Chainline problems

[Coyoteboy]

I came to swap my old cranks for even older ones (both square taper) but
found my new older old cranks (lol) lined the rings up closer to the frame.
Not a big problem but in order to get the right BB to set the new (larger)
rings out from the frame I'm going to need to shimmy the chainline out
towards ~6th cog down at the back on an 8speed block. This seems too far and
is somewhat annoying, especially as I've sacrificed the granny ring for
weight and to get the crank closer to the chainstays. Any suggestions? I'm
trying to extend the life of my frame and didnt want to invest in a whole
new set of cranks as the der-hanger is faulty anyway and the forks are
threaded - it just does the job for now.

 

[Clive George]

"Coyoteboy" <[email protected]> wrote in message
news:[email protected]...
>I came to swap my old cranks for even older ones (both square taper) but
>found my new older old cranks (lol) lined the rings up closer to the frame.
>Not a big problem but in order to get the right BB to set the new (larger)
>rings out from the frame I'm going to need to shimmy the chainline out
>towards ~6th cog down at the back on an 8speed block. This seems too far
>and is somewhat annoying, especially as I've sacrificed the granny ring for
>weight and to get the crank closer to the chainstays. Any suggestions? I'm
>trying to extend the life of my frame and didnt want to invest in a whole
>new set of cranks as the der-hanger is faulty anyway and the forks are
>threaded - it just does the job for now.

If you're using larger rings and they won't clear the chainstay without
moving them out (by fitting the longer BB), you've got no choice in the
matter...

(I'm not entirely sure what you mean by "I'm going to need to shimmy the
chainline out", since the chainline is purely a function of where the cogs
are)

cheers,
clive

 

[Rob Morley]

In article <[email protected]>, Coyoteboy
[email protected] says...
> I came to swap my old cranks for even older ones (both square taper) but
> found my new older old cranks (lol) lined the rings up closer to the frame.
> Not a big problem but in order to get the right BB to set the new (larger)
> rings out from the frame I'm going to need to shimmy the chainline out
> towards ~6th cog down at the back on an 8speed block. This seems too far and
> is somewhat annoying, especially as I've sacrificed the granny ring for
> weight and to get the crank closer to the chainstays. Any suggestions? I'm
> trying to extend the life of my frame and didnt want to invest in a whole
> new set of cranks as the der-hanger is faulty anyway and the forks are
> threaded - it just does the job for now.
>
>
Are the rear dropouts properly aligned with the bottom bracket? It
sounds as if your frame may be out of track.

 

[Coyoteboy]

Clive George wrote:
> "Coyoteboy" <[email protected]> wrote in message
> news:[email protected]...
>> I came to swap my old cranks for even older ones (both square taper)
>> but found my new older old cranks (lol) lined the rings up closer to
>> the frame. Not a big problem but in order to get the right BB to set
>> the new (larger) rings out from the frame I'm going to need to shimmy
>> the chainline out towards ~6th cog down at the back on an 8speed
>> block. This seems too far and is somewhat annoying, especially as I've
>> sacrificed the granny ring for weight and to get the crank closer to
>> the chainstays. Any suggestions? I'm trying to extend the life of my
>> frame and didnt want to invest in a whole new set of cranks as the
>> der-hanger is faulty anyway and the forks are threaded - it just does
>> the job for now.
>
> If you're using larger rings and they won't clear the chainstay without
> moving them out (by fitting the longer BB), you've got no choice in the
> matter...
>
> (I'm not entirely sure what you mean by "I'm going to need to shimmy the
> chainline out", since the chainline is purely a function of where the
> cogs are)
>
> cheers,
> clive

Well i meant that i have no choice but to move the rings out so the line
of the centre ring is way off-centre.

 

[Coyoteboy]

Rob Morley wrote:
> Are the rear dropouts properly aligned with the bottom bracket? It
> sounds as if your frame may be out of track.

Not entirely sure, no. The bike does have a habit of requiring some
right-lean to hold it steady when riding no-handed. I put this down to
my bottom as i seem to require the same on my other bike too! I'm not
sure how im going to try to measure its centrality (word?!)

J

 

[Alan Braggins]

In article <[email protected]>, Coyoteboy wrote:
>Rob Morley wrote:
>> Are the rear dropouts properly aligned with the bottom bracket? It
>> sounds as if your frame may be out of track.
>
>Not entirely sure, no. The bike does have a habit of requiring some
>right-lean to hold it steady when riding no-handed. I put this down to
>my bottom as i seem to require the same on my other bike too! I'm not
>sure how im going to try to measure its centrality (word?!)

See http://www.sheldonbrown.com/frame-spacing.html and scroll down
to "Checking Alignment (Symmetry)".

 

[Dennis Davis]

In the referenced article, Coyoteboy <[email protected]> writes:
>Rob Morley wrote:
>> Are the rear dropouts properly aligned with the bottom bracket? It
>> sounds as if your frame may be out of track.
>
>Not entirely sure, no. The bike does have a habit of requiring some
>right-lean to hold it steady when riding no-handed. I put this down
>to my bottom as i seem to require the same on my other bike too!

Doesn't have to be your physiology. A small amount of lean may
be necessary for counteract the camber of the road[1]. You may
also be "lopsided" if you've cash, keys etc concentrated in one
pocket rather than distributed evenly. And, of course, luggage
distribution on the bike may make you lopsided.

>I'm not sure how im going to try to measure its centrality (word?!)

Sheldon Brown to the rescue. See his string method for checking
frame alignment:

http://sheldonbrown.com/frame-spacing.html

[1] That's why trike riders have forearms like Popeye. They're
constantly heaving on the handlebars to stop the trike veering
into the gutter
--
Dennis Davis, BUCS, University of Bath, Bath, BA2 7AY, UK
[email protected]

 

[Rob Morley]

In article <[email protected]>, Alan Braggins
[email protected] says...
> In article <[email protected]>, Coyoteboy wrote:
> >Rob Morley wrote:
> >> Are the rear dropouts properly aligned with the bottom bracket? It
> >> sounds as if your frame may be out of track.
> >
> >Not entirely sure, no. The bike does have a habit of requiring some
> >right-lean to hold it steady when riding no-handed. I put this down to
> >my bottom as i seem to require the same on my other bike too! I'm not
> >sure how im going to try to measure its centrality (word?!)
>
> See http://www.sheldonbrown.com/frame-spacing.html and scroll down
> to "Checking Alignment (Symmetry)".
>
Alternatively if you have the bottom bracket out just put a 2 foot
straight edge along each side of the shell to check the dropout offset.
That checks just the rear end alignment rather than relying on the head
tube being in the right place too.