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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)

tristen 04-14-11 10:16 PM

Quote:

Originally Posted by Sixty Fiver (Post 12505893)
chain ring teeth x wheel diameter in inches / cog teeth = gear inches.

ah! cheers - i was wondering about that. it's good to know.

do you know why does the sheldon brown calculator asks for crank length? is that his own take on the gear inches calculation?

Sixty Fiver 04-14-11 10:28 PM

Quote:

Originally Posted by tristen (Post 12509152)
ah! cheers - i was wondering about that. it's good to know.

do you know why does the sheldon brown calculator asks for crank length? is that his own take on the gear inches calculation?

Crank length is a factor when you calculate using gain ratios and is not required when you calculate gear inches.

tristen 04-14-11 11:20 PM

thanks again!

er, isn't that bicycle repair man? nice :)

sillygolem 04-20-11 01:19 PM

Quote:

Originally Posted by sillygolem (Post 12507620)
I think I would probably want to go with lower gearing if I was riding a more relaxed geometry.

Came across this when researching cruisers:
http://www.atomiccycles.com/coaster.html

The Coaster Brake Challenge recommends around 50 gear inches for racing cruisers. Note that most of their courses are hilly.

PistaDalMine 05-25-11 01:09 AM

Here is a site to help determine crank length http://www.machinehead-software.co.u...alculator.html

mgeoffriau 05-25-11 11:59 AM

Running 40x16 on my Primus Mootry. Looks like it's just a tick under 67 gear inches. Anyone else running a gear this low? I don't mind spinning but I really have nothing on downhills.

randomstream 07-07-11 09:26 AM

I am making a SS and was wondering if a BMX style gear would work for the rear?

sillygolem 07-15-11 12:49 AM

Quote:

Originally Posted by randomstream (Post 12892580)
I am making a SS and was wondering if a BMX style gear would work for the rear?

Yes.

rosecity 07-20-11 04:40 PM

Quote:

Originally Posted by mgeoffriau (Post 12692554)
Running 40x16 on my Primus Mootry. Looks like it's just a tick under 67 gear inches. Anyone else running a gear this low? I don't mind spinning but I really have nothing on downhills.

I just picked up a 39t FSA chainring and i'm going to be trying it out with either 16t or 18t in the back... never tried a gearing this low before... I usually ride 46x16 in the city with no hills...

Reynolds 08-29-11 03:54 PM

Just built my first SS with a KHS frame and parts I had laying around. 42x17 doesn't need a chain tensioner and is OK for city riding, since I'm not concerned about speed. I'm 60, FWIW.

puppypilgrim 09-03-11 12:03 AM

Quick update, I'm now running 46x20 FW (that's freewheel) for a singlespeed of 61-62 gear inches.

Its not slowing me down any and if anything, my average speed as increased as I am accelerating through corners and climbing faster than I used to. Squirrelli paced me using his bike computer and we were cruising at 19-21 mph. My cadence was 110 rpm with sprint accelerations to 27 mph (145 rpm). Since its a 20T freewheel, I have no issues with spinning out down hills as I can coast. But I do spinout on the flats now when pushing it. This ratio however is a blessing where I live because there is always a headwind blowing - also much easier acceleration and less strain on the knees.

Lilcphoto 09-05-11 10:04 PM

46t Eighth Inch front to 17t all-city rear:

https://lh4.googleusercontent.com/-b...%252520013.JPGhttps://lh4.googleusercontent.com/-7...%252520012.JPG


46t Eighth Inch to 14t Dura-Ace rear:

https://lh5.googleusercontent.com/-y...%252520014.JPGhttps://lh4.googleusercontent.com/-U...%252520011.JPG
Just wanted to share, at least with the Brassknuckle, that the difference between a 14t and a 17t is roughly 1/3rd the dropouts

jlind 09-21-11 08:05 PM

For me, the stock 48x16 on my Bianchi Pista is OK for a track workout without running out of spin, but its 81 inches is too high a gearing for riding around the neighborhood and city. It's relatively flat in the city here and gearing down to 48x18 (~72") is working well for me. There are some good rollers with short but steep grades in the rural areas. I'd have to gear the fixie down further for that, probably by another 8-10 inches into the mid to low 60's.

I share the observation that spinning faster, including on a road bike with a triple chainring and 10 cogs, goes faster. I see too many guys around here mashing their geared road bike pedals with slow cadences when they could be faster if they geared down a cog. Frequently riding a fixed track bike helps for smoother spinning on a geared road bike. FWIW I'm 58, nearly 59.

Great to see this sticky on gearing with its use of gear inches!

Geeeyejo 10-17-11 01:48 PM

I am running 46/18 - 69 inches on the fixie I just completed - it is my first build at 50 yrs old. 15 miles ridden to date, with this AM being my first commute on the bike. There are some small hills on the route and building up speed leading to the hill resulted in minimal effort on the climb. Feels good in the flats as well. I have a brake and coupled with pedal resistance have not had any issues going down steeper hills either...

dannoh 10-18-11 02:37 AM

Running 45/17 here in Maine. Seems good so far. New to fixed gear with in the last 2 month's at 53 yrs old.

hollowmen 10-19-11 08:46 PM

Running a 46 15/17 flipflop, with the 17 being a freewheel. With 700 tires, that puts me at about 81/71.

I'm up northern Indiana. No hills to speak of, and the wind isn't too bad, though given that this is my first ssfg bike, I wish I would have gone a bit lower, but I enjoy it well enough.

Thanks for the thread!

Slaninar 11-02-11 02:06 PM

Question about gearing. :)

From experience on my geared bike 38 with 15 is almost perfect. That's arount 67 gear inches. A bit hard to start from traffic light, but I quickly build up revs and soon almost feel I need a higher gear. Nearest higher is about 71 gear inches (48 with 18) and higher than that is some 77 gear inches (38 with 15) which is too much 99% of the time (except when going down hill).

According to this, on a single speed, guess perfect would be 44/17, or 48/19 (if there is such combination). Is this OK for flat in town use?

iandusud 11-29-11 10:34 AM

Quote:

Originally Posted by puppypilgrim (Post 12506287)
Permit me to add to this discussion. Use the formulas referenced in the posts above to calculate what chain rings and cogs you need.

Online calculators are available here:
http://software.bareknucklebrigade.c...it.applet.html (does not work with Google Chrome)
http://www.sheldonbrown.com/gears/

Your preferred gear inch will depend on:
- how fit you are
- how strong you are
- the terrain you do 90% of your riding
- the wind conditions for the majority of your riding
- how many skid patches you want (if that's important to you)


Since most riders cannot perceive a 1 gear inch difference, consider the following gear ranges with soft edges, not binary precision.

60-65 gear inches = good for older riders or weak knees or touring.

66 gear inches = good all round gear for flats and hills. Not too slow on the flats, not too hard on the hills and wind. Touring is even possible. Great acceleration from standstill.

69 gear inches = near ideal for most people and most applications unless you are exceptionally strong. City gear and hills are feasible.

70-73 gear inches = superb range. At 100 rpm, it produces 21.4 mph (34.5 km/h). At 100 rpm, the force required to turn the pedals is still relatively light. Anything is this gear range produces an excellent balance between acceleration, hill climbing, combating winds and flat road speed. Note that at 20 mph (32.2 km/h), approximately 80% of the power being produced by the human body is being used to overcome air resistance. This is why it is so hard to sustain any speed above 20 mph (32.2 km/h) during a daily commute. If you know how to spin, this gear range will not be slowing you down.

76 -81 gear inches = this range maybe useful in places where there are no hills and where riding with a slow cadence is preferred to riding with a rapid cadence. All other things being equal, one will sweat less pushing a larger gear with a slow cadence at low speeds (say up to 15 mph) versus a lower gear with a high cadence. All bets are off if you push a large gear with a high cadence! This range is also harder on the knees due to the pedal force required to turn the cranks. Acceleration from a standstill will be noticeably slower than gears in the high 60s and low 70s. It's a tall gear for city riding and sprinting from traffic to traffic light and intersections. Hills will also slow you down in a big way.

81 and up gear inches = velodrome racing gears in controlled conditions, and short term training applications.

These are my opinions only based on general observation, lots and lots of reading and learning from others who have gone before.
Victor

A great post Victor. FWIW I've just turned 53 and have built up my first fg in thirty years and am running 69". Perfect for me and corresponds exactly to your comments.

Ian

LesterOfPuppets 12-03-11 09:41 PM

For those doing vertical dropout conversions, this page is amazing!

http://eehouse.org/fixin/fixmeup.php

Muffin Man 01-05-12 07:41 PM

is 51.9 a good starting point for gi on a mtb?

LesterOfPuppets 01-05-12 08:23 PM

Sounds like a pretty good spot. I tried 55.5 on my 26er and found it too high to get up some hills. But it was pretty close to what I want.

BezO 01-10-12 02:58 PM

Great thread!

I'm currently running 46/16 on 700x35c tires (78.1 GI according to bareknucklebrigade.com's Rabbit). Great on flats once I get going. Not so great acceleration compared to other riders I see. And a little tougher than I want on hills.

Question... I'm going up to 17T (73.5 GI) because of the hills and lack of acceleration. I have a flip flop hub though, so I'm wondering what I should put on the other side. Would going up to just 18T (69.4 GI) on the other side make sense? Should I go up 2 teeth with my "other" gear? 46/19 would put me at 65.8 GI. I'm not old nor do I have bad knees (Puppypilgrim's ranges).

Also, how much would I be moving my axle in the track-end flip flopping to 1-2 more teeth? Switching to bigger tires had me add a half link and move the axle about 2/3 of the way back in the track-end, so I don't have much room to play with.

This will be freewheel/freewheel by the way.

Lilcphoto 01-10-12 03:24 PM

It looks as tho my photos got their links cut... but I was able to get 3 teeth difference on mine (14t vs 17t) but if I were you, I'd go 18. That way, if it does feel too easy, you can always swap over to the 16 side.... Though I am a huge fan of low gears and spinning

bigbris1 01-11-12 05:53 PM

hai uncle 60

Nagrom_ 01-20-12 12:10 AM

My current gearing is 52x16, 85.7 GI. I'm buying a new crankset, comes stock with a 46t chainring. If I throw a 14t cog on the back, making it 46x14, 86.7 GI, it should perform pretty much the same, right?

Someone second me...


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