ASK: Square taper or Outboard?

I just noticed that you have changed your chainset to a Shimano SLX with Hollowtech II. I am in the process of building my own version of the Troll, and would appreciate your review in comparison to a square taper build. Is the Hollowtech II bottom bracket reliable? Does it require much maintainance? Did the troll frame need facing to install it? Christian

Previously, I’ve always stuck with square taper and I’m still a fan, especially if you can get your hands on Shimano’s UN72. SKF also do some very nice, reliable square taper bottom brackets too.

The only issue I did find, though, is that ironically sourcing square taper bottom brackets isn’t as easy as it used to be – finding the right size (73mm for the Troll/Ogre) and width – dependant on your cranks – can be problematic. Most places I went to in the back of beyond had 68mm shell bottom brackets, or spindles that were too narrow.

So when I was back in the UK, I moved over to an outboard bearing crankset. I had a spare SLX around, so figured I’d give it a go as an experiment, seeing as I need to fit a new bottom bracket anyway. The wider Q factor has never bothered me, though I guess in theory the bearings – though larger – are more exposed, so prone to more wear.

I don’t expect outboard bearings to last as long but every good bike shop I’ve been to in Latin America’s larger cities stocks them – Shimano ones, at least. They’re easy to fit, and light to carry if you want to pack a spare. And they’re cross-compatible, as it’s simply a case of adjusting the spacers to fit the cranks you have.

If you’re feeling flush, the bearings from Phil Woods can be removed and changed from the cups without a tool, which is a neat feature for touring. They should last a lot longer too.

And yes, I needed to get the Troll faced, which is a quick job.

In theory, outboard bearing bottom brackets are stiffer but more prone to wear. The good news is that they're easy to find and fit.

In theory, outboard bearing bottom brackets are stiffer but more prone to wear. The good news is that they’re adaptable, easy to find and simple to fit.

4 thoughts on “ASK: Square taper or Outboard?

  1. Jack Luke

    I’ve got to say I personally have no problems using outboard bearings for touring, but I really have to recommend you go with something a little posher than the cheapest of the cheap. The reason being that Shimano’s low end offers aren’t sealed on both side of the bearings and really do die very quickly!

    1. Cass Gilbert Post author

      Thanks for your input. The SLX BB lasted ok, but I’ve now upgraded to some fancy Phil Woods. Buttery smooth!

  2. Tom

    The outbound bearings that came with the XT cranks on my Big Dummy lasted from Banff to Mendoza and could have been put up with until Punta Arenas (had some play – Several km of 5cm deep concentrated salt solution on the Salar de Uyuni accelerated the rot somewhat!)

    PS – could you change the title of the link to to bicyclenomad, rather than Banff to the Bottom?

    PPS – now have a chariot CX1 to use once Sprog makes an appearance 🙂 Thanks for your help!

    Tom y Sarah

    1. Cass Gilbert Post author

      I’ve found outboard bearings a bit hit and miss. The Truvativ ones I had in the Ogre (which don’t have a great reputation) lasted a good long time – maybe more than the SLX ones. I’m hoping the Phil set should really go the distance.

      The CX is doing great here in NM. It’s finally warming up, so camping trip is impending…


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