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ThomsonSeatpost Collar

Item # THP0008

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  • Black, 28.6mm ($30.00)
  • Black, 31.8mm ($30.00)
  • Black, 35mm ($30.00)
  • Silver, 28.6mm ($30.00)
  • Silver, 31.8mm ($30.00)
  • Silver, 35mm ($30.00)
  • Black, 36.4mm ($30.00)
  • Silver, 36.4mm ($30.00)
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Item # THP0008

A functional piece of bling to top off your Thomson cockpit.

Thomson has a fitting reputation for reliable, functional and lightweight components. In the same vein as Chris King, they take their time before releasing a product -- when they do, they've done it right. The Thomson Seatclamp is no different. Granted, most of us don't consider a seatclamp a performance component -- that is, until it's not performing. There's not much worse than being on a ride when your seatpost is gently easing its way down into the seat tube.

The Thomson Seatclamp represents the Thomson values in a sleek, simple, lightweight package. While they admit you probably won't win a race because of it, Thomson engineered this beauty to perform -- the bolt is threaded at an angle, about 1.5 degrees off-center, to help provide awesome clamping force -- they say just 20 inch-pounds on the fastener will suffice. It's available in anodized black or silver in 31.8 or 35.0mm sizes.

  • Aluminum with anodized black or silver finish
  • 1.5-degree off-center threaded bolt
  • 18-gram weight
Tech SpecsWeight
Tech Specs
Recommended Use
road cycling
Manufacturer Warranty
5 years

Actual Weight

Actual weights are measured in-house by the Competitive Cyclist team.

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Black, 28.6mm
Black, 31.8mm
Black, 35mm
Silver, 28.6mm
Silver, 31.8mm
Silver, 35mm
Black, 36.4mm
Silver, 36.4mm

Claimed Weight

Claimed weights are provided by the vendor.

Have questions? Chat with a Gearhead

18 g

Reviews & Community


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Elegant and Simple

  • Familiarity: I've put it through the wringer

I have used Thompson on a few of my bikes, Surly Cross Check, Wife's Surly Troll and my new TI 29+. Thomson has done nothing but impress, don't think twice upgrade your components.

Elegant and Simple

Much better than any stock clamp

    This and the Salsa clamp are both great performers. Broke the factory clamp on my 2016 Cannondale Supersix. Had a Thompson 28.6 clamp in my toolbox. Even though the dia. spec is a little different the Thompson is holding my post just fine. Going to order another as a spare.

    Us made brilliance

      A seatpost clamp may not be the first thing you may think of to upgrade on your bike, but if you're running a Thomson stem and post, might as well go all out! It comes with a tiny 3mm hex head bolt, but the design of this will keep your post secure.

      Us made brilliance

      Great little clamp

        Thompson is usually more expensive than their competitors but for good reason. This is a great little seat post clamp. It's clean looking, very light weight and gets the job done.

        Thomson....Nuff said

        • Familiarity: I've put it through the wringer

        I rock Thomson stems and seat post on all my bikes. This is the first time using their seat collar. As all of their other products it has beautiful craftsmanship. Just can't go any better for performance and price.

        It Works

        • Familiarity: I've put it through the wringer

        It is a seat post clamp. It looks nice, it's light and my post hasn't slipped. About all you can ask for from a clamp.

        Solid Clamp

        • Familiarity: I've used it once or twice and have initial impressions

        I'm amazed at the low torque needed to get such a solid hold. I'm guessing this will lessen the chances of ever having to replace it. The last clamp I had popped at 5nm torque. The threads pulled out of the clamp body. This Thomson clamp specs only 2.8nm torque, and it is holding really strong! This is a great seatpost clamp!

        Thomson Seat Post Collar

        • Familiarity: I've put it through the wringer

        I swapped my factory clamp for this. It really cleaned up my bike and the quality is unbeatable. Great product!

        It's the little things...

        • Familiarity: I've used it several times

        Seat collars are simple and only have one job-keep your post from slipping. It is surprising how often something as simple as a seat collar is done badly. Either the collars don't keep the post in place or the collar itself is susceptible to breakage.

        The Thomson collar will not let you down. It is light, it is dependable and elegant. I would say that this simple collar design and finish boards on usable art.

        Upgrade your bike now!

        Clean and good looking

          Got this to replace one that came on the bike. This one looks good on the bike and feels solid. You can 't go wrong with this.

          is the measurement referring to the inside...

          is the measurement referring to the inside diameter? my bike seat tube is 31.8 internally so the seat post clamp should be the larger diameter?

          The measurement does refer to the inside diameter, which is the outside diameter of the seat collar.

          That added bling

          • Familiarity: I've put it through the wringer

          Thomson Post?-Check

          Thomson Stem? Check

          Thomson Bars?-(YEP they make bars!) Check

          Thomson Seat Collar?- NO?!?! What is this, amateur hour? Add that added bit of bling, you know you want to, your bike will thank you.

          Solid piece, set it and forget it

            Would have given this a 5 if it was a little lighter or a little more economical.

            Lets be honest, the only reason 95% of us upgrade from stock is to save weight or add bling. This part is anti-bling but lighter than your average QR factory clamp, but I replaced it on my latest build with a titanium unit weighing 10g that was half the price, so.....

            If my frames seatpost size is 27.2mm ,what...

            If my frames seatpost size is 27.2mm ,what would be the normal clamp tube size?

            Whatever the diameter of your seat tube is. If your front derailleur takes a 34.9 clamp, then you also need a 34.9 seatpost clamp

            I need a clamp for a 63CM Serotta (road...

            I need a clamp for a 63CM Serotta (road bike) w/ a Ti frame - 31.8. I’m using a Thompson 30.9 seatpost, will this fit the fame and clamp down the post?

            Is there a return policy?

            Hey Doug. I don't think the 31.8 will fit your bike. I think you need a 34mm but you could measure the outside diameter of your seat tube if you have calipers and it will give you a number close to what size you will need. Bear in mind we are work in very small increments so you will need to be precise. Aluminum frames with 31.6 seatposts usually run the 35mm clamp but since you have a Ti frame and a 30.9 seatpost you are going to need something in the 44mm range.