Name: Shimano BB-UN300 Square Type Bottom Bracket
Rating: 5.00 (1 reviews)

The Shimano BB-UN300 is a square taper bottom bracket built to deliver long-lasting performance and dependable support for your drivetrain. Designed with Shimano’s renowned durability, it’s ideal for recreational and everyday riding.

Smooth, Stable Operation: Featuring cartridge bearings, the BB-UN300 offers smoother rotation and reduced friction over extended use. Its internal construction ensures a sealed, maintenance-free experience that stands up to weather and debris.

Improved Chainline Stability: The integrated chain line stabilizer helps maintain precise alignment, contributing to better drivetrain performance and gear shifting. This feature is especially valuable in keeping your ride efficient and responsive.

Multiple Structure Options: Whether you ride with a standard setup, E-type front derailleur, or chain case, the BB-UN300 supports all three configurations. This makes it a flexible upgrade or replacement for a wide range of bicycles.

With an aluminum adapter and steel axle, the Shimano BB-UN300 balances strength and weight. It’s a cost-effective solution for riders seeking Shimano reliability without compromising on quality.

Specifications

Model No	BB-UN300
Series	Shimano
Structure\|Standard	Yes
Spindle\|Square Type	Yes

Axle Length/Shell Width (mm)	107\|68 (BC1.37), LL113\|73 (BC1.37), XL118\|73 mm, LL123\|68 (BC1.37), LL123\|73 (BC1.37)
Axle Length/Shell Width (mm)*	D-H\|68 (BC1.37), D-NL 122\|73 (BC1.37), D-EL 127\|68 (BC1.37) *Remarks: w/ Crank Arm Fixing Screws spec. only
Axle Length/Shell Width (mm)**	MM110\|68 (BC1.37), LL113\|68 (BC1.37), 117.5\|68 (BC1.37), XL118\|68 (BC1.37), D-NL 122\|68 (BC1.37) **Remarks: w/ Crank Arm Fixing Screws spec. is available

Features

Smooth Cartridge Bearing Performance: Sealed cartridge bearings ensure low friction and long-lasting smooth rotation with minimal maintenance.
Stable Chainline Support: Built-in chainline stabilizer improves drivetrain alignment for efficient pedaling and precise shifting.
Versatile Structure Compatibility: Compatible with standard, E-type and chain case setups, offering installation flexibility across various bikes.
Durable Construction: Features a sturdy steel axle paired with a lightweight aluminum adapter for a balance of strength and performance.
Multiple Length Options: Available in a wide range of axle lengths and shell widths to match specific frame and crank configurations.

Fit and sizing

Fit: Threaded

Between sizes? from your measurements.

Warranty and support

Shimano Bicycle Components Warranty: Shimano warrants to the original owner that Shimano-branded bicycle components, including STEPS Drive Units and Wheels, are free from defects in materials and workmanship for a period of 2 years. DURA-ACE and XTR components, including DURA-ACE and XTR wheels, are covered for 3 years from the date of original purchase.

Shimano Footwear and Soft Goods Warranty: Shimano footwear and soft goods are covered for 1 year against defects in materials and workmanship.

Lazer Products Warranty: Lazer products are warranted against defects in materials and workmanship for 1 year from the date of purchase.

PRO Products Warranty: PRO branded products are warranted for 2 years against defects in materials and workmanship under normal conditions. Additionally, handlebars, stems, and seat posts from the model year 2017 onwards are covered for 10 years from the date of original purchase.

Wheel Warranty: Shimano warrants all wheels to be free from defects in materials and workmanship. DURA-ACE and XTR wheels are covered for 3 years, while all other wheels are covered for 2 years. Normal wear and tear parts such as bearings, spokes, and braking surfaces are not covered under warranty.

Exclusions: This warranty does not cover:

Products modified, poorly maintained, or used improperly.
Damage resulting from accidents, abuse, or improper assembly.
Wear and tear parts such as bearings, seals, free hubs, and decals.
Damage due to unauthorized repairs or modifications.
Cosmetic damage, including deterioration of the surface finish or appearance.

For any warranty claims, please contact us directly, and we will assist you with the process.

Questions after delivery? Ask TBA Guide or WhatsApp us.

Shipping and returns

We ship across India. Shipping is free on orders above ₹2,000 and ₹99 below that. Cash on delivery is available on orders up to ₹20,000, with a COD charge that depends on the order value. For a delivery estimate, enter your pincode in the box above the add-to-cart button: it shows the courier's own estimate for your address, not a promised date. If a parcel is held up we chase the courier until it is delivered. Full shipping policy

Most Shimano products take a little longer to ship.

Returns can be started within 7 days of delivery on unused items in their original condition with all tags and packaging. Apparel, helmets, gloves and similar items are returnable; wetsuits and products discounted by more than 5% are not. Compatibility questions are not grounds for a return unless our listing was wrong, so ask us before you order if you are unsure. Return shipping is arranged by you; on an accepted return you can choose an exchange, store credit or a refund after shipping and transaction charges. Orders can be cancelled only until they are processed. Full return and refund policy