Custom Urban Cruiser Bicycle

June 14, 2004

So I decided to build my girlfriend a bike for her birthday (June 10) at the start of May. I had never built a custom bike before, or even assembled a normal one, so I had a lot to learn -- and learn I did! I had a concept however, and that was enough to start with. I wanted to create a girl's bike that was super tough, cool, custom and still totally functional. The idea being that she could commute to work on it (just under 2km). I decided on a single-speed to keep it easy, and stayed away from doing a BMX due to their cramped size. I like to be really thorough so nearly every single part of the bike went through a rigorous design and decision process. I ended up cheaping out on a few of the easily changeable components (grips and pedals notably), but I my opinion they don't ruin the final product.

I started with a used Norco girls cruiser frame that I bought for $40 from a non-profit bike store called "Our Community Bikes" -- lots of anti-car vibes there, but they had scads of used parts that sift through. This frame in particular was chosen due to its swoopy tubes, and the wide chain stay clearance to fit fat tires. While I was there, I also picked up a cool old chain guard, a retro sprung seat and a set of Ritchey handlebars.

Next up was wheels and tires. I wanted black wheels, and considered painting a 144 spoke set, but this was going to be a big hassle and wouldn't have turned out well, so I sourced a pair of 24" (cruiser BMX size) Skyway Tuff II mags on eBay. 24" tire selection is pretty limited, but I found some great urban downhill tires from Maxxis that fit the bill perfectly. I filled those with a set of Nokian downhill tubes for a nearly indestructible and trouble free setup.

I was initially going to run a simple coaster (kick-back) brake, but then my friend Nick at work asked me, "how much do you like your girlfriend?". She will be riding it in city traffic -- and in his opinion a coaster brake wasn't going to do. He suggested I use a disc, which sounded good to me, so I ordered a 160mm Avid mechanical disc brake setup. As it turns out, Skyway doesn't make 24” wheels that take disc brakes, so I had to come up with my own solution. I was up for a challenge, so I fired up SolidWorks and got down to business. I quickly discovered that the mounting of the caliper and other factors would require me to build my own front forks while I was at it – sounded fun, so I forged ahead.

At this point I broke out the billet... With the aid of a .dwg file provided to me by Skyway, I designed and machined hubs that mated to "fingers” which fit in every spoke of the wheel. One assembly on each side of the wheel makes for a super supported system. Some custom bike building friends of mine adapted a brake to these same wheels a few years ago with a simple system that yielded catastrophic results, so I went overboard to make sure that the forces would be distributed all over the place and that the central hub of the wheel wouldn’t be affected.

Norco "Santa Cruz" frame

SolidWorks model using Skyway supplied drawing

Finished adaptor hubs

Hub, fingers and disc mounted on wheel

The dropouts needed to be carefully designed to have enough clearance for everything and also have the correct geometry for the caliper and such. For fork tubing, I cut a 4’ length of 1” Ti-3Al-2.5V 1/16” wall titanium tubing in half that I had left over from my Battlebot days. The titanium looks awesome, is super strong, and isn't chrome -– so it fit all the requirements.

Triple clamp in the vise about to start the second CNC operation of three

After op two

Finished triple clamps

Caliper mount/dropout with Avid caliper on titanium tubing

I cranked out a few more parts on CNC mill while I was at it.

Plotting the tool paths for the custom stem

Making chips!

One side done

Finished stem and cap

Once all the critical parts were made, the bike was test assembled. Everything was looking good, and it was now time to get to work on the frame.

Test assembled front forks
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Stem detail
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The whole shebang
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Wheel, hub and dropout detail
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Before I got to the frame, I decided to add to the functionality of the bike and balance it out visually by building a custom rack for the back of the bike. I machined a pair of rails and designed a water-jet cut titanium plate that bolted to the rails.

Moving onto more traditional custom methods, I cut some steel panels and gussets to add some more curves and strength to the frame. Toby from Toby's Cycle Works brazed these into place for me and I went to work smoothing and finishing the fillets to get the frame ready for powder-coating.

The main panel after more than a few hours of sanding, grinding and filling. I used a product called All-Metal to fill up the pinholes and smooth out the fillet. It was on recommendation from a web page I found, saying it makes a good filler for powder coating. Guess what? It didn’t work. The All-Metal couldn’t take the heat, so it was sandblasted out and I ended up using JB Weld as filler – which was quite a bit more trouble to use (mostly due to its 16 hour set-up time), but could take the heat easily.

CNC'd rack rails

Main filler panel

Rear filler panel

Smoooth fillets

At this point I dropped off all the aluminum parts to get anodized black. Although the raw machined finish looked impressive, it was a bit too showy for this application, and the color scheme dictated that they be blacked out. While I was getting the 1/4" titanium rack water-jet cut, I also had the rack stays cut out of a thinner 6-4 titanium along with some “East Van” crosses (a symbol of my notoriously bad neighbourhood) cut for use as a head tube badge.

Although I got the frame back from the powder-coaters on time, the anodizers kept giving me the old “it’ll be ready tomorrow” routine and things were looking grim for finishing the bike for her birthday. But luck had it and I picked up the anodized parts on June 10th at 1pm and got to work bolting everything together.

I managed to finish the bike at around 5:30 and she got it on her birthday and everyone was happy. She knew she was getting a bike, but didn't realize the extent to which I went in the creation of her new ride. I am totally happy with how it turned out and she loves it, so chalk this up as another successful project. I only wish working on my Datsun was this fun and rewarding.

Disc brake detail
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Opposite hub detail
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Head tube badge detail
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Rear rack and rails
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Rack Detail
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Finished bike
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