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Updating Crankset 1990 Trek 950: will it work with original Deore LX groupset?

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Updating Crankset 1990 Trek 950: will it work with original Deore LX groupset?

Old 05-10-21, 02:29 PM
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adam.schwartz4
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Updating Crankset 1990 Trek 950: will it work with original Deore LX groupset?

I found a dream bike last week: a 1990 Trek Singletrack 950. It's in fantastic working order and I'm set to update it into a longhaul Swiss Army Knife all road tourer.

I need to ride with 165mm cranks due to hip problems and will be removing the original 175mm Deore LX cranks. I want to try and keep everything else the same, and so far see no issue with these components in concert.

Can the pros here confirm that this should work?
I'm mainly wondering if I'll need to replace the original derailleurs to use this crank? Really love the Deore flavor and hoping to not do that. Here are my main questions:
  • Will the original LX triple front derailleur work with the new crank? I can't find any manuals for FDM550, but 46/36/26 only has an increase of 2 teeth on the smallest chainring.
  • The RD has a max teeth load of 38 and my rear cassette would put it at 1 tooth over capacity. Big deal?
  • Sugino suggests a 113 bottom bracket, but the chainstays are pretty wide on the 950. Roll with 113 then trial and error?
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Old 05-10-21, 03:52 PM
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Bill Kapaun
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I would suggest the 24T smallest ring and a 12-28 cassette.
Your DER links don't work, but if they are 3X7 speed indexed or thereabouts, they should be good.
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Old 05-10-21, 07:45 PM
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Andrew R Stewart 
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I believe the Sugino crankset will work. The bigger issue will be the ring c-c spacing and less so the ring teeth count. But rink spacing can be widened with .6mm spacers if needed. The issue is a ft shifter that is indexed will move the der an amount based on the ring spacing spec in effect when the system was designed. So duping that spacing is critical to best shifting and minimal chain rub. Andy
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