DM3 Carbon-Steel Single Legged Fork Update, Answers

This thing has not gone away yet?

FEA says those cutouts are just DUMB.

The Left from C-Dale makes sense, and they post all their benefits with stiffness and weight

This just looks stupid and isn’t going to last very long

I do see a small market for this. For people in areas where some days rigid is a better tool then a suspension fork, but they are not a devoted sadist, and do run suspension on a regular basis, and have already committed to Lefties (Ie have good lefty wheels) then this make since. I am one of those. On my 26er, which was my first mountain bike and a cannondale, so all of my wheelsets have a lefty front wheel. I recently tore the thing apart to sell the pricey items, but had the idea of keeping the frame to run rigid and keep the bike as a beater winter bike. This issue came up that if I would do that, not only would I have to buy a rigid fork, but a new front wheel and headset, so this cheap beater project, now will cost a couple hundred bucks. If there was a cheap rigid lefty (which I don’t think this one would be, but hey, cell phones were $1,000 when they first came out) I would throw that fork onto my existing wheels and have a rigid lefty.

Colin S –
Cannondale already has a rigid Lefty fork for its Badboy series of bikes that you may be able to source from your local dealer. I’m not sure how it would affect your geometry but I would look there first for your rigid lefty needs. The use of steel and carbon could allow this fork to be more compliant for a rigid fork but that seems contradictory to the advantages of the lefty design – super stiff so that the fork doesn’t flex and instead goes right into its’ travel. I’m not really sure if I would want a flexy single sided fork… I am glad to see other companies experiment with the concept but I’m not so sure about this one.

While I think the idea is novel, I do have at least one reservation: Galvanic corrosion. Steel and carbon are not friends. Has this somehow been addressed via coatings, or isolation of the materials? If not, then I couldnt endorse the design.

this is NOT an rigid option for the Lefty crowd. it uses a 20mm thru axle, not Cannondale’s tapered variety (25mm to 12 or so).
this fork is really only for those that like the aesthetics.
rigid lefty = black cat bone. look it up, it’s pretty cool.

Too bad it looks cheap and homemade. Hire a designer and try again.

yeah, and welder!!! my dead g’ma can lay down a better bead than that one!

Putting the stiffer material on the inside is the smart way to go– As the geometrical section gets smaller the material stiffness is less effective, unless of course you put a stiffer material there to compensate the reduced geometrical section. This is an engineering solution not like a nasty carbon wrap stem. At some point in most composite structures you’re going to end up with a metal to composite joint, its quite possible to do this and protect agaisnt galvanic corrosion. Regardless of what you think of the looks and functionality of this thing as a fork engineering wise it’s smart.

Hmm, i personally like this for a very simple reason.. rigid, long fork with a 20mm thru axle! (the latter being the most important!)