Monthly Archives: September, 2025

Where the rubber meets the road…

I have a theory, which I’d like to expound, and my clever readers can tell me whether it’s right or wrong.

It came to me in the mid-1980s, this theory, when I got my first car: a Hillman Imp, which I purchased for £90. It had no manuals, and, actually, no ignition key: you had to put an old screwdriver into the slot where the ignition switch had once been, and twist it to start…

Anyway, because I had no documentation, I just guessed at the appropriate pressures for the tyres, and pumped them up to 30 PSI all round. Several months later, in mid-winter, I finally found out that the front of the Imp was so light that the front ones were only supposed to be at 16 PSI. This, I imagine, accounted for the fact that when it was snowing, turning the steering wheel didn’t do very much on its own, and I had to make handbrake turns to get around some of the tighter corners on my daily commute.

And this came back to me, a quarter of a century later, when I got my first electric car: a BMW i3, which had large and very narrow tyres — almost like motorbike wheels — to improve the airflow..

Some of my friends and neighbours said they’d prefer bigger, fatter tyres so there would be more rubber in contact with the road.

But I pointed out that, to a first approximation, this shape didn’t make any difference. And here’s my reasoning:

The thing keeping your car off the ground is the air pressure in the tyres pressing on the patch of tyre that’s in contact with the road. That downward force must equal the pressure in the tyre times the area of contact. Or, to put it another way, if your tyres are at 40psi and your car weighs 2000 lbs, then you must have roughly 50 sq. ins. in contact with the road – 12.5 sq ins per tyre – whatever your shape of tyre.

So, for the same pressure and weight of vehicle, if your tyres are wide, you’ll get a wide, short patch touching the ground. If they’re narrow, you’ll get a longer, thinner patch, but they should be about the same size in either case. Double the pressure, and you’ll halve the area in contact with the ground. Halve it, and you’ll double the area. But buying wider tyres will only make you look more macho.

Now, this is an approximation, partly because tyres aren’t perfect spherical balloons and the area doesn’t change smoothly with the pressure, partly because the forces go towards stretching the rubber as well as supporting the car, and partly because the pressure is providing rigidity to the structure of the tyre, so you get some support from the vertical bits of rubber as well, but the basic principle holds: it’s primarily the pressure, not the shape of the tyre, that’s important in determining how large an area touches the road.

Now, in practice, I came to rather like the long, thin tyres of the i3: they cut through water and slush very well, and were less likely to aquaplane when you encountered a puddle. (A counter-argument, I guess, would be that if there’s a rut on the road, you’re likely to have a higher proportion of your tyre on it for longer if your contact area is long and thin.)

So, yes, the best way to get a better grip is generally to lower the pressure, if you can face the resulting fuel costs. However, even this isn’t as simple as it may seem, because you may remember from your school physics lessons that it’s the perpendicular force times the coefficient of friction that counts; Guillaume Amontons showed in the 17th century that if you’re sliding two surfaces over each other, the area of contact isn’t important – it’s the force with which they’re being pressed together.

If we had perfectly flat roads, increasing the area in contact with the ground would make little difference. But sadly, the roads are getting ever less flat around here, so dropping the pressure a bit will not only get you a better grip as winter approaches… it’ll make the potholes more comfortable too.

Up North and Down South

Campervan in the early morning, with Lindisfarne behind.

Back in late February, while Rose was away, Tilly (may she rest in peace) and I departed on one of our campervan trips. As is often the case when I’m doing these out-of-season jaunts, I set off not really knowing where I would end up, my itinerary being driven partly by the weather forecast, and partly just by a desire to see places I’d heard of but never visited before.

It ended up being a tour mostly of north-east England and south-west Scotland, and I captured rather a lot of video footage over the two-week trip, which I’ve finally managed to edit into something watchable! Watchable for me, anyway: I do this mostly to give me a chance to relive the experience many times over, and I also make the videos available just in case they’re also of interest to others.

Dalcairney Falls

The first part of that certainly works very well: the long reviewing and editing process means I have detailed memories of several of my past trips where there would otherwise be just a vague, hazy recollection. (It also means that the videos are rather longer than if I were making them for someone else!)

But as for the second part — will others watch them too? — well, I appreciate that there are many people, probably most people, for whom the idea of watching extended video footage of other people’s holidays may be a bizarre concept, but there are also a surprising number who do get enjoyment from this kind of thing… especially other campervan & motorhome owners who might be looking for places to visit or stay on their travels.

Over the years I have built up an extensive set of custom lists on Google Maps with titles like ‘Want to go‘ and ‘Overnight stop?‘, which have proved very handy when planning any kind of trip, and many of the little markers they contain have come from watching others’ videos and thinking, “Oooh. That looks rather good…Let me just mark that…”.

Anyway, I’ve now uploaded the first few episodes to a YouTube playlist called Up North & Down South, and the remainder will follow over the next couple of days, in the hope that, as someone once said, “people who like this sort of thing will find this the sort of thing they like”.

First episode here.

It’s not too late to avoid paying for AI…

Back in January I wrote about how Microsoft had increased their Office subscription prices by a third, but you could still get it for the old price by saying that you wanted to cancel, and then selecting the ‘Microsoft 365 Family Classic’, which comes without all of the AI features that lead to the extra cost.

Well, our subscription just came up for renewal… and I found that they’ve now removed that option from the website. In fact, there’s nothing on the website to suggest that writing a letter without the aid of AI is something you might want to do… or appreciating that you might not want to pay for it.

Undeterred, though, I used the online chat system. It was AI, of course, but, to be fair, I was able to get through to a human pretty quickly. She had some standard auto-generated responses about all the wonderful things AI could do for me, and a set of questions she needed to ask me about why I didn’t want AI to improve my productivity in my Office suite. I said, roughly:

  • (a) It costs money.
  • (b) I’m concerned about the environmental impact.
  • (c) Im concerned about the privacy implications.
  • (d) I’ve used the the tools, and know that the supposed productivity improvements are mostly a myth unless you’re writing stuff that nobody would want to read… in which case, why bother?
  • (e) We went to school, so we already know how to write.

I could have added that:

  • (f) I almost never use Microsoft Office, so wouldn’t look there for any of this stuff anyway, and
  • (g) Modern Microsoft apps are quite bloated enough without wanting to add anything more, and
  • (h) The only things I might want to use AI for I can get for free from chat.bing.com or chatgpt.com or aistudio.google.com or claude.ai, so I’d rather spend my 25 quid on fish and chips and beer at a nice waterside pub, thank you very much.

But even without those additions, in the end she admitted that she could actually renew my Microsoft 365 Family Classic subscription for the old price.

So it’s still possible, if you can manage to talk to a human. But I wonder for how much longer…

Misrepresentation

Generally I’m a fan of the Liberal Democrat party here in the UK. Have voted for them on numerous occasions, in fact, though I can’t remember whether I did last time. But I do wish they wouldn’t resort to such nefarious tactics.

Here’s a cheery letter that just came through the door from our MP, Ian Sollom:

Let’s take a look at that bar chart in the bottom right corner:

Basically, it (and the tone of this and other newsletters) is clear: our only close competition in this area was the Conservatives, and Ian gave them a damn good thrashing! Hurrah!

But look more closely at the actual numbers, and you’ll see that the Conservative vote was actually over 97% of the Lib Dem vote! Is that what this chart says to you? And Labour got more than 50% of the Lib Dem number. Don’t get me wrong, I’m still glad they won, but this chart is deliberately misleading – somebody created this, and made a choice to falsify the dimensions.

With the help of a bit of photoshopping, I can show you what the chart should look like to represent the facts accurately:

That looks less like a ‘damn good thrashing’ and more like ‘by the skin of our teeth’!

It wouldn’t surprise me to hear that Mr Sollom isn’t the only one guilty of similar mathematical fraud. I wonder if the Advertising Standards Authority take any interest in political campaigns…

The success of Django… and when the machines take over.

The Django web framework is now 20 years old. Within a few months of its launch, I discovered it, liked it, and we rather daringly decided to bet on it as the basis for the software of my new startup. (Here’s my post from almost exactly 20 years ago, explaining the decision.)

For those not familiar with them, web frameworks like this give you a whole lot of functionality that you need when you want to use your favourite programming language to build web sites and web services. They help you receive HTTP requests, decide what to do based on the URLs, look things up in databases, produce web pages from templates, return the resulting pages in a timely fashion, and a whole lot more besides. You still have to write the code, but you get a lot of lego bricks of the right shape to make it very much easier, and there are a lot of documented conventions about how to go about it so you don’t have to learn, the hard way, the lessons that lots of others had to learn in the past!

Anyway, I had made a similar lucky bet in 1991 when the first version of the Python programming language was released, and I loved it, and was using it just a few weeks later (and have been ever since).

Django was a web framework based on Python, and it has gone on to be a huge success partly because it used Python; partly because of the great design and documentation build by its original founders; partly because of the early support it received from their employer, the Kansas newspaper Lawrence Journal-World, who had the foresight to release it as Open Source; and partly because of the non-profit Django Software Foundation which was later created to look after it.

Over the last two decades Django has gone on to power vast numbers of websites around the world, including some big names like Instagram. And I still enjoy using it after all that time, and have often earned my living from doing so, so my thanks go out to all who have contributed to making it the success story that it is!

Anyway, on a podcast this week of a 20th-birthday panel discussion with Django’s creators, there was an amusing and poignant story from Adrian Holovaty, which explains the second part of the title of this post.

Adrian now runs a company called Soundslice (which also looks rather cool, BTW). And Soundslice recently had a problem: ChatGPT was asserting that their product had a feature which it didn’t in fact have. (No surprises there!) They were getting lots of users signing up and then being disappointed. Adrian says:

“And it was happening, like, dozens of times per day. And so we had this inbound set of users who had a wrong expectation. So we ended up just writing the feature to appease the ChatGPT gods, which I think is the first time, at least to my knowledge, of product decisions being influenced by misinformation from LLMs.”

Note this. Remember this day. It was quicker for them to implement the world as reported by ChatGPT than it was to fix the misinformation that ChatGPT was propagating.

Oh yes.

© Copyright Quentin Stafford-Fraser