emily’s bike stuff
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Initial Brompton Setup

Things To Fix

Most nearly-assembled bikes from a factory have a litany of problems. It’s one reason I’m against direct-to-consumer bikes.1 Sure, they tell you to take them to a bike shop for assembly. But that’s a bad deal for the bike shop.2 And if the bike doesn’t get to a trained mechanic then many subtle problems could be missed — or one might not realize something could/should be better. My Kona Dew-E had so many things to adjust.3

The Brompton came folded up in the box from the distributor and the only assembly was putting the saddle/Pentaclip on.

  1. The seatpost chronically slips. See below.
  2. The barrel adjusters on the brakes were loose and in different states out of the box. They probably shook loose during shipping.
  3. The front fender was misaligned — was able to fix by just rotating the whole assembly at the crown bolt a smidge.
  4. The cable ends weren’t well crimped. I was adjusting the rear brake and its crimped end came off trivially. I swapped them for some pale pink ends.
  5. I think the rear hub had a little more play than it should have. I took the wheel out and tightened the cone from the non-drive side a smidge.

Honestly pretty great for a bike from the internet! Minus the seatpost slipping.

A Brompton rear wheel in a bench vise. The hub says 'Wide Ratio' with the Brompton folding logo.

Fit Tweaks

The stock grips and handlebar backsweep are not great. The (lack of) backsweep puts my wrists in radial deviation. I swapped the grips for the Ergon GS1 Evos. They don’t fit all the way on the bar — they’re about 15mm short. I think that’s probably fine for the riding the Brompton will be doing. Ergon tells you not to do this.

I got the large size but might try the small. I’m right on the sizing border (~8.5" hand circumference) and can’t decide if a smaller grip would feel better. It would happen to take less grip space, too. It’s worth nothing that an Ergon grip with an external clamp bolt instead of internal clamp bolt (like a GP1) may not have worked.

I brought the brake lever reach in — especially needed with the larger Ergon grips.

The front of a Brompton in a bike stand highlighting the handlebars with new grey Ergon grips.

The standard seatpost is just barely long enough for me. I’m 5’8" and flipped the Pentaclip over to have the saddle rails biased upwards. I also placed the Pentaclip further up the seatpost. tbh I really like the Pentaclip. I usually don’t like single-bolt seatposts where fore/aft, height, and saddle pitch are all on the same assembly. But the Pentaclip works surprisingly smoothly. It might just be manufactured well. Not sure. The bolt it comes with is weirdly soft for something specced at 15 Nm though.

I pitched the handlebars inwards toward the saddle a smidge. This means the handlebars stick out more when the bike is folded up. I screwed in the handlebar catch nipple so that the bars could come further into the bike.

I don’t want to know how much of a PITA the repair is if this braze-on ever breaks off.

The black handlebar catch nipple screwed on to a bolt brazed on to the stem.

Tight fold! 😏

Looking above at a folded Brompton showing the stem hinged down with its nipple in the handlebar catch.
A close-up of the handlebar catch nipple seated in the catch.


I swapped the stock 50T chainring for a 38T ring — now all the gears are 24% easier (from 33 – 100 to 25 – 76 gear inches). The crank spider is a hair too big for a 38T ring even though the BCD is correct. There are two points on the chainring at any time where the chain isn’t fully mated with the rim. I tried taking a dremel to some parts of the spider to get the teeth to mesh better. It sorta worked, I didn’t go far enough.

The 38T chainring mounted on the crank spider from the back showing the edge of the crank spider sticking above the valley of the chainring teeth.

The Brompton manual is weirdly insistent on chain length being correct to the exact number of links. They state 100 links for a 50T chainring and 98 links for a 44T chainring. No spec for a 38T. I took only took out two full links and may take another. If you don’t take out enough it will look like the chain tensioner can handle the slack until you fold the bike.

The drivetrain of a Brompton with a 38T chainring and the chain rubbing on itself when folded.


I’m going to spend a while seeing what this bike has to teach me and seeing what Bromptons are all about. If I like it enough I’ll end up putting dynamo lighting on it. In the mean time I needed to get some battery lights on there. I put my favourite rear light on the saddle. I had an old front light and PAUL Gino Light Mount that I improvised with. I’ll have to re-arrange this when I get a bag on the front luggage block but it works well enough. Also phew I miss my StZVO lights with all their optics and beam shaping.

A cylindrical light mount attached to the reflector bracket on the fork crown of a Brompton.

Seatpost Slipping

This one gets its own section because it’s an infamous and stubborn issue with Bromptons. This is the biggest issue I’ve had so far. If you search “seatpost slipping” on r/brompton you’ll find a loooot of results. I’ve only been going on ~2km rides since I’ve been sick but the seatpost slips every time.

Brompton seatposts are designed to operate grease-free. Any contaminant, including fingerprint oil or residues from manufacturing, can cause them to slip. This isn’t called out in the owner’s manual as much as it should be, IMO. A bit in the “Cleaning & Lubrication” section notes not to grease them.

When lubricating your Brompton, avoid getting oil or grease on the seatpost or the wheel rims.

But nowhere do they explicitly say not to touch the seatpost with your hands, which seems to be the long-term solution for many.

A mechanic who’s worked on many Bromptons told me that the quick release nut is frequently under tightened from the factory. There’s some mixed messaging on how much you can safely tighten this before you risk frame damage. The seat clamp datasheet says:

As a guide, with the seat clamp lever forward (i.e. done up), the adjustor nut AN should be tightened with a torque in the range 4-7NM and the maximum closing force needed at the end of the lever while securing the clamp should lie in the range 80-120N. The correct setting will depend on the weight and strength of the user.

The official Brompton YouTube channel says to have at most 3mm of exposed thread past the nylock (timestamped video).

I’ve also heard that the seat post sleeve can be improperly or over-reamed from the factory. This means you need to get a new one and have it reamed with a Brompton-specific tool.

Looking inside the seat tube of a Brompton with the seat sleeve visible.

I ended up:

  1. Degreasing the seatpost and sleeve.
  2. Tightening the nut until there was 3mm of exposed bolt, which ended up being 6Nm.
Calipers reading 2.92mm on the exposed bolt past the quick release nut.

This didn’t fix my issue so I’ve taken it to a local Brompton dealer for a warranty claim. See you soon, yet-to-be-named Brompton! I’ve really enjoyed riding you!

A semi-folded Brompton in the parked position in front of a brick wall at night.

  1. tbh I don’t think most bikes should be sold as completes. Bikes should be sold through your local bike shop with consultation on (at minimum!) contact points (grips, saddle, pedals, bars). ↩︎

  2. Bike shop doesn’t get the margin from a sale. But they get a shitty margin on the high-labor task of assembling a random direct-to-consumer bike. Of course, some are better than others. ↩︎

  3. A particularly annoying one just as an example: the battery mount was not correctly setup. This made it very hard to get the battery in and out. Eventually the mount loosened up enough that the battery lock didn’t even retain the battery. I once had the battery fall out when I accidentally put some pressure on it while carrying the bike. Shimano offers a gauge to align and set the length of the battery mount correctly. But that’s a niche tool and kind of expensive. ↩︎