What size Osymetric chainrings

What size Osymetric chainrings will suit me. That is an often heard question. To compare Osymetric chainrings vs round chainrings we made a Comparison chart. The first column represents the Osymetric chainring. The second column represents the largest diameter of the ring in number of teeth as the third represents the smallest diameter of the Osymetric chainring in number of teeth. The last column gives advice of where to use the ring for.

 

Osymetric

ring

Number teeth

largest diameter

Number teeth

smallest diameter

BCD

(mm)

Suitable for

56

62

51

130

outer ring: Time trial

54

60

49

130 / 135

outer ring: Time trial/ Race

52

58

47

130 / 110

outer ring: Time trial/ Race / Recreational

50

55

45

110

outer ring: Race / Recreational

44

49

40

110 / 135

inner ring: Time trial/ Race

42

47

38

110

inner ring: Race / Recreational

38

42

34

110

inner ring: Race / Climbing time trial / Recreational

34

38

31

74

triple / MTB

24

27

22

64

MTB

*BCD = Bold Circal Diameter.

Diameter

Osymetric chainrings are about 10% larger in diameter in the largest diameter and 10% smaller in the smallest diameter of the chainring. This is what makes the leverage possible and makes is feel like a bigger chainring at the point where you can deliver power and like a smaller chainring in the dead spot. It’s actually a simple principle but so effective. When you ride them you will feel at first the inertia due to the large – small diameter. After a couple of minutes spinning you get used to the feeling and you get the positive effect of them.

BCD

Check the BCD of your crank spider before you decide what size Osymetric chainrings you want to buy to be sure you get the right chainrings that fit on your crank. The standard (old) size for shimano is 130 mm. The compact size of shimano is 110mm. The newest shimano cranks have 110 mm too but they don’t have 5 bolt holes but 4 bolt holes. Campagnolo has 2 BCD’s 113 and 135 and for mtg there are roughly 3 sizes: 104 74 and 64. Check this when you consider new (oval) chainrings.

Do you have more questions about Osymetric chainrings? Visit our page about Osymetric questions