Bicycle Mechanics - Inner chainring size change...?

I am currently using a double 105 38/48 chainring with a 9 speed 12/26 cassette and would like to change the inner ring....I miss some of the lower granny gears of my triple when I hit the long steep hills here in PA. How low can I go without compromising the shifting quality of the 105 group? I want to avoid the expense of the triple conversion. I have done a forum search, but can't find the exact answer that I am looking for. All opinions are needed...thanks in advance!

A quick look at the specs on the Shimano website
http://bike.shimano.com/Road/105/componenttemplate.asp?partnumber=FD-5501-S

shows a 15 t capacity. You are limitted by the bolt circle diameter of 130mm, which takes a 38t ring. Cyclo-cross style gearing (36/48) uses a chainset with a smaller 110mm BCD.
You could fit a tripleizer:
http://www.peterwhitecycles.com/chainrings.asp

Which is the better method (in my situation)?....changing the inner ring or changing the cassette to a wider range such as an 11/34 (if that is even possible).
I am very new to bike building and tinkering....can't ya tell? :D

If you have a 105 road group with 130mm BCD rings, then 38 theeth is the smallest ring available. Anything smaller and the chain would start hitting the chainring carrier bolts.
If you want something lower, eithe get a triple, or get a touring crankset, with 110 BCD rings.

Is changing the cassette to a broader range possible?

Yes. Maybe.

yes, it is very possible. you will need a new rear mech though, one that will take more cogs. I'd say go for the XT MTB rear mech, its on sale at performance right now. with the new mech, you can fit an 11-34 cassette.

Originally posted by Phatman
yes, it is very possible. you will need a new rear mech though, one that will take more cogs. I'd say go for the XT MTB rear mech, its on sale at performance right now. with the new mech, you can fit an 11-34 cassette.

Rear mech? Could you explain what you mean please? I am new to bike building/tweaking and need all the help I can get. Thanks!

Originally posted by kurt64
Rear mech? Could you explain what you mean please?

mech = derailleur = derailer

Your current rear derailleur presumably cannot handle a cog larger than about 26T.

OK...so I need a new long cage derailer (XT), and the cassette (11/34). Do I need to replace or extend the chain as well?

soory, man, I should have used more correct language. "mech" is just easier to type then derailleur. You probably do need to extend the chain. How many miles are on your current chain? It might be worth it to just buy a new chain, and shorten it according to your needs.

Hmmm... if it's a standard 9sp 105 rear der. then I think it should be rated for up to a 27T and you can probably go to a 28T... maybe even higher (30T) if you avoid the upper couple of cogs in the cassette when in the big ring.

I'd like to know what the numbers of the cranksets and the rear cassette mean?

For example, I'm trying to decide what kind of cassette to buy. They are available in these sizes: 11x21, 11x23, 12x23, 12x25, 12x27mm. Is the first number the number of teeth in gear#9 and the last number is the number of teeth in gear#1??

Is that what the "T" in "11T" stands for... teeth?

I'm looking for a high top speed cassette. Lower gears are not concentrated on.... need the high top speed... any suggestions?

And I guess that the size on my triple crank (30x42x52t) is the same as the rear sizing. 30 is the number of teeth on gear #1 and 52 is the number of teeth on gear #3? correct??

If that is correct, then the smaller number of teeth, potentially, the faster.... so for a high top speed for the rear cassette, I'd choose the 11x23?? right??

-Dan the Man-

The T is for teeth. so a 11x21 cassette the smallest cog has 11 teeth and the largest 21 teeth. So you're top gear ratio would be same witha 11x21 and a 11x23, just the jump on the larger cogs is a bit larger. For example top gear might is 23 teeth adn next one down is 21, while with the 11x21 it would go 21 down to 20.. This is just for example and not accurate on what cogs are on that cassette.

Same goes with the crankset 30x42x52t, means the smallest chainring has 30 next one 42 and next 52 teeth.