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What size chain ring and rear sproket should I start with?(13 posts)

What size chain ring and rear sproket should I start with?Ambishawn
Dec 1, 2002 8:44 PM
I am having a hard time locating front chain rings in 42t. I notinced that most street fixes have 42-15 or 42-16 on the web. Where do I get the sprockets and what sizes should I run for mostly level ground.
Sheldon Brown has all the info and parts you need.MB1
Dec 2, 2002 4:07 AM
Go to his Harris Cyclery website and check it out.

BTW, fixed I run 42/16 and 39/15 the wife runs 39/14 so don't feel like you are required to run a 42 chainring.
worry about the ratiobigrider
Dec 2, 2002 11:07 AM
If you have a 39 small chain ring run that. Just calculate the ratio you want first and then figure out the rear cog size. Most people run about a 2.5 for general purpose riding. A 39/16 is around 2.43. If it is flat terrain go to a 15 or 14 cog. A 42/17 is 2.47 ratio
re: What size chain ring and rear sproket should I start with?Steve_0
Dec 2, 2002 11:08 AM
Go to your LBS; they'll be able to get any size chainring you need for about 20 bucks.

I think youre thinking too hard on gearing - just use your multi-geared bike to determine which gear is best for you.
If you dont HAVE a multigear, I wouldnt start above 72 inches.
re: What size chain ring and rear sproket should I start with?fixedgearhead
Dec 2, 2002 12:23 PM
Depending on the topography of your area you should maybe think of 42/16 .You can always use a fixed/fixed rear hub which allows you to use 2 different cogs and reverse the wheel as is needed. Harris cyclery is a great source for all your needs to get started. Later there are other sites you will come to use for specific purchases. Good luck

fixedgearhead
Agree with the different cogs on a flip-flop hubTig
Dec 2, 2002 3:16 PM
I run a 39 X 15 fixed, and use a 16 cog for the freewheel side of the hub. I'm almost always on the fixed side, but like having an extra tooth on the freewheel side for a lower gear. The slightly lower freewheel gear is nice for easy rides and to get home with in case I have a bad day on the fixed (so far, so good!). You never know when a norther will blow through during a ride and have to face 20-30 mph headwinds on the way home, of have some unexpected cramps or something.
is that cheating?trekkie1
Dec 2, 2002 3:50 PM
I thought part of the essense of fixed gear is that you pick your gear, then stick with it no matter what. Having another option, even if only a small change and relatively difficult to change, is akin to riding a multi-gear freewheel bike, isn't it?

For those who have the flip flop option, how often do you use it? Is it truely only for bail out in severe conditions?
Naaaah, just insurance! ;-) -nmTig
Dec 2, 2002 4:00 PM
is that cheating?fixedgearhead
Dec 2, 2002 5:39 PM
I don't think of it as cheating. Around here (Central Ohio) I use only one cog for all the hills. But if I tour and am not sure of the territory, I like the safety of having a lower gear for those climbs that turn out to be monumental. If you read any of the history of early bicycle racing or touring you will find that they all used a second or lower cog on the flip side of the rear. If not, they got off and walked up the hill. Now that I consider, THAT, cheating.(Wink) I would hate to think of my climb up and over the Rockies without the choice of a second gear on the back.

fixedgearhead
cheating what?Steve_0
Dec 3, 2002 5:30 AM
FG isnt a competition.

You can certainly realize the benefits of FG riding, even with a FF hub; Add a tooth on that hilly ride, and sure youre gonna get up the hill easier, but you're also going to be spinning faster on the way down.

Time trialing in a heavy wind or up a hill? Why lose the race when you could have just flipped your wheel around. Triathlon? Not allowed in with fixed; flip the hub around (with a freewheel installed) and youre legal.

Just own one bike ?. I certainly dont want to ride a 90 inch gear when I take an after-dinner putz with the kids.

The only thing FF's are cheating, IMO, is repeated, unnecessary use of the chainwhip.
how fast do you ride and at what cadence?trekkie1
Dec 2, 2002 1:26 PM
Makes a huge difference, how fast you ride and how much do you like to spin? Ultimately, gear selection must be low enough to allow you to climb any hill you encounter, but high enough to either allow you to descend (although you can brake) or hold the speed/cadence you want on flat ground.

Here are some examples:

42x15 @ 100 rpms=22.1 mph
42x15 @ 80 rpms=17.7 mph
42x15 @ 60 rpms=13.2 mph

42x16 @ 100 rpms=20.7 mph
42x16 @ 80 rpms=16.6 mph
42x16 @ 60 rpms=12.4 mph

39x16 @ 100 rpms=19.2 mph
39x16 @ 80 rpms=15.4 mph
39x16 @ 60 rpms=11.5 mph

So, figure out how fast or slow you can tolerate pedaling, then how fast or slow that will make you in what gear. I'd recommend starting a little low geared and then putting on a smaller cog if you want to go faster.
Good Pointbigrider
Dec 3, 2002 6:58 AM
Some riders just prefer a a specific cadence. This web site will let you compute cadence from speed and gearing.

http://www.analyticcycling.com/QCHome_Disc.html

I like using fast cadences and limiting my top speed as opposed to using a painfully slow cadence up a steep hill. We have undulating hills where I ride and some of the grades are routinely 8-10%. Although they are not long you need a little cadence to get up them without throwing down the foot (never, never, never).

So, analyze your speed and your terrain and remember riding fixed will improve your spin and build power when climbing.

BTW, I sprinted the other day on a flat and got up to 28 mph or so on my fixed. I was exceeding a 135 cadence. It is a wild feeling.
Good Pointfixedgearhead
Dec 7, 2002 7:07 AM
I know what you mean. Sometimes when you are spinning out downhill and your legs are a blur it is just like the first time you rode a bike faster than you should have as a kid. Scary but oh so much fun.

fixedgearhead