Converting an old hack to fixed

[Zog The Undenia]

I'm toying with the idea of converting my old "sports bike", now about 20 years old, to fixed rather
than just throwing it away. The rear spacing is 120mm and it has horizontal dropouts, both of which
are ideal. However, the chainset has a 52T ring swaged on and only the 42T ring can be unbolted and
removed. The neatest solution would be to remove the 42T ring, but then I'd need the largest
available 22T sprocket on the back for a reasonable 63" gear (it has 27" wheels). Are there any
disadvantages with running relatively large chainrings, apart from a bit of added weight?

Roger

 

[Johnb]

Zog The Undeniable wrote:

> I'm toying with the idea of converting my old "sports bike", now about 20 years old, to fixed
> rather than just throwing it away. The rear spacing is 120mm and it has horizontal dropouts,
> both of which are ideal. However, the chainset has a 52T ring swaged on and only the 42T ring
> can be unbolted and removed. The neatest solution would be to remove the 42T ring, but then I'd
> need the largest available 22T sprocket on the back for a reasonable 63" gear (it has 27"
> wheels). Are there any disadvantages with running relatively large chainrings, apart from a bit
> of added weight?

It can actually be better and give a smoother ride as the chain has less 'bend' to make and I have
always found there is less chance of the chain coming off.

Also I think big chainrings look cool ;-)

John B (who owns a 68T chainring that has occasionally been used for a fixie)

 

[Ianb]

"JohnB" <[email protected]> wrote in message news:[email protected]...
>
>
> Zog The Undeniable wrote:
>
> > I'm toying with the idea of converting my old "sports
bike", now about
> > 20 years old, to fixed rather than just throwing it
away. The rear
> > spacing is 120mm and it has horizontal dropouts, both of
which are
> > ideal. However, the chainset has a 52T ring swaged on
and only the 42T
> > ring can be unbolted and removed. The neatest solution
would be to
> > remove the 42T ring, but then I'd need the largest
available 22T
> > sprocket on the back for a reasonable 63" gear (it has
27" wheels). Are
> > there any disadvantages with running relatively large
chainrings, apart
> > from a bit of added weight?
>
> It can actually be better and give a smoother ride as the
chain has less
> 'bend' to make and I have always found there is less
chance of the chain
> coming off.
>
> Also I think big chainrings look cool ;-)
>
> John B (who owns a 68T chainring that has occasionally been used
for a fixie)
>

It seems obvious to me that large cogs (fore and aft) would be liable to less wear and so longer
life albeit at cost of more weight (marginal consideration). For instance 50% larger cogs means
that per mile each tooth is tooth is used 33% less. The chain is flexed less and the extra link
or two also reduces the number of chain turns per mile. I have currently 49/21 and 46/20 fixed
bikes. Unfortunately as the "20" has 4 missing teeth at the last count it is overdue for
replacement. However you may well find (like me) that a large fixed cog is hard to find:- LBS1 =
15 is largest LBS2 what is a fixed cog? LBS3 = 16 is largest distant dealer catalogue says 13-16
= £10, 17-20 = £17.50 So, once again we are n the hands of the dealers/makers when it comes to
choosing what WE want.

 

[Andymorris]

IanB wrote:
>
> It seems obvious to me that large cogs (fore and aft) would be liable to less wear and so longer
> life albeit at cost of more weight (marginal consideration). For instance 50% larger cogs means
> that per mile each tooth is tooth is used 33% less.

Err... no:

IF you have the same gear ratio, for each mile traveled the chainrings go round the same
number of times.

The tension on the chain, and so the load on the teeth would be 50% less.

> The chain is flexed less and the extra link or two also reduces the number of chain turns
> per mile.

True

--
Andy Morris

AndyAtJinkasDotFreeserve.Co.UK

Love this: Put an end to Outlook Express's messy quotes
http://home.in.tum.de/~jain/software/oe-quotefix/

 

[Dave Larrington]

IanB wrote:

> However you may well find (like me) that a large fixed cog is hard to find:- LBS1 = 15 is
> largest LBS2 what is a fixed cog? LBS3 = 16 is largest distant dealer catalogue says 13-16 =
> £10, 17-20 = £17.50

St John Street list 1/8 sprockets in sizes 13-22 and 3/32 sprockets in 12-22.

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
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