|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
BB spindle slightly too short
Hello all,
I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico |
Ads |
#2
|
|||
|
|||
BB spindle slightly too short
wrote:
I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? I've actually had some success shimming this way, to salvage toasted cranks. I made a shim from an aluminum beverage can, just a right- angled piece to cover two adjacent faces of the square. I used lots of grease and tightened the bejasus out of the fixing bolt. (This is not something I'd do for a paying customer, but I did it as a "charity case" for a local homeless guy, and it seemed to work pretty well.) Another option is to put a spacer under the right-side bottom bracket mounting ring. This is the traditional item for that: http://harriscyclery.net/itemdetails.cfm?ID=836 Sheldon "Where There's A Will..." Brown +---------------------------------------------------+ | If you oppose making marriage legally available | | to all adults, you are promoting promiscuity. | +---------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
#3
|
|||
|
|||
BB spindle slightly too short
On Dec 10, 4:33 pm, " wrote:
Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... How did you arrive at that diagnosis, especially if the crankset *really is* NOS? Are you certain the BB spindle is symmetrical (L/R)? What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? IMO, a shim of that sort is a real "last resort" measure. Spacer(s) under the right side cup are the easiest/cheapest solution, assuming the problem really does lie with the right crankarm. Any reasonable LBS should have spacers, or buy online: http://www.biketoolsetc.com http://www.loosescrews.com Federico |
#4
|
|||
|
|||
BB spindle slightly too short
|
#5
|
|||
|
|||
BB spindle slightly too short
On Dec 11, 6:21 am, Peter Cole wrote:
wrote: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico I've shimmed the crank, as Sheldon describes, on one bike where I had the same problem. Worked fine -- lots of miles, big rider. I'm curious: did you shim the crank to make a damaged crankarm usable, or to compensate for a too short BB spindle? |
#6
|
|||
|
|||
BB spindle slightly too short
Ozark Bicycle wrote:
On Dec 11, 6:21 am, Peter Cole wrote: wrote: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico I've shimmed the crank, as Sheldon describes, on one bike where I had the same problem. Worked fine -- lots of miles, big rider. I'm curious: did you shim the crank to make a damaged crankarm usable, or to compensate for a too short BB spindle? The latter. |
#7
|
|||
|
|||
BB spindle slightly too short
On Dec 12, 7:35 am, Peter Cole wrote:
Ozark Bicycle wrote: On Dec 11, 6:21 am, Peter Cole wrote: wrote: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico I've shimmed the crank, as Sheldon describes, on one bike where I had the same problem. Worked fine -- lots of miles, big rider. I'm curious: did you shim the crank to make a damaged crankarm usable, or to compensate for a too short BB spindle? The latter. Hmm....you found that method preferable to either installing the proper length BB spindle or placing spacers under the RH cup? |
#8
|
|||
|
|||
BB spindle slightly too short
Ozark Bicycle wrote:
On Dec 12, 7:35 am, Peter Cole wrote: Ozark Bicycle wrote: On Dec 11, 6:21 am, Peter Cole wrote: wrote: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico I've shimmed the crank, as Sheldon describes, on one bike where I had the same problem. Worked fine -- lots of miles, big rider. I'm curious: did you shim the crank to make a damaged crankarm usable, or to compensate for a too short BB spindle? The latter. Hmm....you found that method preferable to either installing the proper length BB spindle or placing spacers under the RH cup? Obviously. I use shims all the time on various locations on bikes, I don't see the problem. |
#9
|
|||
|
|||
BB spindle slightly too short
On Dec 13, 6:54 am, Peter Cole wrote:
Ozark Bicycle wrote: On Dec 12, 7:35 am, Peter Cole wrote: Ozark Bicycle wrote: On Dec 11, 6:21 am, Peter Cole wrote: wrote: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? Thanks, Federico I've shimmed the crank, as Sheldon describes, on one bike where I had the same problem. Worked fine -- lots of miles, big rider. I'm curious: did you shim the crank to make a damaged crankarm usable, or to compensate for a too short BB spindle? The latter. Hmm....you found that method preferable to either installing the proper length BB spindle or placing spacers under the RH cup? Obviously. I use shims all the time on various locations on bikes, I don't see the problem. The problem? A concern about distorting the crankarm/spindle interface, making the crankarm more likely to have a problem fitting a properly sized spindle at another time. |
#10
|
|||
|
|||
BB spindle slightly too short
On Mon, 10 Dec 2007 14:33:00 -0800 (PST), "
may have said: Hello all, I am building my first bike. I bought a BB with a 110mm spindle (square taper) and a new-old-stock Shimano FC-M510 crankset. According to the Shimano's specs, this should give a 47.5mm chainline. My measured chainline is, however, a few mm's shorter. If I remove the crank bolts, I can see that the right crank almost mushrooms the spindle (2mm left), while the left crank definitely has a few more mm's to go. So, the diagnosis seems to be that the right crank isn't really perfect... What should I do? Replace the BB with a 113mm spindle? What if I add a tiny shim between the spindle and the crank? Will it do the trick or just destroy the crank? As long as the inner sprocket adequately clears the chainstay when pedalling, you may not need to worry about it. Unless the front der is too close to the crank to shift properly, or you're in a situation which necessitates that you must go with measurements and numbers alone instead of getting on the bike and trying it out, I'd advise riding it to see which front/rear sprocket combination you'll actually use most. If those would be closer to being aligned by moving the right crank away from the seat tube, by all means, either swap out the BB for a longer one, or add a shim under the right-hand BB flange if that works. (Sometimes the shim isn't useful; I've had 110mm and 113mm BB setups on which a shim under the right flange caused the left crank to hit the chainstay or caused the left cup to bottom out on the end of the shell threads before it clamped the BB.) If the setup you've assembled does an adequate job, I'd use it and not worry about the numbers. -- My email address is antispammed; pull WEEDS if replying via e-mail. Typoes are not a bug, they're a feature. Words processed in a facility that contains nuts. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Another, slightly humorous, short video of me unicycling | Chexjc | Unicycling | 9 | November 19th 06 04:20 PM |
Another, slightly humorous, short video of me unicycling | Chexjc | Unicycling | 1 | November 19th 06 02:05 AM |
Another, slightly humorous, short video of me unicycling | mornish | Unicycling | 0 | November 19th 06 02:02 AM |
108 or 113 BB spindle ?? | Keiron | Techniques | 1 | July 10th 06 05:18 PM |
WTB: Spindle 109 mm | JA \(change to reply\) | Marketplace | 1 | December 23rd 04 04:05 AM |