The Postmaster Part 4: Cranks and Racks

So now with my front rack painted I now have to make the webbing to go with it, I ordered some 3mm thick 1" bridle leather to make it from.

The plan is to arrange the leather strap in a grid of approximately 7cm and sew all the joints together.  The intent is to use this with my elasticated cargo net to carry bags and other luggage on the front rack.

Now onto the cranks, I was quite worried that the bottom bracket threading was going to be the oddball Raleigh 26tpi size, from the outside it measured at the standard 68mm which was a good sign; the Raleigh bottom bracket is typically 70-72mm wide.  After being able to thread the cups that came with the bike into another English threaded bottom bracket I breathed a sigh of relief.  The bottom bracket availability for the Raleigh 26tpi threading is next to zero other than used or new old stock parts, even then the lengths available are very limited.

To setup the chainline, I would have to measure what the original setup was.  The Raleigh cranks that came with the bike were in fantastic condition, no pitting on the chrome and they have a super low 127mm Q-factor with a 44mm chainline.  As a comparison, the Campagnolo Athena carbon crankset I have comes in a 145mm which is considered relatively low for modern cranks.  The super low Q-factor is probably one of the few positives of cottered cranks.

As nice as the Raleigh cranks were, I wanted something a little bit fancier so I ended up bidding on a pair of vintage French Solida cranks which have the traditional 5-pin 50.4 BCD pattern, same as my Nervar cranks that I put on Mr Ramen.  This allows me to have a lot of flexibility with chainrings, as well as looking great with a nice fluting detail and in inlaid Solida logo.  They are in mostly good condition, however there is some pitting on the backside.  I was worried however that being French they would be French threaded pedals and that I would have to get them rethreaded to English, luckily they were English threaded, also they fit the English 9.5mm cotter pins as well.  Typically continental European cottered cranks use a 9mm cotter pin instead.

As for bottom brackets, the original TDC one that came with the bike was quite badly pitted and needed to be replaced.  As this is a commuting bike which I want to maintain as little as possible I would prefer a cartridge bottom bracket.   I considered swapping to a modern square taper setup which has endless options and possibilities, however I love the look of skinny cottered steel cranks and I wanted to keep it in the vintage theme.  Luckily I was able to find a cartridge bottom bracket for cottered cranks, however only in a 135mm spindle size which is 5mm wider than the 130mm spindle that came with the bike.  I would have to just suck it and see, if the cranks I chose would have an acceptable fit in terms of chainline and Q-factor.

If this is over the head of some, I can explain it simply.  Q-factor is the width of the outside faces of pedal holes when installed, a lot of people prefer a narrower Q-factor rather than a super wide one, however this varies from person to person.  Chainline is the horizontal offset of the chain from the centreline of the bike frame, ideally the chain should run in a straight line from the chainring to the sprocket at the back, a large difference between the two means the chain is running at an angle and thus this increases wear and noise.  This is less of a factor on a derailleur bike which has a chain designed to be working at angles, however it is more of an issue when using a single speed/fixed gear chain.

 Fitting the original Raleigh cranks on this bottom bracket gave a 48mm chainline (compared to the original 42-44mm ) which is a touch wide, the Sturmey Archer hub on the rear allows you to adjust the chainline out to 46.5mm which would give a 1.5mm difference, doable but not an ideal setup.  As for the Solida cranks they came out at a still narrow by modern standards 133.5mm and a good 44mm chainline which is about perfect.  This is good, as my only other option for a narrower bottom bracket is to go back to a loose ball setup which requires a lot more maintenance.  That means having to hammer in and out cotter pins each time I need to lubricate or adjust the bottom bracket.

Just a tad heavier than your typical alloy/carbon fibre cranks you find on most bikes today. Although only slightly heavier than the Raleigh cranks.  Compare this with the Campagnolo Athena carbon cranks I have on Phil which come in at 750g including the bottom bracket...

You can see in this picture that the Solida cranks are forged in one piece by looking at the joint where the spider is, this gives the best strength and durability.  However this is a more expensive process as it requires two forging dies, one for the left and a different one for the right.

Compared to the original Raleigh cranks which are of a swaged design which you can see by the pressed bit at the centre of the chainring, the crank arm itself appears to be forged, probably from a single die for both sides to save cost.  The right hand crank is then attached to the chainring by swaging, basically this means the chainring and arm are pressed together.  This is a weaker joint and if it fails it means the chainring will freewheel on the crankarm, not good!

I polished the Solida cranks up and added some red detailing to set off the blue colour of the frame.  All done and ready to go on.  Thanks for reading


  1. Dammit. I really wish I didn't have to rely on Google+ to follow your blog. The retro-grouch in me prefers RSS feeds.