Circe Cycles Eos Tandem

The Circe Eos must be one of the most multi-functional tandems available, without any compromise on outright performance: with the appropriate specification it can perform like a 'normal' tandem, yet it offers a wide range of size adjustment and has a better ability than most to be broken down for travel.

Anyone considering a tandem is already looking at a niche part of the market; if you want it to be suitable for an unusually wide range of sizes then you are in even more of a minority – and one that can be taken apart and stuffed in a suitcase for transport is even more specialist. The Circe Eos can tick all of those boxes if required.

> Buy this online here

Circe Cycles will be known to many of you as the producer of the Helios tandem, a small-wheeled machine that prioritises portability, versatility and adjustment over outright performance. With the Eos, Circe has kept much of what made the Helios popular, but improved the specification and made it a bit more mainstream.

Models

There are two standard specifications, both based on the same one-size-fits-all (and does-it-all) frame: the sportier model (called Sport) offers drop bars, derailleur gears, and 26in (559) wheels; the touring-orientated model (called Tour) offers flat bars, internal hub gears (IHG) from Rohloff, and 24in wheels with fatter tyres.

I chose the Tour model as the basis for this test, but you can also go à la carte to get something that suits your needs exactly. Flat bars with derailleur gears would be easy to achieve; drop bars with IHG would be harder, but various aftermarket adapters are available to help.

As with the Joey from sister company Airnimal, you can take advantage of the interchangeability of fat 24in and thin 26in wheels to have a second set, so that you can change the nature of the bike; the Eos uses the same wheel sizes, so the same opportunities are available. 

Frame and fork

The frame is made from 7005-series heat-treated plain-gauge aluminium with some seriously oversize tubes. The same frame is used for both derailleur and hub-gear models, so is festooned with all the fittings and cable guides required for both, including a front derailleur mount.

There are even brake bosses on the rear for cantilever or V-brakes – but they are only usable with the 24in wheel size.

The unusual frame shape limits where bottle cages can be mounted, so as with the Helios, two of them are on the top tubes, where they tend to get in the way if you use the 'step through' method to climb aboard. A third mount is placed more conventionally on the front down tube.

I couldn't fault the quality of the frame or its paint finish, nor the quality of assembly. If it were my own bike I would shorten a few cables – although most of the 'surplus' is necessary if you want to take full advantage of the size adjustments possible.

The Eos introduces an all-carbon fork with what must be a unique specification: tandem-rated, tapered steerer, disc brake, thru-axle, mudguard and rack fittings – and compatibility with 24 and 26in wheels!

The Eos goes to the extra cost of using an eccentric bottom bracket to take up chain (or belt) slack, rather than the less elegant chain tensioner used on the Helios. The rear triangle also has the split necessary to allow for the fitting of a belt drive.

Components

Let's go through some of the standard specification.

The 24in wheels on the Tour use 36 Sapim Strong butted spokes, which step up from a regular 14g (2mm) to a meatier 13g (2.3mm) for the bend; when combined with the smaller wheel size it all makes for a reassuringly sturdy package.

As standard they are shod with 24 x 1.75in (47-507) Marathon tyres from Schwalbe, which have a reputation for being durable and rugged, and are deservedly the first choice of many. However, some of that robustness undoubtedly comes from a fairly hard rubber compound, which might be why we occasionally suffered from wheelslip when riding hills out of the saddle on damp roads – I doubt that it was our awesome power output to blame. The price of that long life is also reflected in the weight of each tyre: 860g.

Both issues were solved for me with a (no-cost) change to another tyre, again from Schwalbe: the Kojak. At 24 x 1.5in (40-507) these are narrower, but more importantly at 380g each they are lighter, and seem to use a softer compound. That's a weight saving of nearly 1kg from a tyre change alone! You notice that.

The Kojaks suited my current riding conditions better, but the Marathons would have their place in other circumstances. Indeed, I would put them back on for the winter months when puncture resistance was the priority. I am reassured to see that even with a relatively unusual wheel size such options are available.

The Circe-branded cranks are forged and nicely finished, and are mounted onto old-school square taper bottom brackets: it's proven technology that is easily serviceable – and still works. I wouldn't be keen to trade that for any promised increase in stiffness from one of the newer 'standards', and the reduced choice that they bring.

The bolt circle diameter (BCD) is 130mm for the outer rings (meaning a minimum size of 39 teeth), with a 74mm BCD for the inner ring when used as a triple (so down to 24 teeth). It's used 'in-line', so the whole drive is on the right-hand side and no tandem-specific pedal threads are required.

Crank lengths are a personal preference, and there are several to choose from – although the published specification does not make that clear. We chose 170mm and 165mm, to help address the difference in our preferred natural cadence. There's even a 125mm kids' size – and if you want something really unusual, Circe can shorten cranks.

The Shimano MT-6000 Deore hydraulic disc brakes are dependable, and just work. Three-finger levers were used so that the blade on the right-hand lever could reach round the twist-grip gear shifter. The 180mm rotors provided as standard will suit most people, but other sizes are available. When it comes to replacement just be aware that the Rohloff IHG unhelpfully uses a unique four-bolt fitting 'standard'.

The specification isn't very specific about saddles, simply listing Ergon. Again, this is because you have a no-cost opportunity to choose what you want. The recommended Ergon SFC3 partial-gel saddle was acceptable for me, although I won't be getting one for my own use; on the other hand, my wife loved her Bioflex Gel Ozone so much that we will be getting one for our tandem.

I am not normally a fan of kickstands, but the Pletscher Twin Leg could convince me, and I was surprised by how often we used it. In action it supports like the centre stand of a motorbike, but folds away neatly to one side. It can also function as an impromptu workstand, but unfortunately its scope is restricted by the left-hand crank hitting it, thus preventing a full revolution. A slight change in position or shape could solve that.

Additions

Since the Eos is assembled in the UK, it can be customised as required, so I took the opportunity to add a few things.

Unfashionable they might be, but I wanted bar-ends, so the regular grips were replaced with Ergon GP3s for £22 extra. These combine Ergon's usual flat palm rest with an independently adjustable mid-length extension – and a Rohloff shifter-compatible length. No complaints about the comfort, and minimal impact on the packing process when travelling. The standard padded foam sleeve on the rear bar was a hit, and is something else that we will be adopting for our own machine.

Up next was a rear pannier rack, the Racktime Fold-it 24in for £45. The 24in designates shorter struts than normal, so that the rack sits close to the wheel and keeps the weight of any luggage as low as possible. The 'Fold-it' indicates that the rack bolts together. I normally prefer one-piece welded racks without any such potential points of weakness, but the ability to partially dismantle the rack made it possible to include it in the case for travelling.

Equally unfashionable in some quarters are the mudguards. These were proper bolt-on Chromoplastics from SKS for £36, although quick-release Raceblades are also available for £50. The front guard had a single set of stays; I would have preferred two sets of stays to reduce movement over rough surfaces. At the rear, I can't understand why the same bolts are used to mount the mudguard stays and rack when sufficient holes are available to provide separate attachments – with the extra security that brings.

Most manufacturers don't spend money on decent pedals, and fit the cheapest possible option in the knowledge that users will immediately fit their pedal of choice. Circe goes further and supplies no pedals at all, so effectively the initial price doesn't give you a rideable bike. There is a wide range of pedals on offer, mostly from Wellgo. I chose the WAM-M19/QRD-1 for £85/pair, a double-sided SPD-style pedal with a no-tool release facility.

With Wellgo's quick-release system, a 'docking station' screws into the crank, and the pedal itself can be quickly and easily removed without tools: it's a neat trick, and it's great to have for transport or storage. There is a bit of play in the interface, but you don't notice it in action. However, you may well notice the few millimetres increase in Q factor, the distance between the pedals.

Like many other manufacturers, Wellgo claims that its pedals are compatible with Shimano's SPD system and cleats. This is largely true, but I found that their performance with Shimano cleats was far more sensitive to wear than on a Shimano pedal. The more worn the cleats that I used, the less consistent was the ability to unclip – so I only felt safe using my least worn shoes. Of course, you could always use the Wellgo cleats provided, which should offer a better experience.

Rohloff hub

Our Eos used the Rohloff Speedhub 500/14 internal hub gear (IHG), which is included in the recommended specification for the Tour version. IHGs are different to a derailleur gear system – not necessarily better or worse, just different – and I think they suit the bike's intended use rather well, including being packed into a case.

With any IHG, I always appreciate the option to change gear when stationary, the simplicity of sequential gear selection, the ability to change through multiple gears in either direction, and the maintenance advantages of having everything enclosed. The extra strength of a dishless rear wheel is doubly welcome on a tandem.

Many of the previous disadvantages of IHGs have been largely overcome, with wide ranges, more even gear spacing, and the removal of any neutral gear all now readily available. However, the opportunity for on-the-road repairs are still limited – in the unlikely event of this being necessary.

The pinnacle of the IHG world at present is the Rohloff hub (although I suspect that Kindernay could provide serious competition). It offers 14 gears over a 526% range, with evenly spaced jumps. This range can be beaten by a few derailleur systems, but only at the expense of a valueless overlap of gears, and/or unacceptable jumps between them.

> Bike gears: find out why bikes have so many, and the surprising way they’re measured

The hub is an impressive piece of engineering, as it should be: it costs around £1,100. This accounts for about £700 of the price difference over the Shimano 105-equipped Sport model. To a greater degree than with any other IHG, you will notice the concentration of weight around the rear hub – although Rohloff claims that the overall heft is not significantly different to a complete derailleur system. Obviously, it all depends what you are comparing against.

As standard, the gear range supplied is 21in to 111in: I know that I always regret the absence of a lower gear more than a higher gear, so I asked for the lowest gearing possible. This turned out to be 19in to 100in. You can choose other gearing options to suit your needs, without any cost implication. Although tandem use is sanctioned by Rohloff, to maintain your warranty the minimum chainring:sprocket ratio rises from the 1.9:1 for solo use to 2.5:1.

> How to get ultra-low gearing on your bike

Don't tell anyone, but if it were my machine I would be tempted to ignore any restrictions on gearing after the two-year warranty period – or even earlier. Neither of us is particularly powerful, and this hub really does feel capable of handling our maximum output without complaint.

In use, it won't be long before you notice one of the more contentious issues surrounding Rohloff: of all the IHGs that I have used, none come close to making the same level of noise.

A quick bit of explanation is in order: within a Rohloff, the top seven gears are like using a 7-speed cassette in the big ring; the lower seven gears use the same cogs on the equivalent of the small chainring. The problem is that the 'small chainring effect' is achieved through some ratio reduction gearing, which is the primary cause of the noise.

Whereas gears 8 to 14 make a noise comparable to a slightly dry chain, gears 1 to 7 introduce noises not unlike an electric motor, with additional hints of 'knobbly tyre on tarmac'; this varies by gear, and by power input. You probably wouldn't be aware of it if there are other noises such as traffic, wind, or wet roads, but it would certainly be noticeable when winching up a quiet climb.

I am assured that the noise normally quietens down after a few thousand miles. If you think it will be an issue for you, I recommend that you try a fully run-in hub for yourself so that you know what you are letting yourself in for, and balance that against the undoubted advantages of the system – and choose derailleur gearing if it's not for you.

Gates belt drive

A belt drive system is also an option, and again is included in the recommended specification of the Tour version. It is only possible with a single-sprocket system (such as an IHG), and this was a good opportunity to try it out.

The Eos uses the premium Gates Carbon Drive system, CDX, which is claimed to operate within an impressive temperature range of -53°C up to +85°C – which is far beyond my own limits! However, the standard version is not approved for tandem use; since only the rear drive has to cope with the power of both riders, a heavier duty EXP belt is used there – which increases the pitch from 8mm to a chunky 11mm.

There are a few hurdles to overcome to make a frame 'belt drive-ready', including the ability to split the rear triangle, perfect alignment, and (ideally) a frame that is sufficiently stiff to be approved by Gates.

You will immediately notice the lack of any noise in use (which makes Rohloff's contribution all the more noticeable). When the time comes, you will also appreciate the ease of maintenance in virtually all conditions, where a simple wash with water will normally suffice, along with the occasional squirt of silicone spray.

In use, it is important to maintain the correct belt tension: too tight, and it leads to premature wear; too loose, and it can 'ratchet'. Naturally there is a proper workshop tool, but for consumer use 'there's an app for that'. Yes really, there is: you twang the belt like a guitar string, the Carbon Drive app measures the frequency, and you check that it is within the approved range.

I had some concerns about the system before using it: surely it would feel a bit 'soft' compared to a chain? No, just smoother, and less 'mechanical'. Would it be as efficient as a perfect chain? Probably, except perhaps in some exceptional circumstances, but I doubt that users would notice any difference in real life.

To be on the safe side, Gates requires the use of a 'snubber' for the final drive sprocket, which is a little roller that operates a bit like a chain catcher. We had no problems, even when putting out maximum power, out of the saddle, on the steepest of hills.

There is a minor weight saving over a chain drive, but there is also a high price to be paid: it accounts for a substantial £506 of the difference from a chain-driven model, although remember that includes the three chainrings (belt-rings?) as well. However, reports suggest that by the time you have to replace a belt drive system, you would have got through several chains, cogs and even chainrings, so in the long-term the cost difference won't be so great.

When the time does come for replacement, don't expect to find lots of alternative aftermarket brands offering lower pricing or better availability – and be aware that belts from Gates only come in a few pre-determined lengths, so you will always be limited in your gearing options.

The instructions emphasise that a belt can be prone to damage if abused; while it seems to be plenty tough enough in normal use, I was always conscious of its relative fragility compared to a chain. For transport, the drive belt remains in the rear triangle, and the timing belt loops nicely round a wheel – so both can travel with reasonable protection.

If you don't want belt drive, you can choose chain drive from new – or indeed at any point in the future. It is not an irrevocable decision, just a costly one.

Adjustability and fit

There is far more height adjustability on offer here than with any conventional tandem, so that the one frame available really can fit most people.

The maximum height achievable for the 'centre of BB to top of saddle' measurement is frankly in clown bike territory: 92cm at the front, and 96cm at the rear. That's very high.

As for the minimums, you could get down to 56cm at the front (allowing 6cm for the stoker's stem clamp), but it would require about 9cm to be cut off the end of the seatpost. The rear could drop to 42cm.

For those familiar with the Helios, the minimum saddle height is 2cm more at the front and 6cm more at the back, so the Eos isn't quite as friendly to small people.

Just as important is the reach, with stokers often suffering from a cramped cockpit. By increasing the maximum reach on the back by 6cm over the Helios, Circe has matched more conventional machines and made the rear more comfortable for larger riders.

Reach has also increased at the front by 2cm over the Helios: it still took a 150mm stem for me to achieve my perfect position with straight bars, but then I do like a rather long reach.

All this adjustment is achieved with numerous quick-release clamps – you really do have to know how to operate a QR properly with this bike!

For starters there is the standard single QR on the front seatpost, and then the two on the telescoping rear post; incorrect operation here might only result in the wrong saddle height, or perhaps a few elusive creaks. Far more important is the QR used to attach the fork steerer onto its extender – to which are mounted the bar and stem. It's very convenient (and an impressive thing to demonstrate to others), but it is probably the most safety critical QR lever you will ever encounter.

Although the extender is fitted as standard, you could save £70 and leave the standard steerer. In doing so you would reduce the range of height adjustment available, and make removal for transport a bit slower. The QR facility also allows you to pivot the bars without tools, to make the machine narrower for storage.

Incidentally, I had a lot of surplus extender sticking up above my stem. If it were my own bike I would be removing most of it, but it does illustrate that the handlebar could be set very high if necessary.

It's rare to combine an IHG with a QR clamp, but Rohloff has managed it here. It saves a bit of time, but doesn't really save a tool because you still need something for the thru-axle on the Hope front hub. Alternatively, with a change of rear dropouts, you could change to the thru-axle version of the Rohloff hub.

Separation

One advantage that the Eos can have over more conventional tandems is the ability to reduce its size considerably for transport or storage – as long as you pay an extra £575 for the separable system. This allows you to completely remove the two tubes connecting the front and rear triangles.

It would be easy to reduce this cost by only having only one coupling per tube, by simply splitting the frame down the middle; however, this would not be as successful in reducing the size of the finished package. What's more, you would be left with fairly long lengths of unsupported frame tube that would only be attached at one end, and could be vulnerable to damage.

As an added bonus of the system, you can insert a 'triplet kit' – which could also function as a 'social-distancing kit' if there were only the two of you!

Rebuilding is a remarkably easy task to perform, thanks in part to Circe's use of two different attachment methods. In Circe's words: 'The design, using a compression drain pipe and coupled rear top tube, makes for easy re-coupling, the drain pipe effectively holding the two ends of the tandem in place ready for the insertion of, and final alignment with, the coupled top tube.'

What this means is that you only have to fit one tube at a time: I liken it to hanging a removable gate or door, where it can be very difficult to hold everything steady while you try to line up both hinges together – whereas the trick is to have one prong longer than the other, so that you can concentrate on one thing at a time.

> The no-fly guide to taking your bike on holiday…

In use, I couldn't tell that it was a separable frame: if all eight bolts have been tightened up properly, there is no movement or noise.

Apart from the added cost, the only disadvantage is the increase in weight: the net increase of 812g is the result of taking out 324g of frame material and inserting 1,136g of couplings.

There may be a remote chance that the bike could be more easily stolen if you don't take the separability into account when locking the bike, as thieves could potentially remove a frame tube if they knew what they were doing – no special tool is required, as the entire job can be done with a 6mm hex key.

It didn't seem possible that the complete machine could fit into one of Circe's £299 Traveller cases, as not only is it little bigger than the case that I use for my Airnimal Chameleon, it is smaller than most regular bike boxes.

However, it soon becomes apparent that once you have removed those two connecting tubes, what's left is no bigger than a solo machine – and the use of slightly-smaller-than-standard wheels helps to minimise the overall dimensions.

You might be surprised at what can be left on (or has to be taken off) for packing: just be warned that it is not a quick job – and neither is the reassembly task at the other end. It is well within the abilities of anyone with moderate mechanical skills, but it is not a job to be hurried if you want it to all fit in, then arrive without damage, and still be safe to ride afterwards.

> Buyer’s Guide: 17 of the best bike bags and boxes

Both seatposts have a scale marked on them to aid correct positioning during reassembly; I would have liked to see that on the front extend further up so that it could do the same job for the stoker's stem as well.

Although only the right-hand front crank has to come off, I feel that self-extracting fittings would have been useful – even if only on that crank – as this would reduce the tools required when travelling.

I did notice that the hydraulic brake hose to the rear calliper could be vulnerable to contact with the travel case. The folk at Circe tell me that they plan a change so that the hose leaves the calliper at 90 degrees, which could also improve the aesthetics of the routing.

Our complete bike in a single case weighed 31.5kg; that is above the baggage limit for many economy flights, so if that is a problem then either use two smaller cases – or travel in business class and benefit from a more generous allowance!

Our bike alone was 21kg, but that is for a fully featured machine, and is almost as heavy as you can make it. You could easily save a few kilograms with a different specification.

I had planned to make more use of this aspect of the Eos, but as we now know there has rarely been a worse time to be visiting other countries, let alone flying anywhere, so I had to settle for the odd car-assisted trip (which didn't require much disassembly).

Ride and handling

And so to the all-important question: how does it ride? If I can descend at over 50mph, and – separately – take all four hands off the bars, then I am confident that the handling holds no surprises – and that was the case here.

The steering errs on the side of stability more than agility, which is appropriate for the intended use; it will be especially beneficial when loaded.

Note that the steering's trail will vary by a few millimetres when changing between wheel sizes, depending on the size of tyre, so expect to feel a small change if you are swapping wheels.

We were quite happy operating round the narrow lanes in the Chilterns, dodging hazards and attacking hills. We also took advantage of the lower traffic volumes during lockdown to venture onto bigger roads that are normally too busy to be desirable, and offered other challenges: faster descents, sweeping bends, different surfaces – and the Eos could handle it all with aplomb.

We prefer to tackle short hills out of the saddle, and the Eos allowed us to do that without difficulty – as long as we were co-ordinated, of course. As with any tandem, keeping control of a machine with two independent bodies on board is normally the biggest challenge, and in that the Eos did everything that we needed of it.

A frame with large diameter aluminium tubes is ideal for providing enough stiffness for something of this length, but is not normally the ideal starting point for a compliant ride. However, a combination of all that length, chunky tyres, a carbon fork, and long seatposts all help with smoothing the ride.

You could go further and replace the top part of the rear seatpost with a 30.2 mm diameter suspension model if extra comfort were required.

Price and value

The basis for every Eos is the £1,899 frame kit, with some of that price going towards the features that make the frame so adaptable. It includes the fork, headset, and the two unusual seatposts.

It is hard to do a direct comparison between complete machines from different brands, because tandems don't work well with the usual 'groupset comparison' method. You can pay less for a conventional machine with a reasonable specification (such as something from the Orbit Velocity family), but once you start trying to find anything with more directly comparable features then your options go down – and prices go up.

The price for the recommended 'entry-level' specification Eos Sport is £3,699; for the standard Tour model it is £4,899. The machine tested here cost £5,815 on the road.

Summary

The market for any good quality, versatile, adjustable, customisable tandem is neither big nor well served – and even more so for a machine that is specifically designed to accompany you on your travels with relative ease. The Eos is a highly credible contender in this niche of a niche, and builds on much of what made the Helios so popular. While the Eos will perform well as a more conventional machine, you would be missing out if you didn't take advantage of its more unusual abilities.

Verdict

The Eos can work well as a conventional tandem, but comes into its own as an unconventional one