Tandem Tech: Everything you ever need to know

Alee March 29, 2013 2

In this megapost, we will attempt to answer any technical questions you may have about tandem bicycles and components, with a specific focus on bicycle touring.

We also have another article which runs alongside this:

Everything you ever need to know: Tandem FAQ

Tandem Wheels

The wheels on a pannier-laden tandem are arguably the most important component choice. We have destroyed enough rims and spokes that we have learnt that mediocre is not ok. In our experience, the rim and wheel build quality are the two most important elements of a touring wheel (we have cracked rims before we've even broken a spoke!)

In summary, find the strongest rim and best wheelbuilder you can – we guarantee your wheel will last longer.

Rims: If you're touring with lots of weight like us, we recommend only one rim manufacturer – Ryde (formally Rigida). The Andra 30 model is available in both 26″ and 700c is probably the strongest rim available in the world – this is our shining review of the Ryde Andra 30 rim. If you're travelling light, you can get away with the lighter weight options.

Spokes: Tandem bike wheels typically have more spokes than standard bike wheels as this allows for a reduced load on each spoke, nipple, rim hole and across the hub flange. Tandem wheels can be found to have 36, 40 or 48 spokes. If your wheels are on the cheaper side, make sure you use 48 spokes. If you run better quality gear, you can get away with less spokes. We actually have 32 spokes front and rear (as we wanted to use existing hubs) and since having our wheels built properly, we've suffered no spoke breakages on our heavily-laden tandem.

26″ vs 700c: For off-road or heavily-laden touring, you're going to need as much wheel strength as you can get. We found this out the hard way in the middle of Azerbaijan! We strongly recommend 26″ wheels for touring as they are stronger than 700c wheels (due to their smaller diameter and shorter spokes). Check out the Ryde Andra 30 rim as it's the strongest option we've found.

If you tow a trailer, or will be riding with light loads on smooth roads, then 700c wheels are quite advantageous (read: faster). You should read up on our comparison between 26″ and 700c wheels for more information on the matter.

Hub Width: There are a few hub sizes for tandems. 135mm rear spacing is standard for most bicycles, but tandem wheels can be found in 145mm and 160mm. At 160mm wide, rear wheels can be 'dishless' – building a stronger wheel because spoke tension is the same on every spoke.

Trailers

A great way to reduce the load off your tandem wheels is to pull a trailer. We recommend trailers especially for those using tandems on the cheaper side, but trailers are also great for those travelling on off-road journeys.

We personally prefer the manouverability, 'flyability' and reduced overall weight of a tandem without a trailer, but we've invested heavily into strong wheels, so don't see a trailer as a must. Check out Bob or Extrawheel trailers for more.

Handlebars

For front riders on a tandem, handling is much more demanding on the upper body than on a standard bike. This is because the front rider needs to balance out shifts in weight made by the rear rider, in addition to managing the front bags (on a touring tandem) which slow the steering speed. My body took about a month of touring to build up the core strength required to manage our bike properly.

The best way to make handling a tandem easier for the front rider (especially for beginners) is by using a wide, flat handlebar. Wider bars increase the steering leverage and make managing loads much easier, as a lighter force is required to change the handlebar direction.

I run a drop handlebar because I like the positions it offers while touring, but would generally recommend a flat handlebar for most other tandem tourers out there. Make sure to catch our article: All About Bike Touring Handlebars.

For rear tandemists, a flat or bullhorn handlebar is the most popular. These bars need to be relatively wide to make sure they clear the front rider's hips. Drop handlebars are not necessary because rear tandemists are shielded from the wind by the front rider.

Tyres

The same as on any bike, tyre choice is important on tandems.

The wider the tyre, the more the tyre can absorb shock and depressions in the road. Wider tyres at lower pressures offer more stability for tandem bikes on rougher terrain as well as additional comfort to the rear rider – important because rear cyclists cannot prepare for bumps as well as those up front.

You will also find that wider tyres also reduce any tyre, rims or spoke issues because of their ability to absorb more bumps and shock.

As tandems often carry 150-250kg worth of bike and rider, hard wearing tyres are really important. We have had the most success with Schwalbe tyres (Mondial, Supreme or Dureme) because of their exceptional durability and puncture resistance, but Vittoria, Panaracer and Continental make some suitable tyres for tandems. We've done over 20,000-25,000km on our Marathon Mondials!

For our comparison between 26″ and 700c wheels, please click HERE.

Suspension Seatposts

Suspension seatposts are really important for rear tandem riders on roads which are of a low quality. Unlike the front rider, a rear rider is not able to anticipate bumps. When a bump suddlenly occurs, it really hurts! It is best to do everything you can to make the rear rider happy because tandems aren't as fun without them!

The best suspension seatpost on the market is the Cane Creek Thudbuster, which uses an elastomer to absorb any shock from the road. It employs a parallelogram design which doesn't change the cyclists saddle height when active, a common problem amongst other suspension posts.

Gearing

Given that tandems are so fast, most tandemists want lots of top end gears. But tandems can also require lots of low end gears, therefore, a balance must be struck.

Road tandems will require more top end gears than off-road and loaded touring tandems because of their high power to weight figure. I recommend gearing at 10% harder than a solo road bike if your tandem will mainly see flat roads with the odd hill. For those who are keen to ride any kind of road, you will do well with the same or 10% lower gearing than a solo road bike. Road triple cranksets which have a wide gear range and drop down to a 30t front ring, can be perfect for going fast and climbing!

For any other tandem (MTB and touring tandems especially), we recommend about 18 gear inches as the lowest practical gear – this is the same as using the smallest gear on a triple MTB crankset and cassette (24t x 34t). In this gear Kat an I can ride at 4-5km/h if we need to; any slower and we'd be better off walking. You can calculate gear inches HERE.

For information on Rohloff hubs and tandems, scroll down.

Brakes

Tandems often carry two or more times the load of a solo bike, so you're going to need powerful brakes. We recommend the use of disc brakes on all but the lightest weight road tandems.

You can read everything about brakes and touring in our article 'All About Touring Bike Brakes'.

Rim:

Rim brakes work fine for road tandems and touring tandems that stick to the pavement.

There is talk that dragging your rim brakes on a tandem can heat up the rim so much that the tyre blows out. Although this has not happened to us, it has to our friends, so rim brake users should be careful on long descents – take a break from time to time!

Disc:

The best v-brakes can be powerful, but they hold nothing compared to disc brakes. Stopping 150-250kg on a dime really takes a good set of anchors, and disc brakes are the best out there for this.

For a modern tandem, we don't recommend anything but disc brakes for your stopping needs.

Some manufacturers claim that they cannot create a fork with enough flex (comfort) that is disc ready. We have ridden these 'flexy' tandem forks and found them slightly more comfortable, but are not worth the braking power trade off. Get yourself some gel grips/handlebartape/gloves instead.

Disc brake brands that I trust and personally use are Shimano for hydraulic (XT or Saint), or Avid for their mechanical (BB5 or BB7). I have never found Avid to make a good, reliable hydraulic brake. Also note that it is important to use 8″ rotors on tandems because of their ability to cool as well as stop quicker.

For the down-low on brakes for touring bikes, read our article on touring bike brakes HERE.

Tandem Timing Chains, Chainrings and Cranksets

There isn't anything particularly special about timing chains other than the fact that you will need approximately one and a half chains to make it work.

Timing chainrings must both be the same size to give a 1:1 ratio which will allow both the front and rear cranksets to be in phase. It is advisable to use largish chainrings of between 38-44t because the smaller the chainring, the harder the chain pulls (to make up for the fact it is not moving as fast) and the quicker everything wears out.

Timing chains normally run on the non-drive side of a tandem, but you can run timing chains on the non-drive side too. The advantages of running it on the drive side include being able to use conventional cranksets which are often cheaper and come in a range of sizes, and it keeps the greasy chains to one bike side. The disadvantages include the greater challenge of spacing out chainrings, and the fact that you may be limited with shifting options on derailleur gear systems. It is most common to see a drive side setup with an internally geared hub like a Rohloff.

It is possible to use Gates Carbon Drive as a timing belt. This will save you about 250g over a chain and chainrings. In order for Carbon Drive to work on your tandem, the frames boom tube must be 724mm between bottom brackets and you will need to use 130bcd cranks. It is possible to run Carbon Drive on both the drive and non-drive side of your tandem.

Crank Phase

Tandems are traditionally set up to have the cranks/pedals in the same starting location for the front and rear riders. It is also possible to have the cranks out of phase (eg. 90 degrees out) which some riders feel eliminates the 'dead spot' in the pedal stroke.

We have tried our cranks at different phases and feel like in-phase is best; it's best for starting, best for balancing while riding, best for cornering and best for coasting!

Rohloff Hubs On A Tandem Bicycle

Rohloff hubs are perfect for tandems! Rohloff make a tandem hub kit (T) which comes with tandem length cabling (there is nothing special about the hub itself). For the best results, use a tandem frame built with a Rohloff dropout and two eccentric bottom brackets (or one eccentric and sliding dropouts) to adjust the chain length.

Rohloff hubs are available in either 32 or 36 spoke hole. Given that the Rohloff hub flange is so large, the wheel is 'dishless' and the spokes are so short; either spoke count should serve you fine. If given the option, request 36 spokes!

The minimum gear ratio you can run on a Rohloff tandem is 2.5:1. We ride with this ratio (50t on the front and 20t on the rear) and in our lowest gear (18 gear inch) this allows us to ride at 4-5km/h up really steep hills. We are able to chug along at 45km/h in our top gear (95 gear inch) if given the opportunity. If you are riding your tandem on flat roads, you will most likely want your Rohloff gear ratio to be 3:1 or above.

For a comparison between standard cranksets and Rohloff hubs, this page from the manual shows that having a 22t-32t on a derailleur drivetrain is the same low gear as 40t-16t on a Rohloff. Likewise, a top gear equivelent of 54t-12t is achieved on a Rohloff running 50-16t.

Rohloff recommend the using a Rigida Andra 30 rim for 26″ wheel build because the rim holes are drilled on an angle. This allows the nipple to protrude at a straight angle from the rim which in turn reduces any stress to the spoke, nipple and rim.

Make sure you read our article specifically on how to build the strongest Rohloff wheel you can.

For more Rohloff technical information, make sure to check out 15 Reasons Why You Should Ride Rohloff and 18 Ways To Mount A Rohloff Shifter With Drop Handlebars.

Carbon Belt Drive on a Tandem

A Gates Carbon Belt drivetrain is perfect for tandems. The only prerequisites are that your frame needs to be Carbon Drive compatible and you will need to use an internally geared hub (Shimano Alfine or Rohloff).

If you haven't heard of Carbon Drive, the reason we like it is that it is silent, lightweight and maintenance free. For the full low down on Carbon Drive, read our article, Carbon Drive: Everything You Ever Need To Know.

We have found that the Gates Centertrack kit to be leaps and bounds better than the CDC/CDX type, as outlined in our Carbon Drive post. If you're going Carbon Drive make sure you're on Centertrack for both belts! We have published a review of the Centretrack kit, make sure to read it.

Those with derailleur drivetrains can also benefit from a carbon timing belt if your frame has been designed around the right distance between bottom brackets (724mm). This will save 250g from your existing tandem!

Our megapost on 'Carbon Drive: Everything you ever need to know'.

Independent Coasting Systems

On a standard tandem, both riders pedal at the same time, so when one rider wants to rest, it means both riders must rest. Independent coasting systems change this, by promising to make starting, stopping and cornering easier, as well as allowing riders to take independant breaks at times which suits them.

We didn't feel this was necessary for us, but it is worth noting that a company called DaVinci Tandems make bikes around this concept!

Tandem Bikes For Families

There are a few companies making tandem bikes for families. Co-Motion, the manufacturer of our tandem make a series of bikes called the 'Periscope'. The premise behind them is that the rear seat tube is really small with an adjustable seatpost. This allows young children as small as 1.00m and adults alike to be able to be a rear tandemist on the same bike!

Other designs include: Onderwater tandem

Folding Tandems

A few companies make folding tandems – perfect for the space concious (such as caravan owners) and regular public transport users. Although wheels smaller than 26″ are not our style, we can appreciate that for some people a folding tandem is the perfect tandem! Bike Friday are widely accepted as the worlds best folding tandems, and are something we'd like to try one day!

Check out Bike Friday and KHS for more.

Frames: Marathon vs Compact Design

Tandems often come in two frame designs. The 'marathon' frame design employs an addition steel tubeset (called the 'lateral' tube) and the 'compact' frame design does not.

Marathon vs Compact tandem

The advantage of the marathon frame is that lateral stiffness is increased through the additional lateral tubeset, reducing any twisting or shimmy-ing when carrying a lot of gear. It allows frame builders to use smaller diameter, thinner drawn steel tubesets which result in good vertical compliance and vibration dissipation.

Compact frames on the other hand are built with larger diameter and thicker walled tubes, making them a perfectly capable touring tandem too. However, as a result of the heavier tubing, they tend to be stiffer riding as they don’t offer the vibration dampening qualities of the marathon frame.

Frames: Splitting A Tandem Into Smaller Pieces

It is possible to get a tandem frame down to the dimensions of a 26″ wheel! The most common way to split a tandem is using stainless steel S&S couplers. Co-Motion splits their frame into three pieces (four to six couplers) whilst other tandem manufacturers choose to split their frame into two (two to three couplers). Couplers do not decrease the frame strength or stiffness – they increase it!

Other manufacturers have their own techniques for splitting frames, such as Richey with their 'breakway' kit and I have seen a handful of custom jobs completed by frame builders.

Other CyclingAbout Tandem Pages:

Introducing Tan-nay-nay (video)

Our list of initial impressions on travelling in tandem

Build breakdown: Our Co-Motion touring tandem

Making Tan-nay-nay happen

Why did we purchase a tandem?

Why did we choose Co-Motion to build our tandem?

Kat's post on panic attacks touring on a standard bike.

A list of tandem manufacturers and builders (with pricing)

A detailled look into the custom frame building process

Can't find what you're after on CyclingAbout.com?

Our favourite tandem websites include:

Sheldon Brown

Co-Motion Bicycle FAQ

The Blayleys

The Tandem Link

Tandem Geek

 

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