Singlespeed & Fixed Gear - Explain to me, gear inches

I'm the last man out of the cave.

Because tires and wheels are different sizes so simple ratio doesn't provide as much information. Some would argue that gear inches don't provide enough information either.

makes it easier to compare bikes with different sized wheels without having to do very much math

it's another way for people to be vague.

it's another way for people to be vague.


right, I think you are.

why do thermometers have numbers on them?

How else to make a schematic comparison of ,say 44x17 and 50x19. Which is bigger? How would you measure if not in distance travelled?

How else to make a schematic comparison of ,say 44x17 and 50x19. Which is bigger? How would you measure if not in distance travelled?


well if the wheel size is the same it's easy
2.58 vs 2.63

Perhaps I'm getting old an onerous, like 165.

But really, why do gear inches matter to people? I can't for the life of me understand why it @#$@# matters. It seems people obsess over it. I started 42x16. It got easy. I bumped up once to 44x16. Things weren't hard. I built some stamina, some speed, got comfy and went 48x15. Which seems plenty. How would gear inches play into this? It seems to me that it really superflous information.

Or, I'm the last man out of the cave.

Other people obsess over it? Seems you're the one changing your gearing all the time.

Its a way of expressing how easy or hard a gear is. Since there are many equivalent gears, for example a 51/17 is exactly the same as a 48/16, its easier to talk about gear inches, which is the number of inches the bike travels with one revolution of the pedals, than it is to talk about specific CR/cog combinations.

In general, a 70 inch gear is a pretty easy around town gear for the flats. The 42/16 gear you started with is about 70 inches. Track racers usually ride something in the 88-92 inch range. Your 48/15 is about 86 inches, so you are getting up there with the track racers.

Easy to calculate, Cr teeth divided by cog teeth times 27 gives you gear inches.

it's another way for people to be vague.

There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.

I started 42x16. It got easy. I bumped up once to 44x16. Things weren't hard. I built some stamina, some speed, got comfy and went 48x15.
All this means nothing without tyre/wheel size factored in. hence gear inches.

and some will say that gear inches is useless without taking crank length into account. hence sheldon's gain ratios.

There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.
you=wrong.

There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.

That's not exactly how gear inches work and it is still vague compared to gain.

except gear inches doesnt equal distance traveled per crank revolution

circumference= Pi * diameter

gear inches = gear ratio * wheel diameter

actual distance traveled per crank revolution is gear ratio times circumference

a 72 inche gear is equivalent to riding a highweel bike with a 72" front wheel.

read this: http://www.sheldonbrown.com/gain.html

There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.

oh sorry, was i being vague?

But really, why do gear inches matter to people?
One valid reason I can think of is going between offroad 26" and 29" wheeled bikes. In order to keep your gearing consistent, you figure out the gear inches and keep that the same.

I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.

it's another way for people to be vague.

Totally OT, but you know that you spelled "Szyslak" wrong,
right?

Totally OT, but you know that you spelled "Szyslak" wrong,
right?

You're both wrong

http://www.landofthelost.com/images/lilenik.jpg

Sleestaks

One valid reason I can think of is going between offroad 26" and 29" wheeled bikes. In order to keep your gearing consistent, you figure out the gear inches and keep that the same.

I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.
But people do go between different tires often enough. When it snows I put a 32C xcross tire on my rear wheel, which increases the gear inches of my bike.

I need at least 80 inches to stay with my Sat morning geared group ride.

Since there are many equivalent gears, for example a 51/17 is exactly the same as a 48/16,

while we're on the topic:

can someone sum up the advantage/disadvantage (if any) of 2 different combinations that have the same gear inches?

I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.

Ahem.

while we're on the topic:

can someone sum up the advantage/disadvantage (if any) of 2 different combinations that have the same gear inches?

different skid patches
more teeth=longer wear
different virtual chainstay length for magic gear
arguably even-even combos wear longer (says Sheldon)

Karsten of course gear inches are useful. It shouldn't really need explanation. What a silly thing to start a thread about.

If a rider knows his gear inches, and wants to go up a little in effort and speed, or down a little in effort for more controllability, he can look at a gear inch chart and see the cheapest and easiest combination for the result he wants.

I ride a 53 X 19 for 73 inches.

What would I need to do to go to 75 inches?

77 inches?

If I have reference point, or a known starting point, I can make informed choices at how to go where I want.

I don't see that as an obsession but as simple information for making cost effective choices.

Other people obsess over it? Seems you're the one changing your gearing all the time.


You get oil.

That was over a 4 year period.

I need at least 80 inches to stay with my Sat morning geared group ride.

See, this was a my previous understanding. But, in order to maintain speed and keep ahead, I simply bumped 46 to 48. 48, higher, thus harder, but resultant, faster.

I must be dense. I mean, it's like a pebble, a stone, and a brick. You through the pebble, it might hurt someone. Take a stone and throw it, it's gonna leave a mark. But a brick, that's going to be brain damage.

So, you could take physics into it, and explain the whole thing about mass and velocity, and impact and transfer of energy.

But, really. If you need a pebble, you use a pebble. If you need a brick, you use a brick.

Seems like people work to hard to caculate what they are doing and.. don't really enjoy what they are doing.

Or maybe it's a hobby.

I just don't get it. Must be something wrong with me.

A bike with a 35mm tire is geared higher than the same one with a 23mm tire.

dutret had it with post 2, i don't see what is so hard to get here

Seems like people work to hard to caculate what they are doing and.. don't really enjoy what they are doing.

It might seem that way to William in his imagination, but I thoroughly enjoy what I do, and understanding it only adds to the enjoyment.
It also adds to the performance.
I have gained a lot of effieciency and speed from constant refinement, and constant refinement has come from constant study.


People who want to excel at something, or enjoy it to the max, study it.
They don't study it out of some duty or anal obsession, but out of fascination with the subject.

I look at charts of chainrings and cogs and the resulting gear inches and think about things like riding through the Cascade Mountains and what gear combination would let me do that comfortably.
I study the known to gain insight into the unknown.

If you like airplanes you study airplanes and all the silly numbers associated with flight.

If you like women, you study women, often in great detail. :)

Some people who really, really like fixed gear bikes talk about goofy things like gear inches and the fine, maybe even nonexistent differences between cranksets.

Clearly not William's cup of tea.

I can live with that.

Can William live with it?

See, this was a my previous understanding. But, in order to maintain speed and keep ahead, I simply bumped 46 to 48. 48, higher, thus harder, but resultant, faster.

I must be dense. I mean, it's like a pebble, a stone, and a brick. You through the pebble, it might hurt someone. Take a stone and throw it, it's gonna leave a mark. But a brick, that's going to be brain damage.

So, you could take physics into it, and explain the whole thing about mass and velocity, and impact and transfer of energy.

But, really. If you need a pebble, you use a pebble. If you need a brick, you use a brick.

Seems like people work to hard to caculate what they are doing and.. don't really enjoy what they are doing.

Or maybe it's a hobby.

I just don't get it. Must be something wrong with me.

But let's say that you ride a bike geared at 48x16. Someone rolls up with a bike geared at 48x16. Are you pushing the same gear? If the person's wheels are a different diameter than no, your gearing is different. And what about that guy riding 39x13? Is it immediately obvious that he's riding the same gearing, assuming that you both have the same size wheels/tires?

Gear inches make comparisons easier. Instead of saying "I ride a 47x16 with 700x23C tires" I can say "I ride 77 gear inches." You tell me which is easier.

But let's say that you ride a bike geared at 48x16. Someone rolls up with a bike geared at 48x16. Are you pushing the same gear? If the person's wheels are a different diameter than no, your gearing is different. And what about that guy riding 39x13? Is it immediately obvious that he's riding the same gearing, assuming that you both have the same size wheels/tires?

Gear inches make comparisons easier. Instead of saying "I ride a 47x16 with 700x23C tires" I can say "I ride 77 gear inches." You tell me which is easier.

Must be a San Diego thing, cause all I see here fixed is 700cc tires.

Clearly not William's cup of tea.

I can live with that.

Can William live with it?


This post (Mine) is about half poking fun at gear inch geeks, and half wondering the appeal is out of an honest desire to understand why people talk it up so much.

How else to make a schematic comparison of ,say 44x17 and 50x19. Which is bigger? How would you measure if not in distance travelled?


By simple use.

Karsten of course gear inches are useful. It shouldn't really need explanation. What a silly thing to start a thread about.

Uh, lack of knowledge about geek inches never stopped me from riding.

Are gear inch calculators the virtual gun of the keyboard cowboys?

If people didn't know your history on this board, this would have been blasted as a troll post in about thirty seconds. I can sense the scrunched up eyebrows in the responses. :o

If people didn't know your history on this board. :o

What history is that?

:)

So many new folks, I'm pretty much new myself.

which is easier...

knowing that someone with ratio 46x16 is basically the same as 52x18

or

knowing that someone pushing 75.6 gear inches is basically the same as 75.9 gear inches




it should speak for itself.


edit: i didnt read any of this thread

OK Karsten, I will answer your (fairly dumb) question. There are many reasons why gear inches is a useful measurement.

1. If you want to gear up or down a certain amount, often adding or subtracting a teeth from your existing setup (the bonehead method) can have undesirable consequences. It may throw off skid patches, etc.

2. What if you want bigger rings for better wear, but about the same development as your current gear?

3. For different people to be able to meaningfully discuss gearing, a universalizable standard is needed. Gain ratios are a tiny bit better, but crank length makes so little difference that you can get along without it.

4. Say you need a magic gear, and you want it to be well suited to your commute.

5. Maybe you want a setup with all prime numbers, and you want it to be suited to your commute.

6. Maybe you want a setup with all odd numbers, and you want it to be suited to your commute.

7. Maybe you want a setup with all even numbers, and you want it to be suited to your commute.

I could go on; there are all kinds of conceivable situations where calculating gear inches is useful. Knowledge is power. I am bewildered that you do not seem to understand this.

...geek inches...keyboard cowboys...

William pretends to not understand because he likes the attention he gets from belittling the interests of others.

Kinda sad.

What has happened to this forum?

I moderate other forums and I have, in the past, preferred this forum to any other.

I liked the way people wrote here (some great, unpretentious, natural writing here) and their zeal for fixed gear bikes.

I've noticed a number of people who I really admired, like absentr, have disappeared.

Gone away.

Well, maybe this forum has run its course.

Like I said, kinda sad.

Does anyone here remember when I fell on my bike, broke all those ribs and collapsed my lung?

The doctors punched a hole in my chest and put a tube in it to suck my lung back into shape.

I had tubes and wires going all over the place.

I asked for a computer and they gave me one, and I came here while the hospital, almost a living thing itself, sucked at my chest through a tube.
I couldn't hear the suction machine behind the walls going pocketa-pocketa-pocketa, but I could feel it inside me.

I felt so connected, to the hospital, the plumbing, tubing and wiring, and, through the internet, to friends on this forum.

Kind of a universal cosmic thing, y'know?

People hundreds and thousands of miles, even continents away, talked to me real time through the internet while the hospital suctioned out the air between the outside of my lung and the inside of my chest wall.

Not that I felt afraid or alone.

I just couldn't quite understand how I could get hurt so bad by something I loved so much.

I remember absentr took a bad fall that same month, during a race, and got hurt a lot worse than I did.

He recovered and built a bike with pink Phil hubs.

Didn't he?

Anybody remember that?

Well, the pendulum swings first one way and then the other.

Maybe this forum will swing back in a better direction.

way to kill a perfectly petty argument ken!

Totally OT, but you know that you spelled "Szyslak" wrong,
right?

Read: Copyright infringement.

This post (Mine) is about half poking fun at gear inch geeks, and half wondering the appeal is out of an honest desire to understand why people talk it up so much.

Anybody who seriously rides the road or the track is very sensitive to gearing. Gear inches is a way to quantify and experiment with gearing, to find the best gear for you and for different situations.

Now you seem to be of the mindset that "I don't need no stinking gear inches to know whether I'm riding fast or slow, I go by how it feels" but eventually riders will get to the point where a 48/14 is too big because it "feels" too big and a 48/15 is too small because it feels too spinny. Only one tooth difference, right? Well the gear inches are 92 and 86 respectively. A huge difference in gear.

To get a slightly bigger gear, you have to go to a gear chart (or much easier, just calculate it) to find the right CR/cog combination.

53/18 doesn't mean a whole lot to me because I don't have gear charts memorized. But I know that a 92 inch gear, no matter what CR/cog combination achieves that, is way too big for me now.

Must be a San Diego thing, cause all I see here fixed is 700cc tires.



A bike with a 35mm tire is geared higher than the same one with a 23mm tire.



Don't make me quote myself. I get angry when I have to quote myself, and you wouldn't like me when I'm angry.

You're both wrong

http://www.landofthelost.com/images/lilenik.jpg

Sleestaks

Dude, that is awesome. I can't remember the show, was it "land of the lost"?

Must be a San Diego thing, cause all I see here fixed is 700cc tires.
As has been pointed out many times, 23C tires will give you a different gear inch than a 20C or 25C or whatever tire. And I'm sure even in San Diego people are riding with different tire widths. Not to mention I have some really short friends who ride 650C wheels.

But even ignoring the usefulness of gear inches with respect to different wheel sizes, it is still useful for comparison. To give you an example I was recently in a roller race. There is a UCI gear limit to how large a gear you can use while roller racing. That limit is 7.69 development meters (the European equivalent to gear inches). Since you seem to be suggesting that gear inches (and by congruence, development meters) are somewhat pointless, why did the UCI specify the gear limit in development meters instead of gear ratios? Well the problem is that there are dozens of combinations of gear ratios and tire widths that will get you to the limit. To list them would be a lot harder and more confusing that simply saying, "No gear over 7.69 development meters." and let the riders do the calculations themselves (actually the officials mark off 7.69 meters on the floor and roll out your bike).

To give you an example, the following gear ratios and tire sizes will give you 7.69 (or at least, as close as possible) development meters:

for 700x23C tires:
53x15, 51x14, 47x13, 39x11
for 700x20C tires:
48x13, 53x14

...a 48/14 is too big because it "feels" too big and a 48/15 is too small because it feels too spinny. Only one tooth difference, right? Well the gear inches are 92 and 86 respectively. A huge difference in gear.

To get a slightly bigger gear, you have to go to a gear chart (or much easier, just calculate it) to find the right CR/cog combination.

That pretty well explains it, doesn't it?

By simple use.

Ok you go use those 2 gears and switch between them on one bike and tell me if you can notice the difference (wait incl) .. If you say you can -I say bah.. Not because of anything other than I would not believe it.. Simple too..