What's the cone spanner size for cone nut on Shimano WH-R550 Front wheel ? Is it 17mm or 18mm ? I tried with 16, it seems, need more, 1 or 2mm bigger.


  • "I tried with 16, it seems, need more, 1 or 2mm bigger." You answered your own question.
    – cmannett85
    Commented Feb 15, 2012 at 10:57
  • 1
    My experience has been that it's generally a step smaller than the lock nut. Commented Feb 15, 2012 at 11:59
  • I have an idea, clamp 2 tire opener with variable spanner, hopefully my tire opener is thin enouh ( alumunium one)
    – Rick Ant
    Commented Feb 16, 2012 at 6:17
  • 1
    Consider picking up some calipers. They're a lifesaver for measurement questions on bike and around the home. Cheap plastic verniers can be had for under $5 and are accurate to the millimetre. Cheap digital calipers can be $20-$50 and good to 0.1mm when used properly. Or get a tool-for-life and buy dial calipers.
    – Criggie
    Commented Jan 24 at 8:55

2 Answers 2


17mm/15mm is usual for Shimano cones.


EDIT: I took a late look at some pictures of the wheel you mentioned (Shimano WH-R550). It looks quite different from the regular MTB Shimano hubs, so please consider the following answer as applying to regular mountain-bike Shimano hubs.

From my experience with Shimano hubs, there are two parts:

  1. The locknut, which face outwards and make contact with the fork/frame, is usually 17mm. Since you need to tighten it with the other side fixed, you can use a 17mm wrench at one side and a 18mm wrench at the other if you don't want to have two (big/expensive) 17mm wrenches.
  2. Cones are just inside the locknuts and might be 13mm or 14mm, or possibly even different from those. Usually you need a dedicated cone wrench since normal wrenches are too thick to fit in the narrow fitting in the cone.

Some Shimano models have a double-size cone, to allow use of two wrenches of different sizes, so it helps folks who have only one size of cone wrench (Shimano is rarely so considerate).

I waited (and suffered) too much before buying my cone wrenches. If I knew how much a difference they make, I'd have bought them at the same time I bought the bike!

  • locknut is equal to 18mm, cone nut can be 17mm, i bought one for 17mm and 18mm cone wrench, since 16mm doesn't fit and I can not use variable wrench i have, too thick, i wish i have a thin plier (2mm alligator) it will work....for holding when i loosen or tighten the lock nut..
    – Rick Ant
    Commented Feb 16, 2012 at 2:34

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