In order to get into those hard-to-reach slots on hub axle cones you are going to need a good set of cone wrenches. ... Most professional bicycle mechanics will have two of each size cone wrench and in some cases they will actually grind the width of one wrench down to allow it to fit into tighter spaces.

What do you use cone spanners for?

A cone wrench or cone spanner is a tool used in bicycle assembly and maintenance to adjust the cones of cup and cone bearings. Cone wrenches are thinner and lighter than most other open ended wrenches that are used to work on bicycles.

What size wrench do I need for a bike?

It's made up of 4-, 5- and 6mm hex wrenches (the sizes needed for most bike repairs), and the convenient shape provides ample leverage on most bicycle fasteners.