Triathlon - Shoes - one strap vs. two vs. three

I'm looking at buying some tri shoes so I can try leaving them on the bike in T1. I'm curious though, if one strap works just fine, why do most road shoes (like mine) have three. I'm sure the technical answer is greater adjustability, but does this mean if I buy tri shoes I won't be able to get a fit as nice as my road shoes? Will the tri shoes perform differently?

I've got the tri version of the Rocket 7s, with 2 straps and custom orthotics. They fit better than my Sidi Genius road shoes, and I can grab both straps in one hand, so getting out is a few seconds per shoe.

I think if you're planning to leave them on the pedals you'll really prefer the single strap affairs - and probably the Triathlon-specific sort that have the velcro bits swing outwards rather than inwards. Thus they don't get covered with grease or possibly caught in the chainring when you're pedalling along with them open.

The advantage to having several straps is that you can adjust the tension of the shoe to suit the shape of your foot. Some folk in my club have duct-taped the three straps together once they've got them where they want them - not terribly elegant, but it works apparently (and I suppose would increase the aerodynamics of your shoe if done right).

Also tri shoes tend to have little drain holes while not many road shoes do.