Thursday, June 4, 2009

Getting up the hills

It is fair to say that before buying the Christiania I knew nothing about bicycle gearing. In hindsight I wish I had educated myself about the topic before purchasing the bike! On the Christiania you have a choice of a seven or eight speed Shimano hub gears.

I opted for the seven speed (a thumb shifter above) as it was cheaper and I figured one less gear would not worry me. However after riding the bike for a while and learning about gearing it became apparent to me the increased gear range on the 8 speed (a twist shifter) would have been useful.

I don't intend to discuss the details of bicycle gearing here suffice to say that when measuring your gear setup in 'gear inches' - the lower the number the easier it is to pedal uphill! Conversely though, the lower the number the slower you go when pedaling on the flats or downhill. If you wish to get a basic understanding of gear inches I can recommend this article (though it focusses on derailleur gears) and the great articles on the topic at Sheldon Brown's (RIP) website. The rest of this post will assume a basic understanding of gearing terminology.

My Christiania was supplied with a 33T front chain ring and a 18T rear sprocket on the Shimano Nexus 7 speed hub in a 24 inch wheel. When you plug those numbers into Sheldon's fantastic gear calculator you get 7 gears from a low of 27.8 to a high of 68. If I had purchased the Shimano 8 speed hub I would have immediately had a larger gear range of 23.2 to 71. A big improvement especially on the low gear side which is what I needed to get me up the hills. However all was not lost as by lowering the front chainring size, or increasing the rear sprocket size, it is possible to lower the gearing also. Peter from PSBikes was able to supply a 28T front chainring and this lowered the range to 23.6 to 57.7 gear inches -

Note that by reducing the chainring size you of course lose the higher gears which are handy for the flats. At the time though I was quite comfortable with losing the higher gears if it meant less effort pedaling uphill. I rode on that setup for a while but unfortunately a couple of hills near my house are long and fairly steep and of course are on the way back from the shops when I am loaded up with the groceries! Thus I asked Simon from CycleSurgery to change the rear sprocket to a 22T and this lowered the gear range further - 19.3 to 47.2. An 8 speed would have increased that range - 16.1 to 49.3! So I guess from my experience if you are in a hilly area definitely go for the 8 speed and perhaps ask for the 28T front chain ring as a starting point. See how you go on that before deciding about changing the rear sprocket.

But I was still not satisfied! Whilst it was easier to pedal up the hills I still had trouble in a couple of places when fully loaded and I did miss being able to pedal at the higher gear ratios on the flats and downhill. After a lot of Google research I came across the most amazing piece of bicycle gearing equipment I had ever seen. A Schlumpf Mountain Drive -

This device replaces the front crankset and basically puts an additional lower gear (by a factor of 2.5) in your pedals without a second, smaller front chainring! For the technically minded it is a planetary gear system built into the bottom bracket. All you do is click a little button with your heel and you have seven (in my case) extra low gears -
Because of the exceptionally low gearing it gives you when engaged, it is possible to run it with a larger front chainring so you can also obtain the high gears when it is not engaged. It is a bit confusing to explain so perhaps best to show you my setup with the Mountain Drive -
  • Front chainring 42T
  • Rear sprocket 22T
  • Gear range when Mountain Drive NOT engaged is 29 to 71 gear inches.
  • Gear range when Mountain Drive IS engaged is 11 to 28 gear inches.
When the Mountain Drive is engaged I have an effective front chainring size of about 17t! The addition of the Mountain Drive has given me 14 gears from 11 to 71 gear inches none of which overlap. The 11 inch gear gets me easily up any hill I want but only at about 4 km/h! Luckily this lack of speed can be made up on the flats and downhills as I can comfortably pedal along at between 25 and 30 km/h in the high gears. Like the Shimano hub the Mountain Drive gears can be changed when pedaling or stopped - very handy when having to stop pointing up a hill as I can just change to a lower gear and then proceed (something you cannot do on a derailleur system). One thing to note is that the Mountain Drive still works with the rear backpedal brake. However when you are in low gear you must pedal 2.5 times further to actually engage the rear brake! This takes a little getting used to however when in the low gear range I am generally not traveling very fast anyway.

The Mountain Drive was sourced through one of the local recumbent bike dealers and is not cheap. Unfortunately the guy I purchased it off had never actually installed one himself and there were some problems with the installation -
  1. It was not tightened up enough around the bottom bracket and came loose when I was miles from anywhere with no tools
  2. The pedals were cross threaded into the cranks
  3. The 'button' to change gears was also not tightened up and it fell off and got lost leaving me stuck in the high gears with a full load a long way from home!
CycleSurgery fixed problems 1 and 2 while the guy I purchased it off ordered me spare buttons and fixed that up. So my advice is, if you decide on a Mountain Drive make sure the guy putting it on has some experience installing them or get your local bike shop to do it after they have read all the instructions from the website. I would also recommend ordering a chainguard as the Christiania supplied one will not fit with a larger front chain ring and Mountain Drive installed.


  1. Fantastic! I may opt for one of these eventually.... though they're really hard to come by here apparently.

  2. You can order a Schlumpf Mountain Drive directly from the manufacturers website.

  3. I considered doing that but figured I'd be better off getting someone local who knew what they were all about! And by the time it the web price was converted to the Aussie dollar it cost about the same as getting it local.