Give those cranks a spin...
07-30-07, 03:05 AM
#1
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Give those cranks a spin...
since this forum is so much like home for me I won't bother to venture over to the mechanical forum.
I just realized that my BB seems too tight. So here's the question. Ideally if you spin your cranks in reverse, once really hard by hand, how much should they spin?
I just realized that my BB seems too tight. So here's the question. Ideally if you spin your cranks in reverse, once really hard by hand, how much should they spin?
07-30-07, 03:31 AM
#2
Large Member
take the chain off and see how long they spin: should be for ages. (can't give you a definite number as there are all sorts of variables like chainring weight and thus momentum, bearing types, grease packed into the BB, wind resistance of pedals!)
if you can feel any grinding when you turn the crank slowly, that's not good.
if you can feel any grinding when you turn the crank slowly, that's not good.
07-30-07, 03:45 AM
#3
Roman Killer
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Eh, not so true... that's the case with old-school three-piece sets, but the new two-piece mega-exo type stuff doesn't spin nearly as freely... I use ceramic bearings with my K-Force, definitely spins better, but still not for ages...
07-30-07, 04:13 AM
#4
Large Member
OK, my bad... i only use and trust square tapers....
got the last record square taper BB and it's as good as my c record from 20 years ago.
still, grinding is not good no matter what BB you use.
got the last record square taper BB and it's as good as my c record from 20 years ago.
still, grinding is not good no matter what BB you use.
07-30-07, 01:27 PM
#5
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Yeah, mine hardly even spins. I have the 06 Ultegra down there. I don't get any grinding. Honestly though, I get about 1.5 times around. I don't know how long it's been that way. I know practically nothing about the BB so I suppose I should take it to the LBS.
07-30-07, 01:31 PM
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Mine are the same way.
Last edited by Cyclologist; 07-30-07 at 02:52 PM.
07-30-07, 01:33 PM
#7
Throw the stick!!!!
My Chorus UT is the same way, only spins a couple of times. I'm really looking forward to some ceramic bearings for it. Even if they don't help I can brag to all my friends that I have ceramic bearings. Boy oh boy won't they be jealous. 
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07-30-07, 01:42 PM
#8
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Hmm. So is this not a problem. Seems We're getting unnecessary resistance aren't we?
07-30-07, 02:22 PM
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07-30-07, 02:33 PM
#10
Making a kilometer blurry
The seals on the crappy external BBs grab. I guess they never fully break in either. My wife's Dolce has only about 160 miles on it, and hers won't spin four times if I really hit it hard with the chain off.
My 10-year-old Ultegra BB is probably still spinning from the last time I checked.
My 10-year-old Ultegra BB is probably still spinning from the last time I checked.
07-30-07, 02:37 PM
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I AM going to smack you the nect time I see you!
And my BB's spin maybe 8 times if I really sling them around.
07-30-07, 02:45 PM
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I use the shimano outboard bearing BB's and they spin fine (forever though, I'm not sure). I know that if you tighten the little black end cap on the left crank too tight, you end up putting too much load on the bearings. Might want to check that by removing the crank and reinstalling... regrease everything while you're at it... or have your LBS do it.
07-30-07, 06:40 PM
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How new/old is the bike? if it's a new bike it may be tight, check it after a few hundred miles. I have an Ultegra crank and with the Ultegra BB & bearings when I spun it hard it went maybe 1/2 a turn. I installed some ceramic bearings and now when I spin it I get about 1 1/2 - 2 rotations. Those are both with chain on and the chain very clean and lubed.
07-30-07, 09:18 PM
#14
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So on my commute home from work I stopped at Contender bicycle, bicycleresearch.com's "best pro shop in the US" for 2007.
https://www.contenderbicycles.com/
They told me my 1 1/2 spin was normal. Then they tightened up all of my other odds and ends I've been neglecting. Why isn't this a bigger deal to more people?!? Seems to me that resistance is going to really add up.
https://www.contenderbicycles.com/
They told me my 1 1/2 spin was normal. Then they tightened up all of my other odds and ends I've been neglecting. Why isn't this a bigger deal to more people?!? Seems to me that resistance is going to really add up.
