What do you wish you knew?

That the hardest thing about cycling in bad weather is getting started.

Winter proof has no discernable meaning in cycling.

That by far the biggest factor in improving, whether it's fitness, speed, cornering or climbing, is really down to how much you are prepared to try.

And that our preconceptions hold us back. To quote Ken Chlouber:
"You're better than you think you are, you can do more than you think you can".

P.S. I like what crikey said too, but it's no surprise.

That I should have joined a cycle club.

How many 'brownie points' it would cost me.

I wish someone would have told me once you fix one thing on an old bike it will most likely break something else. Or perhaps it's just me?

Cyclocross is much more than a 'hand me down' version of mountain biking. Building your own bikes is one of the most satisfying things you can do.
Riding in a club is great if you use it, rather than getting in a rut.
Riding tubulars is worth every bit of extra effort.
Quality is worth buying, but that doesnt have to be ridiculously expensive.
I should have kept the Vitus framed bike I did the London to Edinburgh on 20 years ago - it was a perfect fit.

I wish I had joined a Club many years ago rather than joining one only recently. The shared experiences, peer challenges and post-ride coffees have been fantastic (although I enjoy still the occasional solo blast).

PS. Glad I have stuck with Campag all through the years!

That it's not about riding hard and killing yourself. It's about riding at a sensible pace and enjoying yourself. (Plus the above comments about carbon and Campagnolo)

That road running would knacker my joints so I would have started cycling 30 years ago instead of 3.

That you should have a dedicated crap weather bike with clearance for 'proper' mudguards.

You can never have too many valve-core removal tools.

That what bikes are made of doesn't matter.
That what groupset you have doesn't matter.
That you can actually get used to a range of different positions on a single bike, and much of bikefitting is not that much use.
That the difference between climbing wheels, aero wheels, light wheels and heavy wheels is not actually very much.
That the difference between a heavy bike and a light bike is not actually very much.

Which all makes me sound like a luddite, but having been there and got the T shirt for all the above, I still like the technical development side of cycling. I'm just much better at spotting the bullshit these days.

I also wish I knew I'd break a spoke today...

that i should have gone campagnolo at the start.

How much it would cost me

Carbon frames are not all that.

That I should have bought alu for my first bike, then carbon for my second, rather than cheap carbon, then good carbon, then replacing the cheap carbon with alu.

That when I bought my good carbon bike, the matt plastic paint finish is a pig to clean, compared to a 'normal' gloss paint job.

That Mavics flex.

Not to sell on my self-built Reynolds 653 with Campag.