Deep in the Weeds: Sugino AT Cranks


Deep in the Weeds is our semi-regular column about bike wrenching, bike bits and getting your ride on. Written by our boy, Ben T. Spokes.

Before jumping into the Gary Fisher dirt drop build I’ve got queued up, I’ve had this cranky crankset issue that needed to be sorted out. The self extracting part of the crank bolt assembly was seized. At some point the crank bolt head got reamed out, and now the spindle and drive side cup is stuck to the crank arm.

These early 1980’s Sugino AT cranks are among my favorites, and well worth trying to save. According to the date code they are from 1981, possibly the first year Sugino date codes were recorded. They appeared on very early Stumpjumpers in that brief period between the TA cranks and the Specialized (flag) branded cranks. They were also fitted to many other high-end mountain, touring and BMX bikes from that era. Sugino struck a great balance of strength, lightness and beauty with this particular model.

Back in the 80’s, I learned a shop technique for solving this type of problem. You simply drill two new deeper holes in the extractor, and with the correct pin spanner, the seized piece should break free.

I’ve successfully used this method many times in the past. Usually, it’ll come out with the first drilling. However, this time around was a bit more involved. Even with the crank secured in the vice and solid purchase and ample leverage from my lengthy custom made pipe spanner, there was still no movement whatsoever. The two new holes gave way immediately.

From the onset I knew this one was gonna be a real bugger. Penetrating oil would just pool around the outside edge of the threads—nothing getting in, nothing coming out. The crank is aluminum and the extractor is steel, so it was obvious that chemical fusing had taken place.

My second attempt involved drilling eight holes spaced evenly around the extractor ring. I was trying to remove a significant amount of material from the unit thereby weakening it. It’s essential to take great care not to run the drill bit into the threads when working in close quarters like these.

As cracks started to form on the inside of the extractor ring oil was now getting in. On the second go with my gorilla warfare pipe spanner the ring of ire finally broke free—and with no damage to the crank threads.

A stuck crank bolt assembly is a harsh reminder why you can almost never use too much grease when building a bike. With a good cleaning and a little metal polish I was able to proceed with my master plan. I installed a set of old red faded Sugino dust caps from about the same era. Also, I filled the engravings on the crank arms with some red paint and then buffed it out to match the overall wear and fade of the caps and crank.

This beast is now ready to kick it again at almost 34 years old.