DIY Mountain Bike Tandem
Latest creation over the cold, wet winter. A tandem mountain bike! Built mainly using spares in the basement. Interested in how I built it? No, well worse luck….
The frame is a cheap steel tandem that you can find in many a location second hand, with different branding, but the benefit of this specific frame is it is reasonably lightweight and can take 203 discs (A must on a tandem rear brake, as you need to drag brake for long descents). It will have parts on it. They will always be really really bad.
The wheels are a set of Force cartridge bearing hubs. Cheap but tough enough to take a beating. They have been built on a set of Spank downhill rims with DT Swiss spokes. These are really important to get right as a buckled wheel on a tandem is no joke. Any large downhill rim will be perfect.
The bike will come with a cheap tandem chainset. It will be made from horrible steel and feel all flexy so feel free to fling it on eBay, or into the fiery depths of the sun. Whichever is more convenient. Instead, I went with a 1×10 chainset with the timing chain on the spider ring. Benefits, you can use a normal chainset! You will need to flip the eccentric BB holder in the front as it probably will be reversed for the original timing chain. If you don’t do this the bottom bracket will sloooooowly loosen off!
203 discs front and rear. Tandems benefit from matching rotor sizes, as unlike normal MTBs the centre of gravity doesn’t move as much. It makes for a better ride and more predictable braking. SLX brakes with an extended rear hose provide enough stopping power.
The front fork… do you like bobbing up and down like a pirate singing a shanty? Probably not. Fit a lockout fork, I found that 120mm travel, although quite ‘slack’ works well with a shorter stem. 100mm travel is probably right. The Rockshoxs are a coil fork, hopefully somewhat more reliable as an air fork may have some issues with the weight of two people. Fortunately we are light enough to get away with it as a riding pair, however, if you are heavier than average you may want to consider a jump fork with a bolt axle, for example, Rockshox Argyles. They also come with a steel steerer tube which is a lot stronger. They cost more than the whole tandem however, so we will just have to keep away from the delicious pies for a while.
You may have to ‘face’ the headtube to fit a quality headset. This is because the frame is quite cheap and a quality headset will ‘bind’ when turning due to it not sitting level in a frame. I used a file and my eyes, but the less budget minded could take it to a bike shop.
Seatposts: Delivered from eBay with the word ‘Cannsucc’ on them.
Beyond that. It's a standard bike. Build one, ride it. But make sure you have a ‘shakedown’ cruise beforehand. The stress upon the components can be considerably higher than a normal bike, and bits may fall off at any time.
Serious Disclaimer: This is a completely homebuilt tandem. It really is not suitable for double black diamond downhill descents so please use your judgement. I have used mainly second-hand non-tandem rated parts for this bike. That is not recommended in the worst kind of ways and will probably cause you to have an accident. It will probably not fall apart, but if it does don’t blame me. This bike is a piece of abstract performance art and it is not meant to be ridden. It may also cause dogs to stare at you sceptically.