golden ratios
 

Have been riding 44x16 in New York/Brooklyn (mostly flat, some bridges, traffic) and as I got more in shape I would like to spin a little less and push a little more, so am thinking to either add a few teeth to my 44 or change the cog to 15 teeth (or add a few teeth to both, etc). I can do the math and will have to guess how much harder I will have to pedal but I was wondering if there are ratios to avoid i.e. that don't work very well, or some other considerations besides skid patches.

In other words, for instance, 44/15 gives a slight increase in development over 44/16 but also a much higher number of skid patches (15 as opposed to 4 for 44/16). So, odd numbers seem better (i.e. 47/16 or 49/16 rather than 48/16) or are there other factors that come into play to negate that, whether these are rational or irrational... (I was referring to the 44/14 ratio - 3.14... and 7 skid patches!)
Thanks.

There should be a medal awarded to whoever made that!

weird, i thought my 46/16 only gave me 1. i'm guessing that chart is assuming you can skid both ways?

a short explaination of how many skid patches is too few/too many and how many gear inches (same) would be useful I think.

or shall I beg 'pon bend'ed knee?

please please please please please please please please please please please please please please please please please please!?

i thought the chart was based on always skidding with the same foot...

more skid patches are better if you plan to skid. If not it doesn't matter.
somewhere around
70-80 for road
80-100 for track
45-65 for off-road

I think its assuming you are only skidding on one side, since it has some odd numbers in it.

Gear inch numbers are higher than than values I got from Sheldon Brown's calculator using 700c wheels. What gives?

The skid patch data is way helpful, methinks I'll forego the 45 tooth zen messenger in favor of a 43...

It looks to me like the gear inches chart is for 27" wheels, probably with 1 1/8" tires. The inches for 700X23 will be slightly lower.

It's based on 27" wheels and the oldey-timey formula: # of chainring teeth * 27" / # of cog teeth.

Gear inches are really only useful as a rough, relative measure (ie, comparing ratio to ratio), so it doesn't really matter that you're getting slightly different measurements. Measuring by gear inches also fails to take crank length into account.

m.

It appears you are absolutely correct. 27 by 1 1/8th, 170mm cranks according to Sheldon. Is the skid patch info the same?

you probably have a 48/16.. that's way more common and it's a 3:1

no, ive got 46/16. i had 48/16, which i knew was 1. my math is just really ****ing bad.
this is sweet though. now i can stop taking my wheel off once a week and rotating it 1/4 turn so i don't wear through it. ha.

You know you could also just easily divide 46 by 16 to see what comes out, and that's your ratio.

2.9. One of my favorites.

the chart refers to always skidding with the same foot forward.

to understand this, keep in mind that a full crank rotation does not equal an whole number of rotations of the wheel, so the spot in contact with the ground changes each rotation. the number of skid spots refers to the number of full crank rotations it takes to return to the original pont of contact with the ground. its all in the ratios.

to find the number of skid spots for your ratio write the number of teeth on the chainring over the number of teeth in the cog- a fraction . then simplify that fraction as much as possible. the denominator is your number of skid spots

for example my ratio 42/16 simplifies to 21/8. that means i have 8 skid spots

who needs math, when you have color coded charts with numbers and ****?

With all these mathematically challenged people on board, I'll ****ing make a fake gear inch chart that says that 44/16 is a lot harder ratio than 50/14 and that 40/20 is halfway between them etc. I'll sneak a link to it into one of these silly threads and practice my evil laugh while people try to pedal 52/12 and scratch their heads.

i thought gear inches was how far the bike travelled with one revolution of the chain ring. i can see how wheel size would make a difference, but whether or not you have 165mm's or 175mm's should'nt affect the revolution of the chainring. it's still only going around once.

am i wrong or am i wrong?

what are the bolded gear inches?
are those like the g-spots of gearing?

golden?

46:18 is 69.

Dinner for two!

no, I think you just did the math wrong. it's 48/16 that gives you one skid patch, two if you can skid ambidexterously.

(46/16 breaks down to 23/8 while 48/16, to 3/1 )

yeah. number of skid patches are determined only by how small you can simplify the denominator of your gear teeth ratio, cause that determines how many times you have to turn the cranks to have the rear wheel come to the same place.

See: http://sheldonbrown.com/chain-life.html

and: http://sheldonbrown.com/fixed.html#skid

Sheldon "Numbers" Brown