How to adjust the rear wheel bearings on a Brompton

I've had my Brompton a little over 6 months and I use it as a daily commuter, but unlike my other bikes that I use for a single ride and then clean and maintain directly afterwards, the Brompton is treated a little harsher and doesn't get my regular attention. Much like a car, I expect the Brompton to work on a daily basis and to just churn out the miles.

However, the rear wheel of a Brompton has few tiny bearings, takes extreme loads, for their size, and doesn't enjoy the labyrinth of seals that a car does. So it will need adjusting, maintaining and replacing in time.

Why do you need to adjust rear bearings?

After taking the chain off to give it a good de-grease and lube, I noticed that the rear wheel was wobbling to the touch. For those familiar, any sideways movement in the rear wheel, is a sign that the bearings need adjustment. Excessive play even after adjustment requires that they be replaced.

The wheel will still turn freely and if you leave it, you'll still be able to ride, but over time this can deform the axle, wreck the rear hub and potentially cause a lock-up of a rear wheel whilst in traffic. It's happened to me in my early care-free days on another bike and I wouldn't recommend it to anyone else.

Bike shop or home mechanic?

For many riders, it may be easier to go to a decent bike shop (who ideally stock Bromptons) and have them strip the rear wheel down, service the hub and then put it all back together and reset the gears. But do expect to pay at least £75 for such a service and for the convenience. For simple bearing adjustment only, then the price may be around £30 - £40.

For those who have the tools, time and inclination, then this post is all about how to adjust the rear wheel bearings on a Brompton 3 speed rear wheel to reduce play. I would imagine the approach would be similar for the 1, 2 and 6 speed rear hub variants too.

If you've never adjusted bearings before, then do expect that you may need to re-adjust the tension of the bearings several times before you get it right. It can be time consuming as you'll need to put the back wheel back on to check the alignment each time, but it's good practice. Word of warning, in that you should never over-tighten bearings. You'll deform them and you will then need to replace them. How do you know when it's too tight? Tricky to say, but in my experience, it's best to gently do up the cones near the bearings to once you feel contact / more resistance, then to take it even slower. You need the bearings to turn freely.

Tools for the job

To adjust the bearings of the rear wheel, you'll need the following tools (in order of appearance):

• Rags to protect handlebar, gears and brake levers whilst the bike is upside down (if that concerns you)
• 5 mm allen / hex key to remove rear brake pads (older models may require a spanner)
• 15 mm spanner to remove rear wheel nuts
• 17 mm cone spanner to adjust rear wheel bearing cones (they're thinner than regular spanners)
• Rags and degreaser to clean parts
• Good quality grease (as ever, I continue to use the excellent Exus E-G01 grease)

How to adjust a Brompton rear wheel to reduce wiggle and play in the bearings

In summary, you'll need to remove the rear wheel, clean and inspect the components, adjust the bearings and refresh the grease, put the wheel back on and check your adjustment. You may then need to repeat the process, except the clean and inspection steps, to adjust the bearings again to reduce resistance or 'wiggle'.

Removing the rear wheel

1. Make sure your Brompton is unfolded and turn it upside down (I used a bike rack)
1. Use a few rags (I use old t-shirts) under the handlebar to stop the bars, gears and brake levers from being scraped
2. Undo and remove the rear brake pads. I'd give them an inspection and clean before you put them back on later (5 mm allen key)
3. Undo and remove the rear bolts on both sides of the rear wheel (15 mm spanner)
4. Unscrew the rear gear cable so that the gear-chain is left to hang out of the wheel axle
5. Undo and remove the bolt on the non-drive side by the chain (15 mm spanner)
6. Taking hold of the chain at the closest point to the axle, unscrew counter-clockwise gently and remove the gear-chain
7. Apply pressure to the chain so that you can give it some slack to be able to remove it from the chain tensioner
8. The chain tensioner will spring back out of the way
9. Remove the chain tensioner by pulling it off of the axle (it just pulls off)
10. Remove the chain from the rear hub sprocket
11. Pull the wheel off the Brompton (and laugh at how tiny it is!)

Adjusting the bearings

You will see two cone / locking nuts on the non-drive / left hand side of the wheel. The one closest to the hub is for setting the bearing tension and the other is to retain that adjustment and reduce pressure from the clamping forces of the wheel nuts.

Give the cone nuts, bearing case and axle a fiddle and see what moves and to become familiar with how it works. By the end of your adjustment there should be no movement between the bearings and the cone nuts.

1. Undo the cone nuts and the bearing cup as far as you can along the axle, but removal is not necessary
2. Use caution, as the bearings may dislodge when the axle is moved and fall to the floor
3. OPTIONAL
1. Using a small screwdriver scrape out the bearings and place them on a rag for cleaning and inspection
2. Use a rag and degreaser to clear out and clean the old grease from within the bearing chamber
3. If there is any significant damage, such as indentations or cracks in the bearing chamber, then seek advice of a Brompton bike shop
4. Use a rag and degreaser to then clean the bearings and bearing retainer (ensuring you don't lose any)
5. If any of the bearings are heavily pot-marked or the retainer is deformed beyond gentle repair, then seek replacement bearings
6. Repeat the steps above on the drive side of the hub (including undoing nuts and bearing cone)
7. Grease both bearing chambers, bearings and the bearing retainer thoroughly
8. Place the drive side bearings in first and push the axle against them so that they will not come out, flip the wheel over and place the non-drive side bearings in
9. Whilst retaining pressure on the drive side, to stop the bearings falling out, using only light pressure, do up the inner cone nut, but allow for slack (3 mm)
10. This will keep the bearings from falling out
4. Now bring the outer cone nut in line with the inner, as this will make it easier to adjust
5. Now bring the inner cone nut closer to the bearings. Hand tight is fine and you should allow for a very small amount of play (< 1mm)
6. Using the cone spanners, hold the closest nut in place and then tighten the outer cone nut against the inner
1. If you do not tighten the outer properly, then this may come loose in time, but hand tight should be sufficient
7. Once tight, you should still have the same very small amount of play in the bearings
1. If it has increased or decreased, then re-adjust
8. Once happy with the adjustment, place the wheel back in the bike, put all of the parts back on in reverse order of the guide above, and spin the wheel
1. Don't replace the brake pads as you may need to remove them again
2. Do turn the bike up the right way when doing up the wheel nuts to ensure proper alignment
9. The wheel should move freely and there should be no discernible sideways play in the wheel
1. If there is play, take apart again and move the inner cone nut closer
2. If there is no play, but the wheel is harder to turn, take apart again and move the inner cone nut further away
10. Repeat until you're happy with the wheel movement
11. Clean and inspect the brake pads and replace onto the bike
12. Ride the bike to ensure gears, brakes and the wheel are working as expected

Hopefully the guide above has helped, but if you have any questions feel free to comment below and I'll get back to you.