Gear > Bike > Time Trial/Triathlon bikes

Tri bikes from Cervélo, Diamondback and Dimond go head-to-head

There’s an arms race going on in triathlon as manufacturers develop a new breed of superbike. We put the latest PB-melting triathlon bikes from Cervélo, Diamondback and Dimond head-to-head in a world-exclusive test

Race day is all that matters. That’s the belief that’s driven Cervélo, Diamondback and Dimond to throw out convention and get radical. There are no trophies for winning in the wind tunnel. What matters is being fast in the race, while carrying everything you need and riding in your perfect aero position. 

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This is no cold war – it’s red hot. Ventum have already shown their hand, TriRig are brandishing a wild new frame and UK firm Reap are poised to strike. But it’s the three bikes we have here that are causing the most fuss. The Cervélo P5X and Diamondback Andean melted the internet when they launched ahead of Kona last year.

Both are the products of long R&D processes and feature unprecedented amounts of integrated storage, plus disc brakes and radical frame shapes. The Dimond is a wild card; it’s a tiny brand by comparison and looking to cause an upset with its V-shape frame. The three bikes line up here in top spec, with the latest electronic groupsets from SRAM and Shimano, and wheels from Enve and HED, the two fastest from our recent grouptest (see issue 335 of 220).

All three claim to be the world’s fastest bike, meaning they’ve all beaten benchmark bikes in private tests. But now they go head to head and when  each one is claiming to be faster than the others the only possible outcome is mutually assured destruction… of PBs. 

Carrying capacity

Payload, and its slick integration, is the new critical metric for tri bikes. Being fast on race day means being as quick when you’re fresh out of T1 and fully loaded with fuel as you are when you’re slurping your last gel a few hours later.

Both the Diamondback and Cervélo use radically shaped frames that follow the arc of the front wheel down below the bottom bracket to fair in the chainset for aero gains. The cavernous spaces within these frames can be used to store your tools and spares out of the wind.

As for fuel, the Cervélo can carry three large, round bottles in aero locations; the Diamondback also has three mounts, though two of them are in the conventional sites on the frame and would require aero bottles. Both bikes can carry three bars and four gels, the Cervélo in its single bento box, the Diamondback split between its two.

The third bike here, the Dimond Brilliant, offers a lot less, just one bottle mount in a sub-optimal position on the down tube and bosses for a bento box on the top tube. So you’d need an aftermarket saddle and aerobar bottle mounts to get a similar carrying capacity to the other two. (The recently announced Dimond Marquise adds internal storage in the frame above the bottom bracket and in the top tube, for an extra £1,000.)

Ah yes, prices. The Dimond Brilliant frame costs £5,999 and this exotic build comes in at a staggering £14,650, including £850 for the custom paint job. Cervélo’s P5X with SRAM eTap and Enve 7.8 wheels is £13,499. Diamondback don’t have UK prices yet; they sell direct and offer the Andean with a menu of groupsets, HED wheels and components. As tested, with SRAM eTap, it costs $7,269 (approximately £6,000). Drop to Ultegra Di2 and it’s $6,519 (around £5,500). A P5X with the same Ultegra Di2 group and HED Jet 6/9 wheels costs £10,499.

Even though it runs the new version of Shimano Dura-Ace Di2, the Dimond initially appeared outmatched by the SRAM eTap on the other two bikes, a groupset that, in its road race guise, has received fervent acclaim and blows Di2 away. But when it comes to tri/TT set-ups, the tables are turned. SRAM’s shift logic still holds up and the bar-end shifters are more ergonomic than Shimano’s but the buttons simply don’t work as well.

Whereas shifting with the Dimond’s Di2 is an easy, instant and a near subconscious action, the SRAM Blips on the base bars feel horrible. Under bar tape they need a real dig from your thumb and they’re so vague that you often miss the switch and don’t get a shift. What’s more, they’re positioned so badly on the Cervélo that out-of-the-saddle shifts are awkward due to the amount of hand movement required to reach the buttons. Amazingly, the bar-end shifters also fail to shift about a third of the time, even when you feel a click. It beggars belief that SRAM dropped the ball so badly on this. We’d choose and recommend Ultegra Di2 over eTap on these bikes every time, let alone Dura-Ace.

Braking is a similar story of questionable progress. Cervélo and Diamondback both say that switching to discs yielded an aero gain but we’d question the braking performance. This Andean is built with the cheaper option of TRP Spyre mechanical calipers nibbling at small, 140mm discs. Power is sorely lacking so spending the extra $60 (around £50) to get the same forceful TRP Hy/Rd system as the Cervélo is a no-brainer. 

The Dimond might appear to be outgunned with its rim brakes but the TriRig OmegaX units are joyfully easy to adjust, well hidden and deliver plenty of power when grabbing the textured brake tracks of the Enve 7.8 rims… once we’d fitted the correct pads, at least.

Mad looks, fast rides

With lots of good aftermarket storage options available, the small gains that two of these bikes make through integration will be irrelevant if they don’t ride well. In total, we rode over 725km on these bikes, including the same 130km route on each of them. As you’d expect, all three feel fast, averaging up to 38km/h on the long rides.

What’s most surprising about these wild-looking bikes is that – for better or worse – they ride like conventional double-triangle frames. All three are impressively stiff under power, even out of the saddle in a low gear, which is what tripped up the seatstay-less Ventum One. Clearly, some brilliant work has been done with the carbon fibre by all the engineers.

On the other hand, for all the missing frame elements on the Dimond and Cervélo bikes, there’s no ‘softride’ aspect to them. The seatstays and seat tubes are missing for aerodynamics, not to allow the chainstays to flex – if they did these bikes would be near unrideable.

That said, compliance is a much more effective method of dissection for this trio than drive stiffness. The Dimond came set up on tubeless 25mm Schwalbe Pro Ones – improving rolling resistance, puncture protection and smoothness; ideal for tri – and it’s good over poor surfaces. Despite its narrow 23mm Continental GP4000 tyres, the Diamondback is even better, taking the edge off the sort of impacts that chip away at your energy. Its HED arm pads aren’t the best but they’re an easy fix.

The Cervélo is the least compliant; too much road noise reaches the saddle and even though the front end is much better, from the fork to the excellent pads, it was the most wearing on our long rides. It’s already on 25mm tyres, but you could switch to a tubeless set-up and drop the pressures a bit. The Diamondback and Cervélo use ISM PS1.1 and PS1.0 saddles respectively. Both perches are good but, like many riders, we only found them comfortable once their wide noses had been pinched in with zip ties.

It’s the Dimond that rides the most like a good road bike though. It’s more agile and has a significant weight advantage – 8.8kg as opposed to an identical 10.26kg for the other two. That weight saving is clearly tangible when climbing or out of the saddle but doesn’t effect its speed on the flat. Interestingly, the Diamondback feels lighter than the Cervélo; the latter always seems like a lot of bike, not only against a gradient but also in tighter corners where it’s prone to understeer if you don’t wrestle it. 

Both SRAM-equipped bikes come with 11-28t cassettes to help you winch them uphill and they’re cleverly spaced, running straight through from the 11t to the 17t sprockets to give you close ratios at speed before increasing in bigger steps – 19t, 22t, 25t and 28t. It’s a much better compromise than Shimano’s 11-28t cassette, which omits the 16t sprocket. But luckily, the Dimond uses a 11-23t Shimano cassette on this build, which is perfect for optimising your cadence on flat and rolling courses.

Blown away

The first thing anyone says when they lay eyes on one of these bikes is “I bet that’s fun on a windy day,” and it’s an understandable reaction. Even the Dimond has a big frame area behind its head tube to catch a breeze and, as for the other two, they look ready to sail away. 

In fact, all three are amazingly well behaved. Even when you’re passing a hedgerow opening at speed, if there’s a strong crosswind blowing, all you feel is an increase in pressure from the side. You don’t get pushed off line, much less across the road.

Your front wheel is far more critical to stability than your frame, so while it’s good to know that these frames didn’t cause issues, the real credit has to go to the rims. It’s a happy coincidence that these three bikes came fitted with the top two wheelsets from our recent grouptest, ensuring no bike was at a major disadvantage.

Both the Enve 7.8 and the HED Jet 6/9 combinations are outstanding. They’re worlds apart on price but the HEDs punch above their weight for speed and stability, and they’re light, too. Both wheelsets have an uncanny ability to shrug off side gusts so you never have to fit a slower, shallower wheel, come off the aerobars or back off the gas to feel confident in the wind. 

We know that the Enves are, ultimately, the fastest and they’re the right choice for a money-no-object build. Enve say that for most people their 7.8s are faster as a pair than using a disc in the back because discs work best at high speeds and lower yaw angles. (Whether they’d still say this if there was a disc in the Enve range is another question.) Diamondback, on the other hand, say the fastest configuration for their Andean is a HED Jet 6 at the front and Jet Disc at the rear.

These three bikes are exciting, motivating, fun and rewarding. But they’re not perfect. Perhaps as a result of shifting into a radical new design paradigm, compromises have been made.

The Andean is stiff under power but lacks a little stiffness in the base bar and fork. The thin, 15mm fork legs and 1in steerer tube flex when you’re working hard out of the saddle. Neither is an issue when you’re hammering along in a tuck, though you might not have your hands as high as you’d like – the stem is shaped to integrate closely with the HED bar but it prevents the aerobars from being angled up. Also its food compartments aren’t huge so you need to consider compact calories and the Garmin mount on top of the bento box, while a good idea, is far too rearward. 

The Cervélo has fewer niggles but they’re more significant. It steers like a bus around roundabouts, feels every bit of its 10.26kg and the ride is too firm. We wouldn’t call it harsh but it’s a rougher ride than its rivals here. The range of position adjustment is huge, so there are no issues there at least.

An altogether more bespoke proposition, the Dimond’s issues arise at the factory and with the build by importer Prestige Cycles. We were disappointed that a bike built especially for this test arrived sloppily prepared. The front brake cable wasn’t tight, the chain was still in its packing grease, the cranks weren’t the requested length and the correct Enve pads hadn’t been fitted. When it comes to custom builds by high-end specialists, this wasn’t a good demonstration of the service. A problem that’s more inherent to the design, however, is the lack of built-in storage and the annoying cable guide behind the stem, which is supposed to be held in place by magnets but kept falling out until we duct taped it.

Need for speed

More than anything else, these bikes have to be fast. As well as hammering them on the road – where they all felt searingly quick and subjectively indistinguishable – we conducted our most scientific testing yet. Some of our testing was conducted on a traffic-free circuit, running four repeats on each bike and, with help from some top aerodynamicists, the results were cross-referenced with recorded weather data to produce a ‘wind normalised’ time for each bike that accounted for even the smallest variations in the wind during the five-hour testing period. We included our long-term test Orbea Ordu Ltd as a reference point on the same Enve 7.8s and ran all the bikes with the same tyres, pressures, positions, clothing and power.

Dimond wouldn’t let us wind-tunnel test the Brilliant and now we know why. It placed last, almost 20 seconds off the Orbea control bike in third.

The Cervélo and Diamondback are blazingly quick. No test bike has yet beaten the Orbea in controlled aero testing to power, yet these two kicked half a minute into it, suggesting they’d pull out five or six minutes over an Ironman bike leg. The difference between the P5X and the Andean was narrow, however: 20:25.2mins to 20:33.3mins. And, perhaps surprisingly given the two brands’ relative aero experience, it’s the Andean that takes the honours. It’s a missile.

Overall verdict

The Diamondback Andean was arguably the underdog against the might of Cervélo but it’s our clear winner. It’s the fastest, smoothest, the best value by miles, carries everything you need and the custom build means you can spec better brakes and shifting than this one had and save money. It’s a genuine bar-raising superbike. But – and it’s a big but – you can’t actually get it in the UK yet. You can order it through Diamondback’s Custom Studio web facility but it’ll be a few months until the bikes are ready to be shipped to the UK. 

The Cervélo P5X is hugely impressive and a close second. Its adjustability and easy breakdown for packing are genius, it carries a lot and it’s rapid, but its price and firm ride are chinks in its armour that it failed to mitigate against the clock.

The Dimond Brilliant places third. It’s really enjoyable to ride and a quick bike. But it’s down on speed against these rivals, lacks storage and, while it looks a million dollars, it also costs a lot.

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