Cranksets (and Bottom Bracket sets).

Over recent decades innovation has resulted in changes to bicycle cranksets and bottom brackets. However most of the new ideas and products don't represent improvements for long distance touring bikes.VWRs are using a Japanese Sugin crankset that has been around since before the advent of "outboard" bottom brackets and "compact" gearing.

In the search by bicycle parts companies for an edge in competition by making bikes lighter, the solid bottom bracket axle was a target. If it could be hollow then it could be lighter. But in order to be hollow it had to be larger in diameter.

The development of outboard bearing systems was the key to being able to use a thin walled and lightweight bit of tubing as the bottom bracket axle. In this setup, the bearings are outside the frame.   

Touring bike folks are fine with this except for two problems.

First, is that the bearing system itself in outboard bottom brackets is problematic. The bearings are small so have the problems of small bearings that are under significant load. Also, they are not supported on their sides properly. It is common for these bottom brackets to last less than 5,000km, even less than 3,000km.

Second, outboard BB systems need special tools that tend to be unique to each brand and not widely available in many countries. Outboard bearings are sealed in the assembly that screws into the BB shell of the frame. So everytime the bearings flog out, the cups have to be removed from the frame. Because they experience greater loads than any other bearing on a bike, they are screwed in very tightly by a long tool. 

Parts companies try to integrate everything so one item depends on specific other components from the same company. Bike designers get dragged along to an extent. Here it was not the cranks or chainwheels that were the problem. It was the bottom brackets.We were early adopters of the outboard system but we discovered their problems. We needed a better bottom bracket. So we asked bike shop mechanics if there were any non-outboard BBs that stood out.

Mechanics unanimously suggested Shimano UN-55 (or 54 as it used to be called). It is a square taper cartridge bottom bracket. The cranks slide onto a square axle end that has a very slight taper. A bolt, into the end of the solid axle, firmly attaches the crank to the axle.

It is the same connection between cranks and BB axle that was universal since the demise of cotter pins over 50 years ago. And the crank removal tool (puller) for this system is available around the world. There are lots of places where it is uncommon. But it is findable.

Shimano UN-55 cartridge bottom bracket set

The BB axle comes in various lengths. In 2012 and 2013 we used 113mm with a 3mm spacer under the right side cup. From 2014 we are using 118mm with no spacer.

Return to Sugino.

To the major parts companies, longevity is not generally considered to be a necessary element of design. Performance and weight trump longevity. They will sell us another one when this one wears out. So it was interesting for us to return to Sugino cranks which we had used in the early 1980s. We reaffirmed that this older design suited to square taper BB axles is the best for touring bikes.

The direction of crank and BB innovation has recently moved even further away from what we'd like. As we discussed in the page about 9 speed gear systems, the inexorable trend to have more cogs in rear cassettes has arrived at "10 speed", and now "11 speed". It was the new 10 speed cassettes that lead to "compact" gearing. These setups have 2 front cogs on a smaller bolt circle diameter (50/34T on 110 bolt circle diameter (BCD)) running to 10 sprockets at the back. These were claimed to do away with the need for triples and this was justification for a reduction in the availability of triple cranksets. This has also resulted in reduced availability of left side STI shift levers for triples. 

That is an interesting discussion. It is getting harder to construct a triple chainwheel system on touring bikes. Options in levers and derailleurs are reducing.  Fortunately, we have been able to satisfy our crankset needs with the UN-55 bottom bracket and the Sugino 110/74 BCD touring triple. This offers sizes down to 24T which, with 32T on the rear cassette, is a cliff-climber.

Availability of chainwheels.

10,000km with luggage and riden mostly in the middle chainring, will be starting to wear this middle ring out, unless you have been rotating chains.  You can flip the middle chainwheel around, so it wears from the opposite direction, but this only buys you a few thousand more k’s at the most. Spare 36T rings for 110 BCD are not hard to come by.  They are light and for a very long trip, why not just carry one?

We regret having to talk about things wearing out. If it was the Rohloff system you would not need to worry about that.  

Sugino Alpina2 600 sq.

Crankset to suit the Rohloff.

The required chainwheel sizes are 40, 42 and 44 but 42 has been chosen as the size for production. With no need for multiple chainwheels, this type of set has a larger (130mm) BCD and is forged to be very stiff. As it happens it is right in the heartland of Sugino. 

Sugino Mighty Comp

Summary.

After years of experience and testing our conclusion has been to fit Shimano UN-55 square taper bottom bracket, and Sugino cranks. On derailleur bikes a 110/74 BCD and 48/36/24 or 46/36/24 chainwheel sizes. On Rohloff bikes we use a 130BCD and 42T. We fit 165mm cranks on smaller framed bikes, 170mm on middle sizes, and  175mm on the largest two sizes. 

 

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