The Build Part III: How long is a bike chain?

Following on from the first two parts of the build project, in this part I finally connect up the cranks to the sprockets and get the derailleurs adjusted.  With combined 'brifters' it makes sense to cable up and adjust the brakes too, just in case the temptation to get on and pedal is too much!

Before the chain can be installed, it needs to be cut to the correct length.  For my build I'm using Campagnolo's Centaur groupset and hence the 10-speed, ultra-narrow Centaur chain.  Prior to the installation I did a bit of research on chain sizing.  Remarkably all bicycle chains come in the same pitch (the distance from one roller to the next) and this is set at 1/2" (half-inch).  Given the bewildering variation in almost every other aspect of the drivetrain, resulting in incompatibility between components from different suppliers, I'm surprised that chain-pitch has remained so constant.  Anyway, this means my 114 link Centaur chain is 57 inches long.

Replacing an existing chain is easy, you just count the links and make the new one the same size.  You have to be careful not to just measure the length because a worn out chain will have stretched a bit and you might end up with an extra inch or two on the new chain.  But with a new build you need a different method.

Chain Length Sizing - Park Tool

Given that I recently bought a Park Master Chain Tool (more below) I thought I'd start at Park's excellent pages aimed at the DIY mechanic.  They outline two methods of sizing the chain for a new build.  The first involves measuring the chain against the two largest cogs without threading it through the rear derailleur and then adding one inch (two links) to compensate.  Their second method is similar but uses a calculator instead, in other words, you put the size (in teeth) of the largest chainring and sprocket into an equation along with the distance from bottom bracket to rear axle.

From the formula they give I put in the distance to the rear axle (16 1/8 inches), my 50T chainring and 25T sprocket and, finally, the additional 1 inch to compensate for the derailleur.  The result is a 52 inch chain.

Chain Length - Sheldon Brown

Sheldon Brown deals with chain length in a longer article on derailleur adjustment.  He uses the same method, in essence, resulting in a chain 1 inch longer than the minimum required to run the large/large combination of chainring and sprocket.  He does hint at a possible reason for this algorithm being the accepted norm: a chain that is too short will cause damage whereas a chain that is too long will only affect gears that you shouldn't be using anyway.

(StackExchange: Setting Chain Length)

The accepted answer on StackExchange simply cites Sheldon Brown, but at the time of writing there is a comment from one of the moderators to the effect that you should allow 2 links (in this case meaning 2 inches I assume from the context) for Shimano.

WikiBooks: Read Derailleur Adjustment

While researching this topic I found another new source of information I didn't know about, there is a wiki book on Bicycles with a detailed section on Maintenance and Repair.  Again, the conventional wisdom is big/big + 1 inch.

Campagnolo Method (pdf)

With all this general advice to be around the large/large method I was surprised when I unpacked my Centaur 10-speed chain and found a completely different method of chain length sizing.  Whereas most people advocate a method which results in the shortest possible chain that can work (on the large/large combination) the Campy method is a small/small based method which results in the longest possible chain than can work without rubbing the derailleur.

The basic idea is to draw the chain tight enough to ensure a small gap at the point where the chain is at its closest approach.  This is the part of the chain feeding in to the lower jockey wheel.  When the derailleur is retracted to take up the slack the lower jockey wheel bends back and upwards reducing the gap to the part of the chain going around the upper jockey wheel to a minimum.  The instructions suggest setting this gap at a maximum of 10-15mm.

To make it easier to follow this method I cut a small piece of card diagonally, 15mm at one end and 10mm at the other:

The result of using this method was that I needed to remove 3 inches (6 links) from the chain.  That makes it a 108 link/54 inch chain, two inches longer than the chain predicted by the equation above.  I think there are several reasons for this difference.  Firstly, I could have stuck with the 34T chain ring that came with the crankset and that might have meant knocking out one more pair of links (taking me down to 53 inches) - which is within an inch of the length predicted by the equation.  And anyway, perhaps these new Centaur 10-speed derailleurs require 2 extra inches, rather than the 1 inch given in the formula.

   

In all of my internet searches (on a range of topics) I quite often got results from the blogger "Sprinter Della Casa" and he is the only one I found who seems to espouse the method of using the longer chain method.  I'm not sure about the rationale but I enjoyed the article: How To - Campy Chain Install, Illustrated.

The Mystery of the Missing Bearing

Installing these new chains always makes me a bit nervous.  Each time the technology is updated the tools become more specialised and the margin for error is reduced.  The Campy tool shown in the illustrated How-To above is obviously the right tool for the job but Park do make a more general purpose tool that might be more useful when working on other bikes too.  Not to mention being cheaper.

Park clearly have a good reputation and other tools I have from them have been flawless but this time they let me down, at least initially.  I had just started breaking the chain to remove the extra 3 inches when I heard an alarming and very audible popping sound.  I examined the tool and the chain and I couldn't see any signs of damage or anything that could have made the noise so I continued pushing the pin through until the handle on the chain tool would go no further.  At this point it was clear something was wrong because the roller had not been pushed all the way out of the link.

The design of the tool is for the pin to sit on a small bearing in the barrel of the tool.  The pin and bearing are held in place with a retaining nut so that they can be changed should the pin become worn or break.

So I unscrewed the retaining nut intending to take the pin out for a closer look.  The pin was stuck fast in the body of the tool.  Now I figured that if the pin didn't protrude from the tool far enough to drive the roller out of the chain then the bearing that should be in there is missing.  Sure enough, it came up short by what would have been the width of the bearing.  I returned the tool for a warranty replacement and got a replacement from the supplier pretty quickly.

This time I checked that the pin and bearing were present.  They were, and I noticed just how snuggly the pin sits in the tool, as you load the pin and bearing into the barrel you can feel the air trapped in the barrel pushing back against the pin.  You have to push it slowly in, giving time for the air to escape around the pin.  My theory is that the bearing was missing originally and that the final part of the barrel is an even tighter fit - as I turned the handle the pressure built up in the barrel until the air popped out, allowing the pin to jam itself in the barrel for good.

  

The Build Part II: Ergo Brifters: under the hood

In The Build Part I, I covered my experiences with installing the Power Torque Campagnolo cranks.  Attaching the other bits of the Centaur groupset to the bike looks pretty straightforward in comparison.

The Saetta frame comes with a 'braze-on' clamp for fixing the front derailleur and the hanger for the rear derailleur was already attached.  The frame was actually shipped with a spare hanger - useful if you come off on a right-hand bend and squash the derailleur in towards the back wheel.  In the past I've had to do this as a running repair but with the precise alignment required for the 10 speed system it looks like the accuracy needs to be more than just by eye.  So that spare hanger may come in handy - in the UK we have a lot of roundabouts and we go around them clockwise which must increase the risk of this sort of accident.

The hardest part of fixing the rear derailleur was tightening the fixing bolt to the correct torque.  The bolt head is recessed in a narrow channel that will not allow me to put the hex socket in so I had to do it by feel with a regular Allen Key.

The Centaur brakes appear identical in the box and it is hard to see, on first look, which is the front and which is the back.  The difference is so obvious to the experienced bike mechanic that it seems not to warrant a mention in the instructions.  I'm glad to see I'm not the only one who felt the need to consult the internet to make sure, as evidenced by this bike forum post.  The answer is of course that the front brake has a longer bolt to allow it to pass through the fork.  Given that fork widths vary, and carbon forks tend to be a bit fat at this point, you may need to get a longer nut to make contact with the brake bolt.  Both Campagnolo and Cinelli thought of this and I had multiple sizes shipped with the brakes and the correct size bolt shipped with the frameset - another item for the spares box but all good.

If I thought the rest of the job would go really quickly I was wrong.  The next step is to put the Ergo levers on the bars and connect them up to the derailleurs (you need to do this before you put the chain on because you are going to need to operate the derailleurs as part of the chain installation procedure - more on that next time).  It is always nice to learn a new word (especially one that dictionary.com doesn't know about yet) and I soon discovered that a 'brifter', far from being the long lost relative of the old Raleigh Grifter, was in fact a common synonym on the internet for 'lever' in this context; being a simple contraction of brake/shifter.

The instruction leaflet that comes with the Campagnolo brifters merely says "Raise the support cover to expose the securing screw" and shows a picture which appears to show the base of the rubber hood being peeled back (as it will be when you install the bar tape) far enough to get a clean line of sight into the head of the bolt which turns out to be a T25 torx head and not a plain hex.  I believe this is impossible.  I would not want to attempt this in a cool environment as I felt I needed all the warmth of my house, combined with the warmth of my hands to make the rubber supple enough to peel easily without tearing but try as I might I could not expose the bolt as shown in the diagram.

I'm not the only one, there are numerous threads in bike discussion forums where people are having trouble with this point.  My favourite is this one, which is a little old now but the technology and the lever shapes are basically the same: Campagnolo Ultra-Shift Mounting Bolt (or: stripping is awesome).  This thread makes a couple of important points.

(1) Don't try and get in from the base of the hood, instead, go in from the top of the hood.  I love this report in the above thread from someone who sought official advice: "The man with whom I spoke at Campy, however, advised instead pulling up the hood from the top of the lever and pushing it back toward the base (i.e., entirely opposite from what the instructions say)".

(2) Even with the hood completely clear of the bolt it may be impossible to get a straight line down to the bolt head for a torque wrench and you risk stripping the soft alloy bolt if you apply too much force this way.  Another quote from the above thread: "I wrestled with the hoods and managed to get enough clearance so that I could get the wrench in straight (or as straight as you can given the placement of the bolt on the body), but I still had that trouble".

There is now an excellent article on BikeRadar.com on How to Fit Campagnolo Ergo Levers.  It shows the solution to (1) and has a fabulous photo of the small rubber 'nib' being removed before the hood is peeled back from the top.  Here is my feeble attempt at a similar picture:

The left-hand lever showing a narrow screw driver head inserted through the lever to free the nib

Close up of the screw driver being used to push the rubber nib back into place

The BikeRadar article also clearly shows the extension on the torque wrench allowing the mechanic to get a straight line into the bolt head.  On my levers this was just not possible because the position and angle of the bolt caused the extension to foul the top of the lever.  So I didn't tighten it up this way because I was concerned about stripping the bolt head.  Instead, I went out to the local auto-parts store and bought a set of Torx-keys (assuming that's what you call something that looks like an Allen key but has Torx heads instead of a plain hex).  I was able to get the short end of the T25 wrench into the bolt head nice and squarely and therefore I could tighten up the bolt enough to prevent slippage, albeit by feel again.  It was still a tight fit, as this picture (this time of the right lever!) illustrates:

T25 wrench inserted under the hood to tighten the clamp bolt

The Build Part I: Power-Torque cranks

So to recap, I have bought my Cinelli Saetta frame and fork through my local bike shop, Howes.  The frame-set comes with its own Columbus headset and Cinelli-branded seat clamp.  My local bike shop fitted them all together for me with the Vai Bianca stem.  The next step for me was to protect the frame with pipe insulation (to prevent knocks during the build) and then fit the saddle and seat post.  I have hooks set up which allow me to suspend my bikes by stem and saddle so fitting these allows me to use the hooks as a work stand.

This seems like an excellent opportunity to introduce an emerging source of information on bike maintenance: bicycles.stackexchange.com.  People who work in the IT industry will be familiar with programmers' Q&A site StackOverflow.  There is a brief wikipedia page on the history of this site.  The stack exchange concept takes the success of this original idea and attempts to stamp it out across a wide range of topics.  The stack exchange on the subject of bicycles seems to be well populated with content.  I put this down to common elements between the mentality of the DIY-bike mechanic and the mentality of the programmer.  So if you are attempting to apply experience gained fiddling with computers to the more mechanical realm of fiddling with bicycles this site will probably be speaking your language.

It seems that my ceiling hooks have saved me from the dilemma of working on a carbon bike using a traditional work stand.  To summarise this thread from stackexchange, if in doubt don't do it and whatever you do don't do up the clamp too tightly!

In my last post, Cranky Delays..., I discussed my choice of gears and chain rings.  Installing the cranks seemed like a sensible first step but as I worked on the bike from my eye-level hooks I did realise that there was a better way to work on the cranks when you need to tighten things up - just add wheels!  It seemed much easier and more natural to applying the forces required to install the crank set with the bike on the ground with wheels and tyres fitted.  I guess it does depend how far from the ground you are.

I've installed a few square-tapered bottom-brackets over the years but the new breed of cranksets with their outboard cups and hollow axles are a completely new experience for me.  The instructions that come with the crankset are pretty scary, emphasising the need to face the bottom bracket before installation.  I actually checked back with the frame dealer before proceeding but they reassured me that the shell was ready to take the new cups and my measurement of the shell width came in at 67.87mm which is within the tolerance.

Fresh from my experience with the chainring bolts (which were stuck fast with thread lock) I must admit I was concerned about the amount of thread locking compound on the supplied cups.

I recall a stuck bottom bracket in my Bianchi many years ago, my local bike mechanic had a neat trick for removing it.  He removed the crank, closed the shop, then welded the spindle to the bottom bracket shell.  Once it had cooled, he refitted the crank and used that to unscrew the shell.  A few scorch marks later and I was upgraded into the world of cartridge bearings.  His summary of the situation: somebody was being mean with the grease.

The instructions that come with the crankset don't mention the need to apply a thread locking compound and in a close look at the installation video it appears that the threads are clean too.

One of the problems with information on the internet is that it tends to be strongly biased towards people with problems.  Bike riders with noiseless, trouble free bottom bracket installations are probably not logging on to complain or post to forums about the issues they're having.  Hopefully they are out riding and enjoying their bikes!  A search for the similar but high-end ultra-torque will throw up threads like this one from the RogueMechanic.  There are all sorts of interesting bits of information (and doubtless mis-information) in this post and its associated comments.  Anyway, for comparison here are the two videos of the Ultra-Torque installation:

Notice that the first 5 minutes of this video show the preparation of the shell, which emphasises the importance of this step.  It is interesting that they left this out of the Power-Torque video.  If you aren't content with doing something the correct way you can always follow the inferior (incorrect?) procedure instead, also documented in an official video!  This one uses copious quantities of Loctite 222, a liquid thread locking compound.

Given that thread-locking compound is basically glue, and that my experience has been skewed towards things getting stuck fast rather than shaking loose in this department, I scraped some of the thread lock out (it would be impossible to get it all out without a suitable solvent I think), applied some grease and tightened the cups up to the recommended torque.

Unlike the bike in the first video, which appears to have right-hand threads on both sides of the shell, my bottom bracket is BSA or 'English' threaded so you have to do up the drive side anti-clockwise.  There is a good article on Wikipedia about bottom brackets in general, including the various sizes.  When ordering the Power-Torque cups you do need to know which you have.  The reason that the drive side has a left-hand thread is to reduce the tendency of precession to undo the cups - the fact that it goes backwards may seem unintuitive but the linked article has a cute animation which demonstrates the effect so that you don't have to do the maths yourself.

If you are convinced that precession is your enemy here then the risk of loosening must be greatest on the drive-side of an italian threaded bottom bracket.  I expect I'll take the drive train apart for servicing at some point and I'll report back on the torque required to undo them - if I have a suitable torque wrench, which brings me to a bit of a gripe...

To help me get the torques right on this part of the project I bought a new torque wrench, on special offer, for a surprisingly cheap price.  I have a small wrench that goes up to 25Nm but this is not enough for the cups, the crank fixing bolt or the pedals.  The wrench I bought was a draper 1/2" drive ratchet type wrench.  I bought it from a fabulous local hardware shop called Mackays - this shop is famous in Cambridge for having the type of expert staff who can find replacements for pretty much any type of weird fixing you throw you at them.  Anyway, the wrench has a reversible ratchet and a scale marked from 30Nm up to a blood-vessel bursting 210Nm.

Armed with my new torque wrench I set about the cups, with the aid of the special purpose Campagnolo tool (I had expected this tool to fit more snuggly on the cups).  I started on the left (non-drive) side of the bike and tightened the cup without any problems.  I then flipped the ratchet and started tightening the drive side.  As I was just learning to use this tool I set the torque to the lowest setting each time (30Nm) to help get the feel of the thing before tightening to the recommended torque.  This was a good thing, because as I tightened the drive side I quickly realised that I was having to put in more effort than expected to get the wrench to break away.  It was only later I noticed the small print on the leaflet that came with the wrench: "IMPORTANT: The torque wrenches detailed in this instruction leaflet are for right hand torquing only.  They are not designed for left hand use."  I finished tightening the drive-side cup by flipping back and forth with the ratchet until I could no longer undo the cup using the specified torque.

So my gripe is why advertise these wrenches as having reversible ratchet heads?  Obvious you might say, it allows you to undo things, just like the guy in the Campagnolo video who clearly uses a similar torque wrench to undo the cups.  But this doesn't explain it, the warnings section of the leaflet kicks off straight away with "Never use the torque wrench to undo bolts, nuts or fasteners, as this will damage the ratchet and the calibrated setting".  I reckon that, at this price, they know that the tool will not be worth calibrating and that it will turn in to a fancy breaker bar after a year or two of use.