A seatpost shim lets you easily fit the 27.2mm diameter ShockStop Seatpost OR Dual-Position Seatpost into your larger seat tube.
This shim will let you easily fit the 27.2mm Dual-Position Seatpost or ShockStop Seatpost into your larger seat tube. Just drop the shim in your frame's seat tube and insert the seatpost. Once installed, the shim is essentially invisible.
• Fits 28.6, 29.8, 30.0, 30.4, 30.9, 31.6, and 31.8mm outer diameter • Fits 27.2mm inner diameter • 100mm (4-inch) length spreads out clamping load along seatpost and frame
27.2-28.6mm - 16 g 27.2-29.8mm - 30 g 27.2-30.0mm - 33 g 27.2-30.4mm - 36 g 27.2-30.9mm - 43 g 27.2-31.6mm - 52 g 27.2-31.8mm - 55 g
100 mm (4 inches)
Can I use a shim to adapt to a non-round or "aero" seatpost?
Unfortunately, the seatpost shim is only designed to adapt our 27.2mm round seatpost to other larger round seatpost diameters (for example, 31.6mm or 30.9mm). If your seatpost is oval or "aero" shaped, then both of our seatposts are not compatible with your bicycle.
My bike has a 25.4mm seatpost. Do you have a shim for that size?
The short answer is no. Both of our seatposts are only available in 27.2mm diameter. Since that is larger than 25.4mm, it is not possible to use a shim to adapt the seatpost to your frame.
To read more Frequently Asked Questions, click here.
Different bikes sometimes have different seatpost diameters. The ShockStop Seatpost and Dual-Position Seatpost are both 27.2mm in diameter, so if your bike's seatpost is larger, you'll need a shim to adapt our seatpost to your bike's frame. Don't worry though, the shims are super-lightweight and essentially invisible once installed.
Not sure what size seatpost you have currently? There are a couple different ways to find out.
• Most seatposts have the diameter printed somewhere near the bottom of the post. You'll need to remove the seatpost from the bike frame (mark your existing seatpost height with a bit of tape before you remove it so you can replace it easily), and look for a number like 27.2, 30.9, or 31.6 (etc.). That is the diameter of the post. • If you know the make, model, and year of your bike, you may be able to look up the seatpost diameter online. Feel free to shoot us an email at email@example.com - we'll see if we can help out. • Ask your local bike shop - they'll be able to accurately measure your bike's seatpost.
Non-compatible posts: Unfortunately, if your bike's seatpost is smaller than 27.2mm (for example, the 25.4mm posts found on some recent model Cannondale Synapses) our seatpost is currently not compatible with your bike. Likewise, if you have a bike with an aero/oval/non-round seatpost, or if your bike has an integrated seatmast, the seatpost is also not compatible.
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