Need help building new bike : bottom bracket and headset ??

[Si]

Hi,

I managed to write off my old road frame earlier in the year and have
bought a new frame - fork combo which I want to build up with the bits
from my old cycle.

There's obviously a massive array of sizes of BBs and headsets out
there so... how do I order the right ones?

I've moved house recently and don't think my LBS is keen or able to
give me too much help here (apologies to all Chepstow LBS owners on
the NG today...)

For the BB, what measurements do I need to know? Face to face across
the bracket mount.. is there also some dimension I need from my crank?

As the the headset... I'll be needing a new stem (the old one was a
split cone - presumably incompatible with cartridge headsets).

Advice appreciated.!!

 

[Simon Brooke]

in message <[email protected]>, Si
('[email protected]') wrote:

> Hi,
>
> I managed to write off my old road frame earlier in the year and have
> bought a new frame - fork combo which I want to build up with the bits
> from my old cycle.
>
> There's obviously a massive array of sizes of BBs and headsets out
> there so... how do I order the right ones?

Road bike bottom bracket shells these days are almost all the same width
(68mm), fortunately. You will need a specific axle length for your
chainset but usually this will be specified with your chainset. If not,
either fit your old bottom bracket baring or take your old bottom
bracket axle with you when choosing a new bottom bracket. Remember that
British threading is different from Italian threading and I'm sure
there's another standard out there which I can't remember (I recently
got very puzzled trying to put an British threaded bottom bracket in
the wrong way round... d'oh!).

If your head tube is a plain tube with square cut ends you need an
'ordinary' threadless headset and this is very easy - they come in inch
or 1 1/8 inch sizes for roadbikes (bigger sizes for some mountain
bikes). Provided you get the right diameter they're all
interchangeable. If your head tube has a machined recess at each end
that is wider in diameter than the main part of the tube this is
intended for an 'integrated' headset, and as these are not
interchangeable you will have to get the one the frame manufacturer
machined it for.

Get some spacers of the appropriate diameter for your steerer so that
you can allow yourself some adjustment room when you first cut your
steerer - otherwise if you later decide you want your stem 10mm higher
you're pretty much shafted.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/
Wannabe a Web designer?
<URL:http://userfriendly.org/cartoons/archives/97dec/19971206.html>

 

[Zog The Undeniable]

Si wrote:

> Hi,
>
> I managed to write off my old road frame earlier in the year and have
> bought a new frame - fork combo which I want to build up with the bits
> from my old cycle.
>
> There's obviously a massive array of sizes of BBs and headsets out
> there so... how do I order the right ones?

For the headset you need to know:

1) Quill or threadless (probably the latter if it's a new fork)
2) Steerer tube nominal diameter, 1" or 1 1/8"
3) Stack height of the headset, but only if you have a threaded fork
that has been cut to size. On a new threadless fork you will be cutting
off excess steerer anyway.

The BB spindle length and taper type will be recommended by the crankset
manufacturer. There are at least five different types of BB taper:

1) JIS standard for Shimano cranks and *most* other square-hole cranks
2) ISO standard for Campagnolo cranks
3) ISIS splined drive
4) Shimano Octalink V1 (mainly for road bikes)
5) Shimano Octalink V2 (for some MTBs)

You also need to know whether the shell in the frame is 68mm, 70mm or
73mm wide and whether it's British, Italian, French or Swiss threaded!
Most BBs are 68mm and British threaded.

> I've moved house recently and don't think my LBS is keen or able to
> give me too much help here (apologies to all Chepstow LBS owners on
> the NG today...)
>
> For the BB, what measurements do I need to know? Face to face across
> the bracket mount.. is there also some dimension I need from my crank?

If your fork is threadless you'll certainly need a new clamp-on stem.