in message <
[email protected]>, Antony
('
[email protected]') wrote:
> Hi, I've not owned a bike for a long time and never have done anything
> other than basic maintenance. Yesterday I bought a £20 hack to get
> about on. It's just a bog-standard mtb-style thing with 15 gears, but
> needs a bit of work. It needs a new chainwheel as teeth are missing so
> I have a few questions . . .
>
> Do I have to replace chainwheel, rear cogs and chain together?
You don't have to but it's usually better to, particularly if they are
in poor conditions - which yours sound as if they are.
> What is involved in replacing the chainwheel?
The chainrings usually bolt onto a 'spider' on the drive-side crank.
There are, unfortunately, a number of different patterns of spider -
the five-spoke ones and two different patterns of four-spoke ones are
quite common but there are others.
However, if they're all fscked, it may be more straightforward to get a
new chainset (i.e. cranks with chainrings already fitted) which you can
get for twenty quid upwards
> Are there standard fittings (screwthread sizes etc) for
> chainwheel/bottom bracket etc?
Most bottom brackets these days are the square taper type. There are a
few splined ones around but they rare. Having said that where the
chainset sits laterally on the taper varies... so you can have lots of
fun with this.
There's what's called the 'pitch circle diameter' - this is the diameter
of the circle which passes through the centre of the bolt holes.
Usually the big and middle chainrings use the same bolt holes (often
110mm PCD) and the small ring uses different boltholes. There's a
useful chart here:
<URL:http://www.sjscycles.com/boltcirclediameter.asp>
> What should I expect to pay for a steel chainwheel and rear cogs?
Between a fiver and about fifty quid for the chain ring, depending how
posh it is. The problem with your five speed rear cogs, they're
probably a 'freewheel' rather than a modern cassette. About a tenner
for a reasonable basic one. You won't get a really expensive one,
because the new bikes are all on cassettes. Note that freewheels are
famous for being a complete bugger to remove.
> Where's the best place to get the parts?
If you've got a good Local Bike Shop it may be worth frequenting because
it is a source of high quality advice. It will be more expensive
than...
> Any good sources on the net?
Plenty.
<URL:http://www.sjscycles.com/>
<URL:http://www.chainreactioncycles.com/>
<URL:http://www.wiggle.co.uk/>
<URL:http://www.edinburgh-bicycle.co.uk/>
--
[email protected] (Simon Brooke)
http://www.jasmine.org.uk/~simon/
;; lovely alternative to rice.
