15-20 mph (im quite a fast runner so that may feedback into how fast i will ride) im gonna be chaving so much
I cycle 12 miles to work and back 4 days a week, averaging anywhere between 16-20mph. On a heavy hybrid. On a quiet cycle track/road combo. Laden with bags, lights, etc. I also cycle in sports shorts (non cycling specific) sports t-shirt (non cycling specific) and a cycling specific high vis jacket, gloves and leg warmers. That is my winter set up and does me well. You dont need full lycra to ride quickly. I chaffed for the first month or two. Now I dont.
Get the bike, get some lights. Get a couple of spare tubes, pump and tyre levers. That will do you for now and then you can add kit as and when you need it. And I agree with what has been said before reference London riding. You will do well to average those sorts of speeds in heavy London traffic. Or suicidal if you do
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