How to handle a custom bike build

The most convenient way to buy a new bike is to choose from the huge range of factory-built bikes offered by dozens of brands. These off-the-rack packages offer great value and prospective buyers can take the bike for a test-ride before making a decision. However, the buyer doesn’t get much say in the selection of componentry or the colour of the bike, though it is possible to swap the saddle or fit a different-sized stem before the bike leaves the store.

At the other end of the spectrum, custom builds allow buyers tailor the bike to suits their every need. If you’re familiar with the Bikes of the Bunch then you’ll know how varied the final result can be. The buyer decides on the priority for the build-be it the latest technology, aerodynamics, weight, value for money, or even a specific era-and then selects each part accordingly. In almost every instance, the buyer doesn’t get a chance to take the bike for a ride before spending their money, nor do they have a clear idea on how the bike will look other than their vision for the final build. The whole process takes a leap of faith, a fair measure of time and effort, but it’s an act of creation that offers immense rewards for the owner.

In the past, riders looking for a custom-build relied heavily on a good bike shop to obtain all the parts they needed, otherwise they spent a lot of time travelling to, or phoning, different shops. Now the internet provides a virtual menu that buyers can research (from the comfort of an office chair, no less) all the parts they need for a custom build.

Half the satisfaction with building a custom bike is researching and collect all the parts you need.

1. Frameset

The logical starting point for any custom build is the frameset because it serves as the core of the bike and provides a template to guide the build. There are few standards when it comes to bike parts and frames can vary widely in their specifications. Rather than anticipate what size headset, seatpost or bottom bracket will be required, pick the frameset first and follow the specifications picking the rest of the parts. If you don’t have a handy list of specifications for the frame then you’ll have spend some time taking measurements before you start shopping: the internal diameter of the seat tube (for the post), external diameter of the seat tube (for the seat post clamp and front derailleur band, if required), external diameter of the fork steerer (for the stem), internal diameter of the head tube (for the headset), and the dimensions and thread type for the bottom bracket. In this instance, you might be best served by visiting a shop to validate your measurements.

Make sure you have a clear idea about the frame geometry you’ll need to ensure a suitable fit. If you’ve opted for a custom frameset, then the framebuilder will work with you to determine the right geometry, which may include advice on stem and crank lengths, and handlebar width. For stock framesets, find one that is a good match with your current ride or get a professional fitting to provide you with the ideal dimensions you’ll need. The effective top tube length and head tube length are generally the most important dimensions to pay attention to.

To keep matters as simple as possible, go hunting for a frameset (ie frame plus forks) rather than sourcing the two separately. There are only a few aftermarket manufacturers to choose from (eg. Enve, Woundup, Easton) and some important variables that you should keep in mind before committing to a new fork. Follow the specifications for the head tube of the frame to decide upon the appropriate steerer size (typically 1″ or 1.125″) and type (threaded or threadless) and select an appropriate rake (the larger the rake, the quicker the steering will be).

The recent introduction of electronic shifting complicates frame choice a little since unique fittings are required to install the battery and wiring, and is the one instance where the choice of groupset has an influence on the design of the frame. If you’re keen to specify an electronic groupset for your custom build then endeavour to choose a frame that has been designed to accommodate the battery and wiring.

The Look 695 frameset comes complete with frame, forks, cranks, bottom bracket, headset, stem and integrated seatpost, but leaves the choice of chainrings up to the buyer providing fittings for both standard and compact chainrings.

2. Fittings

I think of the fittings as the fiddly bits that are required to attach all the parts to the frameset. This includes the headset, bottom bracket, seat post clamp, front derailleur band, cable bosses, fork inserts, and cable guides. Sometimes these bits can be difficult to get and will delay final assembly so it’s best to attend to them as soon as possible.

Headset: many contemporary framesets come complete with a headset. If a headset is required, then consult the head tube specifications to determine what kind of headset is required (see above). If you’re using a threadless headset then make sure you have some matching spacers (eg 1.125″ spacers) for setting the stem height (spacers range in height 1-25mm).

Fork insert: if the frameset uses a threadless headset, then a threaded anchor is required inside the fork steerer to attach the compression bolt. Look for an expanding plug for carbon steerers or a star nut for steel or alloy steerers.

Bottom bracket: the number of bottom bracket standards has grown in recent years with the introduction of various press-fit systems. While the frame specifications will get you started towards finding the right bottom bracket for the frame, it will have to be compatible with the crankset that you intend to use. There are essentially two choices for threaded bottom brackets (English versus Italian) compared to many more threadless types. The latter may also require a specific adapter to accommodate your cranks.

Seat post clamp: needs to match the external diameter of the seat tube.

Front derailleur mount: if there is a tab (a “brazed-on” tab, though many are bolted or riveted now) for the front derailleur on the seat tube, then there is nothing more to do other than buying a front derailleur to suit. In the absence of a tab, measure the external diameter of the seat tube and source a front derailleur with a matching clamp diameter. Alternatively, a separate clamp can be used to substitute for a braze-on tab.

Brake mounts: specific mounts are required for caliper, cantilever, and disc brakes and will be incorporated into the design of the frameset.

Cable stops and guides: most frames provide all the stops and guides you’ll need to install the cables (or wires) but inspect all the cable paths to see if anything is needed. If you’re setting up a CX bike with cantilever brakes, cable guides will be required at the head- and seat-tubes.

Threaded bottom brackets are easy to install and will work with most cranksets, except those devoted to the need threadless systems such as BB30.

3. Groupset

Once upon a time a groupset described a huge ensemble of parts but in recent years it has been pared to the essentials: brake/gear levers, derailleurs, cranks, chain, cassette, and brake calipers. For road bikes, it’s a three way choice: Shimano verus SRAM versus Campagnolo. Importantly, each company designs its shifters to operate with exclusively with their derailleurs so there is no mix ‘n match option here. Such restrictions typically don’t extend the cranks and brake calipers, however each company is able to optimise the performance of the ensemble. There is the option of mixing different levels of componentry for a given brand to economise in places though some levels may be incompatible (eg 10-speed Centaur shifters can’t be used with 11-speed Record derailleurs, for obvious reasons).

For Shimano and Campagnolo, deciding on a specific level of groupset also decides the number of cogs you get in the package. Thus the 2013 Dura Ace groupset is 11-speed, while Ultegra and 105 are 10 speed. Similarly, Campagnolo’s Athena, Chorus, Record and Super Record groups are 11-speed, while the rest of the range is 10-speed. In contrast, all of SRAM’s groups are 10-speed. Then there is the issue of electronic versus mechanical groupsets. Shimano and Campagnolo offer electronic versions of their upper end groupsets that adopt slightly different approaches to the new technology but both comprise a battery, wires and junction boxes, and motorised derailleurs. Since the wires can’t be cut to length, some care has to be taken to order wire lengths that suit the size of the frame.

There are normally a few options to choose from for each part of a groupset that will help tailor their fit to you and/or the frame:

Cranks: the standard length is 172.5mm but riders with short legs may find 167.5 or 170mm lengths provide a better fit; similarly, riders with long legs may find lengths up to 180mm are better suited to them. Road cranksets are typically offered with a choice of standard chainrings (53/39 teeth), compact chainrings (50/34 teeth), and most recently, mid-compact chainrings (52/36 teeth), but other options may be available. Riders looking a wider range of ratios might want to consider a triple chainring crankset (see below) however a wide-range cassette (11-32 teeth) can be paired with a compact double to provide the similar range of ratios. Whatever the size, the ideal chainring combination will allow you to maximise the use of the rear cogs. There’s no point in running standard-sized chainrings if you rarely use the higher gear ratios.

Triple chainrings: both Shimano and Campagnolo offer groupsets with a triple crankset that are suited for touring with heavy loads and climbing long mountain passes with less effort. Triple-specific derailleurs are required to accommodate the extra chainring and a longer chain. A triple-specific shifter (left hand lever) may also be necessary, so in practical terms, switching from a double to a triple requires a lot more hardware than a different crankset.

Bottom bracket: needs to be matched to the specifications of the frame and suit the bearing specifications of the cranks. An adapter may be required to allow a specific set of cranks to be used with certain bottom bracket/bearing systems.

Cassette: the range of cogs that comprise the cassette should suit your needs and the terrain you plan to ride. A straight block (eg 12-13-14-15-16-17-18-19-20-21) is perfect for flat or gently rolling terrain, expand the range to include larger cogs (typically up to 27 teeth, though a wide-range cassette up to 32 teeth is available) for riding steep hills.

Front derailleur: as mentioned above, front derailleurs are designed to fit a braze-on tab or are supplied with an integrated clamp. Most front derailleurs will work with both standard and compact chainrings but a triple-specific derailleur is required for a triple crankset.

Rear derailleur: must be matched to the shifters and the number of cogs in the cassette. The default choice for road bikes is a short cage; choose a derailleur with a long cage if you’re setting the bike up with a triple crankset or a wide-range cassette (11-32 teeth).

Brakes: road bikes usually use caliper brakes but with disc brakes on the horizon, the choice is likely to expand, with cantilever brakes the only other choice (typically found on CX bikes). Once again, the frame specifications will guide your decision here. Road framesets that provide a lot of clearance around the wheels for mudguards and wider tyres (eg. touring frames) may require long-reach brake calipers.

Cables: expect a full complement of cable to be included with the shifter/brake levers. Aftermarket cable sets can improve the quality of shifting and braking compared to stock cable sets; they also offer a wider range of colours and materials too.

An adapter band can be used to attach a front derailleur with a braze-on fitting to a frame.

4. Wheels

There are two big decisions to be made regarding the selection of the wheels: first, the preferred tyre system (clincher, tubular or tubeless), and second, factory- versus custom-built wheels. For the first, match the rim type to the tyre system you wish to use and for the second, see this post for a discussion of the pros and cons of each approach. If you elect to go custom, then you’ll need to source rims, hubs and spokes, which have to be carefully matched. Don’t forget rim tape for clinchers (most factory-built wheelsets come with the tape installed).

The only other detail to attend to is to make sure that the freehub body is compatible with the groupset you intend to use (ie 11-speed Shimano, 10-speed Shimano/SRAM, or Campagnolo). For older framesets, hubs from the same era will generally be required to suit narrower spacing of the rear dropouts.

5. Contact points

Stem: the stem has two diameters, one for the forks, and the other for the bars. The majority of threadless forks have a diameter of 1.125″ and stems to suit these forks are widely available. Handlebar diameters have increased in recent years and the new standard has a diameter of 31.6mm. Opting for bars with larger or smaller diameters will require a stem to match. Once you have the diameters sorted out, all that is left is to choose the length and angle of rise to place the handlebars in the right spot relative to the saddle. Threadless systems use spacers above the top cap of the headset to set the stem height on the fork steerer and are available in 1-25mm increments. If you’re building a bike with threaded forks then a standard quill stem will be required.

Handlebars: in addition to the diameter at the stem, handlebars vary in width and the shape of the drop. The choice of width is essentially a matter of preference, but generally narrow bars are better suited to riders with small builds and narrow shoulders. There are lots of different handlebar shapes on the market but there are two major categories, large/regular versus compact, where the drops and levers are easier to reach on a compact bar.

Seatpost: the diameter of the seatpost must match the internal diameter of the seat tube precisely, where a difference of 0.1mm is significant. Posts vary in their length and by how much the seat clamp is offset from the centreline of the post. Frames with a sloping top tube will require a long post (up to 350mm) and ideally, you should know how much setback (ie how far the centre of the saddle needs to be positioned behind the bottom bracket) is required for the saddle to choose a suitable post.

Saddle: saddle choice is a matter of personal preference and one size fits all (with the exception of the Selle Italia’s Monolink system).

Pedals: like saddles, selecting a suitable pedal is a matter of preference since one thread size fits all road cranksets. Speedplay pedals provide the greatest range of adjustability for positioning the feet on the pedals.

Tyres: straightforward choice here, just match the tyre system to the rims. Most road frames will accommodate tyres up to 25mm wide; check the frameset specifications if you’re thinking of running wider tyres. Ensure the valve stems for the tyres/tubes suit the depth of the rims.

6. Finishing Touches

There are a variety of ways to add a personal touch to a custom build (or your current ride) and it’s worth taking the time to dwell on these last details.

Custom paint: the ultimate in personal touches, turn something that has come off-the-rack into an exotic species, or, make the old/familiar new again. This is where a bike build becomes a work of art and Sun Graphics has to be one of the best artists in the business.

Bar tape: see my recent post on bar tape tech.

Upholstery: Rule #8 dictates that the seat and handlebar tape must match (at the very least). You can personalise a stock saddle with custom leather upholstery from Busyman Bicycles.

Bottle cages: there’s a massive range of bottle cages on the market that can be broken down into different materials, each of which have their own characterisitics.

Custom name stickers: everybody deserves to have their name on the top tube of their bike and a custom-made sticker is surprisingly affordable.

Putting it all together

The obvious strategy is to find a good mechanic to take care of the build. Some bike shops won’t welcome a new customer with a box full of parts acquired from online sources, so it might be worth calling around and getting a few quotes first. Otherwise, hunt down a service-only business where you can talk directly with the mechanic that will do the work for you. If you have some aptitude for mechanics then it’s worth having a crack at it yourself-there’s enormous satisfaction in building your own bike-and you can enlist a mechanic to take care of any jobs that need specialised tools (eg headset cups), check it over, and take care of any fine tuning at the end.

Final Comments

While every rider deserves a custom bike build, it is a demanding process that can overwhelm the uninitiated. However, there is enormous satisfaction in hand-picking each part of your new bike and I believe the results easily justify the extra time and effort.

Abbreviated Checklist