Brompton maintenance

General Maintenance:

The Brompton doesn’t need much in the way of maintenance – the sealed hub gears and galvanised chain make the gearing very durable. So, basically just oil the chain occasionally. Also oil the cables – especially, drip a little oil into the upturned end of the brake cable where it goes into the brakes at the front and back.

Adjusting the Gears:

The 3-speed SRAM hub gear (as fitted to all bikes from ~2001 onwards) is very easy to adjust:

  1. Unfold the bike completely – including the back wheel.
  2. Put the shifter into 3rd gear, and turn the pedals a few times to make sure the hub is in gear.
  3. Push the rod at the end of the toggle chain into the grey plastic fitting on the gear cable. Push it in far enough to remove all the slack in the cable, but not so much that the toggle chain has actually been pulled out a bit.
  4. Test ride the bike to make sure you’ve got it!

The 3-speed Sturmey Archer hub (fitted to older Bromptons) is almost as easy:

  1. Unfold the bike completely – including the back wheel.
  2. Put the shifter into 2nd gear, and turn the pedals a few times to make sure that the hub is in gear.
  3. Have a look at the toggle chain – try pulling it out. You’ll see that the chain is attached to a round rod, if you pull it out far enough.
  4. Tighten the barrel adjuster on the cable until the end of the round rod lines up exactly with the end of the hub axle. Make sure you’re lining up with the axle itself – not the wheelnut or the plastic pulley.
  5. Test ride the bike to make sure you’ve got it!

The 5-speed Sturmey Archer (also fitted to older Bromptons) is a bit more difficult:

  • Unfold the bike completely – including the back wheel.
  • Put the shifter into 2nd gear, and turn the pedals a few times to make sure that the hub is in gear.
  • Have a look at the toggle chain – try pulling it out. You’ll see that the chain is attached to a round rod, and on that rod is a little notch with red or blue paint in it.
  • Tighten the barrel adjuster on the cable until that coloured notch lines up exactly with the end of the hub axle. Make sure you’re lining up with the axle itself – not the wheelnut or the plastic pulley.
  • The 5-speed is more sensitive than the 3-speed – it can be fiddly to see what you’re doing, but try to get this as accurate as possible.
  • Test ride the bike to make sure you’ve got it!

The derailleur system on newer 6-speed bikes does not need any adjustment – it has a self-balancing system which makes up for any cable stretch. At least that’s the theory! If yours isn’t working, first check that the mechanism (especially that long spring) is clean and oiled. If it’s still not shifting cleanly, try opening up the shifter and moving the plastic cable stop one notch further up.

For some reason, on the P-types, Brompton often fit the 3-speed shifter wrongly – it should be fitted with the word “Brompton” completely horizontal, but it’s often fitted angled up a notch, which leads to the outer cable fraying. I always fix this on every Brompton I see.

Fixing a Puncture:

Front wheel punctures are easy on the Brompton, so I’ll concentrate on the back wheel:

  • Turn the bike upside-down – balancing it on the handlebars and saddle if you don’t have a stand.
  • Fold the back wheel over, to reduce the tension in the chain, and unhook the chain from the tensioner arm.
  • Fold the wheel back, and disconnect the hub gear.
  • Unscrew the toggle chain and pull off the toggle pulley (if there is one).
  • Use a 15mm spanner to remove the outer wheel nut and any washers.
  • Take off the chain tensioner – just pull it off the axle.
  • Use a 15mm spanner to undo the wheelnuts – undo them far enough to free the anti-rotation washers as well. Now you cna take the wheel off and repair the puncture.
  • To refit, first refit the wheel – don’t forget to loop the chain over the sprocket! Make sure the anti-rotation washers are in place, and tighten the wheelnuts.
  • Push the tensioner back on. The chain goes under the pulley.
  • Fold the back wheel over, and loop the chain over the tensioner arm pulley. Fold the wheel back.
  • Refit the outer wheel nut and any washers. If there’s a toggle pulley then make sure the tabbed washer lines up with the gear cable. You don’t need to tighten this nut too much.
  • Screw the toggle chain back in, and fit the toggle pulley (if there is one).
  • Adjust the gears as above.

9 Replies to “Brompton maintenance”

  1. The easy way to fix a puncture on the rear is not to take the wheel off at all; release the tyre where the puncture is, get the inner tube out along 4-8 inches, fix the puncture. You can continue your journey within 5 minutes with no grease on your fingers:-)

  2. Could you plse explain the correct way to adjust / tune the 5 speed hub with two wires plse? Can not find a good description anywhere. Thank you.

    1. Hello, the way I’ve done it is to adjust the right shifter as if it was a 3-speed – in the middle gear, the axle rod should line up with the end of the axle. Then with the left shifter, I adjust it so that there’s no cable slack in the low gear.

  3. Hi you state that on P types that the 3 speed changer should be horizontal. I have looked at mine (black plastic changer)and it is fixed in position – there is no obvious way to rotate the changer on the mounting clamp. Please could you tell me how to rotate the changer if it is fixed . thanks

    1. If you remove the bolt that holds it to the clamp, it’ll pull off – the clamp has a series of serrations that hold it in position, you just rotate to a different serration.

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