Cannondale Topstone Carbon Lefty 1

Cannondale's Topstone Carbon Lefty 1 is a technological tour-de-force: a sub-10kg, full suspension gravel bike with a monoblade Lefty fork. It's also a hoot to ride, and well-suited to fast riding on a wide range of surfaces. Yes, it's expensive, but nice things often are.

First things first: do you need a full suspension gravel bike? Given that the Rough Stuff Fellowship have been hoiking Dawes Super Galaxy tourers and suchlike across inappropriate terrain since the 1950s, it's easy to argue you don't need a gravel bike of any sort to have fun off-road.

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And if you're going anywhere you properly need suspension, there's a whole world of mountain bikes out there waiting for you. So is the Topstone a niche within a niche, with limited appeal? I'd argue not.

Off road surfaces are bumpy – stop me if i'm getting too technical – and that's why the trend in gravel biking has been towards larger-chamber tyres. Ten years ago you'd have been hard pressed to find anything bigger than a 700x40c; nowadays 650b wheels and 50mm tyres to fit to them are fairly commonplace.

Go any bigger than that, though, and the tyres don't work nearly as well on the tarmac. Adding a small amount of suspension gives a comfort gain on the rough without really sacrificing speed on the smooth. Provided you do it right.

And Cannondale has done it right with the Topstone Carbon. At the back the suspension is a combination of the frame and the seatpost; there's just a single pivot, between the seatstays and the seat tube.

The rear wheel movement is achieved through flex in the stays, and the damping is just what the carbon layup can provide; it's tuned to the bike's frame size to give a similar response for different sizes of rider. Cannondale claims the system offers up to 30mm of rear wheel travel.

The LockR pivot locks the movement of the two seatstays together so that hits at the back don't twist the wheel out of line.

In terms of a suspension setup it's very simple. There are no shocks or linkages, and because of that it's a very lightweight solution. You don't get the same level of tuning or damping control you'd have with a rear shock, but we're not talking huge amounts of travel here: in use the bike doesn't feel like it has rear suspension, it just feels comfortable, like it's wearing even bigger tyres than the 47mm WTB semi-slicks it comes with.

There's no unusual feedback under pedalling and the bike behaves just like a rigid frame under power, with no noticeable flex from the rear triangle.

If the suspension at the back is as simple as it comes, the opposite is true at the front. The Lefty Oliver fork on this bike is specifically designed for gravel riding, and again gets just 30mm of travel.

The process of adjusting to a monoblade fork like the Lefty Oliver is similar to the process of adjusting to carrying bikes on a rear-mounted carrier on your car: you spend the first few miles fretting it's all going to go horribly wrong, and then you forget about it for the rest of the journey.

There are no issues with the Lefty not being stiff enough to track effectively: none at all. If you didn't look at it, you wouldn't know it was a single-sided fork.

Where the back of the bike doesn't necessarily feel like 'real' suspension, the front does: this is a proper air-sprung unit and you can tune the spring pressure and rebound damping to get the feel you want. On the road you get a bit of wallow when you're standing on the climbs, but with only 30mm of travel it's not really much of an issue.

If you prefer you can lock the fork out on the road. It's not a full lockout: the fork will still respond to bigger hits, but the compression damping is ramped right up so the fork is a lot firmer.

Taking the wheel off means also taking the front brake caliper off, and there's a quick release for that. It's okay in a workshop situation but a bit of a faff on the trail, although of course the single-sided design means there's less need to actually remove the wheel as you can get the tyre off with the wheel still in situ.

The upshot of all the tech Cannondale has crammed into the Topstone is that it's a great bike to pilot over less technical stuff, and it's not compromised on the road either. Even though the approaches to suspension at the front and the rear are very different, the bike feels well balanced.

Geometry

With a stack-to-reach ratio of 1.54 (size L), the Topstone is similar in aggressiveness to the Kinesis Tripster ATR V3  – and for me that's just about the sweet spot for covering distance at speed, yet maintaining good control on unmade surfaces.

Cannondale has opted for a slightly longer rake here, so the front wheel sits a bit further forward; something they call Outfront steering geometry. The idea is it's more stable on rougher terrain, and certainly the Cannondale feels more at home on the bumpier stuff than the Kinesis.

I'd say that's probably more to do with the bigger chamber tyres and suspension than the geometry though; it's always hard to pinpoint exactly what's making the difference when everything's a variable.

If you plan to do much seat-of-the-pants stuff on the Topstone, it's designed to work with an internally-routed dropper post, although this build doesn't include one. If you're running a mechanical 1x drivetrain it's possible to use the redundant shifter to activate the dropper (with the wireless setup on this bike that's not an option, so you'd need a separate bar-mounted lever).

The tyres – a WTB Byway on the rear and a WTB Venture on the front, both 650bx47mm – are probably the perfect combination for sunny, dry bikepacking adventures. It wasn't sunny or dry when I tested this bike, and so they felt a bit compromised: the slick-centred Byway has basically no grip on the slippery chalk of Salisbury Plain in the winter.

The Venture, with its more aggressive tread, is a bit better, though you'd still class it as a semi-slick. Both roll very well on the road, but for mixed surface rides it's definitely a height-of-summer combination for the UK, and I'd sacrifice a bit of speed on tarmac for a less slithery ride on the off-road descents.

On this top-dollar build the WTB tyres roll on Cannondale's HollowGram 23 carbon wheels, which were faultless throughout: stiff, light and true. They're tubeless-ready, and with a 23mm internal rim width they're perfect for the sort of tyre sizes you're likely to fit to a bike like this.

Obviously with a lefty fork it's not straightforward to swap wheelsets if you're not happy with the performance, but there's no reason to suspect that'll be the case here. They're excellent wheels.

Cargo

If you want to load up your bike and head off into the great unknown – or just over the hill for a bivvy – then the Topstone is reasonably well-served with luggage points. You can't really fit much to the fork, with it being one-sided and suspended, but there's plenty of room in the main triangle for a decent frame bag, and the down tube has three mounting points so you can set your bottle cage low for room.

There's a set of top tube mounts for a racing bag, too, and a third set of bottle bosses under the down tube by the bottom bracket. You're not likely to want to fit a pannier rack to a bike like this, and it isn't designed for one, but there's plenty of room for a big bikepacking seatpack.

If you decide you want mudguards there's a removable seatstay bridge to accommodate the rear 'guard. At the front there's a range of aftermarket single-sided mudguards you can fit to the Lefty fork.

This high-end build of the Topstone Lefty Carbon gets a wireless SRAM groupset, a mix of the 12-speed X01 Eagle eTap AXS mountain bike groupset and Force AXS road shifters, and a 40t single ring chainset. With a whopping 10-52t cassette, this bike has a huge gear range across its 12 sprockets.

The 40/10 top gear isn't huge, but it's been enough to keep up with road bikes on the fast bits around here, and at the other end the 40/52 bottom gear is tiny – small enough for winching up steep and technical stuff off-road. The trade off for the range is the gaps between ratios, which are pretty big across the cassette and especially so at either end.

If you're used to the close ratios of a road double transmission that might feel a bit jarring at times, especially in a group on the tarmac bits. I didn't find it a particular issue, and although I did note it from time to time on the road, as soon as the tyres hit gravel it was never a thing I was thinking about. With more of your brain occupied with finding your line and keeping momentum, optimal cadence drops down the list.

The groupset worked flawlessly throughout. You get a button on the left lever to make things easier, and one on the right to make things harder, and that's it. If you're used to mechanical systems it takes a bit of reprogramming to get your head around the fact both levers control the same mech, but it makes sense once you're there.

I find electronic gears work much better across a wide-range cassette than mechanical ones, which tend to need very precise setup to work well with cogs over 40 teeth; that was never an issue with this bike. Nothing about the transmission was, really.

With no wires the groupset doesn't make use of the frame's internal routing, which is a shame because Cannondale has spent a lot of time making it very user-friendly: there's a full-length internal tube inside the frame from entry to exit, so you just poke the cable outer/hose right through.

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On the cheaper mechanical builds of this bike, or for fiddling with the brake hoses on this one, that's a definite time-saver. Not that I needed to fiddle with the brakes on the Topstone: they worked pretty much faultlessly throughout.

I find that stock SRAM brakes are bit more prone to squeaking when wet than their Shimano counterparts, but stopping is never an issue.

There are a couple of other techy bits to note. This bike uses Cannondale's HollowGram SAVE SystemBar, which is semi-integrated: the bar and stem are separate, but designed to look like a single unit. There's 8° of pitch adjustment available, and you can swap the bars or stem for a different length without replacing the whole thing.

The carbon bar has a big flat top section which is very comfortable, and the flat, internally routed and low-frontal-area stem means it's probably more aero too, if you care about such things.

The drop position is fairly shallow, and easily accessible, and there's a bit of give in the bars too, which would probably be noticeable on a rigid-forked version of this bike, but isn't really in this case. There's not a lot of real estate for computers and lights and stuff, but the integrated out-front mount can be used to house them.

On the back wheel the Topstone Carbon has an integrated sensor designed for Cannondale's own app. It automatically records, and will store up to 30 rides between syncs with your smartphone using its on-board memory. The app also tells you when the bike is due a service, based on the miles you've logged.

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If you've spent over six grand on a bike you've probably got a GPS computer knocking about to do the ride recording, but the fuss-free tracking of a single bike's mileage might be useful to you, and it's not like you have to remember anything beyond syncing the bike once a month or so.

Value

So, who's this bike for? Obviously in this build the likely market is restricted a bit, although it's worth noting you can have the mechanically-geared Lefty 3 build of the Topstone Carbon, with the same frame and fork, for not much more than half what you're paying for this bike.

As ever, the law of diminishing returns applies: this bike isn't going to be twice as good, but it's lighter, with a wider gear range thanks to the 12-speed AXS groupset, and both those things are welcome upgrades.

The fact it's a very light rig is going to be of most interest if you're wanting to move fast. For any kind of competitive gravel event, the Topstone Carbon would be an obvious choice. Having ridden the 200km Dirty Reiver in the past, I think a bike like this would be a perfect choice: swap the tyres for something a bit narrower and more aggressive, and let the frame and fork add a bit of cush back.

You'll be thanking the nice folks at Cannondale for the suspension by the end.

If you're just heading out with your mates for overnighters or slamming round the local lanes and trails then it's probably overkill, but it's a lovely bike, and it's your money. I'm not going to tell you you can't have nice things.

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The more you're likely to load it up, the less you're likely to notice the extra weight of the cheaper build though – it keeps the suspension tech but uses cheaper components.

Overall

It's often easy to think of state-of-the-art bikes like this, with their top-spec components and technological innovations, more as look-at-me statements than actual bikes you'd buy. But it's good the boundaries between riding types are blurring, and that companies are trying interesting things.

For all its cleverness, my abiding impression of the Topstone Carbon is of a bike that's a lot of fun. It's light and fast – you can keep up on the road, and shoot off on the gravel. The suspension is a tangible benefit for riding on mixed surfaces at speed, and everything on it works brilliantly. There's lots to like here.

Verdict

Fast, light gravel ripper with top-notch equipment and useful suspension tech