Need some help, not sure if im in the right place- Mtbr.com
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  1. #1
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    Need some help, not sure if im in the right place

    ok well I recently got the urge to race again, I was thinking about converting my Giant STP single speed and race at a local bmx track. I raced bmx for 4 years about 6 years ago lol....I was lookin and cant find any set ups to similar gears I used to rideo n my 20in. I used to ride 44 or 46 in the front and 16 in the rear....the most I can find for front chain rings on our bikes islike 34-38...and 16-18 rear...I think the pedal will run out to quick for that. A bmx track is pretty flat......any help to get started on ratios would help a ton, thank you

  2. #2
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    Check out sheldonbrown.com

    and look at his gear inch calculator. A 38x16 combo on a 26" wheel is actually 10 gear inches higher than a 44x16 gear on a BMX (20") bike.

  3. #3
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    What calculator man?/

  4. #4
    Rusting Steel
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    Salsa makes a 4-bolt 48t chainring. I'm running one on my 26" ss commuter/cross bike. It's 48x18, which is the same Gear Inch as 32x12. Swapping it to a 42x18 shortly (~32x14).

    wheel diameter x # of chain ring teeth / # of cog teeth to get gear inch.

  5. #5
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    so I figured out that a 26in wheel with a 34 tooth chain ring and a 16 tooth cog is almost the same as a 20in 44/16..........the 26" was 55.25, and the 20" was 55, now the 55.25 is that a higher top gear than the 55 or lower........im new to this lol bear with me plz, thanx

  6. #6
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    Here's the calculator...

    Quote Originally Posted by Func413
    so I figured out that a 26in wheel with a 34 tooth chain ring and a 16 tooth cog is almost the same as a 20in 44/16..........the 26" was 55.25, and the 20" was 55, now the 55.25 is that a higher top gear than the 55 or lower........im new to this lol bear with me plz, thanx
    http://sheldonbrown.com/gears/

    The method above gives an approximation of the gear but might not take into account the over-diameter of the wheel including the tire. On a 26" wheel, the rim is 26" in diameter, not the tire. So your calculation above will result in an even higher gear for the MTB. Sheldon's website will allow you to pick a tire size as well as a crankarm length.

    55.25 is higher than 55 gear inches. Gear inches translates to how far your bike will travel forward with one revoltion of the crank. So the MTB would go a quarter of an inch farther than the BMX bike.

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