CrowSeph

Can i install a 147mm q factor crank on my currently bike, wich i removed a 148mm? or should i use any sort of adapter? im afraid to screw the working of my drivetrain.
i have ultegra r8100 di2 12v.

bboy314

Q factor will affect how far apart your pedals are spaced, not the drivetrain or chainline. So you’re fine with this change unless you can’t stand your feet being 1mm further apart.

shelbyfv

If it fits, yes. You will not notice a difference. Obviously you may need derailleur adjustment.

Iride01 

148 to 147mm is only going to be 0.5mm difference in where the pedals are. As far as you, your body can likely accept a large amount of change in q-factor. However, I'd suppose that you could possibly find a crankset that might hit the stays if you were determined and looked hard enough. If you buy a crankset that is appropriate for your bikes genre and number of speeds on the rear, then you are likely always going to be okay for that. Even if you go outside of that some you'll likely be okay. And if you ignored it completely, then still there is probably only a slight chance you'll have interference with the stays.

If you want to worry about it, then you will have to know how thick the crankarms are at the pedal hole and and make a relative assessment based on the current clearance of the existing cranks. Crank length will matter too if the two cranks are different. But still, despite all this, I wouldn't worry too much about it.