Getting Cagey - the Front Derailleur

There is not much to say here - having bought an Ultegra rear derailleur, I am committed to Shimano shifters, so I have to find a Shimano front derailleur.  Keeping up with the standard I have already set, the target unit is a Ultegra 6700 unit, for two chainrings, NOT a triple.


My current ride has the complete 105 groupset, and the front cage and shifters have the triple capability.  Frankly, this is a pain.  Each shift - down or up - requires two taps, the second more of a tuning adjustment to secure the shift.  By selecting a cage, and later a shifter, that does NOT have the triple capacity, I will be able to have secure, single action shifts.

So, how smooth?  I hope very.  Take a look at some early derailleurs.  This is a diagram from the Jo Routens unit from the 1950s.  It is from a New Zealand website (http://bicyclespecialties.blogspot.co.nz/2011/11/jo-routens-front-derailleur-project.html) that follows a project to recreate this early unit.  The finished item looks like this: 


This unit is positively modern in appearance.


Early units utilised a lower cog on an arm that projected below the bike, thereby maintaining chain tension.

This is a  page from a 1935 catalogue.  The unit was robust and reliable enough for it to be used by such cycling greats as Gino Bartali, seen here in the 1936 Giro d'Italia.  



Although the image is monochrome, you ought to visualise the stunning pink colour of his shirt.  


This image is from the website http://www.bikeraceinfo.com/photo-galleries/derailleurs-1.html,   which also has this image of a manual-shift derailleur:

Moving the ratcheted lever, while back-pedalling, shifted the position of the bottom jockey arm.


How times have changed.


Instead of this serious hardware, the Ultegra 6700 unit has a weight of a mere 89 grams, although the old lever version did not need a handlebar shifter.  You still had to take your hand off the bars, though, and back pedal.  

The unit that I bought is for a brazed-on mounting.  Even though I do not yet have a frame, or have even decided on what frame/material etc to commit to, the brazed-on choice is more versatile. If I end up with a frame that has no mount, then I can buy a simple wrap-around clip that mounts brazed-on fittings.


Competition was tight price-wise.  Being July, there were different Tour de France promotions available.  Together with a fluctuating dollar, timing was everything.  Within NZ$4.00 of each other were deals from Wiggle, Probikekit and, the winner by a mere 71 cents, Chainreactioncycles.com.  Part of the deal was a low postage cost (NZ$9.66), while another site, also sending from the United Kingdom, charged NZ$16.78.


The next part of the mission is complex - the wheels; hubs, rims, spokes.  I will find out whether I get the gear as bundled lots or piecewise...don't go away!

Derailed, but not a Train Wreck

Having bought the cassette, I need a means to shift the chain from one sprocket to the other. This cunning device is the rear derailleur. And I say cunning because that is exactly what it is.  With a history almost as long as the modern safety bike, the rear derailleur is a classic case of how technology is a combined process of innovation, adaptation and constant improvement.  And yet, the core technology has remained unchanged for decades, always centred upon the simple elegance of a sliding parallelogram under spring tension.


Derailleurs were originally created for regearing steam engines, and it was not long before the concept was applied to the new chain-drive transmission of the safety bike in the 1880's. A site that covers many early attempts at a workable design is at http://www.users.globalnet.co.uk/~hadland/old_derail.htm

There are two main issues to consider - shifting the chain alignment laterally along the axle line, and maintaining chain tension.  An early design, yet still improved from an earlier effort, is this one from Edmund Hodgkinson in 1899.  As with modern derailleurs, this has a jockey wheel on an arm that moves to maintain tension.


With many engineers competing to produce the first workable, effective, reliable and marketable design, bike derailleurs were cutting edge technology for the time, yet faced a certain discrimination, most notably within the Tour de France, which did not allow riders to use derailleurs until 1937.  Until then, when a rider wanted a new gear, he had to stop and change wheels.


The modern parallelogram derailleur emerged from the confusion to become the industry standard when Campagnolo introduced the Gran Sport in 1949. Starting with a selection of two gears, the rear sprocket number steadily increased to give five for the ubiquitous ten-speed bike of the seventies, through to six, eight and nine, with ten-speed cassettes arriving in 2000.  And in 2011 Campagnolo again led the tech advance with the first 11-speed cassette.


The market was dominated by derailleurs from Campagnolo, Benelux, Suntour, Zeus, Gipiemme, Mavic, Simplex and Shimano.  A few of these manufacturers now focus on other components, and derailleurs are  now principally from Shimano, Campagnolo, and SRAM. 


And here the first distinction in my choice arrives.

my Ukrainian Great-Grands.

First, I am not able to afford the new electronic transmissions, even though the Ultegra Di2 is now on the market.  Also, I'm not using Campagnolo - I'm not stylish enough (my peasant ancestry comes through...see image right).  Also, Campy is a tad too expensive, and all my tools are for Shimano.  SRAM components are compatible with Shimano, with a caveat.

SRAM or Shimano?

The derailleurs must be matched with the shifters.  You cannot use an SRAM-Shimano combination.  The reason is that when you swing the lever, a ratchet pulls the cable a certain distance, which is calibrated with the rear derailleur lateral gearing to make the right sideways shift to the next sprocket.  SRAM and Shimano have different ratchet pull distances, so if you mix SRAM-Shimano, at either end, the derailleur will almost, but not quite, in line with the sprocket of your choice.  This leads to noisy shifting, rattle from poor chain alignment, and progressively worse component wear.  Even if you put up with poor shifting, it will cost you in replacement parts.


I have set a quality level equivalent to Shimano's Ultegra.  For SRAM, the equivalent gruppo is the Force. I spent some time trawling through the different internet sales sites, noting prices of the Ultegra 6700 and the Force derailleurs from each outlet.  The SRAM Force unit is uniformly more expensive, at an average of NZ$48.36 dearer than the Ultegra.  Thinking ahead, whichever I choose is also a commitment to the matched shifters - which have proportionally a similar price differential.  So, Ultegra it is.

Cage Length

A closer look at the range of rear derailleurs shows a range of three cage lengths (short, medium and long).  Keep in mind that the unit must move laterally, and maintain chain tension.  The parallelogram provides the sideways shifting between sprockets, but it is the cage length that maintains tension.  To find the right one, there is a number hidden in the technical document.  I've copied it here.

Total Capacity.  it does not say what it is, only quotes specification.  Could it be important? Is Hokey-Pokey ice-cream important?
We know that cassettes range from straight blocks through to monster touring gears, and the front cranks can be standard, compact or triple, with a range of biggest-smallest tooth combinations.  To calculate your rig's Total Capacity, you add the rear cassette range to the chainring range.  In my case, that becomes:
(28-11)+(53-39) = 17 + 14 = 31.


This number essentially reflects the most extreme gear combinations - biggest rear and big front, and smallest rear and smallest front.  The derailleur has to swing forward as lower gears are selected at the rear, otherwise the chain tension would be too great.  Looking at the specs my combination is not too extreme, and I could get away with a short-cage unit, but there is only a 2-tooth margin of error.  Selecting the GS cage will reduce the overall tension on the transmission.

Having already done the hard yards researching the comparison between 6700 and Force, I just need to check the overall deal including postage.  The best deal was a 6700 GS unit from http://www.wiggle.co.uk/


The upfront purchase cost to me was NZ$104.98.  And postage?  At checkout, I was told that I was NZ$0.02 under the limit for free postage.  Two cents to save $15.  If I let it stand then the next best deal is NZ$108.00 at http://www.ribblecycles.co.uk/, including NZ$13.80 postage.  So, I spent the $4 difference to buy a repair kit, earning me free postage.


The irony is that the derailleur and the repair kit were posted separately...


This choice has committed me to Shimano shifters, and these suckers can be worth more than the frame.  but before them, I need to find a front derailleur.