Enduro Headset Bearing BO 40x52x7mm 45°/45°
Enduro Headset Bearing BO 40x52x7mm 45°/45°
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SKU: SKU: HB-202500
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🧡 Why Riders buy from us
🧡 Why Riders buy from us
Orders are packed ASAP
Most orders are packed and dispatched within an hour. Submit your order before noon PST on weekdays and it'll ship out the same day!
Genuine quality
We source all our products from reputable brands. Our bearings feature: dual lip seals, full complement MAX bearings for pivots, waterproof marine grease for superb wet weather protection and more!
Support the little guy
We work hard to make bike maintenance as easy as possible. As a small team, any show of support means a lot to us! Please tell a friend, leave a review and give us a follow on Instagram.
Professional support
Need help? Have questions? Check out our FAQs or send us a message - We respond quickly and have a boatload of bike repair and product compatibility experience!
60-day returns
We offer free exchanges and hassle free returns! Start an exchange.
✅ Compatible with
✅ Compatible with
This size bearing is also known in the bike Industry by these part numbers:
HSS 6011
BAA0695K
TH-070
TH-070E
MR170
MH-P16
TH MR082
📦 What's included
📦 What's included
ACB 4545 150 BO - 1-1/2 Black Oxide Angular Contact Headset bearing (40mm x 52mm x 7mm: 45x45 deg)
Angular-contact headset bearing featuring anti-corrosion Black oxide/Magnetite treated 52100 High-Carbon Chromium alloy races paired with grade 10 Balls. Black Oxide treatment provides an extra level of corrosion resistance and extended worry-free performance
Bearing Features:
- The Black Oxide headset bearings are treated in multiple chemical baths to achieve a 3 micron anti corrosive depth. This process also provides a secondary advantage of heat treatment making them tougher. The BO races then go through a secondary "super grind” polishing the rolling surface mirror smooth.
- Both Stainless and BO bearings are engineered with the largest balls possible, feature dual-lip seals riding in a micro-groove (labyrinth) and are filled 90% with extra high pressure Almagard 3752 grease for the ultimate protection against sweat and the elements. Enduro Angular Contact (A/C) bearings are designed so all balls are evenly engaged to spread the force over a larger surface area, minimizing wear and maximizing life.
- Static load - 977lbf / 4.34kN
Weight - 24g
Bearing Dimensions:
- Outside Diameter OD: 52mm
- Inside Diameter ID: 40mm
- Height H: 7mm
- Bearing Race Angles: 45x45deg

Product FAQs
When should I replace my headset bearings?
It’s recommended to replace the headset bearings on your mountain bike when they no longer spin smoothly or develop lateral "play". This can be every 1-3 years depending on ride time, trail conditions and your bike’s headset design. Worn headset bearings contribute to poor steering performance, steering assembly "play" which over time can cause frame damage.
Why invest in a quality headset?
Headsets undergo a great deal of mechanical stress and are often exposed to sweat, sports drinks and unsavory conditions; think of dust, mud and creek crossings. The Enduro bearings in this kit feature only 440C stainless steel balls and races to provide long life and superior corrosion resistance. High quality headsets feature "angular contact (AC)" type bearings, which are designed so all balls are evenly engaged to spread the force over a larger surface area, minimizing wear and maximizing life. The headset bearings included in this kit have a limited lifetime warranty. So rest assured that your hard earned money will go a long way!
What are angular contact bearings?
Angular Contact (AC) bearings are designed so all balls are evenly engaged to spread the force over a larger surface area, minimizing wear and maximizing life. Quality angular contact bearings often feature dual-lip seals riding in a micro-groove (labyrinth), and are filled with a high-pressure waterproof grease for the ultimate protection against sweat and the elements.
How do I replace my headset?
We recommend having headsets replaced only by a trained professional. Contact your local bike shop to schedule a service appointment. We offer aftermarket headsets for most makes and models. If you don’t see one for your bike, message us with your bike’s details and we'll do our best to provide one.
— Maintenance made easy —