Tandem bicycle enthusiasts who are also handy with tools often wish to take their hobby to the next level by building their own bike – or by building bikes for other people. Online buying sites are a fertile resource for people looking to build tandem bikes, offering thousands of different parts – including frames – for relatively low prices.
A frame is the foundation of a tandem and usually represents the biggest investment. As such, it is an important element to get right when assembling the pieces for a new bike. There is a wide variety of frames available on eBay, from standard two seater tandems to triplets for three riders, quads for four, quints for five and even more.
The information in this guide will equip you with the knowledge of the ins and outs of tandem bike structure and function, and how to choose and purchase the right one for you on eBay.
Choosing the Right Number of Seats
Unless building a tandem for a competitive team or a couple it can be difficult to know how many seats the tandem should have. Try to work out how many riders will generally be expected to use the bike on a regular basis. If building a bike for a family, establish through conversations which family members are interested in riding regularly and buy a multi-seat tandem frame for that number. If flexibility is crucial then tandem frames that can break apart using S&S couplers can provide the answer. S&S couplers will be discussed later in this buying guide.
Deciding who is Captain
While there are no hard and fast rules, it is often the case that tandem teams or partners stick with their roles, with one riding up front as ‘captain’ or ‘pilot’ and the other behind as ‘stoker’. In addition, the larger rider often rides upfront, partly because positioning a heavier rider to the rear can make the vehicle harder to control for the captain.
Because tandem frames need to fit multiple riders it can be a challenge to find one that suits them all perfectly. Nevertheless, given good planning and the knowledge to sift effectively through the variety of frames on offer, this is more than possible.
Fitting the Frame to the Captain
Where compromises must be made and the team has riders of different heights, it is more important that the bike fits the captain than the stoker(s). As such, it is a good idea to find a tandem frame whose front section has the same measurements as the captain’s solo bicycle. Many tandem frames for sale on online auction sites will cater to this by featuring larger fronts than backs. The rear size is usually 1 – 2 inches shorter than the front. The more riders there are on a tandem, the more important it is for the captain to be seated strongly and comfortably.
Because the captain needs to stand firmly to balance the bike while the stoker dismounts, it is important that the captain has good crotch clearance over the front of the frame. Calculating the full height of the bike from the ground once furnished with wheels is important before buying a frame. However there is some tolerance in the system and if ensuring adequate crotch clearance means the bike frame is slightly too small for the captain, this can be compensated for later by adding a longer handlebar stem to the bike.
Fitting the Stoker
Because the stoker does not have to straddle the frame, it is possible for them to cope with a taller frame than they would be comfortable with on a solo bike. However, it is still important that the stoker(s) does not have to over-reach for the handlebars, so as with the captain on too short a frame, a stoker’s over-long frame can be mitigated by adding a longer handlebar stem. Make sure the stoker will be able to reach the pedals on the finished bike, too.
If the stoker is larger than the captain, frames can be adjusted to fit, or even found at the right size on an online auction site.
Calculating the Bicycle’s Height
As mentioned, before purchasing a frame it is a good idea to calculate how tall the bike will be once it has wheels. To do this, add the radius of a tyred 700C or 26 inch wheel to the height of the bike from dropouts to head tube, seat tube and handlebar tube. Now check how high the bottom brackets will be from the road surface. Ideally the bottom brackets should be about 280 – 290mm or 11 – 12 inches from the ground. Any lower and there is a risk of striking the pedal off the ground. Much higher, and starting and stopping the bike can become more difficult.
The Tandem’s Length
One point to remember when looking for frames is that the back portion of the frame - the rear top tube - should be longer than the stoker’s own solo bike is. If it is, the stoker’s head will be positioned exactly where the captain’s back is. Generally, the newer a tandem frame the longer the top tube will be. Be careful that it is not longer than you require since longer top tubes create more weight and can produce some handling issues.
Convertible Tandem Bike Frames
Most frames on eBay are fixed but there are an increasing number manufactured to come apart via the use of S&S couplers, which can be a boon for those looking to travel with their bike. S&S couplers allow different segments of a frame to be taken apart and put together again without compromising the frame’s strength. They allow the frame to be taken apart in three sections so a bike can be packed into a suitcase.
Although a frame can be separated into two pieces when the couplings are loosened, they hold the frame together in perfect alignment, rigidity and safety as a regular one-piece frame when tightened.
Another, even bigger advantage, that S&S couplings offer is the ability to convert a tandem from a two to a three, four or five seater.
If there are any child stokers on board, and multiple adults, it is possible to put the child(ren) either between the adults in the middle position(s) on a triple or quad or in the back seat(s) behind both adults. The benefit of having the children in the middle is that the parent at the back can more easily communicate with them. Children in the middle is the ideal scenario but sometimes this is not possible when frames do not allow child-size cranks to be installed on th central seat tube(s).
Materials and Tube Thickness
Tandem bicycle frames come in a variety of different materials, the most common being steel. They are also available in aluminium, carbon-fibre and titanium. Material and tube thickness are important considerations if the tandem is to carry heavy loads on a regular basis. Tandems with 3 or more seats multiply the effect of weight, making it even more important to choose a frame that can handle the maximum estimated payload. Aluminium has a good strength to weight ratio but it can be significantly more expensive to buy than steel. If the buyer is looking for a general use two-person tandem frame then steel is adequate.
How to Buy Tandem Bike Frames on eBay
When buying second-hand bike frames from online auction sites it is important to make sure that the frames are strong and have not damaged beyond use. Ask the seller for detailed information on any areas of rust or damage to help make an informed decision about whether to go ahead with the purchase.
To search for tandem frames, type into the search box ‘tandem bicyle frames’, which will bring up the results. Some buyers have a good idea of the type of frame they want to buy, like ‘aluminium triplet tandem bike frame’. Using the search feature will help you find exactly what you want.
When searching through listings, carefully review all the data. Make sure the item matches what you had in mind. Look over the photographs a couple times. Feel free to Ask the Seller a question if you want additional details. Visit the Buying Tips page for more information.
Once you’re ready to buy, either place a Bid, Buy it Now, or put down your Best Offer. Buying with PayPal will ensure the transaction will go smoothly. eBay users are protected by the Buyer Protection Program.
eBay is a great shopping destination for hobbyist or professional tandem bike builders and repairers. When purchasing a tandem frame online take care to consider the measurements of the riders, the type of terrain and weather conditions that the bike is likely to encounter and how existing parts might fit the frame. Also make sure to check eBay images closely for signs of rust and poor maintenance on frames and if the seller is within travelling distance, perhaps ask to visit before making a final purchase.