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Alex’s Custom Titanium Cargo Fat Bike by XACD


And now for something completely different. In another first for the Spanner Bike blog…


Ride a bike? Like to be able to carry stuff?

And when I say carry stuff, I mean carry STUFF? Like small humans or a kitchen sink?

My friend, you’ll be needing a cargo bike.

Cargo bikes have an extended rear frame, often with a platform attached, that let you go large in the carry on luggage stakes. We’ve not seen a cargo bike on the blog before, but handily enough Alex is a huge fan of the car free concept machine and decided to go large in every sense:

Alex – explain yourself!

I’ve had a few custom frames made now, this kid-hauling cargo fat frame is born out of a longstanding hobby of mountain biking in Northern California and a newfound role as father. Nobody made what I wanted, which was a high performance cargo mountain bike that carries “live cargo”, to quote Salsa!

Since brainstorming the project in the fall of 2017, both Surly and Salsa have come out with newer cargo fat bikes, but neither version quite captures what I was really looking for. My goal was a lightweight, human-powered machine that allowed me to share the experience of climbing a mountain with my little one. Enter the custom cargo fat frame project which came from late night studies of designs made by people like Yuba, Xtracycle, and Kona. They all make good cargo bikes, just not ones aimed specifically at mountain biking!

Lots of interesting things going on here – much rack support and thick walled tubing.

Awesome stuff! You mentioned some previous projects, who did you work with on those?

When I set out to have a custom frame made, I was looking for a company that could produce a high quality frame. I considered the raw material source, strength and aesthetic of the welds and, perhaps most importantly, the ability to produce something that accurately reflected the frame drawing.

On previous projects, XACD showed time and time again that they excelled at those tasks. My turnaround times were typically 9 weeks and all my email questions were addressed within 1-2 working days – both big plus points when choosing who to work with.

Working with XACD has been nothing but stellar. In the beginning I think I tested their patience with my sometimes overreaching attention to detail. On occasion I requested changes that made only 1 – 2 mm of difference and maybe no real difference in function. But hey – it made a big difference to me in overall aesthetic appreciation and it was my frame at stake after all! I tried to make life easier for them by grouping together my small changes with each drawing revision. XACD accommodated my style and I get along fine with Porter. I can fully recommend the company!

You can see the detailed work involved here. It’s not going to break that’s for sure! Almost a crime to paint that lovely titanium finish though?

As always it’s about finding someone you feel you can work with. Tell us more about the frame details…

The frame “borrows” the rear deck from a Yuba Boda Boda. That allows it to use all the same Yuba accessories (i.e. “Mini Monkey Bars,” “Soft Spot” seat cushion and foot pegs) and directly mount a Thule Yepp child seat.

The front of the frame is all mountain bike, incorporating the latest U.S. trail bike geometry. It’s got internal routing for a stealth dropper seat post and internally routed rear 1x shifter cable. The hydraulic brake hose is kept external, since my past experience with internal routing had found it to be rather finicky and time consuming to set up!

As for the wheels, I decided on fat bike tires and tubeless carbon rims. The tires offer great traction and comfort, which are two qualities that are appreciated with a baby on-board!

You may notice that the brushed Ti frame is covered with “mango tango” orange sparkle powder coat. Ventana Mountain Bikes in Rancho Cordova, CA provided the finish. Even though the fat tires strike up conversation everywhere I ride the bike, I still wanted the frame to look like your “normal” everyday bicycle.

And a kickstand to match?

XACD also designed and produced the kickstand out of Ti, based on my diagrams and sample kickstand I sent to Xian, China. Sending something over was a new level of collaboration and trust; I’m happy to say that it went well!

Looking good – how did it turn out?

I’m still amazed as to how close each of my frames reflect – to the last mm – their signed off frame drawings. The current frame is no exception. It’s possible that *maybe* the very end of the rear cargo deck is off by half a degree from horizontal. Though overall, the frame is absolutely square where it counts. Once again, I am a satisfied customer!

So… what would you do differently next time?

This is a huge question! First and foremost, I would obtain *all* critical accessories *ahead* of time and design the frame around them.

I neglected to buy the Yepp seat ahead of the final frame design, since I *thought* I knew all I needed about it. I only found out later that the inner supports were rigid and needed to be Dremeled back 7mm on each side to clear my frame’s rack supports!

Secondly, I would have added more rear deck mount locations for the child seat. Not having a cargo bike before, I copied almost verbatim the deck of a Boda Boda “just to play it safe.” Though if I were to do it all again, I’d add not just two but three or four mounting locations (these are the 2.5 x 3.5 inch rectangular holes in the rear deck).

I am finding out that the key to dynamic cargo bike performance is in the weight distribution. The bike simply handles better with baby on top, or in front of, the rear axle, i.e. mid-engined location, if you’re into cars! More mounting locations on the rack would allow me to fine tune the bike’s handling based on what I’m carrying.

Finally, any V2.0 cargo fat frame of mine also will re-evaluate the center of gravity. The lower the cargo, the better the side-to-side weight transfer during pedalling, and the more the set-up will behave like a regular bike. Would a smaller, say 24″ fat tire, with lower rear deck height, be advantageous in comparison to the standard 26″ fat tire? I’d like to find out!

Nice rack!

Just when I think we’ve seen everything…

Along comes Alex with his stellar cargo bike project. Cargo bikes seem to suit being ‘fat’ too, running suspension would be tricky with larger loads and the fat tyres keep the ride smooth.

Cargo bikes are pretty versatile too – it’s not just about luggage, you can fit child seats or even a padded platform seat to carry an adult.

Checking out Alex’s frame design I couldn’t help but notice that the back end of the bike, well, seems to have a lot of tubes in it… 😉

Yep, the rear rack does have a lot of tubes! Design considerations mainly had to do with the hope that kids or an adult can hitch rides in the back. I just need to add some seat cushions on top of the rack and wooden planks on top of the foot rest supports.

The rack tubes also have M5 screw holes so wheel covers can be fitted to separate kids’ feet from spinning spokes. The two diagonal tubes going to the bottom bracket are an experiment in adding some lateral stiffness when pedalling.

Which explains a few things! As Alex says, if he made the frame again he’d perhaps think about a more modular system that could use a removable rack that would tidy the back end of the bike up a bit. Choosing just to carry small humans, as opposed to full sized ones, would also mean less material would be needed.

I’d noticed as well that the design used a shorter wheelbase than normal for a cargo bike. As I suspected, Alex didn’t want to compromise the off road ability of the frame too much:

Yep, for this “first” cargo bike project, I kept the wheelbase on the shorter side to keep the handling relatively “nimble” for a cargo bike!

The other consideration is transport; since I carry my bikes on a hitch-mounted rear rack, I wanted the bike to fit on the back of the car without being too wide.

As Alex mentioned before, there’s plenty of scope to design a 2.0 version of his frame – making it longer and lower to aid the load carrying and seeing what effect that would have on the handling.

I’d certainly like to see what happens as I think he’s made an awesome job of the first one! Have you got a special project that you’d like to share with everyone else? Do drop me a line and say ‘hi’…