, related question should be in it's own thread. And in the
Bicycle Mechanics sub-forum where this thread should have been. Again, IMO, I'll get over it! <grin>
Originally Posted by
mstateglfr
Again, different cranksets have different spider shapes. What you are asking may be possible one one, but not modern ones I have worked on.
Even if it is possible, I dont know why anyone would keep the crank arms attached to the bike. On a Shimano crank its 2 bolts to undo for removal. On a Praxis crank its 1 bolt to undo for removal. Such a simple removal process seems like the obvious way to handle changing chainrings since you then have easy access to the rings and bolts.
For Shimano 4 spoke road cranks it's a toss up for me which is easier. But the chain rings can be removed and replaced without removing the crank from the bike. I've done it both ways to replace the chain rings. The time saved by not taking the crank out of the bike is probably lost by the tad more trouble of getting the crank turned to access the ring bolts for removal and replacement.
The OP's question revolves around them getting a crankset with different size arms that they wish to use. So they have to remove the cranks from the bike regardless.
Apparently the OP couldn't find a deal on one with the ring sizes that they desire and are going to have to swap their current rings to the new crank. That shouldn't be any issue since the OP has a choice of when to install the rings.
However from one model and series version to the next the profiling on the ring spokes might not match the profiling on the crank spider. I have that issue with the Ultegra R8000 rings I use on my 105 5800 crank. But no one but me and the mechanics at the bike shop have ever said anything about it. That is purely cosmetic.