3.6 Cranks

edited February 2011 in Legacy Products
I've been reading a bit and think my knees might benefit from shorter cranks. Knowing zero about bikes or trikes, what cranks would fit my 3.6 crankset? If I can, I'd like them black, like the ones on it now.

Comments

  • Also - how can I determine the model number of the trike? I bought mine used, from the grandson of the original owner and he knew very little about it. I just want to be sure I own a 3.6!!
  • Any length crankarms will fit the 3.6 (also known as the Tour/Cruiser platform). The bottom bracket has a JIS (Japan Industry Standard) square taper axle which accepts a wide range of different cranksets. The stock length is 170mm which works for 99.999% of our customers. Crankarm length is more a factor of femur length than anything else. A really tall person with a really long thigh may prefer 175mm crankarms to improve pedaling efficiency. A really short person with a really short thigh may prefer 165mm crankarms. There is some "buzz" out there regarding 152 or 150mm crankarms. I don't put much credence into this hypothesis, however. 150mm is a great length for a child but on a bike or trike for an adult it's not preferable.

    If you are experiencing knee pain it is probably due to one of two causes; your cadence (RPM of the crankset) or the amount of bend in your knee at full pedal extension.

    First of all, if you are pedaling very slowly using a high gear, you are probably straining your leg muscles and your joints unnecessarily. That is why we offer trikes with so many gears from which to choose; so that you can choose the proper gear for the terrain in which you ride. 60-80 RPM is a good, average cadence for most riders.

    Secondly, if you over-extend your leg to the point that it "locks" straight at the knee your seat needs to be adjusted so that you are closer to the pedals. Conversely, if you do not get sufficient leg extension you can also strain your joints/muscles by being too cramped on the trike. We recommend 10-15 degrees of bend in the knee when the pedal is as far from you as it can go. On your trike this would be at about the 3 o'clock position when viewed from the right side of the trike.

    An easy way to properly position your seat is to put your heel over the pedal axle wearing only socks on your feet. Rotate the pedals. At full pedal extension, your leg should be straight with no bend in the knee. Adjust your seat so this occurs. When you put your shoes on, and have the ball of your foot in the proper pedaling position (ball of foot over the
    pedal axle center-line) you will have about 10-15 degrees of bend at the knee. This is a way of sizing the trike to you for optimum pedaling efficiency. If you move your seat significantly to do this, it may feel a bit odd for your first few rides. This is normal, but you should feel the benefits quickly and will love your new set up.
    Kelli B
    Sales, TerraTrike
  • kellib wrote:
    Any length crankarms will fit the 3.6 (also known as the Tour/Cruiser platform). The bottom bracket has a JIS (Japan Industry Standard) square taper axle which accepts a wide range of different cranksets. The stock length is 170mm which works for 99.999% of our customers. Crankarm length is more a factor of femur length than anything else. A really tall person with a really long thigh may prefer 175mm crankarms to improve pedaling efficiency. A really short person with a really short thigh may prefer 165mm crankarms. There is some "buzz" out there regarding 152 or 150mm crankarms. I don't put much credence into this hypothesis, however. 150mm is a great length for a child but on a bike or trike for an adult it's not preferable.

    If you are experiencing knee pain it is probably due to one of two causes; your cadence (RPM of the crankset) or the amount of bend in your knee at full pedal extension.

    First of all, if you are pedaling very slowly using a high gear, you are probably straining your leg muscles and your joints unnecessarily. That is why we offer trikes with so many gears from which to choose; so that you can choose the proper gear for the terrain in which you ride. 60-80 RPM is a good, average cadence for most riders.

    Secondly, if you over-extend your leg to the point that it "locks" straight at the knee your seat needs to be adjusted so that you are closer to the pedals. Conversely, if you do not get sufficient leg extension you can also strain your joints/muscles by being too cramped on the trike. We recommend 10-15 degrees of bend in the knee when the pedal is as far from you as it can go. On your trike this would be at about the 3 o'clock position when viewed from the right side of the trike.

    An easy way to properly position your seat is to put your heel over the pedal axle wearing only socks on your feet. Rotate the pedals. At full pedal extension, your leg should be straight with no bend in the knee. Adjust your seat so this occurs. When you put your shoes on, and have the ball of your foot in the proper pedaling position (ball of foot over the
    pedal axle center-line) you will have about 10-15 degrees of bend at the knee. This is a way of sizing the trike to you for optimum pedaling efficiency. If you move your seat significantly to do this, it may feel a bit odd for your first few rides. This is normal, but you should feel the benefits quickly and will love your new set up.

    Great post Kelli....... One thing I might add is that the alignment of your cleats if you are using clipless pedals could also be an issue. If you are forcing your foot into a position when clipping in, that is not a natural position for your foot on the pedal , you may want to readjust your cleat alignment. Some people like to have their feet point out at the toe a bit, compared to their heel, ( duck footed), and other riders prefer their toes pointed ( Pigeon toed ) a bit, while other folks like their feet pointed straight ahead. This position will have an effect on the way your knee reacts to your pedaling motion. It's a trial and error situation, requiring a bit of experimenting to find the most comfortable position for the rider with the minimum amount of knee discomfort.
  • Kelli
    Thanks so much for your thoughts on this. I am 5' 10" but have very short legs - inseam is around 28" and I was thinking (from what I've read) that shorter would be better. Thanks for helping me out there.

    On another note... I live in a very hilly area and even the shortest ride would entail climbing pretty steep, to me, trails. I've already seen that even my lowest gear should be lowered. So I'm wondering, without changing anything else, is there a set of crankgears or even an entire new crankset that will fit the 3.6 that would offer a 24 or 26t low gear? And how difficult is it to replace these items?

    I've not read anything bike/trike related since I was in my teens, so right now, my expertise is entirely internet-based - in other words, I've read but not experienced. So please keep that in mind when replying.
    Thanks much for your help.
    Al
  • You can put on a 26t front chain ring. We carry these in stock. You probably don't have the tools to do this so you'd be best off taking it to a bike shop.
    Kelli B
    Sales, TerraTrike
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