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Old 05-03-12, 03:55 AM   #1
3speed
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Does 1/2cm matter?

So I started building up my 90' Miyata 914 tonight with the new-to-me group I got. I put the BB in and bolted the cranks on. I suppose ideally you'd want the same distance between each crank arm and the seat-tube. I measured and the inside of the drive-side crank arm is 1/2cm closer to the seat-tube than the other crank arm. Does that small difference really matter? I've never really measured before, so maybe they're all usually exactly the same distance or maybe 1/2cm isn't really a big deal?
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Old 05-03-12, 04:22 AM   #2
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It wouldn't matter to me. I know some people will notice any slight variation in their bikes but I once checked all of mine and found all sorts of differences in seat height, reach, etc. I thought they were all the same.
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Old 05-03-12, 04:27 AM   #3
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Depends on the crank, bb spindle, bb width... but in the end only the marketing departments "feel" the difference IMHO.
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Old 05-03-12, 04:42 AM   #4
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Some cranks are Asymmetric and the correct BB is longer on the cranks side. Was the BB original to the cranks or are you running a modern BB?
See if Sheldon has it listed. this would be a good start but there is other info if you dig.
http://sheldonbrown.com/bbsize.html
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Old 05-03-12, 05:09 AM   #5
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Get A New Spindle?

Quote:
Originally Posted by 3speed View Post
Does that small difference really matter? I've never really measured before, so maybe they're all usually exactly the same distance or maybe 1/2cm isn't really a big deal?
This will depend on how sensitive your body will be to this misalignment between your femurs and knee joint relative to your pelvis. I'm very concerned about mechanical alignment for my body, so would just pull the old spindle, and search for a new one that has the correct dimensions. That's just me. Wouldn't take much effort or cost a lot. Just replace it...

PG
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Old 05-03-12, 06:40 AM   #6
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good grief
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Old 05-03-12, 06:45 AM   #7
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The 5 mm would not matter to me. Phil's points above are well taken, but my body is already asymmetrical in more ways than I can measure, so I just don't worry about it.

On the other hand, is it possible you put your spindle in backwards?
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Old 05-03-12, 08:08 AM   #8
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Personally I wouldn't worry about it. No one has a perfectly symmetrical body anyway. Many people, for example, have one leg longer than the other, yet we ride with the same length cranks on both sides of the bike.
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Old 05-03-12, 09:01 AM   #9
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Is the spindle symetrical? They're sometimes longer on the drive side. Do you have the spindle in backwards?
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Old 05-03-12, 09:41 AM   #10
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If it moves when it's pedaled then it's cool with me.
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Old 05-03-12, 10:10 AM   #11
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Out of curiosity and because there is a Miyata 916 sitting not twenty feet away from me, I went and measured. Yup, about 5mm difference with the drive side crank being further away from the center line of the bicycle - measured at the spindle. My bike has, however, been fitted with a 9 Speed crank set and transmission.

Then I measured the distance of the crank ends to the chain stays and guess what. Identical measurements.
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Old 05-03-12, 10:19 AM   #12
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Quote:
Originally Posted by randyjawa View Post
Out of curiosity and because there is a Miyata 916 sitting not twenty feet away from me, I went and measured. Yup, about 5mm difference with the drive side crank being further away from the center line of the bicycle - measured at the spindle. My bike has, however, been fitted with a 9 Speed crank set and transmission.

Then I measured the distance of the crank ends to the chain stays and guess what. Identical measurements.
Do you mean identical to the first measurement, ie. a difference of 5mm, or identical to each other?
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Old 05-03-12, 12:29 PM   #13
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I've been telling women for years that size doesn't matter......just sayin'
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Old 05-03-12, 12:45 PM   #14
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Quote:
Do you mean identical to the first measurement, ie. a difference of 5mm, or identical to each other?
Sorry to confuse and good point.

I mean that there was a difference, in measurements, from the bicycle's center-line to the spindle ends. But, when I measured the distance from the pedal ends, of the cranks, to their respective chain stays, that measurement was the same for each side.
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Old 05-03-12, 01:00 PM   #15
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If you put an assymetrical BB in the bike you will have that problem, but it will depend on the crankset. Sincerely for the type of bike you are talking about i wouldt care. You wont take it to a contest to start with, right?
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Old 05-03-12, 01:19 PM   #16
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Thanks, guys. I really didn't think it mattered at all. Just wanted to make sure. And as for spindle, this is actually a newer style sealed BB that came with the 9sp cranks. It's just that the spindle in the BB is slightly longer on the non-drive side. I'm not gonna worry about it at all unless I get surprised by some minor issue once I get it out on the road.
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Old 05-03-12, 02:00 PM   #17
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you can drop a 2mm spacer on the drive side of the bb. that should make it only 1mm closer.

edit: there's actually a 2.5mm spacer that should even it out:
http://www.amazon.com/Wheels-Manufac.../dp/B001AYMP7G
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Old 05-03-12, 06:49 PM   #18
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I would make sure that things like chainring clearance (i.e. with the chainstay) and chainline are in good shape before giving any thought to symmetry.
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Old 05-03-12, 07:43 PM   #19
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5mm is about 1/5 of an inch (holding up a ruler and squinting). Nah, you'll never feel that. For example, for someone with a 32" inseam, that works out to about 0.6% in length. In terms of angle, that is about 0.28 degrees.

Last edited by Paramount1973; 05-03-12 at 07:58 PM.
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Old 05-03-12, 09:37 PM   #20
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Quote:
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I've been telling women for years that size doesn't matter......just sayin'
My wife calls bull****.
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Old 05-04-12, 10:15 AM   #21
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in this case I bet that if you were given the bike to ride and you did not measure it you most likely would have never known.

but as the boys are joking about I would agree that I wish I had 5mm more, and normally it is on the left side!
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