Cables

Now I'm going to show my age with plenty of ignorance thrown in - why do the
cables all go under the bottom bracket instead of over? Can I use a modern
derraileur even thought the cables aren't going underneath the BB?

Thanks.
C_N

Campag_nut wrote:
Now I'm going to show my age with plenty of ignorance thrown in - why do the
cables all go under the bottom bracket instead of over?

Not all, depends very much on the frame

Can I use a modern
derraileur even thought the cables aren't going underneath the BB?

Yup,

Parbs

Yup,

Parbs

Thanks a million Parbs. I thought my ebaying might have been in vain!

Cheers.

On Mar 26, 10:04 pm, "Campag_nut" wrote:
Now I'm going to show my age with plenty of ignorance thrown in - why do the
cables all go under the bottom bracket instead of over? Can I use a modern
derraileur even thought the cables aren't going underneath the BB?

You can with a rear, but the front it will depend on where your cables
run. Most modern road fronts are pulldowns, not pullups, so the cable
will have to pull down on them to work. Running the cable under the
BB shell pretty-much guarantees this will be the case, of course ...

On Mon, 26 Mar 2007 12:04:30 GMT, Campag_nut wrote:

Now I'm going to show my age with plenty of ignorance thrown in - why do the
cables all go under the bottom bracket instead of over?

It's cheaper, looks tidier and prevents interference with wide-range front
derailleurs (as found on on MTBs). The downside is that there's more
friction and likelihood of gunking up.

Can I use a modern
derraileur even thought the cables aren't going underneath the BB?

If you can route the front cable so that it pulls in the correct direction
(usually down these days).

--
Home page: http://members.westnet.com.au/mvw

On Mar 26, 10:04 pm, "Campag_nut" wrote:
Now I'm going to show my age with plenty of ignorance thrown in - why do the
cables all go under the bottom bracket instead of over? Can I use a modern
derraileur even thought the cables aren't going underneath the BB?

Thanks.
C_N

disclaimer - when you say 'over the BB' I am assuming 'run along the
top tube and down the seat tube/seat stay' - not literally 'over the
top of the BB'

Well, from a road bike POV

1. before there was STI/Ergo, the shifters were these little levers on
the down tube. Natural line to run the cables down the down tube.
Under the BB is a natural 'built-in' area to run the cables around to
change the direction to either of the derailleurs. Plus you only need
a cable outer for the last bit to the rear derailleur, saving a few
grammes.

2. With 'brake/shifter' combos - to run cables along the top tube, you
end up with a longer cable for the front derailleur, plus you need to
use cable housing, or some other device, to change directions at the
top tube/seat tube/seat stay junction

FWIW - my 20 year old mountain bike has all the cables run along the
top tube, but the front derailleur is still a 'pull down' so the cable
runs around a pulley at the bottom of the seat tube behind the BB.

phillip brown

"phillip brown" wrote:

disclaimer - when you say 'over the BB' I am assuming 'run along the
top tube and down the seat tube/seat stay' - not literally 'over the
top of the BB'

No, I think he did mean 'over the top of the BB'

Well, from a road bike POV

1. before there was STI/Ergo, the shifters were these little levers on
the down tube. Natural line to run the cables down the down tube.
Under the BB is a natural 'built-in' area

And before STI there were cables that were run down the down tube and under
special cable guides (either brazed onto the frame or clamped on) that
directed the cable past the BB to lead along the chainstay or up to the
front derailleur.

Check out the BB detail (bottom-left pic) on this:
http://www.sheldonbrown.com/retroral...fessional.html


--
Cheers
Peter

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