Shimano RD-R7100 Y3JU9801T inner derailleur cage

Shimano ’s Y3JU9801T inner plate is a genuine spare part designed for the Shimano 105 RD-R7100 12-speed rear derailleur.

Also known as the ‘Inner Plate’, this plate forms the inner part of the derailleur cage, situated on the spoke side. It helps to hold and guide the chain around the rear derailleur pulleys.

Part number Y3JU9801T is officially listed by Shimano in the RD-R7100 exploded view as part no. 11, under the designation ‘Inner plate’.

This part allows you to replace only the damaged section of the derailleur cage rather than having to replace the entire rear derailleur. This is a particularly useful solution when a fall, impact or wear and tear has damaged the inner plate whilst the rest of the derailleur remains in good condition.

The cage plays an important role in guiding the chain: it keeps the pulleys in position and helps ensure the chain runs smoothly between them. A warped or broken cage can therefore disrupt the operation of the drivetrain.

Key features of the Y3JU9801T Shimano

• Genuine Shimano spare part.
• Chape/Inner plate for the rear derailleur.
• Compatible with the Shimano 105 RD-R7100.
• Designed for a 12-speed drivetrain.
• Allows you to replace only the damaged part.
• A cost-effective solution compared to replacing the entire derailleur.
• Helps to maintain and guide the chain correctly.
• Shimano part number: Y3JU9801T.
• Part no. 11 in the RD-R7100 exploded view.

What is the purpose of the rear derailleur’s inner cage?

The rear derailleur cage is the component that surrounds the two pulleys and guides the chain along the lower part of the derailleur.

The inner plate holds the pulley system in place and contributes to the rigidity of the assembly. It therefore helps ensure the chain runs smoothly and that the derailleur functions normally during gear changes.

In the event of an impact, the cage may become bent or damaged. Replacing just the inner plate can then restore the derailleur to working order without having to replace the entire component.

Shimano compatibility: Y3JU9801T

Part number Y3JU9801T is specifically associated with the Shimano 105 RD-R7100 12-speed rear derailleur. Shimano identifies it as the ‘Inner plate’ part, number 11 in the derailleur exploded view.

It is important not to rely solely on the number of speeds to determine compatibility. Derailleur hangers and inner plates may have different dimensions, shapes and mounting systems depending on the generation of derailleur.

Tip: check the exact part number of your derailleur before ordering. For this part, the part number to look for is RD-R7100.

Why replace only the inner cage?

A fall or impact can damage the cage without necessarily affecting the derailleur body, the springs or the gear-changing mechanism.

In this case, replacing only the inner cage (Y3JU9801T ) allows for a targeted repair.

This approach has several advantages:

• lower cost than replacing the entire derailleur
• the original derailleur is retained
• a repair tailored to a localised impact
• maintains the Shimano 105 12-speed configuration
• the option to replace a single part rather than a complete component

Our workshop tip: before replacing the derailleur hanger, also check the condition of the pulleys, the fixing screws and the derailleur body. Following a significant impact, check in particular that the derailleur hanger and the alignment of the assembly have not been affected.

If only the inner plate is damaged and the rest of the derailleur is in good condition, this part offers a logical and cost-effective repair solution.

Technical specifications