Changes to Road bike Gearing

matttyc

Hi All

New to road biking and new to the forum, so a big hello

Just taken up road biking and living in the alps so there are some pretty big hills well mountains to be precise

I've bought my first road bike a 2010 Cannondale Caad 8 triple but i'm still struggling with the hills. I know alot of this is to do with fitness, but will it make a differance if I change the rear cassette from the current SRAM PG950 12/26 to a SRAM PG950 11/34? and would the rear derailer and chain need swapping?

Tks

Matt

jomoj

hi - yes it will make a difference, you'll certainly get lower gears but the downside is that the jumps between gears will be larger. Still, better to be able to ride than push.
You don't say which derailleur you have currently so it's hard to say if you need to change it or not! If it's a SRAM apex then I think you'll be ok but otherwise most road derailleurs max out at about 28T though you may be able to get away with it with some adjustment.

Depending on how much slack there is in the chain you may need to change it. You basically need to have enough chain to run it on the big ring at front and big at back with a few links slack. Although you shouldn't use this gearing combo, if you change into it by accident and the chain is too short you can cause a lot of damage to the rear mech so it's best to be on the safe side.

BUT..

There is also a 2nd way to get lower gears that is cheaper and lower risk and that is to get a smaller front chainring. You should be able to get a 26T to swap for the 30T which will give you a 1:1 gear that should get you up most things.
Shouldn't require any change to chain or rear mech. You might find the front change is a bit clunky but it should still function and you'll get used to it.

robdaykin

if your caad 8 is the same as this one:
http://www.evanscycles.com/products/cannondale/caad-8-tiagra-triple-2010-road-bike-ec020233#features
then your rear derailleur is this one:
http://techdocs.shimano.com/media/techdocs/content/cycle/SI/TIAGRA/RD-4400/5TS0B_EN_v1_m56577569830607031.PDF
which can take a rear cassette with a maximum sprocket size of 27 teeth, minimum 11 teeth, so you have one tooth to go. There is an Ultegra 12-27 cassette in 9 speed, but no SRAM (that I've found). The maximum capacity on the front is 22 teeth, so you could go to a 26/38/48 triple, which is a touring style setup. Total capacity is 37 teeth (rear + front) so 12-27 would fit, but you could not just fit a 26 tooth inner ring, without changing or sacrificing the 52 outer ring.
In order to go to a 34 at the rear you'd need the SRAM Apex rear derailleur, which is 10 speed, and may not be terribly useful. The reason I say that is that I recently tried a 10 speed derailleur on my 9 speed, and could not access all the gears, no matter how I fiddled the setup. That's when I found I'd been shipped the wrong one...

The 9 speed wide range cassette is intended for a mountain bike, so you may be able to get a 9 speed MB derailleur to fit, but I've no idea if that's possible, or advisable, since MB shifters are quite different to road STIs.

I'd be inclined to get the 12-27 cassette and look for a touring triple. If you do both, you should be ok with the chain length. You may need to change the B screw on the rear derailleur (see above document) as it should be setup for the 26 tooth cassette, and may be too close for a 27 without tweaking. 26/27 gives you a bit of a boost in gear, going beyond 1:1.
You might like to look at Spa Cycles in Harrogate for chain rings, though I am not 100% happy with the shifting on the rings I bought from them, compared to Shimano or SRAM rings.

Hope that helps.

Rob

nathancom

Honestly in this case you need to improve your fitness and not mess about with the bike. If you are in the alps and the big hills are too hard at the moment then build up towards them with easier climbs first.