Seatpost Clamp Size: Measure the Frame, Not the Post

Measure the seat tube, not the seatpost

A seatpost clamp is sized to the outside of your frame's seat tube, not to your seatpost. The fastest way to get the number is your bike maker's spec sheet. If you cannot find it, measure the seat tube in millimeters with calipers, then buy the clamp that matches.

That one detail trips up a lot of orders. Say your seatpost is 27.2mm, a common size. The clamp still has to fit around the frame, and the frame is wider than the post that slides inside it. Wolf Tooth's smallest clamp is 28.6mm for exactly that reason.

How do I find my seatpost clamp size?

Start with the bike maker. Search the brand's site with the model, the year, and the frame material. Many brands list the clamp diameter in the geometry or spec table.

No luck there? Measure it yourself.

1. Loosen the old clamp first.Take the tension off the bolt so the clamp is not squeezing the tube while you check it.
2. Measure the seat tube, not the post.Put calipers across the outside of the seat tube, just below the clamp, and read the number in millimeters.
3. Match it to the nearest clamp size.Wolf Tooth says its clamps fit round tubing within 0.5mm of the stated size, so a 34.9mm clamp fits a seat tube that measures anywhere from 34.4mm to 35.4mm.
4. No calipers? Print the template.Wolf Tooth's printable seatpost clamp measurement guide includes a measuring tape and size circles. Print it at 100 percent scale, then set your old clamp on it with the lip facing up.

Paint and manufacturing tolerances mean your reading will rarely land exactly on a size. That is normal. Pick the closest size inside that half-millimeter window.

Wolf Tooth seatpost clamp sizes, in millimeters

28.6 to 39.7mm

The full Wolf Tooth size range

Wolf Tooth lists the bolt-on clamp in 28.6, 29.8, 31.8, 34.9, 36.4, 38.6 and 39.7mm, sized to the outside of the seat tube.

±0.5mm

How far off a seat tube can measure

A Wolf Tooth clamp fits round tubing within half a millimeter of its stated size, which covers paint and frame tolerances.

6 Nm

Maximum clamp bolt torque

Wolf Tooth's general rule for its clamps. Carbon seatposts and dropper posts usually want much less, so check their specs first.

Bolt-on or quick release?

Pick the bolt-on clamp if the saddle height is set and stays set. It is the lighter, cleaner option, and nobody can walk off with your seatpost.

Pick the quick-release clamp if you move the saddle a lot, like dropping it for a descent on a bike with no dropper, or sharing one bike between two riders. Wolf Tooth's QR clamp remembers the torque you set with a 4mm hex key, so every time you close the lever it clamps to that same setting.

We carry the Wolf Tooth Seatpost Clamp and the Wolf Tooth Quick Release Seatpost Clamp in 28.6, 29.8, 31.8 and 34.9mm.

Installing a seatpost clamp

Grease, paste, or nothing depends on what your frame and seatpost are made of. Here is how Wolf Tooth breaks it down for its clamps.

What goes on the seat tube and seatpost

Aluminum or steel

Use grease on a bolt-on clamp. On a quick-release clamp, grease is fine only when both the frame and the seatpost are steel or aluminum.

Carbon

Use carbon paste, never grease, on either clamp type.

Titanium

Use copper paste, never grease, on either clamp type.

Any material

Check your frame and seatpost maker's own recommendation before you apply anything. Theirs wins.

Line up the slot in the clamp with the slot in your seat tube. Some frames slot the front, some the back. If yours has more than one slot, center the clamp's slot between them.

Seat the clamp's inner lip fully on top of the seat tube before you slide the seatpost in. Then set your saddle height and tighten the bolt with a 4mm hex torque wrench. Use the torque printed on your frame or seatpost, and never go past 6 Nm on a Wolf Tooth clamp. A carbon post or a dropper usually wants much less, because too much clamp force can crush a carbon post or make a dropper bind.

One fit exception from Wolf Tooth: older Ibis carbon frames with Ibis's own curved seat collar will not take a standard clamp. Newer Ibis frames with a conventional clamp, like the Ripmo V3 and Ripley V5, will.

Common questions

Is a seatpost clamp the same size as my seatpost?

No. A seatpost clamp is sized to the outside of the frame's seat tube, which is always bigger than the seatpost that slides inside it. Wolf Tooth's clamps start at 28.6mm, so even its smallest is larger than a 27.2mm seatpost.

How do I measure for a seatpost clamp?

Check your bike maker's spec sheet first. If it is not listed, loosen the old clamp and measure the outside of the seat tube with calipers, in millimeters. Pick the clamp size closest to that reading.

What if my seat tube measures between two sizes?

Paint and frame tolerances make that normal. Wolf Tooth clamps fit round tubing within 0.5mm of their stated size, so a reading of 35.2mm still fits a 34.9mm clamp.

How tight should a seatpost clamp be?

Use the torque on your frame or seatpost, set with a torque wrench. Wolf Tooth's general limit for its clamps is 6 Nm, and carbon seatposts and droppers usually need much less.

Should I grease a seatpost clamp?

Only on aluminum or steel. Use carbon paste on a carbon frame or seatpost and copper paste on titanium. On a quick-release clamp, skip grease unless both the frame and seatpost are aluminum or steel.

Bolt-on or quick-release seatpost clamp?

Bolt-on if your saddle height never changes, since it is lighter and harder to tamper with. Quick release if you move the saddle often or share the bike.

Before you order a clamp