Quick Summary
The YELARXI bicycle seat post adapter shim is a 1 pack black alloy shim for converting a 30.9 mm seat post to fit a 31.6 mm seat tube. It is designed for bikes where that size change is needed, including mountain bikes, road bikes, city bikes and electric bicycles.
The adapter is described as an aluminium alloy part with a 60 mm length, a 0.5 mm wall thickness, a 3.5 mm compression slot and a 33.5 mm top flange diameter. If these measurements matter to your frame and seat post combination, check them carefully before choosing an offer.
Key Details
| Detail | Verified information and buyer relevance |
|---|---|
| Brand | YELARXI – useful for identifying the exact adapter shim. |
| Product type | Bicycle seat post adapter shim for changing 30.9 mm to 31.6 mm. |
| Colour | Black. |
| Pack quantity | 1 pack. |
| Material | Aluminium alloy. |
| Length | 60 mm, which is relevant where frame insertion depth matters. |
| Wall thickness | 0.5 mm. |
| Compression slot | 3.5 mm wide. |
| Top flange diameter | 33.5 mm. |
What to Compare Before Buying
- Seat post size: This adapter is for a 30.9 mm seat post. Compare that against the post you already own.
- Seat tube size: It is made for a 31.6 mm seat tube. Check your frame size before ordering.
- Overall measurements: The 60 mm length, 0.5 mm wall thickness and 33.5 mm top flange diameter may matter where space and fit are tight.
- Pack quantity: The listing is for 1 pack, so confirm whether you need one shim or more than one.
Compatibility, Size and Fit
This shim is intended for the 30.9 mm to 31.6 mm seat post and seat tube combination named above. The selected bike frame and post should match those measurements exactly for the intended fit.
Because seat post and frame sizes must align, measure both parts before choosing an offer. That is the main check for this product.
Setup and Correct Use
Installation is described as a simple insert-and-tighten process. The shim goes into the 31.6 mm seat tube, the 30.9 mm seat post slides into the shim, and the seat clamp bolt is then tightened normally.
The product text also states that a torque wrench should be used and that the frame manufacturer’s recommended torque specification should not be exceeded.
Before You Decide
Confirm the 30.9 mm to 31.6 mm size match before choosing an offer. Check the frame and seat post measurements, the 1 pack quantity, and the stated torque guidance for your bike.
