|Any reason not to use this cassette gearing?||vindicator|
Jan 29, 2003 8:46 AM
|I own a pre-packaged 12-23 Ultegra cassette and a pre-packaged 12-27 Ultegra cassette. I'm using the 12-27 now, but I miss my 16. OTOH, I Want to keep my 27 because I don't need it often, but when I need it I NEED IT. Given that I use the big gears so rarely but still want them for desperate times, I don't mind big jumps at the big end. And I like one-tooth jumbs at the small end.
So, is there any reason I couldn't or shouldn't do a little mix and match from both sets and use the following combo:
|because you can't?||mohair_chair|
Jan 29, 2003 8:50 AM
|You can't separate the individual cogs in Shimano cassettes and put them back together the way you want. They aren't built that way.|
Jan 29, 2003 9:00 AM
|Take them apart and you'll immediately see the problem. The larger cogs are permanently (for all practical purposes) attached to each other.
If you want loose gears to do what you want, check out Mavic cassettes. You may need several sets to build what you want, though; they don't shift as well and are heavier, too. Excel sells them.
|I think some can be taken apart||bigrider|
Jan 29, 2003 9:08 AM
|i am not sure which cogset I did it to but there are three long skinny bolts that keep the large cog cluster together. The heads are on the large cog. Others are some sort of rivet deal which can't be taken apart.|
|You can with 105 cassettes||CurtSD|
Jan 29, 2003 9:16 AM
|That's true of Ultegra and DuraAce, but 105 cassettes are all individual cogs. See http://www.sheldonbrown.com/k7.html#9cassettes.|
|no 105 27 tooth? nm||DougSloan|
Jan 29, 2003 9:27 AM
Jan 29, 2003 11:31 AM
|Harris also sells a large selection of custom cassettes. Check 'em out.
|If you need the 27......||bigrider|
Jan 29, 2003 9:05 AM
|The reason they package gears the way they do is to try to keep the increments of change between cogs close. A one tooth change from a 13 cog is 1/13, a 4 tooth change from a 26 cog is 4/26 =2/13. That is twice the increment of change.
Which means that you would really notice the 4 tooth shift between 19 and 23 and 23 and 27 cogs. The very reason you want the lower cogs close is the very reason you don't want to spread out the upper cogs too much. If you NEED the 27 you will NEED the 23 and you will not NEED that huge jump to get there or back when upshifting.
|re: Any reason not to use this cassette gearing?||Thorman|
Jan 29, 2003 9:06 AM
|You can mix and match to some degree, but not the top sets of cogs. Here's a link to Shimano's pdf on the Dura-Ace setup.
|Hmm, boy I'm glad I built my bike on Chorus10 ;) nm||Spunout|
Jan 29, 2003 9:11 AM
|re: Any reason not to use this cassette gearing?||12x23|
Jan 29, 2003 9:18 AM
|I purchased a 13x30 "Century Special" from Sheldon Brown (Harris Cyclery) a couple of years ago that worked well. I just had to run the b-screw in a ways to get the top pulley away from the 30t. It was made up of loose Shimano cogs. I'm not sure, but they may offer loose cogs to get the 12x27 configuration you're looking for.|
|If you can live without the 12...||CurtSD|
Jan 29, 2003 9:22 AM
|you can convert it to 13-14-15-16-17-19-21-24-27. That's what I use. You need a first position 13 cog (with integral spacer) and a 16 cog.|
|Buy a 16 tooth 8 speed cog and a 9 speed spacer||MR_GRUMPY|
Jan 29, 2003 9:39 AM
|Shimano 8 and 9 speed cogs are the same thickness. With the above you can make a 13-27 with the 16.|
|Dagnabit! Thanks for the info. nm||vindicator|
Jan 29, 2003 10:51 AM
|re: Any reason not to use this cassette gearing?||jrm|
Jan 29, 2003 10:54 AM
|Calculate the gear inches using each cassette. Then see which cassette results with the least number of gear inch duplications or gear inches within say 5 gear inches of each other. Then choose the cassette with the least amount of duplication or near gear inches.|
|here's a handy spreadsheet||DougSloan|
Jan 29, 2003 11:04 AM
|I ran loose cogs for years...||brider|
Jan 29, 2003 11:12 AM
|When I got my Ticycles rig (running 8-speed), the bullet ends on the chainstays interfered with the chain on the 12 cog. So I went to an 11 cog with a 52 chainring. In order to do that, I had to buy the 11 separate, take off the big cog of a 12-25 and run it that way loose. So I was running a 11-23 8-speed, all loose. Worked just fine. Just bind it down good when you spin the lockring on, and everything should be okay.|| |