Singlespeed & Fixed Gear - Boy, did I feel stupid

I was on my commute to work the other day, I was riding my fixie with the rack, it's set up 48x17. I was cruising pretty good, the day was good, and the traffic on the bike path was light. I'm in my own world cranking out the miles, when this dude rolls up on a SS. He looks at me and asks if I'm running a &*^^%**(. I had no friggin' idea what he was talking about. He looks at me "you're running 48x17 aren't you?" "Yeah." "Isn't that a &*^^%$^%?" I had no friggin' clue what he was reffering to, except my gearing in inches, and I don't have a friggin' clue. It was like he was speaking Greek, I didn't have an answer. Hell, I didn't think riding a fixed gear I would ever be questioned as to what gear inches I was riding. I figured just riding fixed was cool enuf, now I have to know gear inches? I suck at math. I don't necessarily care what my inches are. I've gone to Sheldon's site and plugged in my numbers, but it doesn't mean anything to me.
But boy did I feel stupid.
Is this an important stat to know? Will I be cooler if I can spout gear inches? I just figured that riding my cobbled together fixies was good enuf.

i believe the gear inch measurement means that for every full revolution of the cranks the bike will travel that far on the ground.

i believe the gear inch measurement means that for every full revolution of the cranks the bike will travel that far on the ground.

Actually, gear inches is an old old old measurement and relates to the equivalent size of a penny-farthing big wheel. When the safety bike was new (two wheels the same size) people needed a way to relate the gearing to that of the penny farthing. If you multiply gear inches by pi then you get the forward travel of one pedal revolution.

Jim

But is it something you have in your cranium, so that when some one asks what you are riding you just blurt it out? I don't know it, I find just the conversation with mere mortals on why I ride a bike, much less a fixed gear a near daunting task, if I started spouting gear inches their eyes wouldn't just glaze over, I'd have to perform CPR to end the conversation.
By the amount of response to this I suppose that answers my question.

Lets play W\it- tomorrow spin hard and gve us an rpm flat out. You are the engine.
Somebody will do the math, engine rpm to torgue\gear ratio>

Calculating gear inches is indeed easy. Here is sheldon's calculator. Plug in the numbers and you will have your result:
<http>http://www.sheldonbrown.com/gears/</http>

for example: 48x17 with 700x25 tire size gives you 84.4 inches. This is how much you travel for one rotation of crank.

Actually, gear inches is an old old old measurement and relates to the equivalent size of a penny-farthing big wheel. When the safety bike was new (two wheels the same size) people needed a way to relate the gearing to that of the penny farthing. If you multiply gear inches by pi then you get the forward travel of one pedal revolution.

Jim

wouldnt you multiply it by 2*pi for one full revolution?

wouldnt you multiply it by 2*pi for one full revolution?

No because the circumference is pi * diameter which is what the gear inch represents. If gear inch = radius then yes it would be: 2 * pi * r

Jim

....for example: 48x17 with 700x25 tire size gives you 84.4 inches. This is how much you travel for one rotation of crank.

Ooops, see above.... gear inch * pi is the travel for one rotation of the crank.

Jim

c'mon guys; teach a guy to fish.

naisme, you already know your gearing (48 by 17). Calculate the ratio by dividing 48 BY 17 (2.82). Multiply by the wheel diameter (lets assume its 27 inches) = 76.14 gear inches.

to answer your other questions, no its not important to know. In fact, its rather useless. As jimv eluded, development is far more useful (how far the bike traveled per one revolution)...so multiply by pi (3.14159) = 239 inches.

No, you wont be cooler to anyone you actually give two wits about. Just ride and enjoy.