Ai-41 IS41/30 Headset Bottom Assembly - silver/IS41/30

Acros Ai-41 IS41/30 Headset Bottom Assembly

Item number: 34878

Worry-free product, made in Germany: The Ai-41 Headset Bottom Assembly by Acros

As a subsidiary of a bearing manufacturer, Acros uses its expertise in bearing technology to develop headsets that won't disappoint. Its particularly high-quality stainless steel bearings, which are more complex to produce but boast outstanding durability, have been setting the standard in the after-market sector for years. Seals optimised for the rough everyday life of a bicycle effectively protect the inner mechanisms of your headset from water and dust, and specially-developed bearing grease ensures a consistent layer of lubrication even at low speeds and high loads. The combination of all these components guarantees a long, worry-free life for your headset, regardless of your riding environment.

Integrated (IS) means that the ball bearings lie directly in the frame and no bearing cups are required. Simple assembly and interchangeability are what make this design unbeatable.

for 1 1/8" lower head tubes combined with standard 1 1/8" steerer tube.


Cross Country, Road
Lower Bearings:
1 1/8"
Steerer Tube:
1 1/8"
integrated (IS)

Technical Information:

stainless steel angular contact cartridge bearings
Bottom Stack Height:
1.1 mm
Bottom Outer Diameter:
41 mm
Bottom Inner Diameter:
30 mm
R3 (metal-reinforced rubber seal)


  • double sealed

Standardized Headset Identification System (S.H.I.S.):

In order to clarify and bring uniformity to a sea of headset standards, manufacturers Acros, Cane Creek, Hope, Race Face, Reset Racing and Ritchey have agreed upon using a shared nomenclature, which will likely include more participating companies in the future. This system takes into account a combination of frame and fork dimensions. Both the top and bottom parts of the headset are marked by two alphanumeric identifiers. The first identifier indicates the type of headset (External Cup, Zero Stack, Integrated) and head tube diameter. The second identifier - separated from the first by a backslash - indicates the diameter of the steerer tube. When referring to a complete headset, the specifications of both top and bottom parts must be combined.


Bearings contained within headset cups that are located outside of the frame (External Cup)
Bearings contained within pressed-in headset cups where the cup and bearings rest inside the frame (Zero Stack)
Bearings that fit directly into a bonded or machined interface that is integrated into the frame (Integrated)

Use the AH-T DIY to press in your headset.


Stainless Steel Bearings
Bearing technology makes up the core of Acros components. Acros has the possibility to adapt its ball bearings optimally to requirements in order to achieve the best possible result. Stainless steel bearings have excellent corrosion protection properties. For rolling bearings, hardenable materials are required, so bearings made of stainless steel are also magnetic.

R3 Seal
The sealing technology is a decisive factor in the design of the Acros components. The R3 seal has a shaped lip with sheet metal reinforcement. The characteristics of this system are outstanding: the pushed on seal is tight, defined and thus guarantees superior functionality with amazingly low friction.

Manufacturer Number:



  • 1 x Acros Ai-41 stainless steel lower bearing
  • 1 x crown race


  • silver/IS41/30: 22 g
  • 100 day return period
  • Online since 1998
  • Trusted Shop 4.89 / 5.00


  • silver/IS41/30, in stock

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