Brompton crankset variations
 

I've noticed stock Bromptons with two different types of drive side cranks: spiderless crank with cheapy looking chainring and integrated chainguard; crankset with 5-arm spider (w/ hidden arm) 130 bcd replaceable chainring and integrated chainguard.

Was there a change to the 130 bcd crank recently and only old builds have the cheapy looking spiderless crank?

Brompton went to the "spider" crank in model year 2013. The change was not on some early 2013s due to parts availability issues. Most Bromptons can be upgraded to the spider crank with the replaceable chainring.

-HANK RYAN-
Norman, Oklahoma USA

Thanks, Hank!

The cheapy cranks are lighter than the ones with replaceable chain rings. They have two disadvantages...when the teeth are worn they must be thrown away and you are stuck with only one size choice. I have used both on my Brompton, though, and the cheapy one is my current choice, partially to offset the weight of the IGH hub and my leather saddle. In over 5000 miles I have not succeeded in either wearing it out or breaking it, although I am fairly light and don't stand up and mash the gears a lot.

the original Stronglight supplied cranks were their standard component for many years.. 3 sizes , 44, 50, 54t.

people bolted on smaller chainrings to the outside with some of the extra holes, for climbing gears,
only to find the swaged on arm spun separately from the chainring..

any 3 piece crank can do , the chainline is rather close in. to dictate what spindle length be used with your choice of cranks..

...even fit a double chainring set..




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My 2013 has the spider cranks; pretty sure it's lighter than the old style. Dura Ace ring and protector removed. :)
I think the bottom bracket is different for each style as well.

The spider crank is machined to only take one chainring on the back side.. as shown..

The current spider crank set utilises a JIS square taper BB. You can replace the stock Brompton JIS BB with Shimano UN55 in 118 or 122,5.

The earlier spiderless crank set utilised an ISO square taper BB.

I have also fitted various Shimano (XT M785, Octalink Ultegra & DuraAce) and FSA (SLK MegaExo & ISIS) cranksets without issue.