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Thread: Double gears

  1. #1
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    Double gears

    I have a 2011 felt Boughmann I think gear ratio of 2.75( 17 teeth in back and 47 in front that I counted) Sometimes it is too small and want more. Is it possible to change the one side of rear tire to have a fixed gear with 12 teeth instead of the current ss and the other side still with the 17 teeth? How much would that make me faster? Also would it just be better to change my front gear to 52?

    If it is what would be the cost to have that changed?

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    Just smang it. EpicSchwinn's Avatar
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    Quote Originally Posted by makosz81 View Post
    I have a 2011 felt Boughmann I think gear ratio of 2.75( 17 teeth in back and 47 in front that I counted) Sometimes it is too small and want more. Is it possible to change the one side of rear tire to have a fixed gear with 12 teeth instead of the current ss and the other side still with the 17 teeth? How much would that make me faster? Also would it just be better to change my front gear to 52?

    If it is what would be the cost to have that changed?
    Gear inches is a more common way to express gearing around here. There's a great calcuator at this site: http://www.sheldonbrown.com/gears/

    Calculating for yours assuming you've got 700c wheels and 25c tires (pretty normal) you're currently at 72.9 gear inches (gi). Most people find that somewhere between 73-75 gear inches is the most practical single combo but this of course depends on how hilly your riding gets. If you live somewhere really flat you could of course push it higher. Using a 12t cog (which is REALLY tiny) you would be at 103.3 gi. Pretty much nobody rides a fixed gear with that high of gi on the street and it's especially dangerous brakeless. My recommendation would be to try maybe a 15 tooth cog if you really feel like you're spinning too fast with your 17. Another alternative is to get really good at spinning at a high cadence. If you haven't been riding fixed for long, you may just not be used to how fast you'll have to pedal some times.

    Oh and I totally forgot to address your main concern. You can only safely run two fixed cogs of you have a Fixed/Fixed hub which isn't super common. Look to see if the extra side has two sets of threads (one bigger and right hand thread, and the outer smaller and left hand). If I'm spoonfeeding this it's only because you're new and I don't know how much background you have with sw8 fixays.

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    I have what seems like two wheel sizes "Vittoria Randonneur wire bead 700X25c front 700x28 rear" thats from the felt web site. So I have to carry 2 different tubes for spares? I am new to riding as a transportation not just fun.

    When you say "Fixed/Fixed hub which isn't super common" do you mean I have to change the current hub to something else instead of replacing the ss on it?

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    Fresh Garbage hairnet's Avatar
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    You can just use the tubes for the narrower tire, they will work for both.

    Your hub is called a flip/flop hub. One side is intended for track/fixed gear and the other for single speed freewheel. You can put a track cog on the SS side, but most people will discourage it because you can't use the same lockring that you have on the fixed gear side of the hub. It is do-able and fine if you use a rear brake and refrain from using your legs to apply pressure to slow down, so you do not end up causing the track cog to slip and unwind. Either way, you need to make sure the cog is real tight
    Quote Originally Posted by Scrodzilla View Post
    I'd rather ride a greasy bowling ball than one of those things.
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    Senior Member redpear's Avatar
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    You may or may not have to. Check the threads on the other side.


    They should look like either side of this hub. Notice how the outside threads have a smaller diameter, to facilitate a lockring. If the threads are a uniform diameter, you won't be able to safely do it without a new rear hub.

    Do you have front and rear brakes?

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    I have just checked the hub on felt site and it says "Felt alloy double-threaded fixed/fixed hi-flanged 28H" I cant look at my bike at the moment.

    So if I do put pressure on the pedals to stop the cog would just unwind (which means the cog will eventually come off?)

    I do not have rear breaks, the bike came with them but I had lbs take them off

    So if I used the tires that are on front wheel to put on back they would fit?

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    bmw
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    Fixed/Fixed - you're set to use two fixed gear cogs. Make sure to use a chain-whip and lock-ring tool to secure the cogs. There are myriad of suggestions as to avoid using chain-whip/lock-ring tools (mashing up a hill, etc) but IMO the safest (avoid being crushed by a car at an intersection) and cheapest (avoid stripping your hub) way to go about it is to invest in the tools once and never have to worry about it ever again.

    **HILPSTER BONUS** some of them come with ironic beer bottle openers!
    Last edited by bmw; 11-23-11 at 11:10 AM.

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    Learning how to spin will probably make you faster than mashing a monster grear ratio... 103 gear inches is way too high of a ratio for any sort of city riding/commuting.
    Quote Originally Posted by Santaria View Post
    because physics has more street cred than tarckstars.

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    Also, a 5 tooth difference between cogs will probably require that you shorten your chain before flipping the wheel. So no fast gear changes.

    My recommendation: a 52t chainring and a 19t cog. You'll keep your current gear ratio the same and have plenty of options when you start going with smaller cogs.
    Quote Originally Posted by Nagrom_ View Post
    I actually just run calipers. Levers are for scrubs.

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    Magnets, how do they work solipsist716's Avatar
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    Another alternative (if you're exclusively running a 3/32" set-up, i.e cog, chainring AND chain) is to pick up a surly dingle cog. It probably won't give you the larger range of GI you're looking for but you'll have a 2-speed fixed gear. It oughta be noted that your chainline will never be perfectly straight while using a dingle.

    surly-dingle-cog-fixed-dual-cassette-cog-3-32-inch-IMG18241.jpg
    Quote Originally Posted by cianm View Post
    How do i tweak my brakes so it will be good for skidding?
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    Quote Originally Posted by solipsist716 View Post
    Another alternative (if you're exclusively running a 3/32" set-up, i.e cog, chainring AND chain) is to pick up a surly dingle cog. It probably won't give you the larger range of GI you're looking for but you'll have a 2-speed fixed gear. It oughta be noted that your chainline will never be perfectly straight while using a dingle.

    surly-dingle-cog-fixed-dual-cassette-cog-3-32-inch-IMG18241.jpg
    Chainline is not a function of the cog.
    Quote Originally Posted by Nagrom_ View Post
    I actually just run calipers. Levers are for scrubs.

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    Fresh Garbage hairnet's Avatar
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    And you dont cross chain with it. Double cog + double crank
    Quote Originally Posted by Scrodzilla View Post
    I'd rather ride a greasy bowling ball than one of those things.
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    Senior Member seau grateau's Avatar
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    *smh* You are not going to ride a 12t cog.
    Quote Originally Posted by adriano View Post
    thanckx.
    Quote Originally Posted by Nagrom_ View Post
    "I made love to your mother dozens of times last week, and she doesnt know what a worn chain ring looks like"

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    Magnets, how do they work solipsist716's Avatar
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    Quote Originally Posted by striknein View Post
    Chainline is not a function of the cog.
    Whoops. I remember reading somewhere that somebody's dingle threw off their chainline. I guess this would happen if they only used one chainring, but they're doin' it wrong from the start if that's so. My bad.
    Quote Originally Posted by cianm View Post
    How do i tweak my brakes so it will be good for skidding?
    Quote Originally Posted by Sixty Fiver View Post
    As Minchin said, praying before a sporting event and winning does not mean that god took time out from torturing and killing babies in Africa to ensure your team's win.

  15. #15
    モㄥ工匕モ 爪モ爪乃モ尺 evilcryalotmore's Avatar
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    What you need to do is get on your lbs road bike and feel the gear ratios. there are a variety of gear ratios for your cause, For example.

    townie bike has a 52 chainring and a 12-21 cassette.

    My track bike has a 53 chainring and a 16 cog.

    my beater bike has a 35 chainring 14 cog

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    Quote Originally Posted by evilcryalotmore View Post
    What you need to do is get on your lbs road bike and feel the gear ratios. there are a variety of gear ratios for your cause, For example.

    townie bike has a 52 chainring and a 12-21 cassette.

    My track bike has a 53 chainring and a 16 cog.

    my beater bike has a 35 chainring 14 cog
    Neither one of your 3 bikes has particularly great gearing for its purpose.

    A townie should not have 65gi for its lowest gear (you should have used the smaller chainring, for example a 39x11-21 would be smart). Your "track" bike with 87gi is pretty high and though you might see other "track" bikes with huge chainrings and small cogs, its stupid and those bikes NEVER see the track. They're nothing more than japanese fashion accessories, and hopefully you've ridden your bike enough to realize its not so practical (see velospace, pedalroom for a good selection of what I'm talking about). Your beater bike's gearing is fine, though with more teeth on the chainring and cog you wont wear stuff out quite as quick as i assume the beater is the one you ride the most.

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    I ride 47:17 as well.

    12 tooth is REALLY really REALLY tiny. As in, you'd have to put your full weight on your pedals when starting off from a stop sign or red light. 47:12 sounds more like a velodrome ratio, but I'm assuming you ride in the streets. Try 15 first, like BikeSchwinn said. I only feel the need for a higher gear ratio when I'm bombing down a hill at 60kmh... you're not spinning fast enough if you're going below these speeds and thinking of moving up.

    Also, if you SOMETIMES, not ALWAYS think that 47:17 is too easy, then 47:12 will be ALWAYS too hard for you.
    If you have a geared bike, try out the same gear ratio and see how damn hard it is. That's what I do before changing any of my gear settings.

  18. #18
    Ride for Life wearyourtruth's Avatar
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    Quote Originally Posted by striknein View Post
    Also, a 5 tooth difference between cogs will probably require that you shorten your chain before flipping the wheel. So no fast gear changes.
    i can't believe this has only been mentioned once so far. it was my first reaction to the OP's questions.

    alright, so you lucked out and have a fixed/fixed rear hub. that means you are correct, you can have one size cog on one side, and another on the other side. when you want, you can simply unbolt the rear wheel, flip it around, and put it on with the other cog. what you need to worry about, though, is that you can only have so much difference in tooth count on your cogs.


    everyone's track ends (on a proper fixed gear) look something like this. the general rule is (and i'll skip the math unless you really want it) that for every tooth you add/remove from your cog, you reduce/extend where your hub sits in the track end by .25". to jump between 12 and 17, that's 1.25" which on many bikes may be possible with some luck, but will put your hub bolted near the end, which is generally not recommended.

    that said, you will also find that a 2-3 cog tooth difference is quite significant, and i think you would find it sufficient (and safer).

    p.s. if you are running a rear brake, flipping to a significantly different cog size is going to completely mess up your brake pad position, just fyi.
    before posting, a "noob" should always ask themselves "could this have been answered by first visiting Sheldon Brown

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  19. #19
    %#&*#%>?% Build your own's Avatar
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    Just get a bigger chainring,something like this

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