I recently bought this carbon fiber full suspension 26er mountain bike frame off of Ebay and built it up, and since there was very little information about these frames, I figured I'd post what I have.

First off, I'm not absolutely certain this is a model KBO4 (the seller didn't specify) but I'm pretty sure. However, I have seen at least one other listing for a very similar frame that had slightly different specs though, so don't assume my specs here will exactly match what you end up with if you buy one of these. For example, mine has a straight head tube (1 1/8 top and bottom), but I've seen another listed that had a tapered head tube.

KB04 Carbon Fiber Mountain Bike Frame


Why would I buy some no-name chinese carbon fiber full suspension frame?

Well, I was just riding along (seriously) and my 2006 Jamis Dakar Comp Full Suspension bike broke at the chainstays.

Broken Jamis Dakar Chainstays

I have several hardtails I ride, but this was my only full suspension bike. And I really wasn't currently interested in spending a bunch of cash on a new 29er or 27.5er full suspension bike. The Dakar frame was out of warranty, and even though this was a known issue with these frames, Jamis wasn't being particularly helpful. Because I have several (actually more than several) bikes, my mileage on this bike was probably equivalent to a 2 or 3 year old bike even though this bike was 7 years old (I bought it new in 2007), and therefore the components were still in good shape (the frame was in real good shape too, well except for the broken parts). Plus I had upgraded some components over the years. So I started looking for a replacement frame that could use most of my parts (Pic below). 

Finding a 4-inch 26er full suspension frame.

It was easy to find 26er hardtail frames, but I already had several 26er hardtails and didn't need another so I was focused on finding a full suspension frame that fit my parts. Well lets just say that with the popularity of larger wheel XC bikes there wasn't much of a selection of 4-inch 26er FS frames in 2014. But then I stumbled upon an Ebay listing for "26ER Mountain Bike Carbon Fiber Full Suspension Frame MTB Carbon Bike Frame 19"" for about $560 with shipping. It looked interesting, but there was not much information on it. Basically all it said was that it was a 19" frame 26er, had a 31.6 seat tube, a 1 1/8" headtube, BSA (68mm English BB) OR BB30 bottom bracket,  and weighed 1800 grams. It truly amazes me when you see a company selling bike frames but not providing anywhere near enough information for the buyer to know if it will fit, what he needs to build it up, etc. Since the frame did not come with a shock, it's kind of important to provide these kinds of specs to the buyer.

I contacted the ebay seller, and he sent me these specs. This is the first time I saw the KB04 model reference, but since I purchased mine from another seller I can't say for certain that this is my frame.

So now I had the geometry, and knew that the eye-to-eye length of the shock was 165mm (which was great because that was the shock I had from my Dakar). Unfortunately the drawing also shows the 130mm measurement on the shock which makes no damn sense to me. It looks like it is from the eye in the front to the back of the canister, but that left almost no room for shock travel. In fact, if you look at the drawing, that couldn't be right if everything was to scale. Other stuff I didn't know? Well for one it doesn't say what the travel of the frame is. So I didn't know if it was a 4-inch frame, though I kind of thought that was the most likely. I also didn't know if there was any shock hardware with it.

And on the geometry of the frame, there were some things that I thought a bit strange. It looks to be a carbon fiber XC frame, possibly a race-type frame, but the specs show a rather short effective top tube, and a slightly slack 69 degree head tube angle. Not exactly XC race geometry. Having purchased some hardtail frames in the past, I've learned that the geometry numbers provided are not always correct. So I'm stuck wondering if those are the actual specs or if some of them are wrong. I didn't necessarily mind the 69 degree head tube angle because I do like riding some techy trails, but I was nervous about that short top tube. I'm an old XC rider an am used to a rather stretched out riding position. I've gotten a little more upright in the last 10 years, but I'm still more old-school XC. 

Then I found a deal I couldn't pass up, though it was a little sketchy. 

As I'm researching this, I came across another Ebay listing for what looked like the same frame (this is why I don't know for sure if this is a KBO4) but being sold from someone in the United States, and for over $100 less. So it looks like a great deal, but now in addition to all the potential issues with buying a no-name Chinese frame that I didn't know a lot about, I also had to take into account that the frame I was now looking at must have been purchased by someone who then decided not to build it up. Why did he not build it up, and why was he now selling it at a loss? 

I had already figured that if I ordered one from China, I needed to be prepared to accept the fact that there may be issues. If anyone believes a $500 no-name frame from China is the same quality as a $2,000 brand name frame, they really need to get back on their medication. So this guy that is selling the frame probably got it from exactly where I was going to order from, and maybe there was something wrong with it when he got it (either a flaw, or something just bad about the design), but how do I know that if I pay a little more and order one direct from China that I wont get a frame with a similar or even worse issue. 

So I ordered it. Not only did I save some money, but I got it very quick (within a few days). Actually, 10 days after I ordered it I had it built and was riding it. Which was pretty amazing considering I had to wait to get the frame before I ordered some parts. It still needed some tweaking, but I  think that was pretty quick.

Here's what I got.

And since the interweb is full of posts by self-proclaimed experts that claim you should never never never clamp a carbon bike by the frame in a bike stand, I figured I'd start by doing exactly that. I should note that this particular clamp allows me to use very little pressure on the frame, so I'm not exactly recommending you do this. 

And here's what I learned.

Surprisingly, the geometry specs listed for the KB04 were very accurate. It does have a 69 degree head tube angle (with my 100mm fork), it does have that short top tube, and what really surprised me is that the listed weight was right on. Every frame or bike I've purchased from more "legitimate" sources were heavier than listed, but this thing was very close. Just under 4 pounds without the BB adapter and just over 4 pounds with the BB adapter (this is all without the shock). It does appear to be a 4-inch travel frame (I measured rear travel assuming a 6 1/2 inch (165mm) shock with 1 1/2 inch of shock stroke). It comes with the shock mounting bolts but no spacers/bushings (more on this later). It takes a 1 1/8 inch zero-stack headset (nice because that was what I had on my Dakar). It comes with a sleeve (needs to be pressed in, more on that later)to convert the bottom bracket from BB30 to a 68mm English BB. 

And here's what was wrong.

I immediately started inspecting the frame and here's what I found. 

The derailleur hanger was seriously out of whack. Actually, it was the drive-side dropout that was out of whack. And oh, there was a crack on the dropout. I'm thinking the original buyer noticed the out-of-whack dropout and tried to "bend" it??? Then heard/saw a crack and promptly put it on Ebay. Obvously I don't know for sure the seller knew, but he probably did. Well I was prepared for some issues, and while this made me a little nervous I quickly evaluated the situation and figured I could make it work. I was pretty sure the "crack" was just in the coating/paint so I didn't think I had another broken frame.

I also noticed some play in one of the pivots. When I dissassembled the pivot to investigate I found I was missing a small bushing/spacer from one side of the pivot. I rigged up a close-enough-for-now replacement and will have to reevaluate later to see if I can leave it as is or need to work something else out. Remember, I sort of bought this second-hand so I don't expect my chances are good at trying to get a replacement. And with a no-name frame, there's no "manufacturer" to go to get replacement parts.

But back to the dropout. In my opinion, the dropout was too far out of whack to just bend the aluminum derailleur hanger a bit and call it a day. So I wanted to see what I could do with the dropout itself. Remember, this isn't steel or aluminum, it's carbon fiber and carbon fiber can't be bent into shape (at least I don't think it can). The problem with the dropout was clearly poor quality control. Something happened in the manufacturing process that allowed the dropout to be formed like this, basically twisted a little. So I had to re-form it, sort of. While it looks like a lot of out-of-whackness at the derailleur hanger, at the dropout itself this is just like a millimeter or so. 

Fixing the dropout.

So I decided I would file off what is sticking out, and fill in what needs to be to make it all nice and straight. 

Yep, that's how I did it. I filed the inside flat, then applied some JB Weld (one of my favorite things) where it needed to be built up on the outside (where the hanger mounts), then filed that flat. Now that all sounds a little easier than it actually was. To know that the derailleur hanger is straight, you need to put the hanger back on and clamp the wheel in place to check it. So I went through that process many times as I filed and filled until I got it pretty close. I figured I could later bend the derailleur hanger a little bit if I needed to. But after building everything up, it shifted real nice so I didn't touch it again. 

Pressing in the BB Sleeve.

As mentioned before, the frame came with a BB30 bottom bracket and an adapter sleeve to use a threaded 68mm English BB.

 I had no intention of getting a BB30 crankset, so my choices were to use the sleeve provided with the frame, or get a different type of adapter online to use my current crankset. I think in some ways getting a different adapter may be a better choice (there are some where you press in the BB30 bearings, then use an adapter to use your cranks with the BB30 bearings), but I was intent on not buying anything I didn't need to. So I decided to press in the BB Sleeve myself using my homemade headset press made out of threaded rod, washers, and nuts (search online, there are plenty of how-to's on homemade headset presses).

I have to say, this one is not for the faint of heart. It took a lot of force to press that sleeve into place. A fine-threaded rod might make this go a little smoother, though I'm not sure how easy they are to find. You cant see in my blurry pic there, but I did put blue loctite inside the BB and on the sleeve before pressing, though it was so tight I'm not sure much if any is still in there. My biggest concern with the pressed in sleeve was the potential for creaking later. I've had bottom bracket creaking before and it's quite annoying. But at least with the threaded BBs you can take them out and grease the threads or use Teflon tape or something to try to stop the creaking. If this pressed in sleeve ends up creaking, I have no idea what can be done to try to fix that. With the force it took to put in in there I had no plans to ever try to take it out. 


My frame used a straight 1 1/8th inch zero-stack headset (and obviously a straight non-tapered fork steerer). The inside of the headtube where the headset sits was a bit sloppy, so I used my dremel to grind off the high spots. I just knocked off the rough parts, so we're talking about a minute or two to do this. I was able to use the headset from my other frame, and it popped in just using a rubber mallet (that's been my experience with a few zero-stack headsets I've installed). 

Shock, Shock Mounting and Shock Hardware.

The frame did come with the two 8mm mounting bolts for the shock, but you'll need to get the proper bushing/reducer kit for your shock. I used my Fox Float R (6.50" x 1.50")from my Dakar, and the kits I ordered were:

Fox Part Number 803-03-165   8x21.8 This is the front/upper.

Fox Part Number 803-03-175   8x27.94 This is the back/lower. I measured the bracket as a little smaller (between 27.94 and the next smaller size 27.43) so I'm not absolutely certain the 27.94 is correct, but it is working.

I was a little surprised at how much higher pressure I'm running in my shock on this frame than on my Dakar. They're both 4-inch bikes with similar (not identical) suspension designs. And you'ld think a shock that needs to move an inch and a half to get 4 inches of travel on two frames should use similar pressure on both. But I was running 135 PSI on my Dakar and am not playing with 160 to 165 PSI on this frame. I'll have to leave that to the engineers to explain. 

Internal Cable Routing?

The frame comes with internal cable routing through the top tube. I'm not sure what I think of this. I ran my rear derailleur hanger through this, but not my brake cable (hydros makes this tricky). I didn't use a front derailleur, so no cable needed there. I will probably plug the open holes though because I don't want crap getting into the frame. And just in case it's not obvious to you, you need to run the cables from back to front before you install the fork so you can use the head tube to access inside the top tube. I'm thinking it will be real tricky trying to fish through there without using the head tube for access. 

Front Derailleur

I didn't use one, at least for now I figured I'd try 1x9 for a while. I did use a Jump Stop that I needed to modify because it mounts too high on the frame due to the pivot. 


When I had the frame opened up, I stuffed some foam pipe insulation in the top tube, down tube, and the bottom of the seat tube. I didn't completely fill the voids, just put in some to help quiet things down because these big open carbon frames can amplify any noises on the bike. 

As it sits in the pic below, the bike weighs just under 27 pounds (including the pump and bottle cage). The frame was almost 3 pounds lighter than my Dakar, and with a little more weight shaving by going 1x up front, I'm over 3 1/2 pounds lighter now. This is with mainly middle-of-the road parts (not weight weenie stuff). Reba fork at 100mm, LX cranks, XM317 rims with XT hubs, X9 rear derailleur and shifter, Juicy 5 rear brake, Hayes Stroker Carbon front brake with 180 rotor, and nothing-special alloy seatpost, bars, and stem.  I was pretty much able to use everything from my Dakar. All I had to buy was the shock hardware, a new seat clamp, a shim to use my old seatpost in the larger seat tube (update: I've since replaced the seatpost with a new one of the correct size), some carbon assembly paste (for the seat tube), the jump stop for 1x9,  some stick-on cable guides, and a new cable/housing for the rear derailleur (I probably could have use my old one, but it was time anyway). All cheap stuff.

Ride Report?

So is this the most amazing riding bike ever? Not really. I've only had a few rides so far and have been making adjustments as I went, so it will be a while before I'm ready to say for certain what I think of the frame. The slacker head tube angle and shorter cockpit did handle some real steep techy downhills well, but obviously that is going to compromise climbing a bit and I noticed that on a steep techy uphill I ride. The good news is it survived it's first few rides and everything seems to be working properly (though I'm still making adjustements, and have some annoying creaking to deal with). Will it break on the next ride? Possibly. Will the pivots on the frame last? Who knows. Will hordes of zombies overrun the planet? Yeah, I'm pretty sure that will happen.

Update September, 2014


I got a couple of good rides in earlier in the week and the bike is feeling pretty good. The short top tube doesn't bother me as much as I thought it would, and I do appreciate the slacker head tube angle on steep techy stuff. It's still kind of a strange setup though, I think a 4-inch XC FS carbon bike should have more of a race-type geometry. If it were a 5-inch slightly heavier frame, that would be nice geo for a trail bike. 

I am getting a few more pedal strikes than on my other bikes, and that's with the shock pretty stiff. It's not horrible, but I do notice it. The BB height with no weight on the bike is right around 13 inches with 2.35 tires, that's not real bad but I would like a little more. I like to hammer into uphills, and that's where I tend to smack anything sticking up. 

I replaced my old seatpost and shim with a properly sized post and that got rid of the horrible seatpost creaking. I do still have some creaking when I stand and pedal hard on climbs and I'm thinking that is probably due to the pressed-in BB sleeve. Not sure what I will do about that. It's not creaking near as loud as the seatpost was, but I like climbing and don't like to hear creaking when I'm doing it. 

I also think I figured out why I have to use so much more air pressure in my shock on this 4-inch bike than the 4-inch bike I took it off of (the Dakar). Well, I got around to trying to measure the travel on my old broken frame and it looks like my old 4-inch frame only had about 3-inches of travel, while this 4-inch frame actually has 4 inches of travel.


I just don't see this as being the type of frame you buy to build your ultimate dream bike. This is a rather simple (I'm assuming patent-free) suspension design, and I'm doubting it can compare to some of the fancier stuff available today.However, if you have a broken 26er 4-inch full squish frame with decent components or want to move components from a hardtail 26er to a full suspension ride, this may not be a bad way to go. But you need to realize what you're getting yourself into when you order a no-name carbon fiber full suspension frame from overseas. If you expect everything to be perfect and think you will be getting instructions with the frame telling you what will fit and how to build it up, this probably isn't for you. 

Also, if you're looking at building up a 4-inch carbon race bike, I'm not sure this is the right frame. Though it's a lightweight frame, the short top tube and 69 degree head tube angle just don't scream "race bike" to me.