Actually on Monday this week, how novel.

An often neglected area on the bike is the transmission – Pedals, Bottom Bracket, Chain and Rear Derailleur – the parts that transmit the massive watts you’re pumping into the pedals to the rear wheel and thus to the road.

There are gains to be had here too and not necessarily expensive ones either.


I shan’t dwell on pedals as they’re primarily a fit component – choosing pedals for low bearing resistance MM Pedalrather than compatibility with your position doesn’t make sense. However – it is worth paying attention to whether your pedals are spinning freely – if they’ve started grinding or become sluggish (don’t assess this on a cold morning when the grease inside has congealed) you will be losing a small amount of power on every pedal stroke. Unfortunately it is impractical to replace the bearings on some of the popular brands so you may be up for new pedals if a simple clean and regrease doesn’t sort things out.

Of course, if you use NZ made Keywin pedals everything can be replaced 🙂

Bottom Bracket

BBs have, in general, been getting steadily slower since traditional style square taper or Octalink systems were abandoned. MM BBFortunately it’s fairly easy to reclaim that squandered Watt by choosing a low friction system. Bike component testing site Friction Facts has some very useful data on this topic.

Additionally it’s important to make sure your cranks are installed correctly – it is quite easy to over-tighten an external BB system and that side load increases bearing friction and decreases longevity.


Clean is good, dirty is bad

Keep that in mind and you’re halfway there on the chain optimisation front. A very slightly dirty chain – to the point that it has MM Chainlost 1% in transmission effectiveness will lose you 30s over a half Ironman 90km. Dirtier is worse (losses can be in the order of several %). There are not massive differences between lubricants (though PTFE based is usually lowest friction) – the important thing is that you clean the chain well and apply your lube of choice.

Once again Friction Facts is a source of all sorts of interesting data on chain wear and optimisation. My general advice is to turn up to your ‘A’ race on a lightly used, clean and lubed chain (obviously with a cassette of matched wear so you don’t get skipping).

Rear Derailleur

The only parts of the rear derailleur that make a real difference to performance are the bearings in the pulley wheels. MM PulleyTitanium bolts, carbon parallelograms and cages save a little weight but that pales into insignificance compared to potential losses of 0.5-1w with the wrong bearings. If you purchase the report from Friction Facts you will see why I stock Hawk Racing products and always upgrade Campagnolo, Shimano 105 & Ultegra bearings (if you don’t wish to purchase the report rest assured that I have used the data in choosing what to stock). This can be addressed for as little as $30 which is why it’s high on my speed/$ marginal gains list.

If we’re to be truly picky there is also a small gain to be had from fitting special cages that allow a larger lower pulley – Friction Facts have tested this too. Note that the Berner cage they mention starts at 269 euro so it’s a fairly pricey 1.76w gain.


Each of these areas may only offer the opportunity to save quite small amounts, but in total it can be a couple of watts that you are sacrificing on every pedal stroke. Even if you’re purchasing a Halo bike (as in top of the line, not themed for a Microsoft game) it is not a safe assumption that the bearings will be of the highest quality. As mentioned above I typically upgrade the rear Derailleur bearings on any bike I sell that is not SRAM or Dura Ace equipped as it is low hanging fruit.

And simple measures like keeping your chain clean and lubed are good practice just in terms of looking after your kit, let alone speed optimisation.

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