I ended up performing a few upgrades to my Brompton pretty well immediately after I got it, and I’ll explain why I believe they are good investments.
Brooks saddle
The first and most compelling and efficient upgrade was to get a Brooks saddle. After just one ride on the Brompton, I loathed the plastic brick of a saddle the thing came with. Maybe it is acceptably comfortable for a lighter, smaller person - but definitely not for my fat ass!
The stock saddle on the Brompton retails for 30 dollars. This sort of stuff is almost always overpriced, so this leads me to believe the this is extremely cheaply made. It has a modicum of cushioning, and I understand why they would make such a light, cheap, resilient saddle the default. But I just bought an expensive bike, and I’ll be damned if I’m going to hate riding it because I have this garbage saddle to contend with.
Probably the most common complaint about a bike is that it’s saddle is uncomfortable. This is because most saddles these days are molded plastic with a bit of foam padding, designed to be of average comfort to the average person. They last forever, are cheap to make, and can take a lot of abuse.
A long time ago, leather saddles were the norm. Even cheap bikes would come with them. It was just accepted that you buy a bike and it comes with a relatively rigid, uncomfortable leather saddle. However, leather has one really appealing property - it can be broken in. Various techniques arose for speaking up the break-in process, usually involving treating the saddle with some kind of natural oil.
Once broken in, the leather saddles would basically be moulded to the particular anatomy of their rider. This would mean that a saddle that is comfortable for you might not be to someone else, but what do you care? Rather than a saddle that’s tailored towards the average, the leather saddle was basically molded to be perfectly comfortable for you and you alone.
Brooks has long been a maker of premier bicycle saddles. Perhaps their most popular model is the B17. I did a bit of research and considered the Cambium version of the saddle, the C17, which is somewhat of a hybrid between leather and plastic. After talking to a few bike experts though, they all recommend I stick with the B17. Supposedly the C17 breaks in faster and is water proof, but will never break in to the same degree as the B17.
So I went for the B17. It was really easy to install on the Brompton. I bought the Brompton toolkit (it fits inside the frame!) and it had the necessary fittings to remove the crappy Brompton saddle. Once removed though, numerous metal plates fell off of the saddle mount. It’s a bit of a trick to keep them together as you install a new saddle. I think they act as spacers, so the mount can hold different sizes of saddle rails. In my case, the rails of the B17 perfectly matched those of the stock Brompton saddle. A few minutes later, I had it mounted! It took a couple of rides to get the saddle adjusted to the right angle, but now I’ll never touch it again.
Before taking the saddle out for a spin though, I applied Brooks’ propriety saddle oil - Proofide. This is a mixture of natural fats and waxes that simultaneously makes the saddle more supple (and therefore easier to break in), as well as acting as a form of mild weather proofing - creating a thin, protective layer of wax on the saddle. I applied proofide every few days for the first couple weeks of having the saddle. It seemed to significantly help with the break in process.
At about 200K the saddle is actually remarkably comfortable! I’m really glad I ended up getting the Brooks. As I was out on a 30K ride, I pulled over to check my GPS. A grey-haired cycling veteran rolled up to my on a neat recumbent bike, and asked about my Brompton. I mentioned that I was breaking in the Brooks saddle, and he remarked that he had one too - a B17, just like me. The only difference is that he has had his for 30 years! He said that it’s still in great condtion, and it’s the only saddle he uses when not in his recumbent contraption.
I definitely do not regret this upgrade one bit! While I debated with the sticker shock a bit, the unparalleled comfort of the saddle and the prospect that I’ll have it for decades to come - maybe even my entire life - has completely sold me on it.