+1 Steve Hogg's take on arch support, 'tho it takes a bit of digging.
My summary:
- arches collapse slightly during hard efforts, causing ankles to roll inward and effects on up the chain.
- arch support helps offset that, maintaining alignment.
- arch support should be higher than for walking shoes, since the feet don't flex in walking motion in stiff cycling shoes.
- adjust amount to how long you feel it after putting on shoes- should be noticeable for some minutes at least.
- DIY is effective- tape pieces of bar tape or cork gasket material to bottom of insole.
