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Alchemy Helios custom carbon frame



Fast and exciting yet comfortable and smooth, the Helios is a beautifully balanced US built carbon fibre racer

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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Alchemy's Helios is impressively fast whether the road points up, down or across. It's wonderfully comfortable as well, both in the geometry that is pitched towards the racier end of the scale, and the compliance afforded by the frame and fork that filters out vibration from rough roads.

Frame: Handbuilt in the US

You might never have heard of Alchemy, but they're doing something few manufacturers are doing; building their own carbon fibre frames in-house. They're based in Denver, Colorado and this Helios is the latest model in the range. They're carbon fibre specialists, though they do include two titanium road bikes and a steel cyclocross bike in their range. But it's carbon fibre they're known for.

And my they've done a superb job of building a beautiful frame. The carbon fibre construction, a tube-to-tube process with the joints carbon wrapped, shows through the transparent lacquer. It's delicately finished with understated decals. As with most custom frame builders, you can pay a bit more and specify the paint finish and decals and create a unique frame.

It helps that Alchemy produce their frames in their own facility, rather than outsourcing to another manufacturer. They started out by using Enve-sourced round tubes in the Xanthus, but the desire to get more creative than simple round tubes led them to acquire the ability to cut their own moulds, opening up a lot more creative freedom. The Arion was the first result of this new manufacturing potential, and they've followed up with the Helios.

Drawing on the aerodynamically shaped tube profiles of the Arion aero road bike, the Helios has a more pleasing stance with gently profiled and flared main tubes. It's a bit less mad looking than the Arion, yet offers some of the aero benefits of those shaped tube profiles. The main tubes have a distinct profile with a rounded leading edge and flare into the head tube, seat tube and bottom bracket.

Deep chainstays are joined by slender seatstays, the bottom bracket shell is oversized and in this case press fit. Up front is a tapered head tube with Alchemy's own fork sliding into the 1 1/8in and 1 1/2in headset bearings. The cables are routed internally, the rear brake inside the top tube and the gear cables inside the down tube. You could specify electronic routing if you were going to build it with an electronic groupset.

Although I didn't have the frame built for me, they do offer six stock sizes if you fall happily onto one of those. I did and this 56cm model fitted my really well. If you're looking to buy an Alchemy the nice people at Mosquito Bikes will give you a full bike fit, send those measurements off to Alchemy and you'll get a perfectly fitting frame, whether it's a custom or stock size.

For reference, this 56cm bike has a 56cm effective top tube, 50cm seat tube, 16cm head tube and 73 degree seat and head angles. Those numbers are what we'd expect of a bike pitched as a performance and race bike, ensuring flighty handling with fast responses, just what you want in a race situation. The short head tube favours a low riding position, but there's nothing to stop you specifying a taller head tube if you went down the custom route.

Build: Custom build with top-drawer parts

The Helios came with some top-drawer components for us to assess the frame. You can buy a frameset for £3,320, including an Enve 2.0 carbon tapered fork and headset, and Mosquito will happily build you a bike to any specification you want. There were no shortcuts in our build, which comprised a Shimano Dura-Ace mechanical groupset, Enve SES 3.4 carbon clincher wheels with 23mm Continental GP4000S II tyres, Enve handlebars, stem, seatpost and a Fizik saddle. If you wanted the same spec, the complete bike would cost you £8,200.

All very nice kit, but I won't dwell on the componentry too much. Suffice to say it was all flawless during the test. The wheels, a real highlight of the package and a good match for the frame, are superbly fast and coped just fine in blustery conditions. The braking performance, with Enve's own brake blocks, puts them right at the top of the carbon wheel pile when it comes to stopping. Lots of power, plenty of modulation, no squeaking and no sudden grabbing.

The Enve finishing kit is lovely stuff, though the single bolt seatpost is fiddly when fitting a saddle, but easy to adjust once you've got the rails around the cradle. I found the bars a touch on the wide side, but that's no problem because if I was buying the bike I would simply ask for a narrower handlebar. That's the beauty of a custom bike build, you can get exactly what you want, in the size you want.

Ride: Fast and wonderfully comfortable

All that little lot produced a 6.8kg build (14.99 lb), and that lack of weight you really notice riding the Helios. It really rips up the road when get on the power. Show it a climb, from a shallow gradient leg stretcher to a wall steep leg breaker, and it scampers up with little hesitation. There's a high level of stiffness around the bottom bracket area that transfers power very efficiently, and it feels very solid under power too.

There's a good level of stiffness at the front, and it does well to resist twisting forces from the head tube to the bottom bracket. This gives the Helios a slightly edgy and darty ride feel, especially coming off the Colnago c60 which is far more measured. That was the defining trait during my time with the Helios, a lively ride character that is very responsive to any sort of steering input. That makes it a thrilling bike to ride, fast-paced and energetic.

It's certainly not the stiffest carbon race frame, but neither is it remotely lacking in this department unless you're a big sprinter who can deliver some serious power to the cranks. Remember that the carbon layup can be completely tuned to your requirements, so you could build it stiffer if you really wanted. I found the ride as is nicely balanced in all situations.

It picks up speed briskly and demonstrates a good ability to handle a sudden injection of pace, which is handy for bridging gaps in a pace line or jumping across to the breakaway, or just getting the jump on your mates for the race to the town sign.

Where the Helios draws another ace card is in the comfort it provides. It's not just smooth, it's buttery smooth, in a way that only a small handful of other carbon frames are. The way it just floats over rough and broken tarmac and absorbs vibrations caused by crumpled road surfaces, such that these imperfections never unsettle the Helios. And that's with 23mm tyres as well, inflated to about 90 psi.

So it's beautifully composed and smooth on all manner of road surfaces, fast when the road points up, down or chasing wheels, gathers momentum with alarming ease, and is a real looker too with the full gamut of custom options available. For a race or fast performance bike the Helios offers everything such a potential customer is seeking. And being so comfortable that you can cruise along on it all day, and finish every ride feeling fresh, is a real attraction.

Yes, it's jolly expensive, but it's similarly priced to a clutch of top-end production bikes, yet offers the full custom treatment that such bikes just don't offer. And that's an appealing prospect if you've got this sort of money to spend on a carbon road bike. Plus there's the rarity value that it offers, which will be a draw for a lot of people.


Fast and exciting yet comfortable and smooth, the Helios is a beautifully balanced US built carbon fibre racer.

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Make and model: Alchemy Helios custom carbon frame

Size tested: 56cm

About the bike

State the frame and fork material and method of construction. List the components used to build up the bike.

  • 44mm straight or tapered head tube 1-1/8' to 1-1/4'
  • Alchemy aero top tube
  • Alchemy shaped down tube
  • Alchemy carbon dropouts
  • Stock or custom geometry and ride characteristics*
  • ENVE 2.0 fork included
  • Headset included
  • PressFit 86 or Threaded BB
  • 100% made in the USA

Tell us what the bike is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about the bike?

"The Helios bridges the gap between our light, round-tube carbon fiber Xanthus and our extreme, aerodynamic Arion. In addition to an aero top tube and round seat tube, we've added a shaped down tube, which is flared at both the head tube and bottom bracket junctions to increase torsional rigidity and aid lightning fast acceleration. The Helios is a progressive all-rounder suited for fast, criterium-style races, as well as long, cerebral climbs."

Frame and fork

Overall rating for frame and fork

Tell us about the build quality and finish of the frame and fork?

Beautifully made and lovely finish.

Tell us about the materials used in the frame and fork?

Full carbon tube-to-tube construction, and made in the US.

Tell us about the geometry of the frame and fork?

Racey and low at the front, producing an exciting ride.

How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?

Spot on.

Riding the bike

Was the bike comfortable to ride? Tell us how you felt about the ride quality.

The comfort this frame offers is astounding.

Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?

Yes, plenty of stiffness where you need it most.

How did the bike transfer power? Did it feel efficient?

Very well. Not the outright stiffest bike, but no slouch.

Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?

Fast and edgy, an exciting ride is offered by the Helios.

Rate the bike for efficiency of power transfer:
Rate the bike for acceleration:
Rate the bike for sprinting:
Rate the bike for high speed stability:
Rate the bike for flat cornering:
Rate the bike for cornering on descents:
Rate the bike for climbing:

Your summary

Did you enjoy riding the bike? Really enjoyed riding this bike.

Would you consider buying the bike? If I had the money, most likely.

Would you recommend the bike to a friend? Yes.

Rate the bike overall for performance:
Rate the bike overall for value:

Overall rating: 9/10

About the tester

Age: 31  Height: 180  Weight: 67kg

I usually ride:   My best bike is:

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, touring, mtb,


David worked on the tech team from 2012-2020. Previously he was editor of and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds, and you can now find him over on his own YouTube channel David Arthur - Just Ride Bikes

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