Bike Forums > Can someone help me "do the math"?
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 Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

 07-08-03, 04:17 PM #1 SD Fixed Traffic shark Thread Starter   Join Date: May 2001 Location: California Bikes: 2 fixies, 1 road, 29er in the works. Posts: 4,612 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 2 Post(s) Can someone help me "do the math"? I know most fixed gears are 48t for the front. On project bike, my gears are 54-48. I'd like to keep the crank the way it is, and just remove the smaller gear. Why? Because the smaller gear is built into the larger, and you can't have the smaller with out the larger. So, if I was considering a 48 - 17 (17/18 flipflop/fixedfree) What woud be correct for a 54? Or, can you give me the formula so I can caculate it myself?
 07-08-03, 04:18 PM #2 SD Fixed Traffic shark Thread Starter   Join Date: May 2001 Location: California Bikes: 2 fixies, 1 road, 29er in the works. Posts: 4,612 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 2 Post(s) Crank I'm working with.
 07-08-03, 04:41 PM #3 roadfix hello     Join Date: May 2003 Location: Los Angeles Bikes: Posts: 18,593 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 65 Post(s) # chainring divided by # cog and take that figure and multiply it by wheel diameter.....equals GEAR INCHES.... in your case with a 54 ring, the closest equivalent will be a 19 & 21 combo... Last edited by roadfix; 07-08-03 at 04:49 PM.
 07-08-03, 04:44 PM #4 SD Fixed Traffic shark Thread Starter   Join Date: May 2001 Location: California Bikes: 2 fixies, 1 road, 29er in the works. Posts: 4,612 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 2 Post(s) Thanks Socal buddy! (Us socal folks stick to gether)
 07-08-03, 05:43 PM #5 shrimpx Senior Member     Join Date: Apr 2003 Location: portland, or Bikes: Posts: 300 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) yeah, so that crankset is no good... i had the same type of thing on my nishiki, and got rid of it. since the chainring is not hooked to the spider via several bolts, and it's merely "pressed" to it, you have a high probability of the chain ring starting to freewheel on the crank axle when most of your acceleration and deceleration force will pass through that "press" point. (since you use your legs for that on a fixie. ) apparently, it's common with those types of cranksets. you can find an old spider-type crankset for cheap probably... then you can easily find a 42T ring for it if it doesn't already come with one. dunno, you might want to try riding that one and see how long it lasts... i love that color, by the way.
 07-08-03, 06:19 PM #6 OneTinSloth (Grouchy)   Join Date: Mar 2003 Bikes: Posts: 3,643 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) yeah...what shrimpx said... and if you're going to ride that crank, definitely go with brakes, i'd say front and rear. you can probably pick up an old bmx style chainring that will have bolt holes for both 110 and 130 bcd, and they'll be 43-45T, so you won't just be stuck with either having to use a 52T or a 42T chainring, plus the BMX style rings are usually anodized different colors, so you can have a whole color scheme going on. WOOHOO!!
 07-08-03, 06:20 PM #7 don d. Guest   Bikes: Posts: n/a Mentioned: Post(s) Tagged: Thread(s) Quoted: Post(s) You can use that 54t cr with a 22t cog to get a ~66 inch gear. Perfectly manageable for most people. A 48-17 = ~76 inch gear. Cogs up to 22t are available at: http://www.bicycleclassics.com/track.html FWIW, after 30 yrs of cycling and 20 yrs in the biz, I've never seen a "sweged"(pressed) crankarm/chainring like you have separate or freewheel. Doesn't mean it hasn't happened, I've just never seen one.
 07-08-03, 09:05 PM #8 BBQ Senior Member     Join Date: Oct 2002 Bikes: Posts: 72 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) This is handy for just such a question: http://www.sheldonbrown.com/gears/
07-09-03, 01:06 AM   #9
shrimpx
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 Originally posted by don d. FWIW, after 30 yrs of cycling and 20 yrs in the biz, I've never seen a "sweged"(pressed) crankarm/chainring like you have separate or freewheel. Doesn't mean it hasn't happened, I've just never seen one.
do you see them often on fixed gear bikes?

i'm sure they're adequate for geared bikes, but i wouldn't trust anything like that on a fix, especially if you ride brakeless. i've never heard of them starting to freewheel on geared bikes, but i did on fixed gears.

 07-09-03, 06:05 AM #10 jasonyates Senior Member   Join Date: May 2003 Location: Chicago, IL Bikes: Bianchi Pista, Miyata track, Schwinn Le Tour fixie Posts: 373 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) I seem to notice 22 tooth cogs for sale on eBay a lot. You should just pick up one of those. -Jason
07-09-03, 07:44 AM   #11
SD Fixed
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 Originally posted by shrimpx i love that color, by the way.
Another reason I don't want to hack the bike. But I'm gonna be shaving all the mounts, etc..

I've semi offered it to anyone who wants it for collection purposes, but no takers. It's rough anyway. I've got some ideas for it though.

ANYWHOO...

Thanks for all the input. I'll have to consider a new crank now instead of saving this one. I'd hate to build the rear hub and then have to buy a new because the crank gave up.

Oh well.

07-09-03, 08:57 AM   #12
don d.
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 Originally posted by shrimpx do you see them often on fixed gear bikes. i've never heard of them starting to freewheel on geared bikes, but i did on fixed gears.
I had one on a fix. My Fuji had a sweged(what you are calling pressed) crankset. I rode that bike to death, even in cyclocross. In addition, I had a tandem that my friends and I rode to death with a Sugino Maxy Tandem crankset on it. Sweged as Sweged can be, and if anything was going to break loose a crank, that was it.

This idea that they are going to "break loose" is a sales ploy used in some shops to get less than knowledgeable customers to upgrade. "Back in the day" these type cranks were on every bike, including track bikes. My main mentor in the sport, an old Hungarian bike racer, hung his old pro bike, a fixed gear road racing bike, in his shop quite proudly with no feelings of inadequacy because it had a sweged crank on it.

But I don"t know, maybe now that there is a single speed "craze", things have changed, aye?

 07-09-03, 03:47 PM #13 SD Fixed Traffic shark Thread Starter   Join Date: May 2001 Location: California Bikes: 2 fixies, 1 road, 29er in the works. Posts: 4,612 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 2 Post(s) Well, I'll take a chance on the crank and see what happens. Thanks for all the help!