Homebay said: "I have no idea what the term "rando specific bike." There is no such animal. It doesn't exist ... As far as I'm concerned, any bike you ride on a randonnee is a rando bike."
One reading of this logic is that there presumably is also no such thing as a racing bike, a touring bike and so on. Presumably, if one rides a Kona Ute in a race, that's a racing bike!
Sorry, but I think that's not very useful way of categorising bikes. I claim to have a rando-specific bike. It was designed specifically for Audax and, yes, it has done PBP. It is designed to be fast, but not as fast as a racer (because over 1200kms you're never trying to ride on the edge). It is designed to be comfortable, because one of the key factors to whether your make it back to Paris is whether your body can survive for 3 plus days. And it is designed to be reliable, to get you home. Thus, its custom Habanero Ti, long wheelbase (inc. 45cm chainstays), slack angles with geometry designed for stability, 36 spoked wheels (Sapium CX-rays on CXP33 rims) shod with 25mm GP4000 tires, a suspension seat post, auxillary brake levers (because one spends plenty of time on the tops in Audax), has a tripple chain ring and a 11-28 on the back (thus minimising those redundant 1 tooth gear ratio differences), has long reach brakes and can accommodate fenders for when rain is forecast, etc etc. Some of this adds to weight over a racer, but Audax is largely constant pace momentum riding, so its a small price to pay to get you home.
Now, you are right that people ride a variety of bikes in Audax events, but that does not mean that there are not rando specific bikes. Of course, some bikes that are marketed as such are really just cheap steel 'light tourers' (fine for those who like that sort of thing), and many serious Audaxers would not consider them to be very good propositions for Audax - especially for longer brevets. But I have also seen one or two "Audax" bikes, or framesets, that seem to have been put together with similar considerations in mind to the ones I mentioned above.
Tom N.
Down Under