Nowadays, bottom brackets have disposable sealed cartridge bearings and, as frames have got beefier, bearings have increased in diameter to allow for lighter, stiffer chainsets using larger axles. And so goes the irresistible march of technological progress. However, while a traditional bottom bracket sits inside the frame and includes the axle in a single unit, Hollowtech bearings sit outside the frame and the axle is integrated into the crank. To check if your BB needs replacing, drop the chain off of the smallest chainring and spin the cranks. The left-hand crank is secured by two pinch bolts the compression cap in the end presses the axle against the bearings while the pinch bolts hold it in place.
Turning the handle will be really easy at first. In Bottom bracket replacing, you can do this as part of your scheduled maintenance depending on your mileage and the quality of parts used. This is a Bottom bracket replacing opportunity to clean the BB face and shell and check for any corrosion. Ray Step 7a: step 7a Amanda Thomas. Viewed 48k times.
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The axle diameter remains 24mm though, so its walls need to be thicker than a BB30 axle to retain rigidity and BB86 systems tend to be slightly heavier than their BB30 equivalents. Pull the crank arm off its spindle — it should slide off easily without much force. But that was not the case. Mail to Friend Mail. Previous Video Next Video. Post as a guest Name. Help Translate iFixit. Home News Product News. Sign up for our newsletter Newsletter. It only takes a minute to sign up. If you answered no Bottlm both All about latino, keep Bottom bracket replacing. Or Bottom bracket replacing to visit local bike repair?
This article will discuss how to remove and install bottom brackets used in threaded shells, including three-piece cranks, threaded "thru-spindle" external bearing cups, and bottom brackets used in T47 shells.
- Once upon a time, all bikes were made of steel.
- This is a pretty messy job.
This article will discuss how to remove and install bottom brackets used in threaded shells, including three-piece cranks, threaded "thru-spindle" external bearing cups, and bottom brackets used in T47 shells. For the two-piece crankset, there is a left and right arm, but the spindle is attached to one of the cranks.
The spindle passes through the bearings in the bottom bracket shell. The common three piece crankset has left and right arms with the bearing and spindle integrated. The right-side drive-side thread is a left-hand thread, which tightens counterclockwise and loosen clockwise. The less common Italian has both left and right sides with right-hand threading. Both sides tighten clockwise and loosen counterclockwise.
Begin by removing both cranks. Inspect the threaded cups for tool fittings. There are many different designs and tool options. Insert the tool fully and remove the non-drive left-side cup by turning counterclockwise, holding the tool firmly to the cup. Remove any internal sleeve. Take note of any spacers under the cup for reassembly. Inspect for arrows indicating direction of tightening and loosening. Begin with thread preparation. New cups may come with dry threadlocker already applied.
Install these as they come. This creates a durable barrier in the threaded joint and prevents corrosion. The liquid compound will provide lubrication when tightening before drying and hardening to seal and keep the cup in securely.
Install any spacers as required on the right-side cup. Thread right side counterclockwise into the shell. Typically this is between 25 to 30Nm. My Account. Trade Resources. What Tools do I need? Two-piece crankset with a thru-spindle bottom bracket.
Example of three-piece crankset. Apply pressure to tool while removing cup. Thread retaining compound. In this article 1 Preliminary Info 2 Removal 3 Installation. Back To Top.
Cambridgeshire Classic March 1. So long story short, I dropped this frame by accident on a sharp corner and it caused a smallish dent. Insert the bottom bracket tool into the bottom bracket. That's about all I've got. I just registered here to ask for help. It has a 30mm diameter axle with pressfit bearings like BB30, but pushes the non-driveside bearing out by 11mm, for a bottom bracket width of 71mm.
Bottom bracket replacing. External threaded bearings
Workshop: Replacing Shimano, Truvativ or FSA bottom brackets - BikeRadar
By justin loretz. High loads are continuously channelled through rotational motion onto the bearings, which take the full brunt of both bodyweight and muscle power. Servicing will rarely involve actually repairing the BB itself. Diagnosis involves listening for rough sounding noises, and feeling for play or lack of smoothness when spinning the cranks. Remove the chain, spin, feel and listen.
Quality aftermarket replacements such those by SKF or Crank Brothers can be worthy alternatives, but generic econo-brand BBs are a bit hit and miss. Make sure the bike is securely positioned and immobile. Using an 8mm or sometimes 10mm Allen key or a 14mm socket on older standard retaining fasteners , remove the bolts on both sides — be prepared to put some welly into it, or use your cheater bar. Any that are worn or shallow risk pulling through without removing the arms.
Loosen the two 5mm bolts clamping the crank arm to the spindle. Now unscrew the nylon retaining bolt with the Shimano crank installation tool TL-FC16 , a sort of lobed insert with a circular handle.
Use a rough cloth or work glove to get a better grip if really stuck. First back the extractor press all the way out, then thread the tool into the arm, nipping it up with an adjustable spanner. ISIS and Octalink versions require a larger diameter stop to help extraction. Turn the draw bolt clockwise, ensuring the arm begins to move. If the tool pulls out of the crank threads, it will need to be removed by a professional. On HollowTech II arms, the safety latch needs to be swung upwards with a screwdriver, releasing the pin from the locator hole in the end of the spindle.
The fit may be snug. Wear gloves, as some crank spiders have sharp machined edges. Unscrew any bottom bracket guide screws that might be protruding into the frame. Ensure that the splined tool is fully engaged and squared up against the cup before loosening to prevent slippage. On HT II external cups, ensure the tool is aligned before applying force. The same thread directions apply see Step 4a. Use a cheater bar if your tool permits.
A judicious blow with a wooden block or mallet can work wonders. Avoid unscrewing the cup with unprotected hands to avoid any metal splinters.
A healthy shot of WD and an old toothbrush works well. Check for corrosion due to moisture, and wipe clean. Grease is best for long-term serviceability, but a generous amount of medium threadlock compound works well for added security. Consider drilling a drainage hole in the BB shell to prevent water ingression. Torque should be quite high somewhere above 35N. Any spacers should be made of metal, should square up nicely and be of the correct diameter.
Tapers and splines should be greased to prevent noise, creaking and corrosion, and a dollop of threadlock on the retaining bolts will prevent loosening. This allows you to use slightly less torque, and may increase the number of removal and installation cycles.
Ensure you use the correct Octalink spline length: short for Shimano XTR, and long for everything else. Apply grease to the crank spindle and insert the crank through to the bearing cups. A good shove should get it to push all the way through to the other side.
Use a rubber mallet to help it along. Line up and slide the arm onto the spindle, then draw it on by tightening the nylon bolt. Press down the safety latch pin. The twin bolt arms should be tightened gradually, a little at a time, until even torque is reached about 15N. Check spacing between the chainstay and inner chainring and crank arm. When retightening crank arms, put them on a bit further up the taper with each removal and reinstallation.
Test the front derailleur. Also, release a bit of cable by turning the shifter barrel adjuster clockwise about a half a turn — just enough to prevent chain rub on the inside of the front mech cage. Loosen the small Allen grub screw, then rotate the ring clockwise until any play is removed but the cranks still spin freely.
Retighten the grub screw. It should be robust enough to allow the use of a cheater bar. Wrap the handle with duct tape to prevent damage and get a better grip, then slide a strong tube onto the handle. Take off both wheels and place entire bike onto the tool, using the frame and body as a lever while steadying the BB cup in the tool with your free hand. Cheat 3: Using a block of wood, give a sharp blow to the tool handle to dislodge a tough external BB cup.
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