Bicycle Travel > Gear Talk

Tandem crankarm length

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CraigJohnston:
I just bought a used Trek T-100 tandem bike.  I think it's going to be fine for me and my 13-year old daughter next summer on Cycle Montana, but I have two concerns that you more experienced cyclists may be able to help me with.  First, the crankarms are 175 mm.  Is this too long? I am 6 foot, and love the 172.5's on my road bike.  My daughter is less than 5 foot tall, and I worry about "beating her up" on the flats.  Would it make that much difference changing the arm lenghts to 170?  Second, my rear gearing only goes to 28T.  Is this a disaster in the making?  I remember how hard it was to climb Rogers and MacDonald pass last summer on my road bike, and I don't want to needlessly suffer.  Any suggestions?

mmullins:
You would probably be fine with the 175/170 set up depending on how tall your daughter is.  I think the difference between 175's and 172.5's wouldn't be noticeable.  I've heard that one reason tandems run shorter rear cranks (other than for shorter stokers) is it balances out a captain who may have a faster spin than the stoker.  I changed from 175/170 to 165/165 (we're both short).  I noticed a pretty big difference going from 175-165.  Unfortunately, my wife feels like I'm spinning her too fast now that we have the same size cranks.

LWB:
Craig,

If you are going to change the rear cranks, you might want to go for 165 for your daughter.

As for gearing, whether the 28 tooth cog gives a low enough gear depends on the size of your little chainring.  Personally I would recommend you have at least a 22 inch low.

We rode the Southern Tier on our tandem (self-contained) and with a low gear of 20 inches (a 20 tooth granny and a 27 tooth big cassette).  It was adequate, but when we headed to Colorado we switched to a 17 inch low gear (20 front / 32 rear).  I think we will stay there.  Our setup is 48/38/20 chainrings and 12-32 cassette.

Lynn

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