One of the repairs being added to our Bike Doctor app (iPhone and Android) is how to remove your bottom bracket.
Why, oh why, would you want to do that?
The bottom bracket is often the source of many irritating creaks on your bike. If you hear creaking as you pedal, then it may well be because there’s dirt or water trapped in the bottom bracket. Or, it may have simply worn out over the course of the thousands of miles you’ve been cycling.
The classic question people ask is: When should you replace it?
Unfortunately, there’s no easy answer. The one we demonstrate in this repair had been in the bike for 2 years. I didn’t think it had worn out, but when we pulled it out of the bike, it was clear that it had gone.
Most mid-priced bikes of around £500 – £800 often have brand less components fitted to save money. It’s worth replacing them with a known brand. This will give you a more reliable service in the long term. It will also generally be more efficient and less noisy. All of which equals a happy cyclist.
How much is a new bottom bracket?
Fortunately, a new bottom bracket isn’t too expensive. The one we replaced it with cost £22. Make sure you replace your bottom bracket with a like-for-like. This will often mean measuring the old bottom bracket (which you can effectively do in a vice) or, more commonly, going to your local bike shop and asking “Can I have a replacement one of these please?”
Bottom brackets (common referred to as BBs) come in many confusing variations. Square taper is the old standard, however there are newer, less common systems such as ISIS, Octalink and through-axle. These have slightly different maintenance instructions, but none the less you’ll find our advice here useful.
How should I know if I need to remove my bottom bracket and replace it?
If you’ve got creaks on your bike and you feel they are coming from that area, then you can try the following steps:
- Check the cranks are tight by trying to wiggle them side to side while holding the frame. Use a long length Allen key to tighten them if they are not.
- Remove your pedals and grease them.
- Check the chainring bolts are greased and tight.
- Check the saddle post is greased and tightened in to position.
If creaks persist then it may well be due to the bottom bracket.
You should also remove it if you’ve simply not serviced your bike in a long time. Generally you should do this once per year.
What tools will I need to remove a bottom bracket?
As with most bike repairs, a number of specialist tools are needed. Obviously, it’s cheaper to buy an entire toolkit that will include everything you’ll need rather than buying bits individually.
- Crank extractor (Also referred to as crank puller) – This is necessary for most systems but some have a one-key release or self-extracting system. This won’t require a crank remover.
- Bottom bracket removal tool
- Allen key – ideally long length
- Adjustable wrench – ideally long length as the cranks and bottom bracket can be fairly jammed in there.
- Grease – use a high quality grease as there’s a lot of fast moving components here that need to spin for a long time.
- Torque wrench – if you want to exactly stick to manufacturers recommended torque. (Optional as this is expensive!)
How to remove a bottom bracket
Note: A very special thank you to Lunar Cycles, which is a bike shop in Camden who’ve helped me bring these repairs to London Cyclist and to the Bike Doctor app.
1. Start by shifting in to the largest chainring. This is useful for protecting your hands in case they slip.
On captive-bolted cranks, you can remove the cranks by removing the fixing bolt which has an 8mm Allen bolt with a washer. Turn counter clockwise to remove. If there’s any washers inside the arm, remove them.
Other systems, as in the picture above will require a crank extractor to pull the crank out.
After you’ve removed the Allen bolt, you’ll need to use the crank extractor. Start by unscrewing the tool all the way until the end is fully retracted.
Then, carefully line up the crank extractor with the threads. Incorrectly fastening while misaligned can result in stripping the crank threads and ultimately ruining the crank. Once you are satisfied the crank extractor is firmly and accurately in place, turn clockwise on the drive side so that you start to feel the crank being pushed off the taper. This will require a lot of effort at first but then will become easy as it comes off.
Repeat on the left side.
2. With both the cranks removed, it is time to remove the bottom bracket. This can be a pain. Especially, if it hasn’t been removed and re-greased in a while.
Start by securely placing the bottom bracket remover onto the left side of the bottom bracket.
3. Unfasten the bottom bracket from the left side in a counter clockwise turn. It is important to not slip as you may damage the threads.
Note that as with any of these repairs, a longer tool (often more expensive) will make a huge difference. If you really can’t get it off, then you’ll need the help of your local bike shop.
Repeat this procedure on the right side and turn it clockwise to loosen the cup holding the bottom bracket in place.
3. With the bottom bracket removed, it is very important to thoroughly clean the bottom bracket area. The dirt here is often the source of creaks. Use degreaser and remove any oxide build-up. If there’s any dirt left, scrub it using a toothbrush with degreaser.
Dry off the area. When it is fully dried, grease the threads using high-quality grease.
If there’s water trapped in the bottom bracket area then this is a bad sign and means it is leaking in to the frame from somewhere. This can potentially be from the bottle cage bolts if they are missing or it is possible as the cups were not properly tightened.
You should also check the condition of the threads. If they look cross threaded then you should get a knowledgeable local bike shop to re-thread them before further damage is done. Also, check the outer face of the bottom bracket is correctly faced. Correctly faced means it is completely square. If it isn’t then the bearings will wear out very rapidly. A local bike shop should be able to get your bottom bracket faced if it needs it.
Check your bottom bracket by spinning the axle and seeing if it freely spins. If you feel it crunching then the ball bearings may be worn. Most bottom brackets are sealed which means they can’t be serviced so they’ll need to be replaced.
4. If you are installing a new bottom bracket then make sure you’ve chosen the correct one for your bike. This can be tricky as there’s a pretty wide variety. Use your existing BB to guide you. Your local bike shop should be able to offer advice if you get stuck.
Put plenty of grease on the threads of the bottom bracket.
The new BB will have a removable side which will typically be on the non-drive side. Remove this and slide the unit in drive side first. This side tightens anti-clockwise. Tighten it by using your hands only. This will allow you to feel whether it’s going in crooked.
If you have Italian cups then these will be marked 36mmx24 TPI. Unlike the English cups, they require clockwise turns to tighten on both sides.
5. With the bottom bracket in place, check from the left side whether it looks correctly aligned inside the frame. There should be equal space around the bottom bracket.
6. The left side can be tightened clockwise. Tighten this using your fingers until there’s only around 1cm of thread left showing.
7. Use a suitable BB removal tool to firmly tighten the drive side first anti-clockwise. This should be followed by the left side which will need to be firmly tightened clockwise. Note this doesn’t need to go all the way in to the frame. If you have a torque wrench then you can use it to tighten it to the manufacturers specifications. This is usually around 50Nm.
8. Grease the taper and then re-install the cranks using an Allen key.
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As seen on The Guardian, BBC and The Independent.