Walshinoz

Hi,

I have a 10 year old roadbike that is kitted out with a Shimano Tiagra groupset. It is 50/34 on the chainwheel and 11/28 (10spd) on the cassette. It is in pretty good nick but don't really want to spend lots of money upgrading ( I would rather put that towards a new bike when the time comes). I have a trip coming up with a few tasty gradients over a few days. So question: Is there any way I can expand the rear cassette to incorporate a bigger granny cog, say a 32t (or a 30t), without having to buy a new groupset / lots of new parts? Is there something similar to the 'oneup' system where I can take one sprocket out of the current cassette and replace with a 32t sprocket in the cassette? Or can I replace with an 11/32 cassette only (if I can get one) without buying a new shifter/derailluer/chain etc? I understand the issue with the cage length, but if I only used a new 32t sprocket whilst in the 34 chainwheel upfront (and adjusted the B screw) would that work? Or am I just barking up the wrong tree?? Just trying not to spend a lot of money.

Many thanks in advance

Cheers, Jason

alcjphil

Which version of 10 speed Tiagra do you have? There are two, 4600 series and 4700 series. If your shift cables are concealed under the bar tape you have the 4700 series version. You will have to verify if your rear derailleur can access a larger rear cog, I don't think that the 4600 version is able to handle a cog that big and the 4700 rear derailleur which can isn't compatible with a 4600 shifter. Not all is lost however because a 4600 shifter will work with a Shimano 9 speed rear derailleur which will allow cogs even bigger than 32 teeth. First thing is to determine which version of 10 speed Tiagra you have before trying to make the changes you want to do

terrymorse 

You're definitely looking at a new cassette, and probably a new chain. You may be able to get by with your existing rear derailleur.

Jenson has an 11-32 cassette on sale for $36.99.

They also have a 10-speed chain for $20.79.

About the Tiagra rear derailleur.

If it's the RD-4700-SS (short cage), the max. cassette spec size is 28T.

But plenty of people use an 11-32 with a short cage derailleur.

Just avoid the "big-big" combination, and you'll likely be fine.

Walshinoz

Thanks for this response. Just checked and the shift cables are under the bar tape, which puts it in the 4700 series?

Walshinoz

Hi Terry,
Many thanks for the reply and advice. That's great, and thanks for finding the cassette, I was struggling! The video is very helpful!!
Very much appreciated
Cheers

Iride01 

Pull up the hood on one of the shifters and the model number will be there on one side of the body or the other.

alcjphil

Tiagra 4700 is the only version of Tiagra that has concealed shift cables, makes it easy to identify

Iride01 

Oh! It's been out so long I figured that they would have updated by now. Nor did I realize it was the first Tiagra model that concealed the cables. Is that true for 5700, 6700 and on up the line?

See you can teach me new things. <grin> Thanks.

biker128pedal

You can also look at the wolf tooth derailleur extender. I have one for 32 tooth cassette for my short cage Ultegra derailleur. Have not made a trip to the mountains so not used it yet.

Walshinoz

Thanks, I'll take a look at that. Always good to hear positive experience.
Much appreciated