Brompton Under 20 Pounds

Is it possible to have a sub-20-pound Brompton? Absolutely!

Can you do it for free? No, but pretty close (as little as about $60).

Should you leave the safety reflectors on your bike because, well, they’re safe? Yes. Am I going to remove them, anyway? For demonstration purposes, yes.

Here are FOUR (relatively) easy Brompton modifications to bring an S1E-X to under 20 pounds.

Before we get started, why bother with lightening-up a Brompton? Are a couple pounds THAT big a deal?

As always, it depends. One of my favorite bikes is Surly’s all-steel Krampus. It’s over 30 pounds, but it rides over sand, snow, mud, and more. Most importantly, I’ve never carried that monster up a flight of stairs, into an elevator, nor tucked it away into an airplane overhead bin. Declaring the obvious here, but we Brompton-lovers carry our bikes a lot, because we can bring our bikes where most other bikes can’t be brought. So, yes, a pound or two does make a difference.

Next, a one-speed Brompton?! Yes, that’s the easiest way to get to less than 20 pounds. Three-speed internally geared hubs, that second rear cog, shifters, shifter cables, and shifter cable housings. It all adds up.

The following four S1E modifications should cost a little less than $300 and can be performed by most people (i.e., you don’t need a bike mechanic). It’s possible to get to under the magical 20 pounds for as little as $60 (more on that, below).

Let’s get started!

Start by purchasing a stock S1E-X Brompton with titanium extremities and Schwalbe Kojak tires. That bike weighs 20.72 pounds with no modifications, straight from Brompton’s London factory. That bike has a suggested retail price of $2,134. Yes, the titanium extremities are pricey, but it’s hard to beat the weight-savings for the price of the “Superlight” option. What’s more, you’re getting more than just the titanium fork and the rear titanium triangle. A Superlight Brompton also includes a lighter headset (aluminum instead of steel), and lighter spokes (single-butted Sapim “Strong” spokes instead of standard, non-butted spokes).

Like the millions of varieties available to customize your Brompton, tons of different ways to get to less than 20 pounds. The following modifications were selected on the basis of biggest-bang-for-buck coupled the hope that a bike mechanic won’t be necessary. With that in mind, I’ve also included modification instructions.


My favorite weight-savings modification, swap-out the standard Brompton seatpost with a lightweight titanium alternative, such as that offered by Ti Parts Workshop. That seatpost will be north of $200. Can you find a cheaper titanium alternative on eBay for a lot less? Yes. Why are two seemingly similar titanium seatposts so different in cost? Because they’re not at all similar. In almost every case, the cheap one is made of a thinner, lesser-grade titanium. You get what you pay for. A Brompton seatpost is long. It’s tasked with carrying a lot of weight, literally. Longer tubing is more susceptible to failure. Don’t cheap-out here. A quality titanium seatpost will save about 6 ounces, leaving another 6 ounces to get under 20 pounds. This one modification gets us halfway to sub-20 pounds.

Brompton Ti seat post

Directions: Remove the Pentaclip and saddle. You’ll need a 5mm hex wrench. Simply loosen the single 5mm-bolt that travels through the Pentaclip until you can wriggle the Pentaclip/saddle free from the top of the seatpost. Don’t remove that long Pentaclip bolt. There are a lot of internal pieces inside that Pentaclip that are a bit tricky to get back into place.

Remove (by hand) the two rubber O-rings found on the top of most Brompton seatposts.

Lift the bike up and allow the seatpost to drop through the bottom. It’s that easy.

Insert the replacement seatpost from the bottom of the bike in the same hole where the original seatpost dropped-out.

Replace the two rubber gaskets and then re-install the Pentaclip/saddle using that 5mm hex wrench. Voila! Also, yes, this is an expensive modification, but if you ever sell your Brompton (to get a different Brompton, of course), it’s easy to re-install the original seatpost and keep (or sell, separately) your fancy titanium seatpost.


Remove the plastic chainguard. 1.5-ounce savings. 4.5 ounces to go.

Chain ring guard

Directions: There are several small Philips head screws that hold the plastic chainguard in place. Those screws are accessed from the back side of the chainguard. A standard Phillips head screwdriver will suffice. Once you’ve found those screws, take them out and the chainguard is free.


Remove the reflectors (see safety disclosure, above). 2.7-ounce savings. 1.8 ounces to go!

Brompton reflectors


Directions: This seems like it should be easy, but it’s a little more involved. Those reflector brackets are nestled within the brake-caliper anchor bolts. You’ll need to remove those anchor bolts, being careful to pay attention to the order of those washers, nuts, and bolt. The 5mm bolt for the caliper brake in the front is accessed from the rear, on the ‘back’ side of the head tube. The rear brake bolt assembly requires a 10mm wrench to remove the Stop Disc. After removing the reflector mounts, re-install the brake caliper pieces in the same order they were found. I suggest doing one side at a time. If you drop one or more pieces during the removal of the reflector, you can look at the other brake-anchor-bolt assembly as a reminder of how they’re installed. If you’re not totally comfortable with this modification, any half-decent bike mechanic should be able to have that done in a matter of minutes, for hopefully not too much.

Another popular modification to save weight, the bottom bracket. The stock Brompton BB is 8.6 ounces. A titanium alternative will save about 5 ounces. The cost of that fancy bottom bracket will set you back about $200, plus the cost of labor if you’re not a bike mechanic. And we’re only 2 ounces away, so let’s focus on something else.


Rather than the bottom bracket, let’s get rid of those clunker Brompton pedals. A pair of stock Brompton pedals are about 14.5 ounces. A lighter-weight alternative, the MKS Promenade Ezy-Ti pedals, available at many locations for as little as $60. Those are 12.6 ounces. Weight savings of 1.9 ounces!

Brompton bottom bracket

Directions: The removal of the right-side pedal needs only a 15mm wrench. Most wrenches are able to fit onto the pedal-bolt (meaning, you don’t necessarily need a special pedal wrench). Although the removal of the folding Brompton pedal is not difficult, it’s difficult for me to succinctly explain in writing. Instead, a link to Brompton’s official removal instructions for the left folding pedal. Pro-tip: that bolt that secures the folding pedal to the crank arm can often be super tight. Also, don’t forget, the left-side pedal bolt is reverse-threaded. To unfasten that bolt, you’ll be turning clockwise.

I’ll go a little bit further with one more relatively easy modification. Those easy-off MKS pedals are great, but they’re even better if you have a pedal holster to keep the greasy left-pedal on the bike (and out of your pocket) when the bike is in its folded position. That pedal holder, which tucks in behind the left-side rear axle bolt weighs about 0.6 ounces, which bounces us back above 20 pounds.

Directions: You’ll need a 15mm wrench to remove/install that axle bolt and install the pedal holder. Be sure to firmly tighten that bold after the pedal holder is in place.

Time for a new saddle. But of course! The stock Brompton saddle is a great seat and it’s super comfortable. If the price of that titanium seatpost is too much, you might be able to achieve the same sub-20-pound S1E by leaving the stock seatpost in place and focusing on a lighter-weight saddle.

That comfortable, durable Brompton saddle weighs 13.4 ounces. Lots of alternative saddles weigh less. One of my favorites, the “Arione” saddle by Fizik with “Kium” (not carbon) saddle rails. That’s closer to 8 ounces, saving a bit more than 5 ounces. That Fizik saddle isn’t inexpensive. A $20 plastic saddle can weigh as little as five ounces. Again, lots to choose from, including that old saddle you might have in the garage.

Brompton Saddle

Directions: Remove the Pentaclip and saddle. You’ll need a 5mm hex wrench. Simply loosen the single 5mm-bolt that travels through the Pentaclip until the you can wriggle the Pentaclip/saddle free from the top of the seatpost. Don’t remove that long Pentaclip bolt. There are a lot of internal pieces inside that Pentaclip that are a bit tricky to get back into place. Unlike the seatpost remove directions, removing the saddle from the Pentaclip is a little more dicey because that long 5mm Pentaclip bolt needs to come all the way out. As long as this is done slowly and carefully, and you hold all of the Pentaclip pieces in place, the old saddle can be removed and the new one installed. But this is often easier said than done. If one or more Pentaclip pieces fall out of place during this process, this could turn into a longer job. Longer meaning 10 or so minutes of frustration as opposed to one minute if none of the Pentaclip pieces fall out of place. For this procedure, it helps if you’re sitting down at a table and the replacement saddle is within easy arm’s-reach once the stock Brompton saddle has been removed.


You’re Brompton S1E-X, comfortably under 20 pounds!