Gear inch/ratio question

Look, I'm a newb and I've just built a ss out of my old Raleigh by removing the gears. It's got a 7 speed cassette on the back and the big chainring from my old mountain bike on the front - giving me 42 / 17 (on 700 x 23c) which by the standards of everyone on here is pathetic (66" or so). However ... I love it. Given my hilly commute I can just about grind up the steepest section although I'm well out of spinning range at a few points on the way home. Best thing is I'm developing power on the slighter inclines and declines. I think I run out of power at about 20mph? Certainly can't spin beyond 25mph.

So do you find your legs strengthening over time? Am I going to want a taller gear in a year or so?

As I've got better at spinning I'm using lower and lower gears. I used to run 74", then 70" but am now hovering around 66-68" (48/19 on my commuter, 49/19 on my long ride fixed wheel).

I find that I can hold a decent pace if needs be, but I've also got up the odd sizeable hill with those gears so it works out nicely for me.

I'm not great shakes at climbing however so prefer to miss out on high top speeds in order to get over any bumps in the road. Plus, if I'm on a long ride I'm invariably not in a hurry!

66" is not pathetic at all, a great gear for long rides with some climbs. <this coming from someone that can't climb for toffee.

I wouldn't change it. You could maybe try low 70s" for a flattish ride like out to cambridge or southend, but I wouldn't be tempted to risk mashing your knees to bits with a big gear. Save the massive gears for riding on a track.

My favourite rides fixed are 30-40 mile climb-fests with 2000ft of climbing or more. I try and avoid routes that take me over ascents that are much steeper than 8 percent though as it's possible I won't get up them. For these rides I ride my normal 48x18 which is the magic 70 gear inches. I know two guys you've each done the Paris-Brest-Paris... on 70 gear inches. They both ride that gear pretty much all the time, and both do pretty epic annual millages on audax rides and stuff.

I take it really easy on the descents but can spin up to 45mph on some days. I didn't used to be able to hold over 25mph for long, but it's fine now so long as the knees feel alright.

If your new to fixed it's certainly beneficial to develop your spinning. Forget about grinding a big gear it's wasting time whilst you could be getting fitter. Keeping a cadence above 80 rpm is good for fitness and suplesse, and you still get a bit of over-gear training on the climbs when that cadence drops a bit.

To develop speed there is some merit in doing shortening bursts in a heavy gear. This is only worth doing when your already pretty fit, and why I've got a smaller cog on the other side of the wheel.