I'm restoring an antique BMX...



J

!Jones

Guest
.... and know *squat* about that kind of gear. Anyone know BMX and
want to give advice?

Right now, I'm shopping eBay for a crank. Are the "spiders" generally
interchangable across crank arms? I see generic spiders for sale
without any crank mentioned. Also, it looks to me like the spindle
tapers are quite different in that branch of the industry.

Anybody wanna talk about matching crank arms, spiders, and BBs on an
old BMX? Actually, it's a Littlejohn tandem that I'm setting up to go
with us when we travel. It'll be kept pretty straight and level (as
opposed to freestyle, jumping, etc), but I kinna want it to be
BMXey... I don't think "BMXey" is in the dictionary; my spell checker
is havin' a cow!

Jones
 
J

jim beam

Guest
!Jones wrote:
> ... and know *squat* about that kind of gear. Anyone know BMX and
> want to give advice?
>
> Right now, I'm shopping eBay for a crank. Are the "spiders" generally
> interchangable across crank arms? I see generic spiders for sale
> without any crank mentioned. Also, it looks to me like the spindle
> tapers are quite different in that branch of the industry.
>
> Anybody wanna talk about matching crank arms, spiders, and BBs on an
> old BMX? Actually, it's a Littlejohn tandem that I'm setting up to go
> with us when we travel. It'll be kept pretty straight and level (as
> opposed to freestyle, jumping, etc), but I kinna want it to be
> BMXey... I don't think "BMXey" is in the dictionary; my spell checker
> is havin' a cow!
>
> Jones
>


see what you can figure out from danscomp.com - it's bmx central.
 
J

!Jones

Guest
On Sat, 11 Aug 2007 07:49:39 -0700, in rec.bicycles.tech jim beam
<[email protected]> wrote:

>!Jones wrote:
>> ... and know *squat* about that kind of gear. Anyone know BMX and
>> want to give advice?
>>
>> Right now, I'm shopping eBay for a crank. Are the "spiders" generally
>> interchangable across crank arms? I see generic spiders for sale
>> without any crank mentioned. Also, it looks to me like the spindle
>> tapers are quite different in that branch of the industry.
>>
>> Anybody wanna talk about matching crank arms, spiders, and BBs on an
>> old BMX? Actually, it's a Littlejohn tandem that I'm setting up to go
>> with us when we travel. It'll be kept pretty straight and level (as
>> opposed to freestyle, jumping, etc), but I kinna want it to be
>> BMXey... I don't think "BMXey" is in the dictionary; my spell checker
>> is havin' a cow!
>>
>> Jones
>>

>
>see what you can figure out from danscomp.com - it's bmx central.


As near as I can tell, the spider/single chainring interchange limited
by the size of the center hole.
 
C

Chalo

Guest
!Jones <[email protected]> wrote:
>
> Right now, I'm shopping eBay for a crank. Are the "spiders" generally
> interchangable across crank arms? I see generic spiders for sale
> without any crank mentioned. Also, it looks to me like the spindle
> tapers are quite different in that branch of the industry.


Today's BMX crank spindles are not tapered; this is to accommodate
widely different thicknesses of chainring and to allow easy adjustment
of chainline. The arms are fixed axially by bolts into the spindle
ends, then clamped onto the spindle with pinch bolts. A few use a
press-fitted, fine pitch spline that likewise does not have a taper.

Adapter spiders for BMX cranks are outdated but still available to
some degree. Since their design, if not their manufacture, is
contemporary with the prevalent use of one-piece cranks, they all have
15/16" bores (like steel plate chainrings or older aluminum rings).
More up-to-date three-piece cranks with 3/4", 7/8", 19mm, or 22mm
spindles are adapted to chainrings with 15/16" bores by the use of
small stepped ring spacers that are often furnished with both the
crank and the chainring:

http://www.danscomp.com/457004.php?cat=PARTS

Chainrings of newer manufacture (about the past 10 years) are likely
to have a 22mm bore and come with an adapter to fit 19mm spindles.

Chalo