Bicycle Mechanics - cassette teeth numbers...
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01-11-09, 05:32 PM
Hello all! I am rebuilding a Fuji Sagres for my wife. I am using parts from another bike and have some nice wheels that I'd like to swap to her new bike. The Fuji's 8 speed cassette has 26, 23, 21, 19, 17, 15, 13, 12. The cassette on the tire I'd like to add has 30, 26, 23, 20, 17, 15, 13, 11. Oh, they are 700x__ wheels- running 700x25 tires. We live in North Virginia and have hills. She also hauls a Burley solo trailer. My question is- which rear cassette would be better for getting up hills... Going fast on the flats or down a hill is no big deal- need to get up the hill first...
Many thanks in advance!
01-12-09, 04:39 AM
Ultimately it depends on the bicycle having the right range of gears for the slope you are ascending, which depends on the front chainring and crank length in addition to the rear cassette. Without knowing that information, it's hard to say. The cassette with the larger numbers will obviously be easier, but it might actually be too easy if the front chainring is smallish or the cranks are long.
The easiest way to tell would be to test the casette you have now, and see if it feels too easy, too hard, or just right.
Sheldon Brown has a lot of information about gearing and gain ratios on his site http://www.sheldonbrown.com/gearing/index.html.
01-12-09, 06:41 AM
Obviously, the 30T cog will provide a lower gear than the 26T.
01-12-09, 08:41 AM
MTB chainrings with 12-26 would give low gears for hills while keeping nicely spaced gears at the back.
01-12-09, 11:54 AM
The 11-30 will give a lower gear for the hills.
To use the 11-30, you may need an MTB rear derailer to handle the large cog and the wrap requirement (depending on your crank chain ring difference) although I've run a road rear derailer on a 30 cog. The spec for road rear derailers is typcailly 27 or 28 max cog. The wrap capacity for short cage is typically about 29, for long cage road 37, and for MTB 45. You compute wrap requirements of your drivetrain by adding the differences between large and small rings and large and small cogs (e.g. if you run 38x53 up front and 11-30 cassette, you will need a rear derailer with wrap of 53-38+30-11 = 34).
You could also mix-n-match cassettes: if the 11 provides a gear she will never use, you could use the 12,13 from the 12-26 and the 15,17,20,23,26,30 from the 11-30 to make a 12-30.
01-12-09, 02:27 PM
You'll probably need to lengthen the chain by 1 link SET (1") if you're not aware of that.
It sounds like the wheel you want to use has the 30T cog. IF not, the LBS should swap cassettes for a minimal fee if you carry the wheels in. Maybe free if you're a good customer and they aren't too busy?
Also, you could swap the 12T for the 11 T and have a potentially? more useful gear???
It's the last cog on the end, so that swap is EASY if you have the lock ring tool and a chain whip.
01-12-09, 07:05 PM
Thanks all for the info! I forgot to add that the 30-11 has a Sram rear derailer with 10 teeth each cog, while the Fuji (26-12) has a Shimano with 13 teeth each cog... Any other help with the new info???? THANKS!
01-12-09, 08:13 PM
Sorry, what do you mean with "Sram rear derailer with 10 teeth each cog" are u talking about the jockey wheels in the rd? Are you talking about two bikes now? Two wheels? are going to put a new rd to match the brand of the cassette? just a little bit confused.
I live in nova, and yes sometimes it gets hilly depending on where do you ride i give you that. I believe that bike the crankest it is triple right? The smallest chain wheel it is like a 28 maybe? 32? The 2003 model had a 32 chain wheel in there. Just have your wife to ride using the smallest chain wheel, problem solved. Second solution? u can carry the trailer i guess
I carry a trailer with two kids and all the paraphernalia they need, so i know what are u talking about. The other thing is that from an ex-racer perspective nobody have seen your wife position neither her habits as a rider. I have seen people riding 10mph using 53x12 and they feel fantastic. Other ones with the seat super low that can hit their chin with the knees but they feel fantastic also. So in my opinion you have to start thinking in those little details before spending money in getting a cassette with 30T. 30T means that now she will be lighter but can she handle the pedals spinning? because with a 30T she will spin more. If she can't handle the cadence there is nothing you could do. You'll put a 35T in there and it will be the same. No offense just trying to make a point, the point is that she might have a cadence/power problem, and a 30 won't fix it because the cadence will "eat her" in the middle of the hill and now she will be even more tired. Putting lighter gears sometimes doesn't fix the problem (band aid maybe), specially if the rider can't handle them. People does not realize that.
Good luck )
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