Shimano LP20, fixie, use a conventional BB?

[still me]

A friend of mine is trying to convert a bike to a fixie. It currently
has an LP20 BB with a 118 designation on the axle. It is rough and
needs replacement.

Questions:
- Can he pull this out and use a conventional Shimano unsealed 68/113
unit from the 80's? Is there anything special about a BB with an LP 20
in it? Is an LP20 a square taper?

- will his chainline be close enough with a 113 in there? Or does he
need to get down to a 110 to make it work? Could he just put a couple
mm of spacers behind the (new) single rear cog to make it line up?

Thanks,

 

[JeffWills]

On May 31, 6:44 pm, still me <[email protected]> wrote:
> A friend of mine is trying to convert a bike to a fixie. It currently
> has an LP20 BB with a 118 designation on the axle. It is rough and
> needs replacement.
>
> Questions:
> - Can he pull this out and use a conventional Shimano unsealed 68/113
> unit from the 80's? Is there anything special about a BB with an LP 20
> in it? Is an LP20 a square taper?
>
> - will his chainline be close enough with a 113 in there? Or does he
> need to get down to a 110 to make it work? Could he just put a couple
> mm of spacers behind the (new) single rear cog to make it line up?
>
> Thanks,

Everything should be fine. The LP20 is a bottom-feeder square taper
BB. The conventional BB will replace it without a hitch. If you want
to get finicky, run a tap through the threads and face the BB shell
before you install the "new" BB.

Jeff

 

[Qui si parla Campagnolo]

On May 31, 8:44 pm, still me <[email protected]> wrote:
> A friend of mine is trying to convert a bike to a fixie. It currently
> has an LP20 BB with a 118 designation on the axle. It is rough and
> needs replacement.
>
> Questions:
> - Can he pull this out and use a conventional Shimano unsealed 68/113
> unit from the 80's? Is there anything special about a BB with an LP 20
> in it? Is an LP20 a square taper?

Yes, just get the length needed for the fixie chainline. Standard JIS
square taper, made today as well(UN-53/73). LP-20 just a low end BB.
>
> - will his chainline be close enough with a 113 in there? Or does he
> need to get down to a 110 to make it work? Could he just put a couple
> mm of spacers behind the (new) single rear cog to make it line up?

Put spacers onto the hub and if there are not enough threads engaged,
you may strip the cog/hub. Go to a decent bike shop, ask for a proper
length BB and let them 'spec' it for you./ We do that all the
time,,put some BBs in, with the crank, and see what is the best
length.
>
> Thanks,

 

[still me]

On Fri, 01 Jun 2007 05:46:35 -0700, Qui si parla Campagnolo
<[email protected]> wrote:


>,put some BBs in, with the crank, and see what is the best
>length.


Follow up length question: How come the LP20 is commonly a 118? I'm
used to that length for classic French, but I thought 113 was the buzz
for Shimano... or is this a less than common LP20?

Thanks,

 

[A Muzi]

> Qui si parla Campagnolo <[email protected]> wrote:
>> put some BBs in, with the crank, and see what is the best
>> length.

still me wrote:
> Follow up length question: How come the LP20 is commonly a 118? I'm
> used to that length for classic French, but I thought 113 was the buzz
> for Shimano... or is this a less than common LP20?

LP20 was the oem unit when cheap (matching quality) cranks commonly used
115, 118, 122, 127mm so it was made in those sizes. Shimano didn't make
a 103mm LP20 because they didn't supply it to manufacturers for use with
the DuraAce crank of the period.

I think sometimes it's overlooked that oem drives all these decisions.
The aftermarket parts market's only a small zit on the butt of the oem
elephant.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971