siren cycles carbon fiber tube cyclocross bike

Siren Cycles‘ has just created their first carbon fiber tubed bicycle, a cyclocross bike….and this one’s actually going to Mike from NoTubes.

Because the lugs are 7005 Aluminum (as are the chainstays, BB and headtube), Siren’s founder Brendan Collier could still make it a full custom bike. Besides geometry, the bike’s set up for disc brake tabs with 135 rear spacing. Headtube is the now-basically-standard 44mm tube used by almost every handmade builder because it allows for just about any steerer tube size and headset.

The carbon tubes were sourced from Rock West Composites in Utah and chosen for specific diameters and thicknesses to tune the ride and feel of the bike. More pics and a bit of Q&A with Brendan after the break…

siren cycles carbon fiber tube cyclocross bike

“The benefit of building a bike like this is I’m able to give our customers the lightweight and ride feel of carbon but still do full custom fit, custom geometry, you know, anyway you want to do it,” Collier said.

This frame retailed around $1,895, including paint, which is done before the frame is fully bonded together, which Collier said made construction pretty tricky. Basically it had to be assembled loose for size, then pulled apart and welded together. Reassembled loose to check for final fit, sent off for powdercoating, brought back for tube prep and then bonded together. This frame ended up right around 3lbs.

siren cycles carbon fiber tube cyclocross bike

Are they going to do more like this?

Collier: “I’m feeling it out, we’re not sure yet. I’m mostly interested in metal, particularly steel, and I want to get better at titanium. We’ll see what kind of response we get.”


  1. Reminds me of an Alan or Vitus from back in day. Actually miss the Vitus 979 – those bikes were practically rolling barcaloungers and a blast on dirt roads.

  2. I’m sorry, that is an unfortunate frame. It absolutely reminds me of the Trek 8900 or Giant CFM (Canine Fecal Matter). While the actual carbon tube is certainly more advanced than those 18 year old frames, this implementation of a carbon aluminum hybrid is as kludgy as it ever was.

  3. I’m going to have to agree with everyone here especially twistyaction. Besides reminding me of an Alan, Vitus or Trek, the concept is dated. The “lugs” could have at least been modestly sculpted for a little flare. And the assembly sounds overly complicated. There’s a reason hybrids like this aren’t done anymore (with the exception of some Ti frames).

  4. I disagree. I think the shade of green looks a little vintage and true, the lugs are pretty boring, neither of which lend themselves to the appeal of the frame. I don’t think it would take much to make this frame look modern… The technology may be dated but doesn’t mean it should be consigned to the history books. This fabrication lends itself to small, independent frame builders and offers a great alternative to high-cost full carbon frames and a normal steel frame whilst still allowing custom geometry.

    I do agree on the complicated assembly technique. Surely you can just mask off the carbon tubes then send it off for powder-coating. Carbon tubes can withstand the oven-baking process of powder-coating can’t they? Powder-coating requires oven temperatures of around 160-20deg (Celsius). Carbon tubes can handle that, no? Or maybe that’s not the reason for the complicated process?

  5. Full aluminum frames also allow for full custom geometry, and so does full steel frames.
    Question is if this carbon tubed frames gives you any advantages above these?
    How much lighter, more compliant, faster etc?

    The design can be worked on, and that horrible color doesn’t help…

  6. I love it. And I think comparing it to an old Trek 8900 (which I owned and raced back in the day when I raced for Truck) and the Giant CFM (I’ll agree with Twisty action on the acronym) is a crime and armchair internet engineering fodder at it’s best to say the least.

    The Trek 8900 road like crap (really should have just gotten their aluminum), had those god awful heavy/thick lugs. Then of course that crap carbon weave tubing an 50 layers of clear on top of them. Giant….sh*t I think the steel frames were lighter. And again, Giant’s aluminum rigs road a ton better.

    Siren is a solid brand that does cool stuff. I’ve seen Fixie Dave’s rig and it’s beautiful. Throw in some of today’s day an age carbon….boohyah. Now get a 3lb frame, custom, with carbon tubes/alloy lugs, all for $1800 an some change? Why bother spending more for a Taiwan made carbon frame you’ll want the new color of the next year?

    No, ride something that’s a classic rig like this. And place your order before Brendan realizes he’s pricing these things too damn cheap.

  7. Yeah, I wouldn’t buy it… a bit too chunky lookin…. But if Brendan keeps working in Ti… and eventually swaps the Alu bits for Ti bits, then this thing will be totally tits. Think Serotta, Indi Fab, Merlin…

  8. its a custom frame for god sakes
    at least do something with the lugs so that it looks a little more classy
    this looks plain and boring and honestly i would have liked to have seen straight steel much more
    the only lugged odd metals i like are carbon and ti
    and steel and carbon but but but but but, when the steel is lugged to it self not brazed, then lugged to the carbon

  9. Rob, I’d like to answer your question regarding powder coating of carbon fiber products, and tubing more specific. Composite tubing is cured at around 275 degrees F while powder coating temperatures typically exceed 350 F. This is the first hurdle to overcome with powder coating. The other issue you will encounter is the requirement to have consistent electrical conductivity to attract the powder particles pre cure. Currently there is only one company ( ) that we are aware of that is capable of powder coating carbon fiber composites using their proprietary system and cures.

What do you think?