conversion to lower gear range
 

In June I bought an REI Novarra Randonee, a touring bike. since then, I'v discovered that the gear range on the low end is not quite low enough to suit me. The bike came with a RD 105 long cage and a freewheel with a high of 28 teeth. I'd like to get a rear cog that goes up to 32, so I know I'll have to change out the RD and the chain. Here are my questions:

1) do I need to change anything else beside the rear derailleur, freewheel, and chain?

2) how do I determine the proper length of the new chain?

Thanks for any advice and observations

It may be simpler to fit a smaller granny chainring (24T).

1: No.
2: Same method as installing a new chain. The chain should be long enough to wrap around the big chainring and big cog, plus ~1 link.

You might be able to get away with using your 105 derailer on a 32 if it works on a 28. I might try it out first before buying a mountain or whatever derailer. As Sheldon says, derailer specs tend to be on the conservative side and you can often push them a little farther than the manufacturer recommends with no ill effects.

As for question 2, http://bicycletutor.com/calculate-chain-length/

You might need a new shifter cable.

For each additional 4 teeth add 2 links (assuming thet the origional chain was the correct length).

If aesthetics are important, the Shimano RD-M531 is availible in silver (but it might cost a few dollars more than the black).

It's a good time to replace the chain rather than sticking a new link in an old chain ..

touring with a load , go for it 24 T granny + a 32 or 34 t cassette ..
[Shimano K cluster if 7 speed is Ideal.]

Go for the 24t front ring. The shifting will be a little tougher at first, but there is no substitute for a low gear when you need it. With the 28 in back you will have a 23 inch gear. Great for climbing with a touring load.

If I'm reading the specs right, the bike comes with a 26 tooth small chainring. Changing from a 26 to a 24 is less of difference than changing the largest rear cog from a 28 to a 32. Not much, really, but it might be worth is when touring.

If it is indeed the long cage, you should be able to go up to a 39 tooth, I'd look at something like a 36

The bike came with a 28 cog and a 30 chain ring. Specs for the 105 long cage say that these sizes are the maximum. If I but a 24 chain ring will it fit the hole pattern on the crank? I plan on trying 32 without changing the DR. As someone above suggested, I might be able to squeez by. But I like the idea of the 24 chain ring better. Thanks for the input.

If your current inner ring is a 30, then I would recommend changing it to a 26-tooth, not a 24-tooth as suggested above. Compared to a 24-tooth, the 26 tooth will make shifts between them slightly smoother, make the cadence change slightly less, and will wear out slightly slower (go for a steel inner ring for touring). Also, make sure that you have a chain retention device mounted inside the inner ring to avoid losing the chain off the inside of the ring when down-shifting (N-Gear Jumpstop is a good model). I'd simply do this for now, and leave the cassette and RD alone unless after rising a bit you feel you still need something lower.

A 24 tooth chainring will fit a Shimano 105 triple crankset. It's the smallest that will fit. As Chris said, this is a large shift, making for a large change in cadence. However, I'm all for going as small as you can go. Smoother shifting is all well a nd good, but when you need a lower gear, all consideration of shifting quality go out the window. FWIW: my lowest gear is a 24/34: http://home.comcast.net/~jeff_wills/...-grr%20008.htm . I don't use this often (in fact, I don't use the granny all that often) but I rode a 7km stretch of 10 to 15% grade this summer: http://tourbc.net/Profiles10/TBC2010D4%20Profile.pdf . That was a long, slow grind, but the rest of the day was worth it.

Go for both a 24t granny ring AND a 32t in the rear. This will give you two gears lower than you have now. And the smaller front ring and larger rear cog will balance each other out and you won't need to change the length of the chain.

If I go with the 24 chain ring, where can i get one that fits a five hole pattern Shimano FC-R453 crank? so far i've found nothing on the web. Thanks

OK, this crankset:
http://techdocs.shimano.com/media/te...9830683054.pdf

I'm 99% sure it's a 74mm bolt circle chainring, which is quite common. Here's a couple:

http://www.universalcycles.com/shopp...80&category=50
http://www.universalcycles.com/shopp...30&category=50
http://www.universalcycles.com/shopp...26&category=50
http://www.universalcycles.com/shopp...68&category=50
http://harriscyclery.net/quality-bic...nsearch=Search

No, the cage length has NOTHING to do with how large a rear cog the rear derailleur will accept. That's a function of the upper pulley's geometry and the derailleur hanger's length. The cage length only controls how much "wrap" capacity the derailleur provides.

Shimano road rear derailleurs have a stated maximum rear cog of 27 or 28T depending on the model and completely irrespective of short or long cage. Experience has shown that on some frames they will work with a larger rear cog but, again. it has nothing to do with cage length.

Jeff,

Thanks for info. I do have just one other question. The sugino chain rings come without pins and ramps. I'm not sure what this means. do I want pins and chains. Thanks again. I'm ready to order what you recommend.

I may have an extra brand new 24 five-hole chainring at the house, i'll check tonight. Yours cheap if it will work, and i'm just down in jackson so shouldn't take long to ship. Don't have the 50 posts quite yet to enable PM function here, but email is schoonerswharf at gee mail. Cheers.

keep on trekkin,

Let me know if you have one. I'll buy it. thanks.

Pins are - well, pins. Short stubby things sticking out on the inside of the chainring. They make shifting (up) smoother by hooking on to the chain and lifting it from the smaller chainring towards the bigger chainring.

Ramps are small cutouts/changes to the tooth profile, also designed to help with shifting by making it easier for the chain to transition to the bigger chainring.

They do make shifting smoother, but they aren't critical. Bike will still shift OK w/o them.

Also you never shift up to the granny ring. So ramps and pins won't ever be used even if they existed on the granny. Dropping a chain off the middle ring onto the granny is darn easy.

Danno's correct- pins and ramps are only for rings you are shifting up to. They're not needed on the inner chainring.

Book 'em, Danno...

I have a 26T Sugino small ring that has never worked well with STI shifting on Shimano triple cranksets, both 42 and 39T middle rings. I recently read that Sugino rings have the teeth offset one way or the other that leads to slightly different spacing between small and middle rings and STI doesn't like it. Anyone know if this is correct and would Race Face or Salsa 26T work better? BTW, the Sugino works fine with the Shimano triple on a friction shifted bike.

My Roadie crank is a 50-40-24 campag triple, But I run friction bar end shifters so never have a compatability problem.
.. Stainless-steel 24t came from Stronglight..
:50: Shifting a derailleur bike is a learned skill not a gear purchase.