Author Topic: checklist for bike purchase  (Read 10212 times)

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Offline damselfli

checklist for bike purchase
« Reply #15 on: April 06, 2005, 07:21:34 pm »
My LBS ended up ordering just the frame and fork from CoMotion, and building it up for me. No problems with the order from CoMotion - it was just what I wanted - and more! Nice details, great paint job. Only thing I don't like (and need to tell them): the location for the shift cables to feed (these neat receivers welded to the sides of the head tube) position the shift cables so that they pull on the front brake when I try to turn the front wheel in a sharp turn (while walking -ie every time I go for a ride, I have to maneuver around the furniture in my living room!)...
The down side to the LBS build-out: while they told me they could build out with Ultegra for the road config and then switch the inner front chainring later for touring, after researching online I am beginning to suspect that they won't actually be able to do that w/ the new Shimano Ultegra 10spd setup... I may have to buy another entire chainring set to get good (low) gears for climbing strenuous hills w/ a full load. I am already committed to buying a second wheel set and rear cogs, but that too seems to be limited by Shimano. I am still trying to learn about it.

I placed another post about panniers... getting ready for a summer tour (I hope!)


Offline RussellSeaton

checklist for bike purchase
« Reply #16 on: April 06, 2005, 09:49:41 pm »
10 speed Ultegra crankset uses 130 mm bolt circle diameter outer and middle chainrings so anything from 38 to 53 or bigger teeth rings will fit these two positions.  The inner chainring uses 74 mm bcd so will fit 24 to 30 teeth rings.  Shimano website shows the 130/74 spec.

Your biggest problem is with the rear cogset.  27 teeth is the largest Shimano 10 speed cog there is.  12-27 is the biggest Shimano 10 speed cassette.  Shimano does show a 16-27 junior gearing 10 speed cassette if that appeals to you.  IRD Interloc Racing Design makes a 12-28 10 speed Shimano compatible cassette so you can get a slightly lower rear cogset.

If you go to the smallest inner ring of 24 teeth, and use the biggest 27 tooth 10 speed rear cassette there is, you end up with the maximum low gear of 24 gear inches.  Maybe low enough for some.


Offline damselfli

checklist for bike purchase
« Reply #17 on: April 07, 2005, 10:29:50 am »
I set my goal for gearing at 18-20 gear-inches for the low end (after reading Sheldon Brown and many other's comments on gearing). I made this clear to my LBS, but when he went to order the components he called saying he couldn't get the 9spd any more. I had originally looked at the Shimano XT 46-34-24 chainring with 11-34 cog (the spec on CoMotion's Norwester touring configuration).

I trust that Sheldon Brown and other experienced touring cyclists know what they are speaking of when they say one needs these low gears (for loaded touring).  I also trusted my LBS.

Looks like I might be stuck. I noticed Harris Cyclery sells special sets by S.B. for touring, and was hoping I could get one to work w/ my front chainrings.


Offline RussellSeaton

checklist for bike purchase
« Reply #18 on: April 07, 2005, 02:57:04 pm »
I'm a firm believer in sub 20 gear inch low gears.  I used a 24x32 low gear in the Alps and Dolomites in 1992 and wished for a lower gear more than a few times.

"Looks like I might be stuck. I noticed Harris Cyclery sells special sets by S.B. for touring, and was hoping I could get one to work w/ my front chainrings."

You are stuck with a low gear of 24x27 unless you change your entire crankset.  Sheldon Brown cannot sell you much to get lower gears.  Your Ultegra 10 speed crankset will take a 24 tooth inner chainring because your triple cranks uses the standard 74mm bcd.  But the problem is the rear cogs for Shimano 10 speed systems.  The largest 10 speed rear cog makes is a 27 tooth.  That is it, nothing bigger for 10 speed.  Interloc Racing Design makes a 28 tooth for Shimano 10 speed.  Using the Shimano 27 tooth rear cog, the lowest gear you can possibly get with Ultegra 10 speed is 24x27.  About 24 gear inches.

An expensive solution is to replace the crankset with one that takes a 20 tooth inner chainring.  58mm bcd.  The TA Zephyr from Peter White Cycles comes to mind as the very high end.  Plus a new bottom bracket.  You can get it with any chainrings you want and a 20 tooth inner chainring.  A 20x27 low gear is about 20 gear inches.  Your 10 speed Ultegra will shift 9 speed cranks just fine.  And the 10 speed chain will work on 9 speed chainrings just fine.

The Shimano STI and front derailleurs are sort of designed to shift well with large chainrings, 53-50, so a mountain bike crank of 44-32-22 may not work well with STI.  And the STI may not shift mountain bike front derailleurs designed for 44-32-22 very well I have heard.  Your bike shop would have to experiment to find a setup that worked well.  Some ingenious bike shop may be able to fit a 9 speed 30 or 32 rear cog onto a 10 speed cassette and get everything to work.  Maybe.