RT

So I wanted to move my 44t ring to the center of my triple crankset (granny ring removed) and put either put a duplicate (spare) ring on the outside as a bashguard, or just get a bash guard. Much to my chagrin, the 110 BCD outer ring is too big for the middle position. The bolt holes lined up, but the ring arms themselves were too long. I realized this after I tried to bolt the ring back into the middle position. I'm guessing this is where the 104 BCD comes into play

Looks like I'm shopping for a 104 BCD 44t ring and a bash guard. Since it is a 1x9, I'm guessing that the chainline might be interfered with if I were to put 44t on the outside and the middle?

Still learning.

bikinfool

So you had a 110 bcd ring you were trying to install on a 104 bcd crankset....probably not. Or were you just dealing with one of the cranks where little games are played with the arm tabs of the chainrings and might just need some artful grinding? 110 bcd is usually 5 arm, so hard to believe the holes would match up to a 104bcd crank which are normally 4 arm. Help to know the crank here...

RT

TruVativ Isoflow.

Well, no. I assumed the crank arm had the same BCD on the outer and middle positions, but it turns out they are slightly different. I would hesitate to grind the arms down as I would encroach upon the bolt holes themselves. I guess I was wondering if it is common for the outer and middle rings to have slightly different arm lengths? Now that I think about it, the BCD is the same since the bolt goes through both rings as planned, the arms are just different lengths. Guess I just needed your response to help me think it through.

bikinfool

It's probably specific crank and chainring dependant. I've read where some of the Shimano chainrings 104bcd don't play nicely with all the 104bcd 4 arm cranks for example, solved in some cases with some artful grinding, so that the chainring would fit on the ears of the crank. Truvativ Isoflow is a 4 arm 64/104 bcd crank afaik. Will the 44t clear your chainstay in the middle position?

DX-MAN

Crankarms DO have the same BCD on the inside and outside; what's different is the 'shelf' against which the chainring rests. It can even differ between different styles of cranks -- for example, the 32t Hone chainring will fit where the standard 44t/104BCD ring goes.

Grind at your own risk. It may work, or it may not.

RT

Yes, the chainstay clearance is there, and yes, DX-MAN, you described it better than I was able to. So I guess I'm looking for a TruVativ 104 BCD 44t ring made for the middle position.