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

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

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

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.

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?

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.

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?

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.

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.

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.

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