Cranksets (and Bottom Bracket sets).

Many cranksets will satisfy your needs as far as some features are concerned. A selection of crank lengths are needed at 165, 170 and 175mm. Cranksets need to be stiff, and well made. For example it is best if the right side crank and the spider that the chainwheels attach to is a single piece of metal. You want the crankset to be reasonably priced.  Spare rings in a range of sizes need to be available.

However there are a few additional features that you are likely to desire. Wanting ticks in all of these boxes narrows the field down.  

• Triples and doubles.

To get the range needed for touring and even city riding with a load of shopping you are best off with three chainwheels. One very good feature of this setup is that your chain is in a straight line far more than it is on a double chainwheel setup. So called compact doubles are not versatile enough but their recent increased use on road racing bikes makes interesting reading.

• Availability of chainwheels in certain sizes.

Rather like with saddles and tyres, you may find you want a slightly different (size) chainwheel to what is on a new bike. Most cyclists will be suited to what is on our standard production but you should not need to know that in advance. If you find your gears to be a little too high or too low, you ought to be able to access a different ring size rather than needing to buy a whole new crankset.

At this point you are restricted to what will fit your cranks and what is available in the market. This is dependent on BCD or “bolt circle diameter” of the cranks. There is, for a triple crank system, one set of five bolts holding the middle and outer ring and another set attaching the inner ring.  Depending on what that BCD is, each crankset has a minimum possible size for the inner ring and for the middle ring. If a crankset has an outer BCD of 130mm, the most common road crank size, then the middle ring can be no smaller than 38T but is normally only available down to 39T. The 110 BCD size on Sugino and some other cranks allows middle chainwheels down to 34T.

36T or 38T are the best sizes for middle rings for the majority of tourers and are also fine for city use.  

On triple cranks with outer 110 BCD, the inner BCD is 74mm. This theoretically offers sizes down to 24T which, with 32T on the rear cassette, is a cliff-climber. We supply bikes with 26T inners but 24T are available in the market.

For these reasons we have selected 110/74 BCD cranks. We could have used mountain bike cranks which offer low chainwheel sizes. But we wanted to keep the Q-factor (how close together your feet are) low.  Also, we wanted square taper bottom bracket axles – see below).

Sugino Alpina2 600 sq.

• Keeping the Q-factor down.

Measured from the outside face of one crank where the pedal screws in to the outside of the crank on the other side, Q factor determines how far apart your feet are. Some people insist it is better to keep it low. No one says that further apart is better. Q factors of cranksets vary from about 135mm to 180mm with most good double ‘road’ cranks hovering around 140mm and most mountain bike cranks being around 175mm, ie, significantly more.  The Sugino set on World Randonneurs comes in at 159mm, which is impressive for a triple.

It is also able to clear a centre two-legged centre stand like the Pletscher on our Trekking bar bike.

• Availability of chainwheels.

If you ride a bike 10,000km mostly in the middle chainwheel, you may have worn that middle ring out, unless you have been rotating chains.  You can flip it around, so it wears from the opposite direction, but this only buys you a few thousand more k’s at the most. Spare rings for 110 BCD are generally available.  

• Compatibility with square taper bottom brackets.

For decades, on quality bikes, the connection between cranks and bottom bracket axles was via a square taper system.

Then various  proprietary crank-to-axle connections appeared. Behind this was a desire to reduce weight. Longevity was less important. Around that time so called “outboard” bearing systems appeared. The idea behind them was to have fatter, tubular axles with the left and right side bottom bracket bearings further apart. This approach put the bearings outside of the frame's bottom bracket shell.  This reduced the moment represented by the distance along the axle between the bearing and the crank attachment point. In theory it was a great idea and the industry supported it.  But now, with years of experience, it has been noticed that the life expectancy of the top of the range square taper bottom bracket  (Shimano UN-54) is significantly greater than those outboard systems. Durability and longevity are big issues for touring bikes and indeed, for any bikes that get a lot of use.  

If you are on a long tour and have some emergency need to make any change to either bottom bracket or cranks, you need availability of compatible parts and you need to either have any specialist tools in your bags or be able to find them locally.  Square taper systems easily come up best on this score. You will always be able to get service on a square taper BB set. Ironically, with a UN-54 you are very unlikely to need it.

Shimano UN-54 cartridge bottom bracket set

Summary.

Our conclusion in 2012 has been to fit Shimano UN-54 square taper bottom bracket, Sugino triple cranks  with 110/74 BCD and 48/36/26 or 46/36/26 chainwheel sizes. We fit 165mm cranks on smaller framed bikes, 170mm on middle sizes, and  175mm on the largest two sizes.