How to Build an Affordable, High Performance, Lightweight Folding Bike: Part 1

There are many different types of folding bikes available in the market. By different, I am referring to the purpose that the folding bike is designed for. Some are designed to be for leisure riding, some for speed, some for touring, and some that are a mixture of different categories. Depending on the target market, each of these type of folding bike will have different grades of components and parts, and of course a different price range.

As an example, my Dahon Boardwalk is built primarily as a touring and commuting bike. The rear rack allows panniers to be carried for touring or commuting, while the full fenders block most of the splashes from wet roads. A double kickstand is also included for practicality's sake. However, look beneath the surface and a different type of bike can be spotted. Drop bars and slim Kojak tires reveal the speedy desire of the bike, while a quality Shimano Ultegra Di2 groupset ensures good power transfer and effortless electronic shifting. Folding size is not ideal due to the size of the drop bar, neither is the weight due to the variety of accessories installed on the bike. The total weight of the rear rack, kickstand and fenders is already 1.4kg.

My Dahon Boardwalk, mainly a touring / commuting bike

Recently, I had the idea to start a new project, to build a new folding bike with different objectives. The three keywords for this new folding bike would be Lightweight, High Performance and Affordable. What do these keywords mean? Here are my definitions:

Lightweight
In order to reduce the weight of a folding bike, lightweight components will need to be used. This means paying more for high end components that weigh less. Any accessories that are not essential to function will not be installed, for example fenders or kickstand. However, one thing that I will not sacrifice is safety. There are some components that are really lightweight, but they may not be safe to use as they are fragile and may break easily. This is especially critical for parts such as the brake levers or handlebar. Examples of lightweight bikes in the Dahon or Tern range would be the the Dahon MuSL (8.7kg without pedals) or Verge X20 (9.3kg without pedals). In my opinion, a folding bike is only considered lightweight if it weighs less than 10kg without any accessories.

High Performance
This means using good quality components that function well, with specifications that are comparable in function with high end bikes. A single speed folding bike would of course weigh the least, but in my opinion, high performance would be defined as a bike that has a reliable 2x10 speed drivetrain, with quality braking components and a smooth rolling wheelset. The components need not be of the top end range (such as Dura-Ace or SRAM Red), but they should have a performance that is at least 80-90% of the top end components. As a reference, I will be using the Verge P20 and Verge X20 (both 20 speeds) for component comparison.

Affordable
It is quite difficult to define what is affordable, as this is very subjective. What may be affordable to you may be too expensive for me. In this case, I would be using the price range of Tern bikes as a rough guide. Tern folding bike prices range from $500+ to $4000+, so the range is quite big. To me, affordable would mean below the $2000 price point. Although this may seem quite high, this is actually a reasonable price to pay for a lightweight, high performance folding bike.

As you may already know, these 3 keywords tend to contradict each other. For example:
1) A lightweight bike that is high performance will likely not be affordable. An example would be the Dahon MuEX (no longer in production) or Tern Verge X20. These bike models weigh below 9.3kg (without pedals), but cost more than $4000 each.

Tern Verge X20. Lightweight and high performance, but quite expensive too.

2) A lightweight bike that is affordable is quite difficult to find. Other than a single speed bike, practically all affordable bikes weigh quite a bit (>10kg) as they don't use lightweight or high end components.

3) A high performance bike that is affordable is also quite hard to come by. Most high performance components don't come cheap, and even if they do, they are not the lightest around. A good example would be the recently launched Tern Verge P20. By my definition it is a high performance bike (20 speeds with a decent wheelset and drivetrain), and is still affordable at $1700. However, the weight is 11.0kg which is not considered lightweight.

Tern Verge P20. Relatively affordable and high performance, but not in the lightweight category.

To start off the project, I first needed to quantify the targets. Using keywords alone would be difficult as there are no measurable targets or objectives. Thus I decided to put some numbers to support each of the keywords.

Lightweight - Target weight would be that of the Tern Verge X20, at less than or equal to 9.3kg without pedals.
High Performance - 20 speed road drivetrain, using at least a Shimano 105 drivetrain and shifting components, with Deore and above V brake components and a smooth rolling wheelset + tires.
Affordable - To keep the total component price to below $2000. The lower the better.

So far there are no Dahon or Tern folding bikes that I know of that fulfill these criteria (20 speeds, <9.3kg, <SGD $2000).

Other than these targets, another important objective is to achieve a compact folding size. This means a flat handlebar folding bike (which is also more lightweight than a drop bar or bullhorn bar folding bike).

Before actually getting the parts for this bike project, I created a simple Excel spreadsheet that totaled up the weights and prices for each of the components. This allowed me to swap components easily to compare the weight and price differences.

Estimated components to be used and their respective estimtated weights

According to the Excel table, the total weight of the bike will be around 8.8kg without pedals, and 9.2kg including the Shimano PD-A530 SPD Pedals. This is a theoretical value based on estimated weights. The weight of the individual components are estimated based on previous samples or information available online.

In the following sections of this post, I will be listing out in more detail the various components that make up the bike, along with the weight and price of each part. Each of the parts were weighed with a digital weighing scale, and the prices are rounded up to the nearest $5 (including shipping costs). The source of the pricing will also be given (although it may not necessarily be where I got it from).

If necessary, I will also give some justification as to why I chose that component instead of another. As a bonus, I will also offer alternative choices for further cost reduction, weight reduction or better performance.

Frame
Model: Dahon MuEX Frame 
Estimated Weight: 2400 grams
Actual Weight: 2340 grams (includes seatpost shim, seatpost clamp, RD hanger and FD roller)
Source: Taobao
Price: $450 (including shipping)

The frame is the most important part of the bike. With a good frame, you can put a wide variety of components on it, and there would not be any major compatibility issues. The top end Dahon MuEX frame is one of the best folding bike frames you can find out there, being lightweight and stiff. Selecting a Dahon frame also ensures that compatible aftermarket parts and accessories can be found easily.

The frame comes with the metal seatpost shim, seatpost clamp, RD hanger and FD roller.

Dahon MuEX frame, a good platform to build on!

Fork
Model: Dahon Puro U7 Aluminium Fork for Mu Frame 
Estimated Weight: 440 grams
Actual Weight: 488 grams (including steel compression bolt)
Source: Taobao
Price: 0. Included as a package with the MuEX frame.

The lightweight Dahon Puro U7 aluminium fork is included as a package with the frame, thus there is no need to purchase separately. In fact, the package includes many items, such as the fork, handlepost, seatpost and headset.

Original Dahon aluminium fork for Mu frames

It was during installation that I realised that although the compression bolt for the fork is included, the brass shim is not. Although the bolt can be installed without the brass shim, it is better to include the shim, in order to ensure a more consistent tightening torque.

Brass shim for Dahon compression bolt

Goes onto the base of the handlepost before tightening the compression bolt on top.

Handlepost
Model: Fnhon 31.5cm, dual bolt 
Estimated Weight: 524 grams
Actual Weight: 542 grams
Source: Taobao
Price: 0. Included as a package with the MuEX frame.
Alternatives: Fnhon handleposts of other lengths, or the 4 bolt handlepost

This is a Fnhon 31.5cm, dual bolt handlepost. For more details and pictures please click on this link. Similarly, this component is included as a package with the frame.

For an installation guide on Dahon / Fnhon handlepost, check out this blog post for the details.

Fnhon 31.5cm, dual bolt handlepost

Headset
Model: LitePro Headset
Estimated Weight: 80 grams
Actual Weight: 72 grams
Source: Taobao
Price: 0. Included as a package with the MuEX frame.

I shall not go into details for the headset, it is a pretty standard LitePro headset. For a LitePro headset installation guide, check out this link.

I had asked for a black coloured headset for the bike, but they sent over a red coloured one instead. In the end it looks pretty good as the red cover matches the red accents on the frame.

 LitePro headset

Wheelset
Model: Wheelsport Sunny 406 wheelset 
Estimated Weight: 1144 grams (same as Wheelsport Smart 1.0)
Actual Weight: Front wheel is 484 grams. rear wheel is 698 grams. This excludes the weight of the Velox cloth rim tape.
Including rim tape, the weight is 495 grams for the front wheel, 709 grams for the rear wheel. In total the wheelset weight (including rim tape) is 1204 grams
Source: MyBikeShop
Price: $350
Alternatives: Wheelsport Smart 1.0 ($480), Kinetix Pro ($600+)

The original price of this Wheelsport wheelset is $380, but you might be able to get a discount if you don't need the bike shop to install the wheelset, change tires or cassette for you.

I chose this Wheelsport Sunny wheelset as it is affordable and with good performance. Previously I was using the Wheelsport Smart 1.0 wheelset and I find it to be very good. Thus I believe that the Wheelsport Sunny wheelset would have a similar performance. The main difference between the Sunny and the Smart 1.0 is that the Smart 1.0 has a higher profile rim. Other than that the hubs and spokes look pretty similar.

Using the lightweight Kinetix Pro rims will save even more weight, perhaps up to 150 grams compared to the Wheelsport Sunny. However it is much more expensive.

The Wheelsport Sunny and Smart 1.0 has 20 spokes in front, and 24 spokes on the rear. The Kinetix Pro has 14 spokes in front and 16 spokes on the rear wheel.

Wheelsport Sunny wheels in black colour

Closeup look at the front wheel

Closeup look at the rear wheel

I found that almost all of the spoke holes on the rim has some burrs, which can cut through the inner tube if the rim tape is not properly laid. Since I have removed the original plastic rim tape, I decided to take the effort to deburr the holes with a file. It was quite a lot of work due to the many spoke holes.

Filing the side of the spoke holes to remove burrs. I could not use a deburring tool as there were insufficient space between the rim walls to use the tool effectively.

Good quality Velox cloth rim tape. This is much better than plastic rim tapes at protecting the tube from the sharp edges of the rim spoke holes.

Tires
Model: Panaracer Minits Lite, 20x1.25", folding bead 
Estimated Weight: 340 grams/pair
Actual Weight: 342 grams/pair (folding bead)
Source: MyBikeShop
Price: $80/pair
Alternatives: Schwalbe Kojak 20x1.35" folding (460 grams,$120/pair), Schwalbe Durano 20x1.1" (380 grams/pair), Schwalbe Ultremo ZX 20x0.9" (290 grams/pair)
These are really fast rolling tires from Panaracer. They are also lightweight and cheaper, which helps to keep the weight down. My first choice was actually Schwalbe Durano tires, but they were out of stock at MyBikeShop. Always get folding tires as they are lighter and easier to install/remove from the rims.

Panaracer Minits Lite folding bead tires, 20x1.25"

Inner Tubes
Model: Schwalbe SV6A Extra Light Tubes (Presta) 
Estimated Weight: 130 grams/pair
Actual Weight: 132 grams/pair
Source: MyBikeShop
Price: $30/pair
Alternatives: Schwalbe SV6 Tubes (190 grams/pair, Presta)
Using lightweight tubes can save some weight, but the reduced thickness or size might slightly increase the chance of getting a puncture. These are old tubes that were patched, but they are working fine.

Schwalbe SV6A Extra Light Tubes

Claimed weight of 65 grams is accurate!

Quick Release Skewers
Model: Agogo extra light titanium skewers, 74/130mm 
Estimated Weight: 42 grams/pair
Actual Weight: 43 grams/pair
Source: MyBikeShop
Price: $45/pair
Alternatives: Wheelsport original QR skewers, 113 grams/pair

This is a rather optional item, as you can just use the original Wheelsport QR skewers to save money. But I decided to try out this QR skewer as it can save quite a bit of weight. This Agogo skewer construction is actually not too bad as it does not use a rubber washer under the QR lever, which means the clamping force is better. For more details on good vs bad QR skewers please refer to this link.

The only thing to take note is that the titanium center axle tends to stretch a bit, so there is a need to re-tighten the QR lever once in a while.

Very lightweight Agogo titanium QR skewers

This post is getting really long, so I shall continue with the other components for this bike project in the second part of this guide.

The second part of the guide is now up! Click here to continue~