Bicycle Mechanics - Need lower gears - new cassette?

Hi all,

Been the proud owner of a new C'dale Caad9-6 for a month or so. I'm finding I don't have low enough gears for the hills near me, (long, steep) lest I want to totally destroy my legs before getting in shape.

Current gearing on the bike is 39/53 - 12/26. Seems my most cost effective way to achieve lower gearing would be to replace the rear cassette. Couple of questions:

a) How hard to do myself? (I'm handy with a wrench)
b) Will there need to be a rd adjustment?
c) What would you all suggest for the new cassette for an effective change?
d) The group on the bike is Tiagra, will the rd be able to handle it without a problem?

Thanks,
Patrick

Having the 53-39 in front will not help you much no matter what you change on the back.
I just went to a 50-39-24 on front.

I agree with 10... a triple is a good solution to consider that will resolve your problem. Then you can go as low as you want and enjoy ultra close ratios.
http://i17.photobucket.com/albums/b90/compost_bin/bicycle/IMG_2604.jpg
I run a 14-15-16-17-18-20-23 with one and love it.


Greg

I have 14 -25 cassette.
It is great.
Used it at The Indy Track Ride last week.

http://i256.photobucket.com/albums/hh187/10wheels/09%20Indy%20Ride/42ridebike.jpg

Thanks all,

What about the possibility of switching to a compact double?
I understand switching to the triple may cost some significant coin.

Patrick

I have 14 -25 cassette.
It is great.
Used it at The Indy Track Ride last week.

http://i256.photobucket.com/albums/hh187/10wheels/09%20Indy%20Ride/42ridebike.jpg

Hey 10... :)

Is that the real Indy 500 "Brickyard" strip? Wow... what a real piece of history.:thumb:
I bet it was a riot going all the way around. Did you need to use all of the banking in the corners?;)


Greg

The official specs (at least as per a quick googling) say 27t is the limit in the rear. In practice, with some adjustment of the b-tension screw you can probably get a fair bit more than that. Mountain cassettes often offer a 28t variant which should work without problems, and you could probably go as high as a 30t, but I would be hesitant and would wait for some people who run that show up to comment about it.

To replace a cassette, you'd need a cassette lockring tool, a chain whip, and a wrench big enough to use the lockring tool (at least if it's not attached to one), and the installation is pretty simple (at least speaking for the standardized 8-9 speed compatible freehubs). Going to a triple up front is a good option, but definitely a more costly one, especially if you need to buy tools for it as well.

The official specs (at least as per a quick googling) say 27t is the limit in the rear. In practice, with some adjustment of the b-tension screw you can probably get a fair bit more than that.

I keep hearing this on the forum yet almost nobody understands where this 27t figure comes from or how it can actually be less or more, in practice. Shimano isn't going to write a whole page on how they came up with that figure, nor are they going to explain how max cog spec is actually calculated for every individual frame and rear wheel.

It's not possible. So they state one number. Of course it's going to vary between bikes. Go read barnetts chapter on rear deraileurs if you want to understand why the 27t figure is a guideline and not a hard limit.

Thanks all,

What about the possibility of switching to a compact double?
I understand switching to the triple may cost some significant coin.

Patrick

I got back into road riding about a year ago (after >10 years of mountain riding), and bought a bike with a compact crankset (34-50). I am not sure how much a compact crankset will cost, but I do love the expanded range of gears. The guys I ride with have 39-52 chainrings and initially looked down upon my compact with slight disapproval. However, let them laugh as I spin my way up grades. Bottom line - I like my compact!

Thanks all,

What about the possibility of switching to a compact double?
I understand switching to the triple may cost some significant coin.

Patrick

Not really. You can buy a cheap shimano triple with steel rings for $30 MSRP. $80 if you want AL rings.

I got back into road riding about a year ago (after >10 years of mountain riding), and bought a bike with a compact crankset (34-50). I am not sure how much a compact crankset will cost, but I do love the expanded range of gears. The guys I ride with have 39-52 chainrings and initially looked down upon my compact with slight disapproval. However, let them laugh as I spin my way up grades. Bottom line - I like my compact!

I also ride with a 50/34 compact double. I swapped out the 11-24 rear cassette for a 12-27 which yields another 4 gear-inches in the lowest gear combination. It makes some of the steeper and longer hills a little more bearable.

Cassette swapping is easy of you have the right tools. Swapping out the front rings is a little more involved, but easily doable if you are mechanically inclined.

I keep hearing this on the forum yet almost nobody understands where this 27t figure comes from or how it can actually be less or more, in practice. Shimano isn't going to write a whole page on how they came up with that figure, nor are they going to explain how max cog spec is actually calculated for every individual frame and rear wheel.

It's not possible. So they state one number. Of course it's going to vary between bikes. Go read barnetts chapter on rear deraileurs if you want to understand why the 27t figure is a guideline and not a hard limit.

There's a nifty little adjustment screw on the Sora to put the top pulley exactly where you want it in relation to the largest cassette cog. I cranked it almost all the way out to put the upper pulley really close to the 14-23 cassette...
http://i17.photobucket.com/albums/b90/compost_bin/bicycle/IMG_2576.jpg

... and it shifts swell. The directions say you can put the pulley as close as you can to the largest cog as long as the pulley teeth don't actually contact the teeth of the cog. I don't see any reason why it wouldn't work just fine with a 28T. From what I can tell, any larger than that might be pushing it. Shimano specs it's chain wrapping ability as a maximum of 29 teeth, but I'm running 31 teeth total difference on my 24-34-46 triple with absolutely no problems at all. :)

Greg

What about the possibility of switching to a compact double?
I understand switching to the triple may cost some significant coin.

That's certainly a possibility.

1. If it was my bike, the first thing that I would do would be to figure out what gears I actually used and what gear ratios I needed to handle the hills that I normally rode. I also recommend determing a favorite gear for flat roads with no wind.

2. Take a pocket calculator and work out the gear inches for every single chainring and rear cog combination that you have now or are considering.

3. Once you do that, check out your spreadsheets for your favorite flat road gear. You'd like for that gear to fall in the middle of your cassette so you'll have some trim gears both ways without having to change chainrings. Skip this step at your own peril.

4. After you do all that, one combination (standard double, compact double, triple crankset) will stand out as "right" for you. If you buy anything else, you'll be dissatisfied and all you'll succeed in doing is to add that cost onto the "right" combination that you'll eventually get for yourself.

A compact double works great for me, but it's not for everybody.

I think the compact double could be the better choice.

Alternatively, you could go with a mountain cassette like a 12-34. With it you would need a mountain type rear derailleur. This setup would shift very well but the downside is the big ratio jumps from cog to cog. On a flatter ride you would sometimes find yourself "between gears".
With a compact double you could go with the more common 34-50 rings but there are other possibilities like 34-48 or 36-50, etc.

Al

If you'd like to use a self calculating gear spreadsheet... here's a really nifty one. :)

United Bicycle Institute Gear Calculator (http://www.bikeschool.com/gearcalc/gear_calc.cgi)

I play with it all the time to see if I can come up with the most "perfect" sets of ratios.:thumb:


Greg

I'll second the compact-crank suggestions. You don't have much room for a larger cog in the rear, 28t max really or about 8% lower than what you have now. A compact crank will let you run a 34t inner ring and give you 13% lower gearing.

You can get a Shimano Tiagra/RSX crankset with 50/34t chainrings for about $70. Add $5 for the crank-puller tool and you're all set.

Try a cheap 12-30 cassette, or pull a small gear, perhaps a 14t, to add a 30t gear (run a 12-13-15-etc.). Usually need to get the chain length just right for this to work, wrapping around the large-large combination without much slack. This would be the cheapest option.

12-30 works well on my 7 and 8 speed short cage DA and 105 equipped bikes, standard 39/53, or 38/53 cranks. 13-32 worked ok on an older 7 speed with 42/52 cranks.

Just want to thank everyone for their advice. I purchased a compact crankset and installed this weekend.
Very happy. Gave me the lower gearing I was looking for, while not being overly complicated nor expensive. Took about 15 min. to install the cranks, 10 min to lower the FD, and another 10 to shorten the chain. (3 links) A little setup re: limit screws on FD, fine adjustments, and I was in business. Shifting is comparable to my previous 39/53 setup, perhaps a tad slower, but perfectly acceptable.

A nice benefit of the swap is that it seems I have more use of the center part of my cassette, not just high or low. My cadence has increased, and just a more pleasurable experience overall. I can finally push my top gears. Seems rather than my upper thighs taking a beating, my calves are coming into the picture.

Thanks again,
Patrick