complicated gearing.

slimreaper

Hi
I have been trawling through threads looking at gearing options for the last hour and am no nearer to finding an answer to my question.
I have 53/39 chainrings and a 12-25 9-speed casette at present. I don't have a problem with the gearing whilst cycling round my local area (some moderate hills). I have an upcoming sportive with some hilly bits, and am worried about not being able to get up them.
I have found by looking at various threads that I should be able to fit a 12-28 cassette, with my short cage shimano mech, but what make would this be and where could I find one?
Also, what size would the smallest chainring I could fit be? Shimano's website says the max front difference would be 16 teeth, i.e. a 37 tooth ring, are these available, and could I fit this with a 12-28 cassette?
I really dont want to change my mech, but might I need a new chain for these changes.
I would appreciate any advice
Cheers
Andy

maddog 2

you can't get a 12-28 in Shimano in 9 speed. SRAM do a compatible one which is 11-28 though. See http://www.chainreactioncycles.com/Mode ... delID=5045 However, you're at the limits of what a road rear mech can handle in terms of sprocket size.

12-27 is possible in Shimano, but it doesn't give you much more than you've got already.

Your best bet is to fit a compact chainset, say 34/50 and use all of your existing kit. Depending on what BB you currently run it should be a simple swap.

topdude

As above, if you want to keep your existing rear mech you would be better off fitting a compact chainset, either a Tiagra hollowtech 34 / 50 with external bearing cups for about £40.
Or possibly a Stronglight one ( they do a variety of sizes with even less teeth ) and might fit your existing bottom bracket if it is a square taper for about the same money.
If that is not quite enough then try a 12 / 27 cassette as well.
Your rear mech should be ok if you carefully adjust the length of chain and don't expect to use the small/small, large/large sprocket combinations.
Good luck.

nmcgann

I wouldn't bother messing with your chainrings, a new set of good rings (TA, or similar) can be as much as an entire chainset. Also a non-compact Shimano road crank will only take a 38T inner ring as the smallest size.

I'd recommend a compact crankset (34/50) a wide range cassette (12-27) and a new chain. This is a pretty easy combination of bits to fit given the right tools - the worst thing will probably be getting the front shifting to work properly with the smaller chainrings. If you are not comfortable with adjusting the mechs and indexing get someone experienced (or a good local shop) to help.

To get an appreciably wider gearing range you would need to go to a triple chainset or use a MTB rear mech and cassette. Most people seem to be pretty happy with a 34/50 and 12-27 setup for hilly sportifs though.

Neil

DavidBelcher

topdude wrote:

Or possibly a Stronglight one ( they do a variety of sizes with even less teeth ) and might fit your existing bottom bracket if it is a square taper for about the same money.

The Impact Compact seems to fit the bill;

http://www.stronglight.com/stronglight/ ... actcompact

It takes a square-taper BB set, 107mm axle length. I think the UK retail price is about 45-50 quid.

David

slimreaper

Thanks guys for your posts.
I guess compact is the wat to go.
Assuming this is what I will go for, will it require a new front mech too? Also my current BB is a UN-25 which I think is square taper?
Is it worth/can I upgrade the BB to octalink?
Thanks
Andy