# Gear ratio



## Todd_Pearce (Oct 15, 2012)

I am currently running 48/21 and getting 16.6 mph before starting to spin out, I would like to go faster on flats (I would like to get to 18.5-19ish ) My question is am I going to see major difference going to a 20 cog or would it be better to go to 19 also what is that going to do to my climbing?? I can do a little harder on climbs but not significantly harder.


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## bonefamily (May 17, 2011)

You will notice a difference going from a 21t to a 20t, but perhaps not as much as you think. I assume you are using 25c tires from your post in another thread which currently puts you at about 60 gear inches. Going to a 20t will put you more at about 63 gear inches. There will be a notable difference and how much depends on your strength and fitness. Moving to a 19t will put you at about 66.5 gear inches. IMO, a good medium gear is 65 inches but some consider that low and prefer closer to 70 inches.

With a 48/21 gear at 90 rpm's is about 16 mph. 90 rpm's is not really considered spinning out, however some have faster leg speed than others. I would suggest to work on your leg speed and see if you can't find a happy medium between it and a slightly higher gear. If you plan on doing alot of climbing, the lower gear comes in handy. 

Here is a good calculator to figuring all this stuff out:

http://www.sheldonbrown.com/gears/


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## UrbanPrimitive (Jun 14, 2009)

Bonefamily hit a lot of good points. I'm in the 70+ gear inch camp. I'm a bit of a masher, and when I'm in shape I like to push around 78-81 gear inches (in south eastern Michigan, pretty darn flat).

Historically one of the reasons racers trained in the early season by riding fixed was to develop their spin. Producing power while spinning at 140rpm isn't something that comes naturally to many, if any, people. Riding fixed forces the rider to develop power and spin at far ends of the spectrum. In the long term it can significantly change your riding form. My boss started training fixed in the '70s and now turns around 120rpm most of the time. 

Unless you have a medical issue limiting your safe heart rate range or leg mobility/stability, spinning out at 90rpm suggests more riding is called for. The more you ride at high cadence the more comfortable you will be spinning, and the higher you can push it. It seems likely that adjusting your gearing will be a consideration as eventually. Until your leg strength catches up, letting you grind up those hills, working on cadence is probably the place to start.


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## Aggdaddy (Jun 18, 2010)

I think my bike came with a 16t cog and I'm using the stock 46t ring. From the Sheldon Brown website that was mentioned, that puts me at about 75.8 gear inches.

Feels good when the wind is on the back. Not so good on the front. But I use this bike for training so its all good. If I get up to about 90 to 100 cadence, I think I am doing about 19+ But I am usually doing 18 comfortably with or without the wind. Mild wind that is.


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## David Loving (Jun 13, 2008)

Try a 19.


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## wooglin (Feb 22, 2002)

+1 on the spin faster. 90rpm ain't much. 

THEN put on a bigger gear.


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## Todd_Pearce (Oct 15, 2012)

Bonefamily thanks for the reply, a lot of our rides have flats and hills in them and I would like to go faster than 16.6 top speed ( that's what I meant by spinning out) at 48/21 the hills were doable, could be a little harder and that would be ok, I would like to get to about 18.5--19 mph on flats. On the same ride with geared bike I am crusing at 21-22 +. ( 50/19 ). I know I will never get that speed and still do the same hills with SS. But looking to get a bit faster.


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## Todd_Pearce (Oct 15, 2012)

To everyone else who replied I would also like to thank you( did not see all replies from email notification ) @Urban I really don't like to spin, something I might have to get used to.. I like to hammer it and have long fast rides. I built SS to get stronger on hills, did not realize I was going to have to sacrifice so much speed..


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## rider9 (May 27, 2011)

I was using a 46/16 (75.6 gear-inches), which was fine in the flat areas near my house. I tried to ride it through some hills and found my motor couldn't handle that well, yet. I just switched my bike over to 46/18 (69 gear-inches). I will ride it tonight to see if that helps.

+1 on improving your spinning. You can improve to a higher spin if you work on it.


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## David Loving (Jun 13, 2008)

I find a single speed does better for me if it's at about 64-66. The hills go easier. The fixed gear I go a little closer to 70. I do not really ride those ss and fixed for speed, however - just for exercise and to get places.


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## JCavilia (Sep 12, 2005)

Todd_Pearce said:


> To everyone else who replied I would also like to thank you( did not see all replies from email notification ) @Urban I really don't like to spin, something I might have to get used to.. I like to hammer it and have long fast rides. I built SS to get stronger on hills, did not realize I was going to have to sacrifice so much speed..


Here's a little more math. You're running a 60-inch gear, spinning about 90 on the flats, going about 16 mph, you don't want to spin faster, and you want to go about 19 mph. A 70-inch gear puts you there. Get an 18-tooth cog.


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## wtfbbq (Apr 5, 2012)

Todd_Pearce said:


> I am currently running 48/21 and getting 16.6 mph before starting to spin out, I would like to go faster on flats (I would like to get to 18.5-19ish ) My question is am I going to see major difference going to a 20 cog or would it be better to go to 19 also what is that going to do to my climbing?? I can do a little harder on climbs but not significantly harder.


All this really depends on you fitness and how steep and long your hills are. I ride routes with rolling hills and find I like a 46x17 which is nominally a 73 inch gear. I've been able to hold my own on group rides where it doesn't turn into a total hammerfest. I feel pretty comfortable spinning the flats at 100-105rpm if I want to go fast.

FWIW, I've done a local Strava sprint KOM 1/3 mile slightly downhill at 32 mph in that gearing. Learning how to spin is easier than it sounds ... Just commit to increasing your cadence for a few weeks and you'll be surprised how much faster you turn the pedals.


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## serious (May 2, 2006)

Todd_Pearce said:


> To everyone else who replied I would also like to thank you( did not see all replies from email notification ) @Urban I really don't like to spin, something I might have to get used to.. I like to hammer it and have long fast rides. I built SS to get stronger on hills, did not realize I was going to have to sacrifice so much speed..


You should go to 48x18. Even that requires good spinning skills on flats. I am not a great spinner so I ride 48x16, but I am in good shape and race single speed mtb. The climbs can be hard and occasionally I have to grind and mash a steep hill, but I have to do that on the mountain bike all the time so great cross training.


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## BianchiJoe (Jul 22, 2005)

David Loving said:


> I find a single speed does better for me if it's at about 64-66. The hills go easier. The fixed gear I go a little closer to 70. I do not really ride those ss and fixed for speed, however - just for exercise and to get places.


Ditto. 42 X 17 gets me up pretty much anything, but my geared friends drop me on the flats. I'm still moving along pretty well, and it's a very comfortable gear for commuting, when I have a pack on my back.


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## Todd_Pearce (Oct 15, 2012)

After all that talk about going to 20 or 19 I actually went down to a 17 and so far so good. Thanks for all your input.


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## alrsv1 (Oct 26, 2012)

I'm running 44/14 with 170 cranks and 26" wheels, the gear calculator says that's 81.7 gear inches. I find it perfect for commuting around Sydney. Just annoying when I get stopped at lights as it takes a bit of effort to wind it up again.


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## Wingard64 (Oct 29, 2012)

That's real good power for sure!


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## JCavilia (Sep 12, 2005)

Todd_Pearce said:


> After all that talk about going to 20 or 19 I actually went down to a 17 and so far so good. Thanks for all your input.


Probably a good choice. 74.3-inch gear. At 90 rpm, you're just a hair under 20 mph.


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