David Mercer grew up in the small, community-orientated town of Hillcrest, KwaZulu-Natal and spent a great deal of his childhood riding bicycles after school and on weekends with friends in the surrounding countryside and farming areas, practicing their skills on the local tracks. At an early age, Mercer was drawn to the mechanics of how bicycles worked – both in their simplicity and complexity.

“I’ve been mad about bikes since as far back as I can remember,” says Mercer. “I started out with my first BMX when I was about six-years-old and quickly got into the racing scene – that scene was particularly healthy at the time where we lived, and when I was 13, my parents gave me my first mountain bike.”

“This completely blew the doors off my world. Suddenly the horizon was just that much further away. You could cover bigger distances and just explore more and do more than what we had been doing on our BMX’s.”

David Mercer with a recently completed MTB frame

“Together with a good mate of mine, virtually every afternoon, we started exploring the farms and sugarcane fields and the various plantations around Hillcrest. Our little home territory just grew,” continued Mercer.

“It was around about that time, maybe I was 14 or 15-years-old, that I really started thinking about framebuilding. I had read an article in a Mountain Biking UK magazine that had focussed on UK-based framebuilders, some of whom had pivoted from building traditional road frames and were now building mountain bike frames to supply this growing trend of mountain bike riding.”

“These were the guys that all the big companies were watching because they were able to build something, go out there and try it – riding it the very next week – and then coming back and tweaking and changing stuff a week or two later. They were the ones really driving all the innovation. And I thought that was very cool. I wanted to be one of those guys.”

“But as I got older, I started to realise that my dreams of becoming a framebuilder may be a bit far-fetched and financially irresponsible. So I fell back to my other boyhood dream of becoming a veterinarian and when I finished school, I went off to Onderstepoort and completed my studies and became a vet and then moved to Cape Town.”

Custom details: a shaped seatstay bridge with a stylised brass logo handcut with a jeweller’s saw

“I worked in an after-hours position and this afforded me a lot of time off during the day. We would work for a week at a time and then have a week off. It was very demanding work – I’d start my shift at 18:00 and knock off the following morning at about 08:00. The shifts were long and very intense, but then you’d have an entire week off to go and do whatever you wanted to.”

“Supposedly you were meant to go and catch up on sleep and rest and recuperate – but what young, mid 20-year-old does that!?”

“So, I spent my off days climbing and running and riding, mixed with lots of road trips, just living it up. But as time went on, I found myself becoming more and more disgruntled with the veterinary work. In a clinical setting like that there just isn’t a lot of room for creativity.”

“After being in practice for 10 years, I got to a point where I had become completely burnt out on all the clinical work and I desperately wanted to be able to have something to show for my time. I found myself continuously circling back to this idea of framebuilding. The idea still seemed so far-fetched – the nuances of framebuilding.”

The business end of a MTB frame – filed and sanded brass fillets attaching the head tube to the top and down tubes. Internal cable routing port silver soldered into the downtube

“It’s not just building frames – it’s also the design – how it all comes together in order for the bicycle to handle like you want it to. And then you have to consider all the different scenarios – the different use-case scenarios, all the different handling characteristics.”

Becoming a framebuilder
Bicycle framebuilding in South Africa traces its roots as far back as the 1860s to late 19th century metalworking, when early bicycles evolved from wooden structures into welded and brazed steel assemblies. As cycling gained popularity in Europe, blacksmiths, carriage makers and tube specialists adapted existing skills to produce lightweight frames from drawn steel tubing. By the 1890s, lugged construction had emerged, allowing tubes to be joined accurately using brazing rather than forging. This method improved consistency and made small-scale production possible.

During the early 20th century, specialist framebuilders began refining geometry and tube selection for road racing and utility cycling. Manufacturers developed butted tubing to reduce weight while maintaining strength. Framebuilding became a trade that combined workshop practice with rider feedback, shaping designs over decades. While materials have changed, many of the core joining techniques established in this period remain in use today.

Smooth brass fillets at the bottom bracket junction – the meeting point of downtube, seat-tube and chainstays. The threaded bottom bracket shell will house the bottom bracket bearings through which the crank spindle passes

Handmade bicycle framebuilding is a practical craft of metalworking embedded in workshop processes rather than automation. Most frames start with steel, titanium or aluminium tubing, selected for wall thickness, diameter and intended load. Steel is still widely used because it can be cut, mitred and joined with basic shop equipment and controlled heat.

Tube preparation is largely manual and framebuilders cut mitres using hole saws, files or milling fixtures to ensure close contact at each joint. Alignment tables and surface plates are used to control geometry during tacking and final joining. Joining is typically done by brazing or TIG welding. Brazing, whether lugged or fillet, relies on capillary action and precise heat control. TIG welding offers faster joins but demands accuracy to avoid distortion. Mercer has concentrated and refined his technique of brazing rather than welding.

Measuring tools are fundamental to the process and calipers, straight edges, angle gauges and frame alignment tools are used repeatedly as the frame progresses. After joining, frames are checked for straightness and cold-set where required. Finishing includes cleaning joints, chasing threads and facing bearing surfaces. It’s a labour-intensive process with consistency achieved through method and technique rather than volume. Although Mercer has some basic designs he bases his frames on, all of his frames are custom builds.

Top view of the bottom bracket junction

“I have always been a very visual arts-driven kind of person and enjoyed drawing. But metalworking and brazing was completely foreign to me. I’d never done much of that,” explains Mercer.

“But I had a lot of experience in cycling so I poured over a lot of the geometry parts and I thought I knew what it was about these bikes that I enjoyed riding that made them handle the way that they did. And that became my kind of starting point when I eventually set out to start drawing up my own frames.”

“Initially I did a lot of reading. This was in about 2009 and 2010. The Internet back then was also a much friendlier place and I would hang around in forums, too nervous to really ask too many questions, I just kind of hovered in the wings and waited for the right questions to be asked absorbing the discussions.”

“Through this process I found so many really good and constructive videos. It was a time when nearly every framebuilder had their own blog and I devoured those. I think my journey would have been a lot different if I had started out now.”

Headtube junction. Twin cable ports are silver brazed into the down tube and a custom cutout brass eland lopes across the top tube. Machined reinforcement rings at the top and bottom of the headtube help prevent flaring after years of abuse

“I also managed to get my hands on some old textbooks, and one in particular – The Paterek Manual for Bicycle Framebuilders – I read religiously.”

“All of this formed my instruction, though it involved no practical instruction. So when I eventually decided to set myself up, I bought a very small gas welding setup, a Harris-style oxygen acetylene torch and a number of tips along with some large industrial bottles. Then I set about teaching myself how to brass braze.”

“Those early attempts shall we say were way more exciting than they should have been. There were a lot of explosions and pops and bangs,” laughs Mercer.

“I kept thinking, ‘surely this is not how it’s supposed to go!’”

The Mercer workshop

“But I just kept persevering, trying one thing after the other. I wasn’t building anything of consequence yet – things like burglar guards for the house, coat hooks and simple bicycle-related tools including a wheel truing stand, a dishing tool, a derailleur-hanger straightener tool and a few other things. I still didn’t really think I could actually become a bicycle framebuilder.”

“But eventually one thing led to another and after about two years of dabbling with this, my wife convinced me to buy my first tube set and build a frame, perhaps in the hope that we could move on from this whole saga,” chuckles Mercer.

“So I did that – it was the beginning of 2013. I had to import the tubing as there just aren’t any local suppliers. We actually import all of our bicycle tubing and some of the frame components from places like the UK and Italy. Some of my material I import directly from the manufacturers, but there is one supplier in particular in the UK that is kind of a one-stop-shop for all my different component needs. It’s hard to beat because they do the all the sourcing from all over the world – you’ll have bits that come from the US, bits that come from Taiwan and bits that come from other countries. It makes my job a lot easier.”

Frames awaiting repair or attention. Besides building new, custom frames, Mercer also undertakes repairs and restorations on older and classic frames

“That first frame actually came together far easier than I could have imagined and before I knew it, friends were clamouring to have me build them a frame. My first 10 frames were all for mates or mates of mates. I sort of looked at that as an apprenticeship to myself.”

“I had tried to approach some of the older framebuilders locally for further guidance, and one in particular, Francois du Toit. He was still building at the time, albeit erratically, but I didn’t always leave his workshop feeling like I had been welcomed.”

“You must remember though, these legacy framebuilders and the brands that they built frames for locally like Lejeune, Peugeot and Gemini had had their whole world’s turned upside down by the big international manufacturers. South African framebuilding had been at its peak in the 1980s and 1990s due to sanctions and post 1994 the market was flooded with imports. The other challenge the local framebuilders faced was the emergence of aluminium frames. The local industry collapsed virtually overnight and these guys that had factories now found themselves having to focus on a much smaller clientele.”

A recent experiment: a pair of adjustable handlebars – the ends can be swapped out for different profiles in 22.2mm tube in order to accommodate different riding styles. After considering different names such as the Low-Bar, The Wander Bar and Bar-Bar, Mercer settled on calling them the Cruise-Bar

“That avenue of me looking to learn from other local framebuilders was very quickly shut down. I think Francois basically told me, ‘You don’t want to get into this industry’, but I was determined so I continued to bumble along.”

“Through trial and error, I found techniques and ways that worked for me and resonated with what I had read and seen in the videos I had watched.”

“One of my biggest breakthroughs came in early 2014 when I decided to go to the UK and exhibit at the BESPOKED handmade bike show. At this stage I was still working part time as a vet and framebuilding in a little converted granny flat down the side of the house at home.”

“I had been invited to go over to the UK and to the show by Matthew Souter, an expat South African who had faced some of the same challenges as I did when it came to trying to find apprenticeships locally in South Africa. But the opportunity to work under and learn from him in his workshop was one I couldn’t pass up. In fact, it was the first time I had ever seen someone else wielding the torch and I was a sponge, I just sucked up every bit of information that I could. He pointed out a few things to change in my technique and I was that much better for it.”

The lugged headtube – downtube junction and flat fork crown on a classic lugged frame

“The show was likewise very rewarding. I was able to meet some of the framebuilders that I had been idolising and having them compliment my work helped me realise that I was actually doing a good job. The visit turned out to be equal parts instructive and encouraging.”

“When I returned home, I decided it was time to take an even more part time position as a vet and focus more closely on my framebuilding.”

“Shortly after I got back though, I landed up with a perforated gastric ulcer. The prognosis wasn’t good at all and after I woke up from the operation, I had a lot of time to think. I had a young family and realised that being a vet was an easy way to make money, but it wasn’t a way to nourish my soul.”

“At the beginning of 2017 I decided to give up vet work altogether and focus on my workshop.”

Headtube-toptube lug and custom, silver-soldered, stainless steel brake cable hanger on a classic lugged frame

“As I became more exposed to further aspects of the industry, I realised that the metalworking of framebuilding borders on structural engineering and art and sculpture. I wanted to build frames that were beautiful. Even the simplest of frames has to have a purity of line and cleanliness about it. I love the fine details – the hand carved flourishes, the lug detailing.”

“I work exclusively with steel for my frame tubes. But within that there are so many different alloys of steel. Mostly I work with chromium-molybdenum steel alloys, or chromoly as it is often referred to, and I also work with a manganese-moly steel alloy. The chromoly is a 4130 or 25CrMo4 steel as it is sometimes known, depending on where I am sourcing it from. It’s known for its high strength-to-weight ratios, toughness and weldability. Of course, some of the suppliers have their own secret recipes but generally speaking, a chromoly is the best suited material for my application.”

A silver-soldered lugged seat junction on a classic frame

“One of my suppliers makes an alloy called Nivachrome – a patented high-quality steel alloy that’s been developed specifically for high-performance bicycle frames. It’s a nickel – vanadium chromoly steel. They also manufacture an alloy called Omnicrom – a low-carbon chromoly steel alloy with Niobium. These alloys allow for very thin walls in the frame tubing.”

Bike frame tubes are butted at the ends and tubes have varying wall thickness and lengths, being thicker at stress points (like joints) for strength and thinner in the middle to reduce weight and add comfort/flex. This makes frames stronger, lighter, and more pleasant to ride. “You choose wall thicknesses depending on the application of the bicycle,” explains Mercer.

“Typically, you’re looking at wall thicknesses of around 0.9mm or 1mm at the ends of the tube or the butted profile section, and then a ramp down in thickness where the tube tapers down to 0.6mm in the middle. With something like the specially heat-treated Omnicrom – these thickness can be down to 0.6mm at the butted profile section and down to 0.4mm in the centre. These are still relatively large diameter tubes and you can even squeeze them and watch them flex like an aluminium drink can.”

The essence of speed: a naked track bike with gothic, webbed fillet-brazed junctions. Track bikes are designed for racing around a velodrome and they have no freewheel and no brakes. When the wheels are turning, so too are the cranks

“If I compare the quality of today’s materials with what was available even as recently as the 1970s and 1980s, we really are living in the golden age of the quality of steel tubing that we can build with. Back then the tube diameters were much thinner, but the material thicknesses were also much greater.”

The process
“Typically, someone will reach out to me saying that they are keen to commission a custom bike. By and large the majority of my customers are local but about a quarter of my frames go overseas – though even then, there seems to be some kind of strong South African connection.”

“Most of the time these customers are approaching me because they want something special. They’re tired of riding bikes that you can just pick off the shelf, they want something they can develop a relationship with. Cycling will already be such a big part of their lives that they want something to be an extension of that.”

Neo-Retro: a classic inspired, lugged frameset, completed with a modern component groupset

“This is followed by a discussion about the type of bike that they want to build, the kind of riding they do, we might talk about bikes that they have enjoyed in the past. We will discuss fit, size and handling and whether they have ever really had a proper bike fit performed, and do they have any bikes we can use as a rough template to start working from. Then they’ll come in to the workshop for a discussion – if they can’t we do this over the phone or a Zoom call.”

“There are so many factors to take into consideration – is the person looking for a bike for endurance rides or are they a fast-paced racer? Then we start to look at the kind of components that are going to be hung on the frame, what groupset is going to work – the parts that make up the drivetrain of the bike, its cogs, the chain, bottom brackets, the crank, the derailleurs and brakes of the bike – and what standards we need to be working with in order to run that groupset. These components I can source locally, although the majority of them are imported. We will also discuss what tyre sizes they are looking to run.”

A classic, yet modern, lugged all-road frame. This one is ready to be built up and has generous room for larger tyres and canti-lever brakes. It should be equally at home on quiet backroads, greenbelt paths and everything in between

“Within the range of tube sets to choose from, again, there are so many profiles to choose from. Mountain bike tube sets tend to be a bit more standard, but when it comes to your gravel and road bikes there are an enormous number of variations all designed to distribute the forces and increase or decrease stiffness. Are you a seated rider or do you spend a lot of time riding out of the saddle? – all these factors need to be considered. The tube sets are generally accompanied with a set of guidelines and I will tend to work within them, but each custom build is different. Some customers will already have a very good idea of what tube set they want and their minds are already made up in terms of what they want.”

“Sometimes you can only really see how something might pull together by looking at it three dimensionally – all the components have been sourced and you start to model it up here in the workshop to get an idea of how it’s all going to come together.”

A few bikes and frames on display outside the Mercer workshop

“When it comes to what I personally like to build, my preferences change. This is both in terms of what I have been riding and what I have been building a lot of.”

“There is this return to the tangible, stuff that we can hold and feel and when you’re getting something that’s been handmade like one of my bike frames, then you’ve met the person that’s made this for you. Something has resonated between us and you can frequently pop into the workshop and see how the process is progressing,” reflects Mercer.

In terms of conventional tooling, Mercer makes use of two lathes, a drill press, a cut-off saw, a range of hand tools, some power files, an angel grinder, plenty of abrasive cloth for cleaning up fillets and dressing mitres and cleaning frames before they go off for painting.

A boardtrack racer inspired this moped build from last 2024. Mercer modified an existing beach-cruiser frame adding reinforcements and gussets wherever necessary. With its 66cc 2 stroke engine it gets up to a rather frightening 60km per hour and will do 40km to the litre. Completely besotted on 2-stroke stoke, Mercer is currently building a bigger, badder version around a 100cc engine

Mercer’s range of handmade bikes include road bikes, mountain bikes and gravel bikes, in both fillet brazed and lugged styles. All Mercer’s bikes are either silver soldered or brass brazed. He also offers tailored one-on-one framebuilding experiences including short introductory courses, to longer, more comprehensive experiences. You do not require any previous experience and will be guided through each step of the process.

Mercer has operated his workshop from The Bijou located in Cape Town since 2018. It’s an old Art Deco cinema that has been repurposed into a multi-use workspace that houses a collection of craftspeople, including blacksmith, Conrad Hicks.

Mercer may be the only classic steel-frame bicycle framebuilder left in South Africa and outsourcing builds is not something that will ever be on his list of things to do.

For further information contact David Mercer on +27 84 554 3762, email david@mercerbikes.co.za or visit: https://mercerbikes.co.za