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I'm wondering if pedal washers are necessary, or even recommended, when riding with a carbon crank, in order to avoid damage to one's crank arms?

The main reason I ask is because I prefer to ride with the smallest possible Q-Factor, and having any type of washer in place increases this insofar as ones feet will be positioned farther apart.

The Q Factor of a bicycle is the distance between the pedal attachment points on the crank arms, when measured parallel to the bottom bracket axle. It may also be referred to as the "tread" of the crankset. The term was coined by Grant Petersen during his time at Bridgestone Bicycles.

Can I safely ride my carbon crank, sans pedal washers, without worrying about long term damage to the crank arms?

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  • Some pedal systems will also allow you to narrow your stance much more than the 1-2mm associated with washers, that the washers are immaterial (i.e., with washers you can still narrow your pedaling stance such that your feet rub the crank.)
    – Rider_X
    Nov 6 '15 at 21:31
  • I've never used washers between cranks and pedals. You want as many threads engaged as possible, and washers will reduce the engagement.
    – Criggie
    Nov 6 '15 at 22:21
  • @Rider_X which pedal systems specifically?
    – ebrohman
    Nov 7 '15 at 0:19
  • Whoever down-voted this question, explain yourself.
    – ebrohman
    Nov 7 '15 at 0:22
  • @ebrohman - Speedplay sells axels of different lengths to allow you to change the stance by a fair amount. Shimano SPD-SL cleats have a fair bit of lateral adjustments (i.e., you can move the shoes inbound enough to tough the cranks).
    – Rider_X
    Nov 7 '15 at 0:25
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If the instructions that come with the pedals tell you to use the washers with carbon cranks then you should do it. The reason for the washers is that that they keep the axle from rubbing against the crank and thus damaging the carbon when tightening the pedals.Oh yes, and you can compensate the thickness of the washers by moving each cleat 0.5mm outside.

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    Moving your cleats to compensate for having washers, is, IMO, a very bad idea. That affects where your feet bones are pushing on the pedals, and your entire body mechanics on the bike for that matter, and if you are already fitted, this could completely destroy your fit and could lead to serious knee problems.
    – ebrohman
    Nov 26 '16 at 14:56
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If the crank arms in question are like my Campagnolo arms, then there will be no pedal or washer contact with the carbon. The carbon arm will have a threaded steel insert onto which the pedal will screw. The pedal flange and washer diam. are no wider than the threaded insert, which is held with Loctite.

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