2 Bicycles - Gears
As stated, we chose Rohloff speed hub gears. The Rohloff has 14 equally spaced gears, but the actual range covered can be selected to order. We were a bit concerned as to whether 14 gears would be sufficient, as we had previously had 27 gears on our mountain bicycles. Or had we? A typical mountain bicycle has three front chain wheels and 9 rear sprockets = 27 gears yes? Well actually no. The table below shows the relevant gear ratios (Chain wheel teeth / Sprocket teeth) for all 27 gear combinations.
In order to prevent excessive chain set wear, it is recommended that any
mountain bicycle user should not mesh the smallest front cog with the
largest rear cog and vice versa, (although many do). This means that
you can effectively discount the lowest and top gears, (those highlighted in violet). 27 down to 23.
Four of the gear combinations are exactly the same, (those highlighted in red). 23 down to 21.
On further examination you will see that 7 of the remaining combination
shows differences in gear ratio from their nearest value of less than
6%. These are very small step differences that the user hardly notices
in practice, often shifting two or three at a time. So, if we ignore
these and take the next nearest values the new "refined" ratios we end
up with 14 "effective" gears.
This still leaves the gear ratio differences uneven, ranging from 6.9%
60 16.7%. Cleverly, the Rohloff system spaces the ratios very nearly
equal at 13.6%. It makes for a very smooth transitional gear sequence as
opposed to the clattering of the conventional derailleur.
We selected a 38 tooth chain wheel as we are more bothered about getting
up the hills than maintaining good top speeds. This selection has
proven to be very suitable for our style of riding, i.e. leisurely. Only
occasionally, when going along the flat with a following wind do we
feel that we could do
with another one or two top gears on our bicycles. The lower gears are
ideal for taking a full load up a 15% incline. Much beyond that and you
are into pushing your bicycles up hill, (at least we are).
It is possible to fit two front rings and use a conventional gears
selector, but frankly we feel this introduces the very thing that we
have eliminated by getting rid of the derailleur and doesn't really
give that much advantage to us. It would be great if Rohloff could
design a two or three gear drive to fit in the bottom bracket casing to
give greater range.
When we were
in West Yorkshire we met a guy from the Netherlands who was riding a new
bicycle from the Netherlands company, Santos. We were salivating at this
bicycle. It is equipped with the Rohloff
gears, but Santos have also developed the use of Carbon Fibre belt
drive system, which we believe Rohloff
are fully endorsing. The only issue is that it cannot be split apart
for fitting, so Santos developed a special break point in the rear
frame. Unfortunately having shelled out thousands for our bicycles we
are not about to change to the new drive at all soon.
One slight complaint. We talked about the low maintenance. In
fact they are, but you do have to change the oil once every 1000km,
which comes around surprisingly quickly when you are touring. You can
only buy the oil from Rohloff
as a kit and thus probably pay a lot more for it than you need to. Of
course you have to use their oil as otherwise if there is a problem you
have no recourse to complain.
There is one other issue that relates to the installation of Rohloff
gears into the wheels, which we will touch on in the section on wheels.
Our Thorn Nomads are now four years old and in the last two years we
have completed well over 20,000km. They have performed very well and we
are generally very satisfied. We have a had a few issues that are worth
mentioning. The only failure that we had was in the original Mavic
wheels, (see detail discussion below). We have fitted new chains and
changed around the front and rear cogs. This summer I noticed one of the
Gear Hub oil seals was leaking so I have replaced the seals in both
hubs just to be sure. We have also replaced our bottom brackets.
One point of failure has been the bottle mount boss at the bottom of the sloping tube of the frame. The frame has SS couplings which means there is no possibility for water to drain out of the bottom of the tube. Over time water ingresses and pools at the bottom of the tube. This causes the boss to rust and in both bikes the boss has completely rusted and fallen out of the frame. We had to have them re-welded and resprayed.
We have also resprayed our frames twice.
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