I was out for a ride with my friend Bernard last week. We were about an hour in, on a hot afternoon, when he pulled over, took out an Allen key and dropped his saddle by a few millimetres.Its a hot day, he said, as if that amounted to an explanation.I probed deeper.I like to put my saddle down a little on a hot day. It feels right, he said.If Im honest, Id been hoping for some bucket-of-blue-steam nonsense about the bike having expanded in the heat, something I could possibly mock in print. But if he wants to do it because it feels right, well, who am I to argue?Bernard has strong opinions on the whole world of bike-fit and bike-fitting. Bike fit, he likes to declare, is a myth. He especially likes saying it to riders whove had a professional bike fit.And its true that in Bernards bike-riding youth, and even in mine just about, bike fit didnt really exist as a specialism. Although if you went to a bespoke frame builder (the common premium option until carbon fibre took over), the frame builder would usually have some sort of home-brew system for working out frame geometry from body dimensions. (Luckily, the systems were adaptable enough that if your bike came out of the building-jig looking totally different, as it usually did, that would be just fine too.)He still prefers to ignore all that. If it looks right, it is right, has always been his guiding principle. This means that you take whats more or less average among people you want to be like, and authoritatively declare it to be correct. It only recently struck me that this is exactly how ChatGPT works.When pressed for more details about what looks right, it turns out he has a whole range of rules-of-thumb. There is a formula for saddle height above the bottom bracket axle, which is 0.833 multiplied by your inside leg. Your bars are in the right place when, if you bend your elbows a bit, not as much as if youre driving a breakaway, more as if youre trying to make your reflection in a shop window look a bit less embarrassing, the top of the bars obscures your view of the front hub.Your saddle should be level unless youre a triathlete, time triallist or some other sort of weirdo, and the tip of the saddle should be, 60-65 mm behind the bottom bracket, unless youre a triathlete, time triallist, or some other sort of weirdo. Your cranks will be, 170 mm, unless youre a Gen-Z fashion victim, in which case theyll be 155 mm until you bloody grow up a bit.Thats bike-fit by Bernard. The thing is, I reckon his system is not a million miles out. If you used it, it would do. It helps that humans are adaptable. A few millimetres one way or another doesnt make much difference to most of us we can accommodate it.There are some things Bernards system misses. You could work out your preferred saddle by trial and error, but the errors these days are getting towards 200 a go, so its useful to find a shortcut. And many people really benefit from detailed fitting around cleat positions and angles, and insoles to prevent knee issues.And hes right that you should never be afraid to tinker. You can always change it back. Eddy Merckx used to not infrequently stop mid-race and change his saddle height he always carried a little spanner just in case. It amuses me that in this respect, if in absolutely no other, my friend Bernard resembles the greatest rider of all time.Although Merckx probably never looked at his reflection in a shop window and felt embarrassed.