The Project:

Since June 2008 I have been riding a Giant TCR Alliance. Over the years I have swapped out many parts, and the bike is becoming like George Washington's axe. New handle, new head but still the same axe. How long will a composite frame last, with the carbon-alloy joins? Since I have been happily replacing parts as they wear out, the obvious question is this: instead of buying a new bike assembled, how much would it cost to buy a new bike piece by piece? Only one way to find out...

Sunday, March 24, 2013

How to Build a Bike

How to Build a Bike

Not many people truly build bikes; to do so would be to build the frame, and possibly the components, as well.  I do not have an engineering workshop, nor the expertise to craft what is now a high degree of precision engineering in the design and execution of a modern gear system. There are people who build their own frames, but they are typically building in steel, as aluminium and titanium require a higher level of expertise with welding. And no-one build carbon frames in their garage.

Frame construction aside, the rest is assembly.  For this project I have approached the ideal as closely as possible, designing my own frame to suit my own physical measurements and riding style.  A Chinese titanium engineering company built the frame, and all that remains is for me to assemble the many components into a working bike. 

The build began with the wheels.  Lacing rims is a practised skill, and a good how-to guide is (surprise) found on Sheldon Brown's site.  Even without reading this resource, the keys to success are patience, care, and methodical approach.  There is no real right or wrong lacing pattern - take a look at spoke lacing patterns of different bikes that you see, and a range of possibilities becomes evident.  

My front wheel is an unconventional pattern, with spokes paired at the rim from the same side of the hub, with a double cross-over tension pattern.  Tips that I can mention for wheel-building include these two gems.  To insert a nipple, screw a spare spoke into the flanged end of the nipple, and you can then poke the nipple through the rim hole, and a couple of turns will anchor it onto the wheel spoke.  You can then reverse-turn the spare spoke to release it.

Also, I prefer to lace all of the spokes through the hub first, and then start securing them to the nipples, one set at a time; you have four sets of spokes, two each side of the hub.  Inside-outside lacing, each set anchored at four-hole intervals around the rim.  The lacing pattern comes from the four-hole sequence around the rim holes.

For these two wheels, I used a wheel stand for the entire build, although in the past I have laced the spokes with the rim on my lap, and trued them with the hub mounted in my bike, using the brake pads to spot waves in the rim.  My rear wheel is a traditional lace pattern with alternating left-right hub sides to the rim, and I needed to use the frame to get the dishing centred.  
The rear wheel spokes are asymmetrical, owing to the inset of the freewheel.  Periodically I would dismount the hub, lay the rim across two padded surfaces, and push the hub in to realign the dishing.  A few times around the rim retensioning the spokes, and the rim was done, true and centred.

Now, back to the frame.  First on board was the cable guide.  Being under the bottom bracket and not really visible, it is easy to overlook.  Next, the fork and headset assembly.

Putting the headset, spacers and stem in place on the steering tube, in place in the head tube, Run a pencil around the top edge of the steering tube.  The tube needs to be cut off three mm down from the stem top edge.  To do this properly I knocked up a simple mitre box - three pieces of MDF glued and nailed to another MDF piece, each with a 30 mm hole bored and in line with each other.  To make the cut line visible, wrap a piece of masking tape around the tube, the tape edge along the pencil mark.  Measure 3 mm down from the edge of the tape, marking points as you rotate the tube.  Join the dots, and you have a cut line.  With the tube secured in the mitre box score around the tube with a fine-tooth hacksaw blade, and keep rotating the tube as you cut deeper.  When the tube is cut through, use a fine metal file to smooth down the rough edges, and then fold some 1000 grit sandpaper around the edge and smooth the edge flat, inside and out.

When reassembled, the top cap fits down into the 3 mm space between the top of the tube and the top of the stem.  The compression plug keeps it all nice and tight.  You can then tighten the stem, and bolt the bars to the front of the stem.  Suddenly, it begins to look like a bike...

The rear derailleur can be bolted on at any time, so now is good.  Before positioning the front derailleur, you must install the bottom bracket, and then the crankset.  You can now secure the front unit the correct distance from the top of the crank.

The brakes go on next.  It is always good to get the back end cable mounts in place first.  With the brakes on, slip the shifters onto the bars and tighten them into position.  You can now install the cables.  Now, mount the wheels into the drop-outs, with the cassette installed on the rear freewheel.

Mount the brake cables first, and hold the housings in place against the handlebar position grooves with a couple of turns of electrical tape.  Always get the housing cut with a cm to spare, so if you stuff up a housing cut you can still tidy it up.  When you cut the housing (always before pushing the cable through!) use a spoke to open up the squashed housing core.  Simply push the threaded end in and give it a couple of turns.  Run some grease over the length of the cable before you push it through.  
Secure the cable to the brakes, and ALWAYS read the manufacturer's instruction paper before doing anything.  This also give instructions on how to correctly set the cable tension.  Test the lever-brake action, and then cut the cable with about 5-7 cm to spare, and use some pliers to crimp the aluminium end cap onto the end of the cable.

Before connecting the gear cables, follow the manufacturer's instructions to set the top and bottom limits for the derailleurs. Install the chain, making sure that you have the right number of links (rear derailleur instructions have clear notes on how to do this for your own set-up).  For my build, I ended up removing four links.  You can now connect the gear cables, and if you have not taken any short-cuts the gears will need minimal tuning.  Mine needed a minor tweak to the rear cable barrel-end adjuster, and all was good, shifting up and down cleanly and positively.

All that remains is the cosmetic and practical bits.  RIm tape, tubes and tyres, saddle, seatpost and clamp, handlebar tape, and pedals.  All done, the bike is now assembled.

So, how does it ride?  Very smooth, and the fit is spot on.  After the first ride (93 km) I felt no fatigue at all, almost as if I hadn't been for a ride at all.  One would expect this, as I designed the bike to match my own physical measurements and riding style.  And that is something that you can only really achieve with a professional bike fit service, finding a bike to suit you.  I could quite likely have achieved a similar ride by finding a bike of the right size frame, and tweaking the set up to suit, but then, I would not be able to say that it was my bike - designed and assembled by myself - would I?