'Upgrading' to skinny tyres pointless for London commuting

I win:

Riding at 120psi on clinchers is for masochists, unless you're ~100kg (in which case you'd be better off running 25s at <120psi anyway).

We've done this to death in other threads.

Anything close to 100psi is definite pinch-flat territory for me. Only at above 120psi do I feel remotely confident when on the bike.

I'm with the ignorant majority also. I should get a t-shirt for this. :-)

Hellooooooo.

Oh hai!

Waydaminit, are you the t-shirt seller? I'll have mine in 4XL pleez. You are a luv.

^^ You could at least take a photo with enough of the vernier scale to be able to read it properly. This thread is so arsey those tenths of mm might matter.

I run my 23s between 120 and 80 psi, since that's what I pump them up to and what they've gone down to the next time I get round to it. Can't say I've noticed at which point I get most punctures and I'm unlikely to in future either.

Soz

Neil, was that the 27c challenge tyres you were using?

Yarp

If that turn out to be 31mm on a 24mm rims, then I wonder what my 33.3c will measured on the same rims.

After reading this thread I was a bit surprised about the research into rolling resistance so I thought I would test it out for myself in a 'real world' setting to see what the difference is.

First week: I put a 25 on the rear and kept a 23 up front. Both pumped up to 100psi. My commute is 8.8miles and has two good long uninterrupted stretches (0.8mi and 0.9mi) so I can get up to a good speed and maintain it.
For the first couple of days it was hard to discern much difference, but as I got more 'attuned' to the road feel it became clear that there is a significant impact. The rear in particular felt much more 'smooth' and had a better 'flow'. It needed a bit less rider input to maintain the cruising speed. Up front I began to really feel the tyre 'sticking' to the road and there was a sense of the rest of the bike pushing it forward.
When I checked back my average commute times on Strava I was an amazing 0.6mph faster on average.

Second week: As a control, I swapped the tyres and pumped back up to 100psi. By now it was easy to feel the difference. The front (now 25) was rolling along freely, but at the back I was really feeling having to push the 23 to keep it at the same pace.
I was only able to record 3 days as it was raining heavily so I took the tube the other days, but it was 0.4mph slower than the previous week, but still 0.2mph faster than my average on both 23s.

In conclusion, it does seem that the rolling resistance of tyres has an impact in the 'real world' and I am changing back to 25 at the back, 23 at the front as I only have one 25.

Northern. I don't like it, but it goes where I need to go.

Northern. I don't like it, but it goes where I need to go.

Racist.

...Both pumped up to 100psi.

That's probably a bit high, depending on the weight on the wheel. Usually you want more air in the back tyre than front.

I rode a mountain bike and changed the tyres to thinner ones. The time to get to work was the same, but it felt a lot easier with myself not being out of breathe as much and possibvly less lactic acid in my legs.

Super scientifical studyfication going on here..

I rode from Ealing to Forest hill last night on 22mm tubs, it took less time than on my other bike with 32mm clinchers because I didn't have to stop 3 times to fix fucking punct*res

I ate a whole family bucket of KFC. It was much harder taking a shit the next day than in had been when i ate a small portion of curried prunes, which co-incidentally was like a nail bomb going off in my toilet.

Less lactic acid from chewing or possibly less contact area with my sphincter?

You need to factor in the weight, 80kg in says a 5mm square contact point vs. 80kg in a 1cm square - which would you reckon spread the weight evenly?

Pressure = force per unit area

Bigger tyre = bigger contact patch

Common misconception. In fact the pressure between the road and the tyre is pretty much exactly the same as the pressure you inflate the tyre to whatever tyre size. If you put more weight on the tyre then the contact area spreads out to keep the same pressure.

So, for a larger and smaller width tyre at the same pressure with the same rider they will have the same contact area. The key to rolling resistance is the shape of the contact area (I suspect Tester has already covered this but here it is anyway). The thinner tyre has a long thin contact area whereas the wider tyre has a wider shorter contact area.

Rolling resistance comes from the losses caused by internal friction in the tyre and between the tyre and inner tube so the more you bend the tyre, the more energy you lose. If you imagine the contact area as a flattening of the circular shape of the tyre against the road then you can imagine that it's much harder to flatten a long thin strip than a short fat strip because of the curvature of the tyre. So the long thin strip causes larger energy losses in the tyre (at the same pressure). For the same reason, larger diameter wheels have lower rolling resistance due to the increased curvature of the tyres and higher pressure reduces the length of the contact strip and will also reduce rolling resistance (on a hard surface)

But it's all a play off between aero, weight, rolling losses AND comfort so there's no one size fits all answer.

I ate a whole family bucket of KFC. It was much harder taking a shit the next day than in had been when i ate a small portion of curried prunes, which co-incidentally was like a nail bomb going off in my toilet.

Less lactic acid from chewing or possibly less contact area with my sphincter?
repped for services to science.

I rode to uni, but stopped to buy a pack of quavers, paying in small denomination coins. I then arrived earlier than I did the day before when I had set off at the same time. I therefore deduce that buying quavers makes for faster cycling and reduces the net weight of the rider and bicycle, due to being such a lightweight snack, while costing a relatively heavyweight amount of coins. Although I did wait at a traffic light for a bit one of the days, so maybe that removes all effects of the quavers. Or indeed tyre choice

i'm pointless, can i be commuted?

After reading this thread I was a bit surprised about the research into rolling resistance so I thought I would test it out for myself in a 'real world' setting to see what the difference is.

other people have alluded to it but I am going to say it outright.

I don't think your appreication of the scientific method or your understanding of the word control is particularly good as your study is very weak. In fact I think we have more proof that stoping and buying quavers will lower your commute time.

Science?! what is this evil art you speak of? by the power of my magic beans (23c front, 25c rear) be gone!

Thoughts?

Try not doing your belt up too tight. Fine if you're riding on a perfectly flat surface but not on our roads.