Bicycle Travel > Gear Talk

Tandem crankarm length


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?

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.


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.



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