3.06.2007

Oops!

Last month I got a new wheelset and decided to go with a 15 rear cog
instead of my normal 16. The 15t would create 15 [thanks Pixel] wear
spots from skids, whereas the 16 creates one. All seemed fine. I ran
this ratio during Monstertrack and everyday on my daily commute.

So after I switched my clips and cleats out for pedals and toeclips,
I noticed it was nearly impossible to skid. I really had to stomp hard
to skid. I remembered a gear calculator that I had used a year or so
ago and re-visited this helpful tool.

For NYC, Boston and other relatively flat cities, +/- 75" is recommended.
You'll find it's easier to take off at lights, skid and yes, do wheelies.
Overall, it just makes it an easier ride.

This is what my 46:15 gave me:


 CRxFW     ChainRing x FreeWheel
 GI        Gear Inches
 GIdf      Percentage of increase between present GI value and the
           next sequential GI value.
 DI        Distance traveled in INCHES in a single pedal rotation
 diff      Difference in INCHES between the present DI value and 
           the next sequential DI value. 
 DF        Distance traveled in FEET in a single pedal rotation
           displayed as FEET' INCHES.decimal_remainder"
 PRPM      Pedal Rotations Per Mile
 RT        Gear Ratios

 Wheel Diameter: 28.50 inches
 Gears: 46   15
---------------------------------------------------------------------------
 SP  CRxFW    GI      GIdf      DI      diff      DF        PRPM      RT
---------------------------------------------------------------------------
 1>  46x15   87.40    0.00%   274.57    0.00   22'10.57"   230.76   1:3.07

No wonder my legs are always aching!

Time to switch it back to 46:16, which gives me +/- 80"

After some consultation with my friend Aaron, he linked me to this topic
on Bikeforums.

2 comments:

Aaron W. said...

If you switch your chainring out to a 47 it will barely up the gear inches but drastically increase the skid patches from 8 (46x16) to 16 (47x16), both of which are based on ambidextrous skidding.

Prolly said...

What determines the number of patches?

47:16

SP CRxFW GI GIdf DI diff DF PRPM RT
---------------------------------------------------------------------------
1> 47x16 83.72 0.00% 263.01 0.00 21'11.01" 240.90 1:2.94

48:16

SP CRxFW GI GIdf DI diff DF PRPM RT
---------------------------------------------------------------------------
1> 48x16 85.50 0.00% 268.61 0.00 22' 4.61" 235.88 1:3.00