I use Rotor rings on my bikes and have done for years. I currently run a 54/39 on my tri bike and 39 is the smallest ring you can run with a 54 ring. I think a maximum difference of about 13-14 is what they recommend but the 39 still works fine.

BCD is the diameter of the bolts mounting your chainring and if you have 130 BCD you are stuck with going 39 as the smallest Rotor ring you can run on your cranks. If you want a smaller inner ring and to run 110 BCD you will need new cranks.

PERFECT RESPONSE!!!...

BCD = Bolt Circle Diameter

I am on the hunt for a 130BCD....39 Teeth

thanks Shambolic!!!

No worries. Happy to be of service...

His answer was good.

A cassette is a 2min swap job. So usually a place to start to improve gear range.

What rear derailleur model is yours?

rear is 11-28.

i am going to swap out my front inner to a 39 (from a 42).


SO I will have FRONT: 54-39 & BACK: 11-28.

I use Rotor cranks rings on all of my bikes, and have for years. You may run into an upshift issue if you go with a 54/39 combo. That's a 15 tooth difference jump, and you may have some pick-up problems when going into the big ring. I say "may", not 100% sure. I run a 53/39 on one bike, and a 52/36 on another. Both work fine for me, but I don't ride them much except for races, so the big ring pick-up pins are still quite sharp. Look at the big ring pick-up pins and see if the shoulders appear to be rounded down and not crisp 90degree angles. Just a suggestion.

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Team Zoot-Texas, and Pickle Juice