|Re: Custom Cassette Questions||sam-g|
Jan 8, 2003 6:38 PM
|I'm building a custom cassette to give me a larger range on my double equal to the range on a triple for riding the Bicycle Tour of Colorado this summer. Currently I have 50/36 TA chainrings on a Ritchie crank and will be getting a DA 12/27 cassette. My plan is to purchase (from Harris Cyclery) a 30T cog to replace either the 12T or 14T cog. (A 36/30 is equal to 30/25.) I'd like advice on the following:
What cog should I replace, the 12T or 14T? If I replace the 12T, I'll have to buy a new 13T with spacer but my main concern is keeping more usable gears and having enough high gear for the down hills.
Who has the best 30T cog to work smoothly with Shimano HG ramps on a DA cassette? I'd still like smooth shifting.
Which XTR Rear Der should I buy to handle the larger range? I think I'll need a GS, but should it be a 952, 953 or 960. What's the difference?
Will my current DA Double Front Der still work properly?
Any advice would be appreciated. Thanks.
|here's my advice||Funston|
Jan 8, 2003 7:21 PM
|Get your priorities straightened out. The most important thing is to get in shape for the ride. If you're gonna slack off in the personal physical department, no amount of juggling the components of your bike will guarantee success. That said, unless you're a helpless lardass or 72 years old, I'd say a 12-27 would be sufficient with a 50/36 front end. But if you insist, then a compatible mountain cassette (11-32 maybe), a long cage derailleur, and a new chain should give you the margin that you want. But the first priority is to get into reasonable riding shape.|
|here's my advice||sam-g|
Jan 9, 2003 8:38 AM
|I guess free advise is worth what you pay for it. Thanks for responding, but I was really looking for technical advice as this is the "Component forum". FYI, even though I'm 53, I'm training for my 7th marathon and normally finish in the top 25 to 30% of my age group. My priorities are straight, but I also recognize my limitations, both financial and physical, especially regarding long 20 mile climbs.
From my questions, you can tell that I already know that I need wide range cassette and long cage rear der to give me the range I'm seeking on my double. Any technical advice would be appreciated.
|re: Re: Custom Cassette Questions||CurtSD|
Jan 9, 2003 8:04 AM
|I can't help you with the derailler question, but the cassette issue is pretty easy. Get a 1st position 13 cog - with an integral spacer. Replace the 12 and 13 cogs from your 12/27 with your new 13, add the 30, and you're set. Shifting should be fine - I do something similar with mine - I start with a 12/27, and convert them into 13/27 with a 16 cog (13,14,15,16,17,19,21,24,27). You can start with either a DA or ultegra cassette. If you haven't already bought any of the parts, Harris Cyclery sells cassettes that have already been customized into exactly what you're describing - see http://www.sheldonbrown.com/harris/k7.html#9cassettes. They can also sell you individual cogs if you'd like to do it yourself. I'll bet they can answer your derailler question too.
Personally, I wouldn't worry about your high gears - the thin air at altitude lets you pick up a lot of speed in a hurry going downhill, so you'd spin out a 50/12 almost as quickly as a 50/13.
Hope that helps.
Jan 9, 2003 9:35 AM
|I haven't tried running a 30 cog with a road derailleur but I do modify my cassettes the way you have described. I put a Shimano 9-speed 14-28 (14,15,16,17,19,21,23,25,28) on my wife's bike using parts from www.sheldonbrown.com (Harris Cyclery). I run 13-25, 13-26, and 13-27 cassettes, all include a 16.
|re: Re: Custom Cassette Questions||Rusty Coggs|
Jan 9, 2003 8:37 AM
|Your derailer might handle a 30 cog,even tho the spec is 27,spec is usually conservative.Seems like I have heard of 30 tooth capability with 9 speed Shimano road derailers.The front derailer does not know what is on the rear.The short cage GS952 will do it, and you probably don't want the rapid rise 953.|
|re: Re: Custom Cassette Questions||sam-g|
Jan 9, 2003 9:07 AM
|That's an interesting option. I'll try shifting with my existing DA rear der with the 30T cog before springing for a new XTR. Just out of curiosity, what does the rapid rise feature really do and why wouldn't I want it for basically the same money? I'm also leaning toward dropping the 12T cog to add the 30T, I guess I'll be coasting down the mountains for the most part.
|re: Re: Custom Cassette Questions||Rusty Coggs|
Jan 9, 2003 10:20 AM
|You may have to fiddle with the 'B' tension screw on the back of the derailer.Make sure chain is long enough.Rapid rise has an extra spring in it that helps the derailer shift to larger cogs.don't know about compatibility,and don't think it necessary for your application.|
|Some answers for you||LC|
Jan 9, 2003 10:58 AM
|Keep the 12 cog, you need that for down hill with that 50T. I would take out the 13 to make room for the 30.
A GS type XT or XTR der would handle up to a 32 cog and has enough range to handle the difference of your set up so your fine. I am not sure about which model is which, but one of them is likely a rapid rise type and they all work well.
You don't need a new front der.
Jan 9, 2003 11:07 AM
|XT and XTR will both go to 34, the XT cassettes are available in both 32 and 34. The XTR is only a 12-34, it is very light weight and fairly expensive. Both derailleurs are available NON-Rapid Rise, and I don't think RR is adviseable anyway.|
Jan 9, 2003 1:40 PM
|If you don't already know you love it, I wouldn't buy it. It has its aficionados, but they seem few & far between.|
|your correct about 34||LC|
Jan 10, 2003 10:19 AM
|If you want XTR, the M952 is the standard type and the M953 is the rapid rise. You will want to get the RD-M952-GS, it has enough capacity (22 max front difference) to handle your 50-36 = 14 difference. The SGS would work too, but may look funny on a road bike being so long and will be a little slower shifting.|| |