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Old 08-19-11, 09:50 AM   #1
asmac
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Noob bike builder needs advice

I'm planning to put together a touring bike built on a Salsa Vaya frame http://salsacycles.com/bikes/vaya/va...e_frame_build/ . I've settled on SRAM x.9 9-speed rear derailer and x.9 trigger shifters but am very confused about the crankset and front derailers.

First, I notice on many bikes, including my own, that the manufacturer specifies higher quality components for the rear than the front of the drive train. Does that indicate that the front components are less critical? Cranksets in particular seem to range vastly in price and I have no idea how to proceed. Component weight is not a big issue for me and ny advice would be welcome. Are chainrings and bottom brackets normally separate purchases from the crankset?

Second, I'm looking for a 22-32-44 crankset compatible with the SRAM 9 speed rear derailer but most cranksets i see say they are 10 speed. Does this refer to the spacing between chainrings? Will a 10-speed crankset work with a 9-speed chain and cassette?

Third, will another brand of front derailer work with the SRAM x.9 trigger shifters? The built Vayas come with a bottom pull derailer but I can't tell if it's high or low mount. How can you tell? What difference does it make?

Fourth and final question, how are "mountain bike" components different from "road bike" components? Is it only the size of tubes they mount to and the style of handlebar they are intended for?

I know it's a lot of questions and I wil very much appreciate any information you can provide.
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Old 08-19-11, 10:22 AM   #2
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Taking one of the questions one at a time.

1- the reason that so many bikes come with a better Rd than FD is economics and competitive pressure. When choosing the components for a production bike makers balance the cost against the added perceived value at retail. They divide components into the ones that add value and the ones that most people miss. The RD is one of the most visible items and they'll use an upgrade just so that can say "xxx derailleur", while skimping of the less obvious FD and sometimes the shifters. You'll see all kinds of things like that, including better cranks on cheaper bottom brackets, cheap bar in a nice stem, etc.

2- there should still be some 9s triples out there, but if not you can buy a 10s crank. The difference is the chainrings will be a bit closer together. Most 9s chains will run fine on 10s cranks, though you might be slightly more limited in chain angle when crossing an inner ring to the outer cassette.

3-It's generally best to stay within brand, and sometimes even within type (road vs mtb) between levers and derailleurs. The various brands have different cable response ratios (the distance the RD moves relative to the cable movement) and often don't mix well with each other.

4-much of the difference between mtb and road stuff is marketing, though road stuff is usually built around drop bars, and mtb for upright. Also some mtb stuff might be built tougher or more abuse resistant than comparable road stuff. As long as the function suits your needs, there no harm in using mtb on the road or vice versa. (I use an mtb crank on my touring road bike)
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Old 08-19-11, 11:15 AM   #3
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a handlebar diameter difference separates things, road is 1.6mm larger in diameter,
22.2, vs 23.8 .. 7/8" vs ~15/16"
so controls are less than interchangeable ..
this is most of the bar outside the center clamp portion.. ..

9>10 speed is a marketing effort to drive buyers to spend more money .
planned obsolescence..
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Old 08-19-11, 11:40 AM   #4
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Don't quote me on this with your given configuration, but I think you might be better off with a 10sp chain if running a 10 sp crank and 9 sp cassette.
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Old 08-20-11, 07:31 AM   #5
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It's becoming clear(er)...

Thank you all for the information. It helps a great deal.

I've found a source of shims, both for cranksets and for front derailer clamps. I expect it's old news on this forum but here's the link: http://branfordbike.com/product/le-t...p-shim-878.htm These should make it possible for me to stay within the x.9 family and look at all cranksets.

Just a couple of questions remain (for today!!):

1. What factors determine if you need a a high mount or low mount FD?

2. Is a 10s chain significantly weaker than a 9s chain? (I'm big and can seriously stress a drivetrain)

3. At a modest price point, ($100-$150) are the crankset, chainrings & BB typically separate items or should I be expecting a complete set?

Thanks, again.
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Old 08-20-11, 07:45 AM   #6
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asmac,
1. I think this is referring to whether the FD cable is routed along the top tube (like most mountain bikes) or routed under the bottom bracket (like most road bikes). Usually referred to as top pull or bottom pull, use what your frame is spec'd for.
2. Not significantly.
3. Generally these are seperate items, but external BB cranksets may have a BB included.

Brad
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Old 08-20-11, 08:22 AM   #7
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Quote:
Originally Posted by asmac View Post


Just a couple of questions remain (for today!!):

1. What factors determine if you need a a high mount or low mount FD?

2. Is a 10s chain significantly weaker than a 9s chain? (I'm big and can seriously stress a drivetrain)
The descriptions high and low mount refer to the relative height of the cage and mounting clamp. If there's nothing in the general area at the top of the chainrings either will be OK, but if you need to clear something, like possibly a low water bottle boss then you'll need a low mount.

The cable pull direction is more critical. Most are bottom pull, for cables coming up from the BB, but if your cable is routed along the top tube and coming down from there, you'll need a top pull. Some derailleurs work both ways.

10s chains aren't any weaker, but will wear out faster by virtue of being narrow. If you're both big and strong, and ride hills, you'll already be seeing shorter chain life than a 160# rider in the plains. I suggest you see if you can get by with a narrow 9s chain, which is both less expensive and should have longer life. I put aside a bunch of Sram PC-80r chains for my 10s Chorus drivetrain because at the time the Campy 10s chain was the only option, and I didn't want to deal with their pin system. I'm still using these and never had any issues.
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Old 08-20-11, 07:51 PM   #8
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Excellent... this is very confidence-inspiring. One bit of knowledge at a time!
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