Magic Gear Ratio Help

Hi all,

So I have aquired a SS rode bike, which runs a magic gear of 53x17 (82 inches or thereabouts)

Now I want something a little lower, something around the 70 mark.

I know you can do some calculation as to chain link length and each tooth on the chain ring or sproket equates to something. I think I read it on Sheldon Browns site at some point, but it made my head hurt.

Can anyone do the maths and tell me what else would work, or the maths I need to do to work it out?




I haven’t tried this, but it should work for you. You could test by checking that 53x17 is in the shaded band for your bike’s chainstay length.

Looking at the chart though, there are no lower gears that are exactly the same, but 43x15 or 40x16 are quite close (+/- 5mm of chainstay length)

Here’s a tip to make things a bit simpler for you. If you already know what magic gear works, all you have to do is +/- 4 teeth to find suitable gears. For example: 53 x 17 = 70 total teeth. 49 x 17 = 66 total teeth (4 less than the original) or 48 x 18 should work as well. Basically, work out a gear combination that you like but make sure that the total number of teeth adds up to the right total (i.e. 58, 62, 66, 70, 74, 78 etc, etc). It may not work for the extreme ends but should be close.


And then get a 1/2 link too.


CAUTION: Hard Man Riding.

Heeelloooow … haven’t heard from you in awhile …

Come on Tristian, you know how I can’t push a gear… :smiley:

With your legs? :smiley:

I thought exactly the same thing!