Saturday, June 9, 2012

How Low Can I Go?

When I bought my Cruzbike Sofrider, it came with double front crank (with 48 teeth on the big cog and 34 teeth (48T/34T)) and a rear cassette that goes from 11T to 32T.  With this setup, the bike has a range of 26 to 107 gear inches.  (For those unfamiliar, "gear inch" refers to equivalent size wheel without any additional gearing.  For example, 60 gear inches is equivalent to riding a large penny-farthing bicycle with a 60" front wheel).

Almost immediately I realized I wanted more range and although it took me twoattempts, I installed a triple crankset (48T/38T/28T).  This decreased the low end of my gearing to 21.5 gear inches.  This was a big improvement and made a big difference, both when pulling a trailer on "regular" hills and when riding solo up very large hills. It was a big improvement, but it wasn't enough.

After the Bloomin' Metric Century and the problem I had on that large hill, I started thinking about what I wanted to do.  After asking on the 'Bent Riders Online forum and deciding that it was at least worth trying, I ordered a 22T cog.  This is equivalent to just below 17 gear inches (or a reduction of a third over the original crankset in terms of number of teeth or gear inches).

Today, I pulled the crankset, removed the old cog and put on the new one.

Crankset with the original 28T granny gear.

Crankset with the new 22T granny gear with the original gear to the right.  The new gear really does look a loot smaller, doesn't it.

My bike being held on the bike stand after reattaching the crank.

After taking it for a short test drive, I realized I needed to shorten the chain.  The reason is that the diameter of the 22T cog is significantly smaller than the 28T cog and that the chain was too long to be in the small front cog and the higher (meaning smaller in number of teeth and therefore also diameter) gears.

I ended up removing a couple more links than I meant to because the first time I pushed the pin out of the chain, I pushed it completely out and wasn't able to get it back in.  After reading online, I realized my mistake and made sure to leave the pin in the second time.  I had to break the chain one more time (again, I was smart and careful enough to leave the pin in) because I hadn't routed the chain correctly through the rear derailleur.

Here I'm using the chain-breaking tool.  I recommend removing the wheel before trying this.

The second time I was smart enough to leave the pin in and not push it completely out. The white bag is being held by my daughter so the camera phone would focus on the pin and not the floor.

With the new setup, I can still (barely) make it into the large cog on the crankset and the largest (lowest) cog on the rear cassette.  You're not supposed to use this gear and I tried to avoid it before, but I'll try harder now.  I can be in the granny gear on the crankset and easily make it to the 5th gear on the cassette.  I can make it into the 6th gear, but it isn't entirely happy.

Since I had installed a new granny gear, I needed hills on which to try it out. After putting the kids to bed, I took the bike out for an 11 mile ride that went up Flax Hill road (one of the worst hills around here) twice.  I averaged 14 mph, which is my fastest ride (over 10 miles) ever.  Not bad considering I did Flax Hill twice.

I like the lower granny gear, but the difference between the medium cog on the crankset (38T) and this gear (22T) is quite noticeable.  When changing from the second cog to the granny, I also need to move the rear derailleur from the 1st (biggest) gear to 4th or 5th gear if I don't want to spin out (meaning spinning but not turning the wheel because it's moving too quickly).  I had similar problems when shifting out of the granny gear and if I didn't change from a high rear gear (say, 5th) in the granny gear to a much lower rear gear for the middle cog on the crankset, I found that it was too hard to peddle.

The first time I went of Flax Hill road, I did use the smallest gear on the bike, but found that I didn't really need to (the GPS claims my speed was as low as 3.6 mph here).  The second time I went up the hill, I found the lowest gear quite comfortable although for that particular hill, I would have been quite o.k. in the next highest gear.   Here the GPS doesn't report as low a speed, it does show me averaging 4.5 MPH for most of the last part of the hill,

For now, I think I'll go up a size to the 24T ring as the granny gear on the crankset.  In the future, I'll consider replacing the middle 38T chanring with something smaller (say, a 34T).  Definitely learned a lot playing with this.  More tweaking coming soon.


  1. First, get yourself some Quick Links (aka Power Link, Master Link etc)for your chain...they make chain maintenance and repair a lot easier.

    Second, what about going to an 11-34 cassette, and back to your original 48/38/28t, so your range would be 20-106 gear inches. Or if you went with a 26t granny instead of the 28, your lowest gearing would be 18.7, and your drivetrain would likely be happier and shift more reliably.

  2. If I were clever enough to take my chain of to service it, then, yes, those would work well. My understanding about the quick links is that they ahve to be installed, so if you want to shorten your chain, you still have to remove regular links. If I haven't done already done it, when I replace this chain, I'll install the quick links in the next one.

    I've thought about changing the cassette, but in my case, if I went to 11-34, I'd probably want to change from an 8 speed cassette to a 9 speed and that means (at least 1) new shifter(s). I might do this eventually, but that's a lot more work.

    Part of it, I think, is just getting used to it. I think it eventually makes more sense to have a tight cassette with larger differences in the gears in the crankset.

    1. 1. Yes if you want to install quick links in a chain without them, then you have to knock out 2 pins all the way, and not lose the little roller bit in between the side plates. It is worth getting though, as it allows for fast chain removal without tools,(cleaning chain is SO much easier!) and also can allow you to insert links into a too-short chain as needed, more easily.

      2. Sorry about not realizing that Cruz didn't use a 9spd back end. Is your spacing 135mm back there? If so, then going 9spd wouldn't involve spreading the dropouts to accomodate a 135mm hub.

      And to AKTux, how do you bridge? I have tried, and cannot manage it on my Giro26-Euromesh. I just spin up the hills (11-34 9spd, 52-42-30). Slowest I have seen myself go was 3.4mph uphill.

  3. Personally, I find it difficult to maintain balance and keep the bike upright at such low gears and speed. Even at 28(crank)and 32 at the cassette, the gear inches are already so low for me. How do you do it?

    I prefer to "bridge" at extreme gradients, but again I only weigh 67Kgs, my homemade MBB is about 20Kgs. I haven't tried to "bridge" for longer than 50 meters at a time though, so maybe I may need the super low gears one day.

  4. I once posted this on the cruzbike website. The success of "bridge" technique may depend on the bike geometry so it may or may not work for you. So here goes:
    On climbing short steep grades (more than 8%) or even accelerating, I realized that if I 'get out of the saddle' i.e. raise my bottom off the seat so that the only contact with the bike is at my pedals, handlebar and just below my shoulder, the bike jumps forward with such amazing power. In effect, my torso forms a plunk between the top of the back rest and the pedals. With practice I can now sustain this for 10, 20, 30 meters at a time. It requires a strong core(stomach muscles). It will raise your heart rate very rapidly. I don't think it's very energy efficient, but my oh my, it is very very powerful.