Why I built Trithings: short legs, three bikes and a tyre pressure chart I nearly laminated

By Brian McGuigan · 16 October 2026 · 5 min read

Hi, I'm Brian McGuigan. I'm 37, I discovered cycling two summers ago and I fell head over heels for it. This is the story of how a €200 mountain bike, three frame sizes I'm not totally sure about and a lot of questions to ChatGPT ended up as Trithings.

It started with a €200 mountain bike

My mates were riding single track around Hoofddorp in the Netherlands and I wanted in. So I bought my first adult bike: a €200 mountain bike from a brand I'd never heard of, called Cloot.

To pick the size I asked AI for a recommendation, did a bit of googling, and pulled the trigger. Happy enough.

Then I learnt the oldest lesson in cycling: buy cheap, buy often. That bike was never meant to take the amount of rough stuff I threw at it every week, and it let me know. Plenty of breakdowns. Some were great, because fixing a bike on the fly with your mates is a brilliant way to learn. Others ended with me phoning my wife to come and collect me and calling the day short, sometimes before it had even begun. Sorry, love.

Three bikes, three size calculators, one conclusion

My next bike was a Canyon Lux, and it was a big step up. The days of unreliability were gone. I used Canyon's bike size calculator, which said small or medium. Lots of googling and ChatGPT later I went for the medium. Apparently medium is more stable, which is a good thing, right?

Then I discovered road cycling and took to it straight away. You get to go fast. Awesome. So I bought a Giant TCR, used the calculator again, got small or medium again, and went for the medium again.

Some of my mates ride gravel, so next came a Canyon Grizl. Same tool, same answer, small or medium. This time I went small.

After all that spending and googling, here is what I actually learnt:

I have short legs.
Size calculators are rough and ready. They give you a starting point, and I'm not knocking that, but they stop right where you need them most. When you are between two sizes they have nothing more to say.
I now prefer to ride a small frame with a longer stem. It's a bit more aggressive and I like it. My medium frames feel slightly too big for me.

It's not a train smash, and I love all three bikes. But with that much money going on a bike, I wish I could have checked more easily and chosen better. So I wanted to build a bike size calculator that helps people in that in-between spot.

Then came the mid-life crisis

Like any 37 year old having what can only be described as a mid-life crisis, I signed up for triathlons. That opened up a whole new world of information, pain, investment and humbling lessons about what my body can and can't do.

I finished three triathlons last year and I've signed up for three more next year, with plenty of cycling and running races in between. Along the way I lost 15 kg, and I got competitive. I'm keen to squeeze out every bit of performance I can.

Tyres were the logical place to start

Tyres are the bit of the bike that actually touches the ground, so they matter a lot. I run tubeless on all my bikes. (The Zwift bike doesn't count.)

Getting tubeless pressure right means thinking about a few things before every ride:

which bike I'm on
my weight, which has been shifting
whether it has been raining
whether this is an easy ride or race day

I've got three bikes, so that was three sets of numbers to remember. Every time, I asked ChatGPT. I seriously considered making a table of weights, bikes and conditions, printing it, laminating it and sticking it on the bike shed wall.

Then I thought: why not build a site and an app instead? That is how everything began. I was also asking ChatGPT about nutrition before every long session, so that went on the list too.

So what is Trithings?

It's a garage and a set of tools, all in one place. You add your bikes and kit once, and the tools work from what you own, so there is nothing to retype. Right now there are six free tools:

You don't need an account to use them. An account just keeps your garage safe and brings it to every device.

One honest note. I'm a keen amateur, not a bike fitter, a coach or a doctor. I try to build the tools on published sources and be upfront about where I've had to make an assumption. Treat the answers as a solid starting point, and if your body, your fitter or your coach disagrees, believe them.

What comes next

This section is where the guides will live: bikes, swim, run, race day, nutrition and kit, written for people who are as keen and as slightly obsessive as I've become. Deals and price comparison are coming too, and after that, the app.

If I can save one person from buying the wrong size frame, or from laminating a tyre pressure chart, I'll be happy.

See you out there,

Brian