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#1
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determining correct BB spindle length
How does one determine what bottom bracket spindle length to get? I'm
asking what I need to measure on the bike to make sure I get a length that will give me a good chainline.This is for a newer road racing frame that had no bottom bracket when I got it so I have nothing to compare it to. I'm using a square taper crankset (FSA carbon) and have found FSA ultimax BBs online at reasonable prices. I would prefer having the big chainring line up with middle of the cogset. Is there a measurement or combination of measurements I can make to come to a reasonable number? |
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#2
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determining correct BB spindle length
On Jun 29, 9:22 am, zencycle wrote:
How does one determine what bottom bracket spindle length to get? I'm asking what I need to measure on the bike to make sure I get a length that will give me a good chainline.This is for a newer road racing frame that had no bottom bracket when I got it so I have nothing to compare it to. I'm using a square taper crankset (FSA carbon) and have found FSA ultimax BBs online at reasonable prices. I would prefer having the big chainring line up with middle of the cogset. Is there a measurement or combination of measurements I can make to come to a reasonable number? In your case, the crank is recent enough that you should be able to dig up a recommended spindle length. FSA can probably tell you pretty quickly if you call them. Recommended spindle lengths are a length chosen to give decent chainline when used alongside the rear drivetrain parts the crank is intended for, ie a 130-spaced road hub in your case. The trick with recommended spindle lengths is that sometimes they'd be a little longer than would give optimal chainline, in order to pre-emptively work around the many frames with clearance issues. |
#3
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determining correct BB spindle length
zencycle wrote:
How does one determine what bottom bracket spindle length to get? I'm asking what I need to measure on the bike to make sure I get a length that will give me a good chainline.This is for a newer road racing frame that had no bottom bracket when I got it so I have nothing to compare it to. I'm using a square taper crankset (FSA carbon) and have found FSA ultimax BBs online at reasonable prices. I would prefer having the big chainring line up with middle of the cogset. Is there a measurement or combination of measurements I can make to come to a reasonable number? The usual litany- Thread matches frame, spindle matches crank. FSA singles are 108, doubles 113, triples 118 all symmetric. Yes, that is counterintuitive (you'd expect that 5mm overall on a symmetric spindle would add only 2.5mm per side). Crank designers have a wide latitude of choices about the relationship of spindle to rings to pedal. You can't look at an unknown crank and 'see' the spindle length readily. -- Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971 |
#4
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determining correct BB spindle length
On Jun 29, 12:45 pm, Nate Knutson wrote:
On Jun 29, 9:22 am, zencycle wrote: How does one determine what bottom bracket spindle length to get? I'm asking what I need to measure on the bike to make sure I get a length that will give me a good chainline.This is for a newer road racing frame that had no bottom bracket when I got it so I have nothing to compare it to. I'm using a square taper crankset (FSA carbon) and have found FSA ultimax BBs online at reasonable prices. I would prefer having the big chainring line up with middle of the cogset. Is there a measurement or combination of measurements I can make to come to a reasonable number? In your case, the crank is recent enough that you should be able to dig up a recommended spindle length. FSA can probably tell you pretty quickly if you call them. Recommended spindle lengths are a length chosen to give decent chainline when used alongside the rear drivetrain parts the crank is intended for, ie a 130-spaced road hub in your case. The trick with recommended spindle lengths is that sometimes they'd be a little longer than would give optimal chainline, in order to pre-emptively work around the many frames with clearance issues. Thanks, I actually posted the question to their tech support before I posted here, but whoi knows when/if I'll hear back. |
#5
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determining correct BB spindle length
On Jun 29, 1:58 pm, A Muzi wrote:
zencycle wrote: How does one determine what bottom bracket spindle length to get? I'm asking what I need to measure on the bike to make sure I get a length that will give me a good chainline.This is for a newer road racing frame that had no bottom bracket when I got it so I have nothing to compare it to. I'm using a square taper crankset (FSA carbon) and have found FSA ultimax BBs online at reasonable prices. I would prefer having the big chainring line up with middle of the cogset. Is there a measurement or combination of measurements I can make to come to a reasonable number? The usual litany- Thread matches frame, spindle matches crank. FSA singles are 108, doubles 113, triples 118 all symmetric. Yes, that is counterintuitive (you'd expect that 5mm overall on a symmetric spindle would add only 2.5mm per side). Crank designers have a wide latitude of choices about the relationship of spindle to rings to pedal. You can't look at an unknown crank and 'see' the spindle length readily. -- Andrew Muziwww.yellowjersey.org Open every day since 1 April, 1971 Except that they offer the ultimax in six different sizes. I tried a Specialized 113 I had lying around but the chainline ended up with the big ring lined up on the 14 (12x23 9sp) and I couldn't push the 'fixed' cup side any further into the BB shell, but i'm thinking the 103 they offer would be a bit short. I don't want to spend $100 on yet _another_ bike part I'll never use.This is why I was hoping for some sort of silly measurement like 'hub spacing times .75 +\- Xmm times the number of cogs you want to offset....' or some **** like that.Since this is a JIS standard, is there a spec regarding how far into the crank arm the spindle is supposed to seat? |
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