When/How to Add Granny Gears?

1) Easiest/cheapest: Replace your cassette with a 12x25 or 12x27 (will also require a longer chain)

2) More expensive: If you are using a standard double crank (39/53), replace with a compact crank (e.g. 34/50) (may also require a new bottom bracket)

I ride nothing but hills, and my power/weight ratio stinks, so I use a 34/50 and an 11x28 MTB cassette on my litespeed road bike. NEVER been happier. I can finally ride long enough to get a good workout and not be fried and limping around for 3 days afterwards.

Save your 12x23 in case you want to put it back on someday (although if you don't there's nothing wrong with that).

It's all about finding the right gearing for you.

Ditch the 12-23 and get a 12-27 you will not regret it

I went from an 11x23 to a 12x27, and I didn't have to get a longer chain.  But I had fairly low mileage on the bike at that time, if the mileage was higher I would have had to replace it just because you can't use a new cassette with an old chain. 

The MTB cassette is a good idea, but I don't think they come in 10-speed.  I miss my 11 sometimes going down big hills. 

Very timely thread. I'm starting to ride more and more hills and was going to talk to my LBS about changing my gearing. The group of people I ride with seem to have gears that allow them to have a much easier spin with a higher cadence than what I can attain in my easiest gear. And this includes other people with tri bikes as well.

I plan on sighing up for Ironman Wisconsin 2008. I will be doing ALL my hill training on my tri bike because that's what I'll be riding in the race. Can't say I would see the advantage of riding one bike for training and another for the race.

Yea, start with changing your cassette to a 12-27.

If that doesn't do it for you go either with a compact double or see if you can even convert your bike to a triple. That way you have the 52 for downhill and I personally love the 42 for flats and even hills, but if that is still too much you still have the 30 to fall into for really steep climbs.  

I replaced an 11-23 Dura Ace with a 12-27 Dura Ace, I took the 11 off the old Cassette and put it on the new 27 after I took the 14 off of the 27 and ended up with a 11-27 and it works fine.

It might need a little bit of adjustment, but you shouldn't need to replace or modify anything.  

The only time you might change the rear derailleur would be if you were putting a triple on the front.  Its quite common to use mountain bike rear derailleurs with a triple. 

Generally speaking, no. That said, I recently did a project on my wife's bike where I replaced her triple crank with a compact crank and a MTB cassette(11-34). I had to go with a new rear deraileur because the 34 tooth cog on the cassette exceeded the capacity of her existing deraileur. Going from a 12-23 to a 12-27 is not a big deal and will not exceed the capacity of even a short-cage deraileur.

It depends upon the derailer, but likely not. I have a mid-90s ultegra derailer and I run an 11x28 cog with no problems.

If you have a triple, then you likely have a long-cage rear der already, so in that case almost surely not.

For more info, I refer you to sheldon brown.

Nashbar-brand cassettes are $20 - they don't have 10-spd yet though.

Well, in an effort to give the LBS some Business I dropped it off today and the Ultegra 12/27 is $85 with $15 to install for $100.  I could get the same cassette on Performance bike for $54.99+8.75 Shipping= $63.74.  However, I have absolutely NO CLUE on how to change it myself and figure if I buy from PB and try it myself and screw it up I'm SoL.  So, for $36 additional, I guess it's worth it (in my case) to have LBS do it.  However, he did say that I might need a new chain, since the old chain has worn with the old cassette (approx 1075 miles on both) and the old chain might "jump" because the teeth might not line up with the old chain.  I have read this online and most recommend chaging cassette then seeing how chain reacts to cassette.

Did any of you have an old beater that you practiced on when learning how to do repairs? I'm thinking of getting something cheap off Craig's list so I can practice before I move on to DIY on my one and only training/racing bike.

Changing cassette and chain are the easiest types of bike repair you can find. For the price the LBS is charging you can get the cassette, a new chain, and the tools you will need: a cassette tool ($8) a chain whip ($20) and a chain tool ($15). Then buy a copy of Zinn or visit the park Tool website for some how-to-do-it instructions.

That's a good idea.

Good advice from bear - I will only add that you can make a chain whip for free using a piece of your old chain, a 12" piece of lumber, and a nail. Used one like that for years before I finally got a factory-made one.