"Matt O'Toole" <
[email protected]> wrote in message
news:[email protected]...
>
> "John Rees" <
[email protected]> wrote in message
news:[email protected]...
>
> > "Matt O'Toole" <
[email protected]> wrote in message
> >
news:[email protected]...
>
> > > I'm considering a used bike with Shimano RSX. I think
it's 2-3 years old.
> > I
> > > don't know if the rear is 7 or 8 speed, but the front
is a double and I
> > need a
> > > triple.
> > >
> > > What would I need to convert it, besides the new
crank? A bottom bracket?
> > New
> > > derailer(s)? Is the left shifter compatible (if not,
I guess that would
> > be the
> > > dealbreaker).
>
> > What size of chainring bolts does the RSX crankset have?
130? 110? 94?
> > If it's either of the latter two, all you have to do is
get smaller
> > chainrings, and then you change northing
else(probably). I know some older
> > RSX uses a 110 bolt centre, which would permit mounting
smaller chanrings.
> >
> > What size are on the crankset now? If it's 52/42 or
53/39, you could switch
> > to something like 50/34 and get the gearing you are
seeking without having
> > to add a third chainring. In order to go triple, you
would need a:
> > - New bottom bracket (the old will be to short)
> > - New crankset
> > - Prob new front der
> > - Prob new rear der (or at least a longer cage)
> > - New left (front) shifter).
> >
> > Compare that to just putting smaller front chainrings: If RSX crankset is 110BCD all you
> > need is:
> > - 110 BCD 50 tooth big ring
> > - 110 BCD 34 tooth inner ring. Done
> >
> > Or, if it's 130 BCD, you would need:
> > - 110 BCD crankset, with a 50 and 34 chainring Done
>
> Yeah, no kidding. A 34/48 crank with a 12-28 cassette
would be just dandy. But
> all common 110/74 cranks are triples anyway, and two new
chainrings (34/48) for
> a 110/74 crank can be more expensive than a new derailer
and BB for the same.
> It's the STI unit that's really expensive. Awhile back I
thought Sheldon
> mentioned that all RSX left shifters were both
double/triple compatible.
>
> BTW, I found out this one is a 7sp drivetrain. It looks
like it has a standard
> (130mm, 39/53) crank. So it has whatever left brifter
came with those.
>
> Matt O.
>
If it's a standard Shimano RSX seven speed double crank it'll be 110mm BCD - FC-A410 with 46-36
steel rings.....
http://bernd.sluka.de/Fahrrad/Shimano/TM/FC-A410_1995.gif
'Course, the crank could be eight speed RSX, with a seven speed shifter set
