Well, as a relatively new regular cyclist and neophyte mechanic, I am a little proud of a recent accomplishment. When I had my new wheel built recently, the shop had a 12-21 7-speed cassette in stock so I told them to use it even though it was not exactly what I wanted. I really wanted something with 1-tooth steps, since I figured it would be easier to work with in my current program to increase cadence. There really is no such cog. So I ordered a 14-32 from Bike Nashbar for $17.95, disassembled both cassettes and built a 14,15,16,17,18,19,21. I love it! Using my 38 chainring, each step is about 4 chain inches, almost imperceptible going from 19-18-17-16 where I am working on building cadence in the 85-90 range. Now, these gears and cadence may not be impressive to you guys who can push 52-12 120 all day long, but it is where I am right now. When I get to the point where the 14 is holding me back, I will put the 12 and 13 back on and make a more suitable combination. In the meanwhile, spending this 20-30 bucks (hand to get a chain whip and freewheel remover, too) allowed me to get by with my 7 speed shifter and rear derailleur for now. It also gave me a little more experience and confidence working on my bike.
For you experienced guys, is there anything I should double check to make sure this setup is OK?
Good for you. Don't see what you want in stores? Build your own.
As long as the derailleur does not contact the largest sprocket on th new cassette, and can shift easily through the range, then the bike... and you... should be happy with the result.
Actually, I'm a bit jealous... When I was learning all of this, I was building Frankenstein nightmare sprocket combinations... In an attempt to create the Swiss Army Bike. I ruined two good derailleurs, on two different bikes, before I figured out what I was doing.
As for the investment in tools... Can't have too many. You'll use them again, believe me.
Did you use a vice as well to remove the free wheel? I've seen a vice used at the bike shop combined with a chain whip. I have the key to remove the freewheel but it seems to slip all the time when I use it with a wrench.
Up your goal to 100 rpm, when you're not thinking about it your rpm drops by 10 rpm. After you get to 100 rpm, keep going and work for higher and higher rpm capability. If you can spin very fast 160+ rpm your muscles will "fire" more efficiently, your stroke will get smoother and and your overall technique and power will improve. ( National team members are required to be able to spin 300 rpm on ergometers or stationary bikes). I'm not saying to ride at these high rpms, just do it in the spring and occasionally during the year to train your muscles.
When using a vice to work on a cogset/freewheel as mentioned above it is a good idea to get a tool called a "freewheel vise" that fits into the bench vice. The tool is basically two extending/expanding rods with blocks on the ends fitted with notched posts that fit the freewheel teeth. You fit the bottom cog into the tool to hold the cogset/freewheel and clamp the tool into the bench vice.
I had no problem using the chainwhip and freewheel remover. The trick is to put the freewheel remover on then replace the quick release nut to hold the remover in place to keep it from slipping.
As for cadence, 100+ is my target. Right now, 80 is all I can do for long periods. I push it as high as 100-120 for short periods, just to get my muscles used to moving that fast. My objective is gradual but consistent improvement.
Thanks for the affirmations!
Pat, 100 is my short term goal, but I do aspire to faster cadence as I improve.
To those who may have been hesitant to try something like this, give it a shot. You just have to be careful to keep things in order, spacers, etc. Now I have this "corn cob" for my extremely flat daily commuting, but in 5-10 minutes I can throw together different combinations for hilly rides.
Cambronne, thanks for the caution on derailleur clearance. The original cogset before the 12-21 was a 13-34, so I guess I have the range. I will keep an eye on clearance when I change the combination.
The neat thing I am finding with this 1-tooth cog increment is that it fools me into higher gears than before. Before, I might ride the 19 for a long time because the jump to 17 (8 or so chain inches) felt harder and made the cadence (85-90) a bit of a struggle, so I would hesitate to shift. Now, the small step from 19 to 18 (about 4 inches) is nearly imperceptible so I make that shift and after a couple of minutes maybe make e next little shift to the same 17, but it feels easier than before because I have sneaked up on it. Sneaking up/fooling myself is a big part of my training philosophy - tiny, hardly noticeable increases eventually add up to respectable improvement.
Thanks again for everyone's input.
Full marks for bucking the system.
Buying whole cassettes is one way of rolling your own, but its probably better to buy the cogs individually. You can do this with some 3rd party manufacturers like Marchisio. When your most heavily used cog wears out, you can replace that on its own.
You can also chose spacers to suit your tranmission system, ie to use a Shimano freehub with a Campy derailleur and changer, or visa-versa.
In some quarters, Shimano cogs are called pre-worn. For long term abuse, cogs with a thicker and deeper profile will last better, but may not change gear as quickly.
Actually, at 17.95 it was cheaper to buy the genuine Shimano cassette than individual sprockets, especially since the smallest cog has to have the built in spacer and threads for the lockring. Those small cogs cost $15.95 by themselves. In this case, the cost of the cassette and tools (chainwhip and freewheel remover) was less than just buying the individual sprockets! Plus I have the big cogs I can use for a hilly country cassette.
The third hand (www.thethirdhand.com) has always stocked seperate cogs and all of the nice little bits and parts as well as the tools to do this sort of do it yourself work.
Unfortunately, these guys are going out of business and will be closing April 15 - so if you need any weird little parts etc. check them out. No affiliation, they just have served me well over the years and I'm sorry to see them go.