Originally Posted by
FBinNY
you don't have much choice here. If you want to use the ring on your current cranks, it has to match the BCD. hopefully, you can find cranks in the future wit the same BCD, but shoud be a secondary consideration, since the price difference for new cranks with and without rings is very narrow.
The best advice is either buy the ring to use now, and worry about new cranks if/when you buy them. Or, if the plan is yo buy cranks very soon, pass on the ring and move up the crank buy. Sometimes, when you try to kill two birds with one stone, you end up killing neither.
Originally Posted by
SkyDog75
The chainring size you'd want is determined by your crankset. Your crankset may have a bolt circle diameter of 110, 130, or something else. Pick the size/type that fits your crankset.
Crank arm length isn't a significant factor when choosing the BCD of a crankset. What is significant is how low you need your gearing to go. A 130 mm BCD can't take a ring smaller than 38 teeth. If you want lower gearing than that, 110 is a common BCD that allows for lower gearing.
I'm afraid that in my haste to post I've not been very clear. It is is my intention to purchase a crankset (not chainring). Original post corrected now.
At present the bike has a single chainring with crank arms 170mm riveted on. I can't remove the crank arms so they come off as well. All that will remain is the square taper bottom bracket.
It is the replacement crankset that comes with a choice of BCD 110, 130 or 4 arm Shimano Ultegra.
I have not yet chosen the crank arms that will go with it. But for future consideration which BCD would be best if crank arm experimentation is to be done?
PS. I'm the eyeing the Redline Microline 110mm BCD 155mm crank arms as they seem reasonably priced for shorter arms.