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  1. #1
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    Crankset size, fixed vs. road

    My road ride has a 172.5 (I've ridden 170 w/no discernible difference). I have a new track frame and the deal included a 165 drive-side Campy C-Record crank-arm w/no chain ring. A few ???

    1) Is the 165 too small (I'm 68" w/a 30 inseam)?
    2) If #1 is fine, where do I get a 165 crank arm and chain ring?
    3) I'm fairly fit so what size chain ring and rear sprocket will allow me to ride at 22 mph (assuming 90-95 rpm....I know there is a conversion table out there somewhere)?

    Thanks for the help to a newbie fixie-SS'er

  2. #2
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    1) I have a 172.5 on my road bike and a 170 on my fixie. I don't think that I'd go smaller unless, perhaps, I was going to race on the track. However, crank length is a personal preference thing and 165 doesn't sound absurdly small.

    2) There's a sticky on this forum about plces to buy fixie stuff.

    3) I'd experiemnt with different gear ratios before picking. There's a ton of threads on this. I am confused why you want to be able to go 22 mph. Why? How long do you want to go that fast? On what terrain do you want to go 22 mph? etc?
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars. Laurent Fignon

  3. #3
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    Pablo is right: 170 is probably the "norm," alhough 165s are certainly common. I have a 32" inseam and run 165mm Sugino RDs, and they work/fit/feel fine. I found it interesting that they simply drill the pedal hole further up the crankarm to achieve this; the arm itself is the same length as for 170s and perhaps the 175s.

    If you want to replace the whole crank, these are available in any number of places, but HarrisCyclery is probably the most obvious:
    http://www.sheldonbrown.com/harris/c...30-single.html

    If you're looking just for the non-drive-side Campy arm, you're going to have to do some digging on eBay; I don't know of any online places that sell individual arms, although a local dealer might be able to help you out there.

    The Suginos come equipped with a 48T chainring, but I have no idea how to choose a gear ratio based on average speed. Again, Harris Cyclery's Sheldon Brown has a calculator that gives you gear inches, gain ratios, and Meters Development figures for any chainring/cog combo you plug into it, and you'll find your answer there, if anywhere:

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

    Most people start with something in the neighborhood of a 70-inch gear and adjust from there, amassing a small collection of cogs and 'rings along the way. If you live somewhere flat, you can start with 75" or so.

    Sorry for the longwinded response. Hope this helps.

  4. #4
    wim
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    I'm fairly fit so what size chain ring and rear sprocket will allow me to ride at 22 mph (assuming 90-95 rpm.
    Here's a simple, but useful calculator

    http://www.fixedgeargallery.com/articles/steve-cadence/

    Agree with the 70" gear as a good starting point. As a matter of fact, after experimenting with all sorts of gear inches over a long time, many fixed riders come back to 70" or so and never leave. If you're going on group rides with geared people, you need to go higher so you can stay with the group—an 81" gear (3 : 1 ratio) works for me.

  5. #5
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    I'm using 170's w/ a track frame and have never had a pedal strike on the road or velodrome...also FWIW 73GI (49/18) works great on the road for me. So far as speed goes, to calculate it works like this for (48/16 i.e 3:1 gearing)

    95rpm x 3 x 83" (approx wheel circumference) = 23655 in/min

    =22.4 mph

    though 80 gi is too big for most people on the road

  6. #6
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    The math isn't that hard

    To go 22 mph at 90 rpm's you need about an 82 inch gear, roughly 48/15. That's a good bit taller than most people use for a road fixie. I use about a 73-inch (39/14). Most people say 70 is about right. You need to experiment. Try riding around on your road bike in one gear, forcing yourself to pedal constantly (even downhill). That will give you a little idea.

    Terminology note: "crank length" is the term. "Crankset size" sounds like you're talking about bolt circle diameter.

    Many people use a shorter crank for fixed (easier to spin, more cornering clearance). 165 doesn't sound too short for you.

    Branford Bike used to sell individual left Campy cranks (I bought one). I don't know if the new management has them, but you can check.

    As for buying a ring, the 165mm crank arm length is irrelevant. You need to know the bolt circle diameter. Campy non-compact is usually 135 mm. Sheldon explains how to measure here:
    http://www.sheldonbrown.com/gloss_bo-z.html#bcd

  7. #7
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    Quote Originally Posted by BigDaddySmooth
    2) If #1 is fine, where do I get a 165 crank arm and chain ring?
    Buy a road double crank and some short stack chainring bolts and remove the outside ring. Voila, a fixie/ss crank.

  8. #8
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    Chorus Double

    So if I have a 53/39 Chorus lying around, I can pull off the 53? Something about that doesn't sound right.

  9. #9
    Yo no fui.
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    I have a 48 x 16 and putting 90 rpms even on the flats takes a toll.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars. Laurent Fignon

  10. #10
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    Quote Originally Posted by BigDaddySmooth
    So if I have a 53/39 Chorus lying around, I can pull off the 53? Something about that doesn't sound right.
    It will work perfectly. I've converted three Ultegra doubles to SS/fixie cranks with no issues. It's a common alteration. Chorus should be no problem either. You'll just need some short stack/BMX chainring bolts. The ones that are in there are too tall because there two rings. All you need is a hex key (4mm?) and maybe one of those little chainring bolt wrenches. Those bolts can be a little sticky sometimes.
    Attached Thumbnails Attached Thumbnails Crankset size, fixed vs. road-fixie-cranks.jpg  
    Attached Images Attached Images  

  11. #11
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    Why not?

    Quote Originally Posted by BigDaddySmooth
    So if I have a 53/39 Chorus lying around, I can pull off the 53? Something about that doesn't sound right.
    Standard practice among phixie-conversion-phreaks. You can even fine-tune your chainline a bit (if you need to) by mounting the ring on either side of the spider.

  12. #12
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    Hey, Pablo

    Quote Originally Posted by Pablo
    I have a 48 x 16 and putting 90 rpms even on the flats takes a toll.
    If you're anything like me, going 21 mph for any length of time on the flats takes a toll -- in any gear ;)

    With my 39 x 14 it's close to 100 rpms for that speed. I can do it for a while. I did a little cadence counting this morning when I was trying to beat a red light on my commute. If I counted right, I held about 130 for half a block -- that's 28 mph (okay, it was just slightly downhill).

  13. #13
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    Why 22 mph

    Now you guys are really going to think I'm nuts. I may use the track frame as my tri bike. The track frame in question is a Spectrum. It was designed as a pursuit and the STA is 75, the TT is sloping downward w/respect to the head tube and the set-up is 650c front, 700 rear. Since I'm only going to do tri's a few times per year, I 1) don't want ot buy a tri-specfic bike and 2) deal w/the hassle of altering my road bike---but this one may be what I really end up doing.

    I picked 22 mph as that is a figure which will be competitive but still leave me something for the run, which will call for about a 7 minute/mile pace for a 10K.

  14. #14
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    fixin' to tri som'thin' new

    Ah, very interesting, and puts a whole new spin on it (so to speak). First question: are your tri courses pretty flat? if so, this may work. If they're rolling or hilly, I'm skeptical.

    If you can go out and test yourself on these courses, go out on your road bike, pick the appropriate gear, and see if you can maintain the target cadence and speed -- keeping in mind that the more aero position will make you faster. The gear you've suggested may not be too high in that setting.

    Also, check the USATriathlon rules; you probably have to have 2 brakes.

  15. #15
    Yo no fui.
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    Quote Originally Posted by JCavilia
    If you're anything like me, going 21 mph for any length of time on the flats takes a toll -- in any gear ;)

    With my 39 x 14 it's close to 100 rpms for that speed. I can do it for a while. I did a little cadence counting this morning when I was trying to beat a red light on my commute. If I counted right, I held about 130 for half a block -- that's 28 mph (okay, it was just slightly downhill).
    130? Wow. I started with a 48x16 because it came on my bike initially and I'm a bit of a masher although I can spin pretty well on my road bike. I used to live where it was hilly and the bigger gear really helped on the downhill becasue at 130 I'd be bouncing all over the place and my heart might explode. Now, I keep the 48x16 to help me with my power and it works out great for intervals on the flats or hills becasue it's pretty hard to spin out.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars. Laurent Fignon

  16. #16
    wim
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    Not that unusual.

    Now you guys are really going to think I'm nuts. I may use the track frame as my tri bike
    I've seen many fast time trials ridden on fixed gears, even in slightly rolling terrain. The problem is somewhat unpredictable wind speed the day of the event—if it blows hard enough, you'll be overgeared against the wind and undergeared riding with it. At the very least, pack a couple of alternative cogs and get good at changing them quickly before your start time. If the course is out-and-back and it's in line with the prevailing wind direction, fixed is a bad idea.

    Check the tri rules, as JCavilia said. I remember the USCF requiring two independent brakes, with the backpedaling ability of a fixed gear counting as one of the two.
    Last edited by wim; 08-02-2007 at 11:54 AM.

  17. #17
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    Like getting to Carnegie Hall

    Quote Originally Posted by Pablo
    130? Wow. I started with a 48x16 because it came on my bike initially and I'm a bit of a masher although I can spin pretty well on my road bike. I used to live where it was hilly and the bigger gear really helped on the downhill becasue at 130 I'd be bouncing all over the place and my heart might explode. Now, I keep the 48x16 to help me with my power and it works out great for intervals on the flats or hills becasue it's pretty hard to spin out.
    practice, practice, practice. I commute on fixed year-round. I have probably ridden 9 or 10 thousand miles on fixed gears now, and it's become second nature. My commute is pretty flat, but occasionally I take it out on a hillier route, and I'll get over 150 rpm on the descents, and I can do that for a few hundred yards without bouncing. It takes concentration, though, and it's scary. If I put on a taller gear I couldn't make it up those same hills, where I'm out of the saddle grinding at 35 rpms.

  18. #18
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    I found one!

    Quote Originally Posted by BigDaddySmooth
    My road ride has a 172.5 (I've ridden 170 w/no discernible difference). I have a new track frame and the deal included a 165 drive-side Campy C-Record crank-arm w/no chain ring. A few ???

    1) Is the 165 too small (I'm 68" w/a 30 inseam)?
    2) If #1 is fine, where do I get a 165 crank arm and chain ring?
    3) I'm fairly fit so what size chain ring and rear sprocket will allow me to ride at 22 mph (assuming 90-95 rpm....I know there is a conversion table out there somewhere)?
    I found one! Dude you'd got buy this. Even if you think 165 is too small (I run a 166.5 and I have a 32 inch inseam) a Vintage Campy crankset is always worth much more than an individual arm.


    http://cgi.ebay.com/Campagnolo-Super...QQcmdZViewItem

    BTW: I run about 70 gear inches, 48:18 and I can go pretty much anywhere.

    Brad

  19. #19
    Yo no fui.
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    Carnegie Hall? I prefer Red Rocks.

    Quote Originally Posted by JCavilia
    practice, practice, practice. I commute on fixed year-round. I have probably ridden 9 or 10 thousand miles on fixed gears now, and it's become second nature. My commute is pretty flat, but occasionally I take it out on a hillier route, and I'll get over 150 rpm on the descents, and I can do that for a few hundred yards without bouncing. It takes concentration, though, and it's scary. If I put on a taller gear I couldn't make it up those same hills, where I'm out of the saddle grinding at 35 rpms.
    I can spin pretty fast when needed, although I'm just guessing. Maybe I can get up there too. Who knows? I don't have a cadence meter. When I really get spinning, I find it helpful to lift my rear slightly off the saddle.
    "It is better to conquer yourself, than to win a thousand battles." -Dhammapada

    "Fact is only what you believe; fact and fiction work as a team." Jack Johnson

    "A true cyclist sometimes has to bite the dust before he can reach the stars. Laurent Fignon

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