Sunday, June 24, 2012

How Low Can I Go, Part II

A couple weeks ago I wrote about putting a 22T granny gear on my bike.  It is still taking me a while to get used to it as I now have to shift both front and rear derailleurs at the same time so that I am not just spinning when I drop into the tiny gear.  I've found that because of this, I use the granny gear less, but that it really does nicely lower my range.

One problem with this gear, also because the large difference in size between the granny and middle gear (38T), is that the chain will fall off the granny gear when I'm shifting down to it.  To stop this problem I bought a (34.9mm) N-Gear Jump Stop Chain Guide.  Because of the pulley near the bottom bracket for the front derailleur, I couldn't get it quite as far down as I would have wanted, but it does seem to have stopped the problem.

Chain-stop from the front.

Chain stop from the side

When I originally put the triple crank on the bike, I found that the chain actually fell off the crankset less frequently than with the original double. With the small granny gear, the problem was worse than with the original double.

In the same vein as the last post, I moved the seat on my Sofrider as far forward as possible as well as lowered the angle of the seat. Lowering the angle means I've reduced my cross section to the wind.  Moving the seat forwards means that hopefully my center of mass is now closer to the front wheel to help with wheel slippage when climbing.

You'd think that when somebody is writing about this in a blog called The Recumbent Quant, there would be a quantitative measurement about how much forward the seat has moved, or by how much the angle has changed.  Well, don't worry.  I'm disappointed in myself too for not having these things.  My guess is that the seat angle changed from 50 degrees to about 45 degrees.  Part of me would like to be able to lower the seat even more, but given that I use it to pull a trail-a-bike, I think this is about as low as it can go.

New seat position.  It few centimeters further forward and probably about 5 degrees more horizontal.

 I've been riding this way for about a week.  I guess the biggest surprise is that there really isn't much of a difference while riding.  The handlebars are further away and feel a bit less "cramped" (although it was never really a problem before) and the viewing angle to my bike computer is a bit worse.  And I had to extend the boom so the bottom bracket/crankset moved a bit more forward. So I can tell that the seat is in a different position, but the bike basically feels the same when I'm riding it.

Another possible difference is that by tilting the seat back, I'm able to ride further without "recumbutt" (which is having your butt fall asleep (this is much better than having your "what-what" fall asleep)..  This is a problem that I used to have on longer rides.  I haven't had any symptoms yet, but I've only ridden for just over 16 miles since I made the change.  I'll probably eventually add padding to the seat bottom as well.

I do feel as if I am cruising at a little faster on flat terrain and on my maiden voyage, I hit 39 mph on a course that I've ridden on before without realizing I got anywhere near that fast.  And the next day was my fastest every time commuting to work.  All of that being said, I'm not really yet convinced how much of a difference it has made (although it's pretty clear that it hasn't gotten any worse).  Time will tell.


  1. Looks good Charles! If you want to lower the seat back further to say 35 to 40deg you may need to bend and reinforce the seat-post.

    Well, this may not work with a stiff Aluminium-alloy post but a steel one can be bent and reinforced around the bend. You can ask at the cruzbike site form further ideas.

    Look at mine, my seat back starts at 35 deg lower back then curves up to approx 50deg near the shoulder area, here:

    It does feel very aero.

  2. Thanks! I've heard the same thing: bending an aluminum (alloy) seat post is difficult, but a steel/chrome-alloy one would probably work.

    In my case, I need clearance to pull the trail-a-bike, so I'm not sure that I can go much lower than I am (although looking at my picture, maybe there is some room).

  3. Hello and thank You for your scripts.
    On my single crank sofrider, I've problem too: the chain sometimes fell off shifting gears, on the right side.
    In your opinion, how can I solve my problem?