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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)

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Old 09-04-10, 03:04 AM   #1
polobreaka
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crank length make a difference?

my brother has a 56cm subrosa malum. his gear is 48/16 (81 gear inch) with 165mm crank length. seat height measured from center bottom bracket to top of seat is 27.5 inches. he runs platform bmx pedals with straps.

i have a 53cm raleigh rush hour. my gearing is 39/14 (75.2 gear inch) with 170mm sugino messenger cranks. the 170mm length crank came with the bike when i bought it used. my seat height measured from center bottom bracket to top of seat is 27 inches. i have mks gr9 pedals with cages and single strap.

i rode his bike and i feel way more control on his bike than on my bike. i can trackstand with ease and skid easier than on my bike. i am able to seat skid stop and i cant do it at all on my bike.

i would assume my gearing would be easier to slowdown/skid/stop than his. the only thing i can think of is crank length. i thought longer crank length would make things easier to ride and stop.

i want to make my bike ride as well as my brother's bike. what are your opinions?

thanks!

Last edited by polobreaka; 09-04-10 at 12:43 PM. Reason: corrections
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Old 09-04-10, 03:20 AM   #2
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I didn't know Subrosa started making fixed gears, then again, a lot of BMX companies are making them nowadays...

74'5" inches?!$@?$@$?!@#?!@?#!@
I'm sure you meant cm.

Crank length should not matter, probably the difference in geometries or maybe he runs a much tighter chain then you do, many factors but crank length is probably not the reason why.
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Old 09-04-10, 04:13 AM   #3
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Thanks! Youre correct, i meant CM not inches. Mistyped that.

Should geometry really matter if im standing to do a trackstand? Since im only holding the handle bar and standing on the pedals. His chain is actually a little more loose than mine.

Longer crankarms gives me a wider stance and longer strokes, more torque to pull a stop/slowdown.
Shorter crankarms will be more narrow in stance and shorter stroke (faster revolution around).

Hmm i dont get it.
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Old 09-04-10, 06:53 AM   #4
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crank length certainly means something.
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Old 09-04-10, 10:36 AM   #5
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crank length certainly means something.
care to explain? thanks
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Old 09-04-10, 10:49 AM   #6
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Could be that your frame is too small. 53 to 56 is kind of a jump, and if the 56 is more your size then it makes sense that you'd feel more in control on it.
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Old 09-04-10, 10:53 AM   #7
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just get a subrosa for yourself, duhh! ;D

but i agree on the size thing. perhaps the rush hour is small?
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Old 09-04-10, 11:01 AM   #8
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im 5'5 with inseam 30. im suppose to be riding a 51 at most, but this 53 fits smaller and im comfortable on it. i can flat foot both side with my balls resting on top tube with no discomfortable and still have room to sit down on top tube if i want. i sat on my friend's giro 52.5cm and it feels slightly taller than mine. and my friend with a 50cm cinelli feels like the height of mine. so different manufactures have different feel even though the sizing is says smaller. the 56cm subrosa definitely is tall for me, but riding around the parking lot, for a good 30 minutes just trying things, i definitely feel more confident stopping sooner than on my bike. i can seat skid/stop on the subrosa with ease, but when i try on my bike..my knee feels like it wants to explode.
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Old 09-04-10, 11:05 AM   #9
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the top tube clearance doesn't matter.
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Old 09-04-10, 11:38 AM   #10
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hmm ok, i thought thats how you usually decide if a bike is too small or too big for you.
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Old 09-04-10, 11:51 AM   #11
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It matters to the extent that it's one of the dimensions of a frame, but proper fit starts with top-tube length.
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Old 09-04-10, 12:00 PM   #12
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The difference between 165s and 170s is so tiny, only a very experienced rider might notice the difference. All else being equal, long cranks are easier to pedal, but limit your cadence because you are pedaling larger circles. However, in your case. all is not equal. You were comparing two different bikes of different sizes, gear ratios, and geometries.
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Old 09-04-10, 12:42 PM   #13
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The difference between 165s and 170s is so tiny, only a very experienced rider might notice the difference. All else being equal, long cranks are easier to pedal, but limit your cadence because you are pedaling larger circles. However, in your case. all is not equal. You were comparing two different bikes of different sizes, gear ratios, and geometries.
you're right, 10mm difference is very minimal to notice any difference from me (unexperienced rider). if by pedaling larger circles, wouldnt that mean i wont be spinning out as soon as if im on 165mm arms?

so comparing the 2 different gear ratios - 75.2 gear in vs 81 gear in - wouldnt the 75.2" be easier to ride and stop vs the 81"?

here are some more measurements and specs of the bike to give you an idea on the dimensions of each bike.

mine (53cm rush hour) / his (56cm subrosa):

gearing - 39/14 (75.2") / 48/16 (81")
top tube length (center to center head tube - seat tube) - 21in / 22.5in
seat post angle (measure from center of BB) - 14.2* / 14*
seat height (measure from center of BB to top of seat) - 27in / 27.5in
head tube angle - 16.5* / 16.5*
stem - 80mm / 90mm
handle bars - nitto drop bullhorns 40cm / volume cutter risers
pedals - MKS gr9 with soma cage and MKS single strap / Odyssey BMX platform with Blaq strap
wheels - front and rear = 27" / front and rear = 27"
wheel base (center front hub to center rear hub) - 39in / 39in
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Old 09-04-10, 12:51 PM   #14
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I've found that I can trackstand a lot more easily after taking a good dump in the morning.
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Old 09-04-10, 12:59 PM   #15
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check out the difference in hip angle between a 5'3" rider and a 6'5" rider. 165mm to 180mm cant cover it.
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Old 09-04-10, 01:04 PM   #16
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I've found that I can trackstand a lot more easily after taking a good dump in the morning.
i took a dump before riding btw.

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check out the difference in hip angle between a 5'3" rider and a 6'5" rider. 165mm to 180mm cant cover it.
sorry, i dont get it.
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Old 09-04-10, 02:04 PM   #17
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Length matters. More leverage.

I imagine you can trackstand because you can make finer adjustments with the same level of muscle control. Longer cranks should help you skid, but the problem is that your ankles, knees, and hips are connected to that longer lever and all that linkage starts to impact the strength which you can apply.

Purely anecdotal: I rode 175 on my mtb for 10 years. One day I switched to 180s and for the two weeks after my knees hurt and my sit bones created sore spots. I lowered my seat 5mm and everything is fine.

So, can I tell the dif between the crank lengths? Not after five minutes, but after two weeks I can.
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Old 09-04-10, 02:52 PM   #18
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Length matters. More leverage.

I imagine you can trackstand because you can make finer adjustments with the same level of muscle control. Longer cranks should help you skid, but the problem is that your ankles, knees, and hips are connected to that longer lever and all that linkage starts to impact the strength which you can apply.

Purely anecdotal: I rode 175 on my mtb for 10 years. One day I switched to 180s and for the two weeks after my knees hurt and my sit bones created sore spots. I lowered my seat 5mm and everything is fine.

So, can I tell the dif between the crank lengths? Not after five minutes, but after two weeks I can.
exactly what i was thinking, longer cranks = more leverage. more leverage = easier to pedal, easier to stop/skid. but it doesnt seem to be the case here. i know there are a lot of things to consider, but i have listed some specs that matters and to give a better idea between these 2 bikes. i know you guys are more knowledgeable than i am. thats why i want your opinions/advices.
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Old 09-05-10, 12:49 AM   #19
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anyone else?
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Old 09-05-10, 02:04 AM   #20
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I went from 170mm cranks to 165's on my Europa and it felt like going up a gear as far as effort goes. Mind you, since the change I've been spinning quickly and smoothly but that might because fitting the new cranks coincided with me parking the geared bike and moving exclusively to the fixed. Now that I'm trying to climb decent hills, I'm wondering if going back to 170's mightn't be a good move for the extra leverage going up.

There's really only one way I'll ever know - try the 170 cranks and, unfortunately, I would suggest that the same answer applies to the OP.

On a related note, my geared bike had 172.5mm cranks, the Europa at that time, had 170's. I always felt just a wee bit cramped on the geared bike, dunno why, can't explain it, just that little thought that kept popping into my head. The geared bike had octalink cranks that went the way of all octalink cranks ie, they refused to stay tight, so I had to buy new cranks and, seeing I was buying new, ordered 170mm cranks. I could detect no difference in effort ability to spin, but I no longer had that nagging feeling that I'm cramped - instantly more comfortable.

Maybe there's a similar subliminal thing going on with the Europa and her new 165's.

Some aspects of bike fit come down to how it feels to the rider ... on that bike. This is why experienced riders who tinker with their bikes (as opposed to living with what the factory delivered), wind up with a shed full of bits.

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Old 09-05-10, 04:26 AM   #21
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I went from 170mm cranks to 165's on my Europa and it felt like going up a gear as far as effort goes.
If you want to increase your leverage, you should change your gear ratio, not your crank length. Adding or subtracting even 1 tooth from your chainring will have a much larger effect on your overall gearing than changing your cranklength by 5mm. You should choose a cranklength that is suitable for your height and it most comfortable to you. Never change your crank length to compensate for the wrong gear ratio. Change your gear ratio instead.

http://sheldonbrown.com/gears/
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Old 09-05-10, 07:52 AM   #22
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If you want to increase your leverage, you should change your gear ratio, not your crank length. Adding or subtracting even 1 tooth from your chainring will have a much larger effect on your overall gearing than changing your cranklength by 5mm. You should choose a cranklength that is suitable for your height and it most comfortable to you. Never change your crank length to compensate for the wrong gear ratio. Change your gear ratio instead.

http://sheldonbrown.com/gears/
Yeah, that makes sense.

To be honest, I hadn't thought too much about this except to note that the shorter cranks felt harder to push and this happened at a time when I'd started climbing big hills. I might still whack the 170's back on for a test, but only because I might have another use for the 165's (for my bike polo bike) and in the meantime, I'll continue to work on my strength. My gearing's about right at the moment - I still have to walk up the steepest part of the worst hill I face, but seeing that's a 10% gradient, I don't really mind (and it's only 200m).

Richard
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Old 09-05-10, 09:41 AM   #23
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The difference between 165s and 170s is so tiny, only a very experienced rider might notice the difference. All else being equal, long cranks are easier to pedal, but limit your cadence because you are pedaling larger circles. However, in your case. all is not equal. You were comparing two different bikes of different sizes, gear ratios, and geometries.
I lost about 4 or 5 MPH off my top speed going 165 -> 170. It wasn't glaringly obvious, but I could tell something was different riding around town. I wouldn't describe myself as an incredibly experienced rider, just a commuter. I think the crank length is fairly important. That said, my friend has a 165 on one side and 170 on the other (stripped one) and he doesn't seem to notice.
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Old 09-05-10, 12:13 PM   #24
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If you want to increase your leverage, you should change your gear ratio, not your crank length. Adding or subtracting even 1 tooth from your chainring will have a much larger effect on your overall gearing than changing your cranklength by 5mm. You should choose a cranklength that is suitable for your height and it most comfortable to you. Never change your crank length to compensate for the wrong gear ratio. Change your gear ratio instead.

http://sheldonbrown.com/gears/
so what is consider a 'suitable' cranklength for my height at 5'5? where can i find that info?
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Old 09-05-10, 02:21 PM   #25
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http://www.cptips.com/crnklth.htm

For FGs I like somewhat shorter cranks than is normally recommended for a geared bike. For example, I'm barely over 6' and I normally ride 172.5-175 mm cranks on road bikes and on FG bikes I ride 167.5-170 mm cranks. Track riders, in general, use shorter cranks that road cyclists. The shorter cranks avoid pedal strike and allows one to sustain a higher than normal cadence. This normally isn't a concern on geared bikes, since you can always shift into a higher gear when the cadence gets too fast, but on a FG, you are often stuck pedaling at very high cadences, especially if you ride hills.

At your height, I would probably choose 165s, but a few mm variation in either direction isn't going to make that much of a difference.

Last edited by mihlbach; 09-05-10 at 02:29 PM.
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