BC Junior Gears

mikel123
mikel123 Posts: 17
edited November 2009 in Workshop
This season i have been using a 52 front 14 rear gearing ratio...
That's what junior gears are, but iv just bought a new BMC, and the gearing is 50 front, 12 rear...

is this the same gear? i really dont want to have to buy new chainrings and cassette
Changing the spec from where i bought it from is not an option.

Anyone know?

Comments

  • JeffP
    JeffP Posts: 2
    mikel, you´ll find that your new gear of 50-12 gives you 116 inches, whereas your 52-14 gives you 121 inches.
    To calculate a gear divide the number of chainring teeth by the number of sprocket teeth, then multiply the result by the diameter of your wheel. I assume you´re using 28" wheels, you can always recalculate substituting 26 or whatever instead.
    Want some advice from an old senior? DON`T change anything, son, just learn to pedal faster if the gear is lighter. Trust me, your knees and joints will thank you in thirty years time:-).
    If you feel that you must change stuff, get your local bike shop to check out a new cassette for you, then at least you can keep the front chainrings. If they know their stuff, they´ll find a cassette that´ll give you the same gear ratios you had before. Try pedalling faster first, though!!!
  • Thank you Jeff, your not the only rider than has recommended smaller gears at my age!
    Ill give what you said a shot, increasing my pedaling cadence, after all, we go throughout winter training in the small ring just spinning the legs, should do me good!

    Again, Thank you.
  • andrew_s
    andrew_s Posts: 2,511
    Your old 52/14 gears are about 100 inches (27*52/14)
    Your new 50/12 gears are about 112 inches (27*50/12). This will be higher than is allowed under junior racing, so you'd have to lock out the 12 and possibly 13 cogs with the rear mech limit screw to compete.
    There are 13- and 14-up cassettes available, but you may have to order them in rather than just call in at the LBS.
  • JeffP wrote:
    mikel, you´ll find that your new gear of 50-12 gives you 116 inches, whereas your 52-14 gives you 121 inches.

    Nope, Andrew_S has it closer :wink:
    andrew_s wrote:
    Your old 52/14 gears are about 100 inches (27*52/14)
    Your new 50/12 gears are about 112 inches (27*50/12).
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  • John.T
    John.T Posts: 3,698
    Alternatively try here. Switch it to gear inches and the tyre size you are using for greater accuracy.
    http://sheldonbrown.com/gears/
    Bookmark this site for future reference. It has a lot of good info.
    http://www.sheldonbrown.com/
  • If you really want to check it for accuracy, then you will need to roll it out along a measured line of the distance one revolution of the pedals make in the highest gear. That's what is done at events to check the gears, and takes into account of the tyres used.

    When my children wer racing youth and junior, I bought a small chainring of the correct size and used the full range of gears on the casstte
    Recipe: shave legs sparingly, rub in embrocation and drizzle with freshly squeezed baby oil.
  • Pross
    Pross Posts: 42,206
    Maximum junior gear is 7.93m which is achieved exactly by 52 x 14. The closest you can get with a 50t chainring without exceeding this is 7.63m with 50 x 14 (taken from BC's own gear table). By my maths that means you'll have to pedal 4% faster than anyone on the maximum gear to go the same speed i.e. 104 rpm when they are at 100 rpm.

    BC have obviosly increased the maximum gear in the past 15 years or so as 52 x 15 was the closest combination 'in my day'.