Excuse my possible ignorance, but if I can skid with either foot back does that double the amount of skid patches that I will have on my tires? I ride a 48/16. Thanks!

Yes, ambidextrous skidding does double the number of skid patches.

Thanks a bunch!

48/16 factors out to 3/1. So you only have 1 skid patch. Since both your c-ring and cog are even toothed, skidding ambidextrously won't make a difference. Still only 1 skid patch.

Duh, I didn't even read that part of the sentence...If you're really worried about it throw a 17t cog on there and you will be golden.

Also, the double skid patch thing only works if you have an odd denominator, an even one will give you the same number of skid patches even if you can skid with either foot forward (what moki just said).

in this case ambidextrous skidding WILL create a second skid patch. math is fun.

edit: it's an odd numerator that determines whether or not you double the patches.

With the 17t cog will that be a faster/slower gear, and will I need a new/longer chain?

The 17t will give you a lower gear. I ride 48 x 17 and like it a lot, much better for my knees than what I was pushing before. How much room do you have to spare in your dropouts? With a one tooth change, you probably won't need a new chain (well, another link) unless you're already right on the edge.

so many track bikes come with 48/16 gearing and people ride them on the street.

i feel bad for those people for not knowing better.

In this case, yes. 2 skid patches is what you'll get.
Since each pedal rotation causes the rear wheel to rotate 3 times, 1/2 pedal rotation will produce 1-1/2 rear wheel rotations -
If, however you were for some reason running 38-19 or 36-18 or some other combination that created a wheel to pedal rotation ratio of 2-1, then ambidextrous skidding wouldn't help, because 1/2 pedal rotation would produce 1 wheel rotation.

If you like the ratio don't bother getting a new cog - just be sure that occasionally you loosen the rear track nuts, pull the chain off the cog, rotate the rear wheel a little bit, then tighten up the chain and track nuts again. That way you'll be applying the uneven wear to different sections of the tire. It will take about a minute.

if you are worried about your ratio being too low with a 48x17 you can also up your chainring to a 50t to get you closer to the 3-1 ratio you had. that still gives you 17 skid patches (34 if you're ambidextrious). the only problem would be using a 51t, because that would put you back exactly on 3-1.

with a 50x17 ratio up from a 48x16 you would probably have to add a little to your chain, though... so it just depends what your priorities are.

I love 47 chainrings. 47 is a prime number so (given the skid patch theorem) you can swap cogs all you want and you will always have a large number of skid patches.

to be completely honest, though, my bike doesn't go more than a couple weeks without the rear wheel coming off, either for a flat or cleaning or repair of some kind. just taking the wheel on and off changes the skid spot as long as you don't put it back on in the same spot in relation to the cranks.