A30 Cranks

• It depends on the type of bottom bracket shell your frame has.  We make bottom brackets to fit BSA, T47 external, T47 internal, PF30, and PF86/92 bottom bracket shells.  Once you determine which style you need, order that bottom bracket with the 30mm spindle/bearing option to fit the M30 crank.
• The chainring depends on 1x or 2x set up, and what chainline you need.  Chainline is determined from frame specs and rear axle spacing which is available from the frame manufacturer. Once you get this info, navigate to the correct Chainrings page on our website.
  • 1x MR30 TSR 3mm offset ring for 49mm chainline
  • 1x MR30 TSR Boost/0mm offset ring for 52mm chainline
  • 1x MR30 TSR 3mm offset ring (flipped outward) for 55mm chainline for SRAM Transmission etc./Rolf/Superboost
  • 2x v2 VBC rings for 47.5mm chainline (measured between the rings)

How can I figure out if the A30 crank will fit my bike?

• Generally speaking, this is not a common crank so be careful.  You are probably better off with an M30 crank, but if you really want to use the A30, get out your calipers and read on….
• There are three basic measurements/clearances you need to confirm (digital calipers are best for this):
  • Bottom bracket OBW (Outer Bearing Width) when mounted (with seals) does not exceed 97mm
    • Add the shell width to the width of the cups with seals, or mount the BB (with seals) and measure the width
  • Crank arms don’t hit the frame
    • The chart above has a “Width between crank arms for chainstay clearance” measurement of 137mm for the A30 crank
      • Outside width of the chainstays measured at 190mm (that’s about the end of the crank arm) behind the BB center can be no wider than 125mm.  That gives you at least 6mm of clearance between each arm and the chainstay. (137mm – 125mm)/2 = 6mm
  • Chainring doesn’t hit the frame
    • Determine which of the four chainlines you need (Non Boost 49mm, Boost 52mm, SRAM Transmission etc 55mm, or 2x VBC 47.5mm)
    • Determine how many teeth you want
    • Now check out the “MR30 Crank and Chainring Dimensional Drawings” document below
    • Find the “Y2” dimension (that’s the radius of the chainring) for the chainring size/teeth you want
    • Measuring from the center of the BB shell, put a pencil mark at the Y2 dimension on your chainstay (this is where the chainring teeth will pass the chainstay)
    • Measure the outside width of the chainstays at this spot, and divide by 2.
    • Subtract this measurement from the chainline number you chose, and this gives you your chainring to chainstay gap/clearance
      • 5mm would be the minimum gap we’d like to see between the ring and chainstay, more if your frame is kind of flexy
    • Ex: You want to run a 3mm offset (facing inward) 42T 1x TSR ring
      • Your chainline will be 49mm
      • The Y2/radius measurement for the 42T ring is 90.2mm
      • Let’s assume your chainstays are 80mm wide measured at 90.2mm behind the BB center
      • 49mm – (80mm/2) = 9mm.  This is the gap between the ring and your chainstay
        • 5mm would be the minimum gap we’d like to see between the ring and chainstay, more if your frame is kind of flexy
    • If your frame has asymmetrical chainstays you’ll have to figure out a different way to measure for chainring clearance.  All the specs are in the “MR30 Crank and Chainring Dimensional Drawings” document in Technical Documents.