Wider cassette range for Tiagra group set

russello

A quick query to ask some advice re: my tiagra 9 speed group set.

I currently run a compact chainset with 12-25 cassette, and i was wondering how to get a bit more help for my unfit body up the hills of kent and sussex.

Can I use a 10 speed shimano 105 cassette 12-27 with my current set up, and is it as simple as just changing over the cassette? if not, any ideas on what i would need to do.

If this is not the best way to give me a bit more range on a compact, can anyone suggest how i can get a wider gear set up, using my 9 speed compact set up as the base.

Any help appreciated.

Russell

richa

10spd is not an option... But 9spd 12-27 are widely available:
http://www.chainreactioncycles.com/Mode ... delID=1094

Weejie54

Or, if you don't mind using other makes, 13-28:

http://www.parker-international.co.uk/1 ... o-9sp.html

Mixed reviews of Miche Primato. I've had no problems with them.

jgsi

You could use a Shimano Saint 9 speed mtb block 11-34 if you are desparate.

Cleat Eastwood

there is a cheaper option for 9 speed 12 27 its a BBB 12 - 27 cassette.

http://cgi.ebay.co.uk/BBB-Drivetrain-Sh ... 61ca28d0f9

Buckled_Rims

You'll need a 9 speed cassette. You can't mix and match 9 speed and 10 speed drive units, 10 speed stuff is designed for narrow chains.

12-28 is right on the limit of your rear dérailleur, unless you change that for a long reach RD, then you'll be able to put a MTB 11-34 on.

The easiest option is a simple 9 speed 12-27 cassette, that'll take about 60 seconds to change if you buy from a LBS and ask them to do it for you (don't forget to take in the rear wheel).

salsarider79

If you go for anything bigger than a 27tooth rear cog, you will need to change the rear derailler to a long cage, and also fit a longer chain.
It's fairly complicated, but basically, a short or medium cage rear derailler won't be able to handle changing to a 34tooth cog. The rear derailler is designed to take at most a 27tooth rear cog, but could get away with a 28tooth cog.
You also have a max number of teeth between the smallest ratio and largest ratio. On a compact you have 34tooth inner ring and 50tooth outer ring a difference of 16teeth. With a short cage you can have a max difference of 31teeth
31 - 16 = 15
So you can have a max difference of 15teeth on the rear
25 - 12 = 13
So you could go for a 12/27 cassette with 27tooth biggest cog rear, and it would be okay. The long cage (Known as GS) can run a max 37tooth max difference, which would allow you to go for a bigger cassette, but any gearing smaller than 34/27 is going to be so slow, I'd walk.

Hope that makes sense.

Weejie54

The rear derailler is designed to take at most a 27tooth rear cog, but could get away with a 28tooth cog.

I've yet to encounter a significant problem with a 28t rear sprocket on short cage mechs. I've even gone as far as a 29t with a Campy Chorus rear mech. I don't imagine it would have handled any more than that, however. The Tiagra seems to be able to handle as much as a 30t according to some sources - even though it is listed as having a 27t limit.

russello

Thanks for all the advice. Off to the internet and my LBS - then some hills.

Russell

salsarider79

Weejie54 wrote:

I've yet to encounter a significant problem with a 28t rear sprocket on short cage mechs. I've even gone as far as a 29t with a Campy Chorus rear mech. I don't imagine it would have handled any more than that, however. The Tiagra seems to be able to handle as much as a 30t according to some sources - even though it is listed as having a 27t limit.

You can get away with bigger cassettes and maybe you could run a 29t. What I'm talking about is the maximum number of teeth difference between the biggest and smallest ratio. Once you exceed that (31t on the short cage, 37t for the long cage) you can start to run into shifting problems. For example: It is possible that you will have to run the chain too short, otherwise on the small to small cogs the chain will hang slack.
As the bike in question has a compact, there is a limit on the maximum size of cassette. A 13/29 cassette would be slightly larger and would need a longer chain but should be okay as it's not too much bigger than the recommended maximum. I would still not recommend going for anything larger than a 12/27. Also, as I said in previous post, anything above 34/27 and I'd walk....
I'm taking my advice from Shimano's website, and have been a bike mechanic for several years. However all the advice on here is just opinion, and I know that I'm not always right.

John.T

A long cage Shimano rear mech (GS) will not take any larger rear sprocket than a short cage (SS) one. It only takes a larger tooth difference for use with a triple. If you want to go larger than 27 (28 max) then you must use a MTB one.
All the information you need (and more) is in the 'sticky' at the top of this section.

Weejie54

You can get away with bigger cassettes and maybe you could run a 29t. What I'm talking about is the maximum number of teeth difference between the biggest and smallest ratio. Once you exceed that (31t on the short cage, 37t for the long cage) you can start to run into shifting problems. For example: It is possible that you will have to run the chain too short, otherwise on the small to small cogs the chain will hang slack.
As the bike in question has a compact, there is a limit on the maximum size of cassette. A 13/29 cassette would be slightly larger and would need a longer chain but should be okay as it's not too much bigger than the recommended maximum. I would still not recommend going for anything larger than a 12/27. Also, as I said in previous post, anything above 34/27 and I'd walk....

Absolutely. However, if a 27t is considered not low enough, you could run a 13-28 rather than a 12-27. You sacrifice a higher gear but it might not matter to someone struggling with hill climbing.

lvquestpaddler

Following the "sticky" thread I've just been outside with my drill and 3.5mm bit, dismantled an 11-32 HG50 cassette, took the 28T sprocket and put it with my 12-25 ditching the 14T to make room. It now has 12,13,15,17,19,21,23,25 and 28 and is a better solution than paying £39 for an Ultegra one or an SRAM PG950 which has 11,12,13,14,16,18,21,24,28.
Closer ratios and a cheap fix! Need to fit the 34T chainring when it arrives and that's as low as it goes for me, any lower and I'll walk, that's why I got spd's and MO86 shoes not walking anywhere in "real" road shoes
BTW I did need to adjust the "B" screw to lower the cage a fraction but it's running fine....

Weejie54

Following the "sticky" thread I've just been outside with my drill and 3.5mm bit,

One area where Campy saves you time. No need for a drill to separate sprockets. The upmarket combined sprockets are a bugger though.