Custom carbon fiber narrow road saddle

This is a project that I have been working on since this summer (lots of delays) and have been thinking about for even longer. The thought is that you can create pretty much any saddle design using carbon fiber. One of the main complaints I have about the current saddle design is that they are too wide in front for road riding. So here’s what I did. (Note, captions are above pictures.)

WARNING: This write up is four posts and 36 picture long. Sorry and/or you’re welcome for that.

I started out with an old KH CF base (velo design) as a template.

I added sides made out of plastic and duct-tape

I then coated the mold with paste wax and sprayed several layers of hair spray to help the paster come out.

I mixed the plaster (using a vibrating plate to remove all air bubbles)

And poured the mold

The paster mold with the plastic sides removed

Another view of the mold with the KH base still attached.

The mold removed from the base

Another view of the mold

The mold after trimming the sides down smooth

I then changed the shape of the mold to make my narrower base. I used an angle grinder and a sanding block to smooth the cuts.

I coated the mold in epoxy so that the it would be smooth and wouldn’t stick to the carbon fiber and resin as well.

I raised the mold up so it would be easier to apply the layers of CF and let it dry

This is my work space all ready to lay up the carbon fiber. I have an old piece of glass (from the junk yard) that I laid the carbon fiber weave on. I would saturate it with epoxy resin before carefully laying it on the mold. I used the glass because it was smooth and the resin filled CF wouldn’t stick to it much.

I had two large pieces of twill weave (criss-cross) carbon fiber, a layer of fiber glass for structural support, and a few scraps of cf to reinforce sections. I would have used more layers but cf is quite expensive and I got all of these pieces as scraps from a friend’s project. I layered on piece of cf, then the fiberglass layer, then another layer of cf. Finally I added the cf scraps in places that I thought need a bit extra help. Finally, there is a layer of peal ply (what’s that?) used to soak up extra resin and apply a downward pressure (with my hands) to compress all the layers together.

Here’s the new cf saddle on the mold after drying and removing the peel ply

Removing the new base from the mold was quite difficult and in the end cracked the mold in half

after cleaning up the edges of the new base

A comparison with the KH base. My base was significantly lighter and had more flex than the KH base. It is also much thinning so it clearly use fewer layers than the KH base used.

I next had to drill the base. I used t-nuts in the base. The t-nuts have 3 prongs to keep them from spinning, but I bent two of them down to simply drilling.

I also had to drill a small hole for the remaining prong.

For the t-nuts for the seat post, they were too close to each other so I used a Dremel to trim down the width so they all fit.

I added a piece of rubber so the post didn’t squeak and cause wear against the cf. I also cover all the edges in duct tape since they are sharp and would cut the seat cover.

The t-nuts protrude a bit through the base so I had to widen the holes in the KH adjustable post to get them to fit.

The final base bottom view.

And final base top view.

I then glued the t-nuts into place using gorilla glue as suggested by Peat in the NNC base thread. Wet glue:

Dry glue. It got a bit messy and went through to the other side a bit.

Nothing a knife and a bit of sanding can’t fix.

I used impact foam to test the saddle because it is thin. I didn’t want to cut the foam right away in case I wasn’t happy with it so I use duct tape wrapped very tightly around the nose of the foam to round it over the edges and make it fit the narrow nose of the base. An interesting result is that it doesn’t have a sharp edge on the side of saddle like most saddles do. Instead it curves around more gradually.

Top view of the foam curved around.

I also just taped the cover on temporarily.

Finished saddle, top view.

Finished saddle, side view.

It weighs around 500g with the KH/Thompson adjustable post. Compared to more than double that (~1100g) for a KH Fusion Freeride saddle with KH adjustable post (same length).

I have now ridden it to class (about 1 mile) for about a week and done one 2 hour ride on my ungeared 36. The verdict is out on how much I like it. It is definitely hard, and it starts out a bit uncomfortable, but it remains about the uncomfortable for the whole ride; whereas the KH Freeride saddle feels great at first, but awful after an hour or so. This seems to be similar to my and others reactions to using the KH Street saddle or Naomi saddle for distance. I also ride road bikes and compare this saddle with those.

I also know that how a saddle feels on an ungeared and geared 36er differs but I won’t have a chance to try it geared up for a few months at least. I’ll try to post a picture of it mounted on my 36 in the next few days. I’m using a frame-mounted handle similar to this one:

Very cool and nice write up.

Nice job, but why go to all that trouble to build a curved CF seat?

I noticed you went to a thinner profile, this is part of what I like about flattening seats (the side bend inwards) and the NNC (it’s narrower than the KH base), but I have found that a well padded taint is necessary on the flat seats to compensate for the loss of the upward turned nose (which serves to hold the pelvis back on the seat.

Let us know how you like the new seat :slight_smile:

I thought about making it thinner when I started this project back in June but flat seats were not all the rage then. The problem that I was trying to solve was that regular uni saddles cause my legs to rub in front and bow slightly outwards. The most efficient method of pedaling is when your knees are facing directly forwards. I’m not sold that flat seats are the solution. I’m going to make a ghetto one soon to test it out.

I’m not sure about using the Naomi foam, and I like your idea of adding some padding to certain areas. I might have to give that a go.

Okay, yeah flat seats are interesting, not sure that a totally flat seat is the best, mine all have some sag at the waist (NNC) or some nose upturn (ghetto). But the NNC with a gel pad is the most comfortable seat I have used.

I’m mostly satisfied with my seats, but I have been playing with ways of mounting my grab bars to get them above the seat and closer to my “crotch”.

So using my custom KH aftermarket seat stiffener bar mount (KH Plate with a piece of MTB bar welded vertically), I drilled a hole in the base and the “above seat” stiffener, centered between the grab handle mounting holes, then flipped the KH plate so the mount pokes out the top of the seat base :sunglasses:

I still need to pad out the seat and modify a cover to go around the mount, should be done by the weekend, but the mock up is very nice, gets my hand above my knees and keeps it in close so I don’t feel like I’m reaching quite so far. :slight_smile:

Is that a Powderhorn 24 picture?

Nice writeup. Great project- it’s good to see you got it on the road.

It’s good to see another saddle project. With so many styles of bike saddles, it makes sense that there will be more than just a couple of styles of uni saddles.

I personally have not had problems with the width in the front of the commercially available bases. I have however found that less curvature makes a HUGE difference. The Flatfish is great, but I’ve had great success with the seat soup method of modifying the KH bases too. It made the KH Street much more tolerable.

Thanks Scott for sharing the project!

Not exactly the base I desire; but very nice writeup (and pictures), thank you very much for that! (plz don’t make the pics go 404 - it’s useful).
…and maybe one day I’ll try that to, just for the fun of it.


Excuse me for my ignorance, but what is the seat soup method? Thanks!

“seat soup” is essentially a cheap way to get a flattened seat, not quick or easy, but doable by the average handy person. The best seat to modify is either the Nimbus Gel or KH Street (gel), models after 2008 have the new KH base which is stronger than the Velo base.

I boiled a seat last night.

I’m planning on doing the seat-soup method soon too, so I’ll compare a flat seat to a narrow seat (and I’ll probably swap around foam to test that too). It will be a few weeks at least though.

Dave, the Powderhorn picture is just to show what bars I’m using. Since my base obviously cannot use KH bars.

Leo, the pics are on my own site not imagebucket so they shouldn’t be going anywhere.

One thing I realized is that by using the same curvature as the Velo bases but using thinning foam actually makes the base seem more curved because there is less padding in the middle to flatten the saddle out. If I did this again I would definitely flatten the seat to some degree. After trying the ghetto saddle, we’ll see how much flatting I want to do.

Cool write up!

I like the narrowing idea. I’m not a seat expert, but I’ve used a Freeride and a bike saddle with my aerobars. The narrowness of the bike saddle was nice until I got to italy and realized how I felt like I had little control on hills or high speeds. I really need some amount of curve, just not quite so wide where the legs rub. So basically what it looks like you’ve done here.

I see how it might seem more curved like you said so maybe a little flatter is good.