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-   -   Uncle Sixty's Gearing Primer for Newbs (http://www.bikeforums.net/singlespeed-fixed-gear/716371-uncle-sixtys-gearing-primer-newbs.html)

Sixty Fiver 02-27-11 07:10 PM

Uncle Sixty's Gearing Primer for Newbs
 
So, you just built your first fixed gear or single speed and now you are obsessing over the question we have all asked ourselves... "What gear ratio should I use?".

And then, you start a thread asking the question that has been asked a thousand times.

If you want to calculate gear inches go here:

Sheldon Brown's Gear Inch Calculator

Rabbit Calculator

When you get that number calculated it might not mean a thing to you so maybe this will help.

When you buy a stock bike many companies set them up with a gearing in the high 70's which is what most folks would use if they were riding on the track, if your name is Boonen and have knees and legs of steel you might be running something in the mid to high 80's or the very low 90's.

For the rest of us mortals a gearing of 72 seems to be just about right for healthy individuals as this is low enough that you can tackle reasonable hills, ride into the wind, and still dial it up when you need to haul some ass.

If you want to go fast on a fixed gear you will need to learn how to spin efficiently at higher rpms which will make your knees, heart, and lungs very happy.

If you live in hill country or like to tour on your fixed gear a lower gearing can be preferable and I would suggest running a double stepped hub to give you a couple of gears to play with.

If you ride in the winter something in the high 50 to low 60 gear inch range will allow you to slog through some pretty nasty snow and allow you to do seated skids to keep your weight balanced and prevent wipe outs.

My fixed gear road bike runs a 72/80 and the 72 gets the lions share of use while my winter bike ran a 59, and my vintage club bike has a 69/76.

The cheapest way to change gearing is to change your rear cog and running the largest combination of chain ring and cog to get your desired gearing will make your drive more efficient and reduce drive train wear... and a 52:17 (80 gi) looks pretty badass to boot.

Messengers usually don't run monster gearing... when I did this I ran 76 gear inches in the summer and worked in a pretty flat area.

I Have a Bike 02-27-11 07:13 PM

I smell a new sticky

Scrodzilla 02-27-11 07:22 PM

Your nose knows.

Motopecane 02-27-11 07:32 PM

Thank you for this.

xkillemallx16 02-27-11 07:40 PM

Quote:

Originally Posted by Sixty Fiver (Post 12288916)
Messengers usually don't run monster gearing... when I did this I ran 76 gear inches in the summer and worked in a pretty flat area.

a large amount of messengers used geared bikes too.

Sixty Fiver 02-27-11 07:53 PM

Quote:

Originally Posted by xkillemallx16 (Post 12289097)
a large amount of messengers used geared bikes too.

I could post a gearing primer for that as well but this is ss/fg and in here we know that multiple gears are for people over 45.

:D

Squirrelli 02-27-11 08:10 PM

I'd like to contribute my little calculation formula without using a program...

Basically, charing (44) divided by cog (17) times tire size in inches (23c or 26.275") = 68 gi

All you have to do is remember the number for your tire and you're good to go. Here's a list of popular tire sizes:

23c - 26.275"
25c - 26.375"
28c - 26.775"
32c - 27"
35c - 27.175"
38c - 27.3"

I find this very useful when I don't have internet handy.

Sixty Fiver 02-27-11 09:14 PM

Squirelli - The manual calculation works really well... actual diameter will vary depending on tyre sizes and some of us run other wheel sizes on or fg bikes... 26 inch mtb tyres and 20 inch wheels will have greater variance than road tyres due to different tread patterns and the 20 inch tyres on my folder are actually 19.5 since they are low profile, high performance tyres.

Ken Cox 02-27-11 09:54 PM

I like Bare Knuckle Brigade's Rabbit Applet for studying gear ratios:

http://software.bareknucklebrigade.c...it.applet.html

Lilcphoto 02-27-11 09:57 PM

Quote:

Originally Posted by Ken Cox (Post 12289738)
I like Bare Knuckle Brigade's Rabbit Applet for studying gear ratios:

http://software.bareknucklebrigade.c...it.applet.html

Google Chrome Browser doesn't seem to like that one... So I use All-City's

1nput0utput 02-27-11 10:12 PM

Quote:

Originally Posted by Lilcphoto (Post 12289752)
Google Chrome Browser doesn't seem to like that one... So I use All-City's

Unfortunately that one only allows 622 mm BSD wheels and doesn't account for different crank arm lengths. The other ones have a much larger selection of wheel sizes and variable crank arm lengths.

Sixty Fiver 02-27-11 11:02 PM

Quote:

Originally Posted by Ken Cox (Post 12289738)
I like Bare Knuckle Brigade's Rabbit Applet for studying gear ratios:

http://software.bareknucklebrigade.c...it.applet.html

This is also a very good application and will add the link to the OP.

Crank length has nothing to do with calculating gear inches and is only a factor if you are calculating gain ratios... for as much as I loved Sheldon his preference for this and prediction that an inch based measurement would fade away, I still prefer gear inches.

puppypilgrim 02-28-11 01:21 AM

I prefer Gear Inches too! Currently 72 on my road bike and 66 on my folding bike. SS\FG riders (not hipsters) march to the beat of a different drum I guess.

markaitch 02-28-11 09:08 AM

finally...
a thread that i think is really helpful...glad it got made into a sticky!
anyway, i am never completely happy with the gear ratio (or gear inches) i have on my road bike at any given moment.
yeah, i know that's part of fg/ss riding, but i still have plenty of q's on this subject & hope that you guys will bear with me if i come back here on occasion with some of them.

Sixty Fiver 02-28-11 10:57 AM

mark - There are many helpful threads here... the sticky guide is full of them.

Decepticondc5 02-28-11 02:03 PM

noob question:

would a persons weight affect what gear ratio they should select?

Squirrelli 02-28-11 02:25 PM

Not necessarily, it depends on the person's ability to use that ratio.

For example:

http://www.pixalo.com/gallery/data/5...y_filtered.jpg

Chris Hoy, 200lbs, claimed to ride 52/14 ratio in all his races.

Compared to Eddy Merckx during his Hour Record:

http://1.bp.blogspot.com/_tmCXlTvwjk...eddy-mercx.jpg

He is only about 170lbs or so but he is able to push a 53/11 gear to set the record.

In summation, a riders weight does not necessarily affect the ability of the rider to use the gear to the fullest, quite the contrary, a lot of track riders are pretty massive like:

Kevin Sireau

http://www1.pictures.zimbio.com/gi/K...yFi-66vTql.jpg


Theo Bos

http://www.crooze.fm/images/stories/...s_op_piste.jpg

Gregory Bauge

http://farm3.static.flickr.com/2456/...ebbb487bd4.jpg

But there are skinny road riders that could push a huge gear as well:

Alberto Contador:

http://www.chicagosuburbsonline.com/...dor_astana.jpg

Andy Schleck

http://www.roadbikeaction.com/conten...bikeaction.jpg

All in all, weight doesn't matter much, it's the strength of the rider that counts.

funkycharms 02-28-11 02:44 PM

just the thread I was looking for, thanks!

Decepticondc5 02-28-11 02:55 PM

thank you squirrelli :thumb:

famous amos 02-28-11 04:28 PM

BTW OP, 52x17 isn't 72gi, its more like 80.

caloso 02-28-11 04:41 PM

Very nice.

FWIW, I ran a 52-15 for a flat 10 mile TT last summer. I was 30 seconds faster than the previous year on my geared bike, but that was probably due to the aero helmet and shoe covers. ;)

Sixty Fiver 02-28-11 04:43 PM

Quote:

Originally Posted by famous amos (Post 12293530)
BTW OP, 52x17 isn't 72gi, its more like 80.

Thanks !

Got my numbers swapped... my 52 with a 17 /19 is a 72/80 gearing.

Used to rock a single gearing of 83 gear inches and that was my daily driver for 5000 miles... dropped that back to 76 after that and just found that I could go even faster.

In the old days, time trialists would run a 76 inch gear to do a sub hour 40 (25 miles) and this was also the gearing road racers used for much of their spring training.

I f'd up my back some years ago and the resulting nerve damage affects my left leg which makes it hard for me to mash as big a gear and usually find myself running that 72 which I can spin like a gerbil on crack.

1nput0utput 02-28-11 08:17 PM

Quote:

Originally Posted by Sixty Fiver (Post 12293592)
… spin like a gerbil on crack.

Excellent mental image.

NikZak 02-28-11 11:17 PM

i think this thread should be subtitled:

"Now noobs have no excuse to post new threads about gear inches every three days"

revelstone 03-21-11 03:25 PM

exceptions to every rule
 
Quote:

Originally Posted by Sixty Fiver (Post 12289170)
I could post a gearing primer for that as well but this is ss/fg and in here we know that multiple gears are for people over 45.

:D

now now lets not write anything in stone. i ride a ss/fg, 700 wheels, 44/16 gearing. and i like it more than my 21 speed mountain bike that's spending most of march and the rest of summer and most of it not all of fall in the shed. same as last year. i'll be 55 on my next birthday.


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