All about the SRAM T47 bottom bracket

Bottom Bracket

The bottom bracket allows you to mount the crank in the frame and allows the crank to rotate while pedaling. There are many types of bottom brackets. Here, we'll discuss a SRAM T47 bottom bracket. T47 is a new type. The T stands for "threaded," or with a screw thread. 47 indicates the diameter of the screw thread in millimeters. Naturally, the thread diameter in the frame must also be 47 mm for this bottom bracket. However, there's another important measurement for bottom brackets: the width (also in millimeters). The width of the bottom bracket must match the width of the frame (measured at the cups where you screw the bottom bracket into).

Level of difficulty

Installing and removing a T47 bottom bracket is a moderately difficult job. In this blog post, I'll explain how to do it. I recommend removing the bottom bracket once every 12 months. This prevents it from getting so stuck that you can no longer loosen it. It also allows you to check if the bottom bracket is still running smoothly or needs replacing. It also gives you a good opportunity to clean everything thoroughly. The lifespan of a bottom bracket depends on factors such as weather and maintenance. To remove the bottom bracket, you first need to remove the crank. Here's how.

For which bike?

SRAM T47 bottom brackets (00.6418.033.003 or 001) are used in the Laval Road series. Make sure you have the correct bottom bracket. The width of the bottom bracket (77 mm or 85.5 mm in this case) must match the width of the bottom bracket shell of your frame.

Materials required

• T47 bottom bracket tool (link)

• Torque wrench (link)

• Degreaser (link)

• Dry lint-free cloth

• Assembly paste (link)

• Bike assembly stand

Installing a T47 bottom-bracket

• Place the bike in a bike stand.

• Remove any dirt from the frame.

• If brake cables and shifting wires run through the frame, check that they don't interfere with installing the bottom bracket shell.

• Clean the frame threads with degreaser and a lint-free cloth.

• Apply a thin layer of assembly paste to the frame threads.

• Apply a thin layer of assembly paste to the bottom bracket shell threads.

• Remove the left cup from the bottom bracket shell by carefully pulling it off. You can identify the left cup by the letter L on the shell. The left is the "non-drive-side." The right is the "drive-side" (the side of the bike where the sprockets and chain are located). The letters L and R are also printed on the cylindrical bottom bracket shell.

• Turn the left cup clockwise into the left-hand threads of the frame until hand-tight. It may take a while to find the right thread. The tightening direction is also indicated on the cups.

• Turn the right cup, including the cylindrical sleeve, counterclockwise by hand and tighten it into the right-hand thread of the frame. It may take a moment to find the thread. The tightening direction is also indicated on the cups. Be careful not to get any cables or wires in the way.

• Tighten both cups with the bottom bracket tool. Ensure the correct direction of rotation. Be careful not to damage the frame with the bottom bracket tool.

• Tighten both cups to the correct torque using the bottom bracket tool and the torque wrench. The torque is indicated in Nm on the bottom bracket. Ensure the correct direction of rotation.

• If applicable, install the included spacers. Consult SRAM.com for the correct thickness of the spacers for non-Laval bikes.

• For Laval bikes, contact us to determine which spacers to install on which side. If you replace or clean a bottom bracket, replace the spacers that were on the bike.

• To install a spacer onto the bottom bracket, press it firmly until you hear a slight click.

Un(!)installing a T47 bottom-bracket

• Place the bike in a bike stand.

• Using the bottom bracket tool, loosen the left cup counterclockwise. The tightening direction is indicated by an arrow on the cup, so loosening is the opposite direction. Do this carefully to avoid damage. You may need to apply considerable force.

• Using the bottom bracket tool, loosen the right cup clockwise. The tightening direction is indicated by an arrow on the cup, so loosening is the opposite direction. Do this carefully to avoid damage. You may need to apply considerable force.

• Clean the frame threads with degreaser and a lint-free cloth.

• Clean the threads of both frame cups with degreaser and a lint-free cloth.

• Remove any dirt from the frame.

• Check that the brake cables and shift wires are still properly secured (so they don't get in the way when installing the bottom bracket).

Checking a T47 bottom-bracket

• Place the bike in a bike stand.

• Remove the chain from the front sprockets.

• For a single-speed bike (1 front sprockets):

  • Shift the rear derailleur to the smallest cog.

  • Push the bottom of the derailleur cage towards the front of the bike to release the chain tension.

  • Remove the chain from the front sprockets. Tip! Drape a cloth over the right chainstay to prevent chain grease from getting on the chainstay.

• For a double-speed bike (2 front sprockets), it's easiest to remove the chain via the power link (since the front derailleur cage prevents you from removing the chain from the front sprockets). Here's how.

• Now turn the crankset and feel if it moves smoothly. The resistance should be comparable to that of a new bottom bracket shell.

• Give the crankset a slight crank and release it. Check that the crankset gradually slows down and doesn't suddenly stop.

• If the crankset still turns smoothly and gradually stops, the bottom bracket is still working. If not, you'll need to disassemble the cranks and investigate the cause.

  • Here's how to disassemble the cranks.

• Once the cranks are removed, you can inspect the bottom bracket.

• First, remove dirt and grease with a lint-free cloth.

• First, check that both blue O-rings (left and right cups of the bottom bracket) are still in place and in good condition. If not, the bottom bracket needs to be replaced.

• Then, with one or two fingers inside the cup, try turning the bearings of the left cup. Then, the bearings of the right cup. If these don't turn or turn with difficulty, the bottom bracket needs to be replaced.