Cannondale’s Topstone Lab71 is worth every penny… providing you build your own

The Topstone Lab71 frameset elevates the Topstone's already high performance, but Cannondale could have refined it further.

Lab71 is Cannondale's highest tier in both design and construction. It is usually reserved for professionally raced bikes, so when Cannondale announced a Lab71 version of the rowdy, fun and not necessarily built-for-racing Topstone Carbon, I knew I wanted to try it.

While you can buy a complete Lab71 bike, I wanted to try building one for myself, giving me the choice to pick proven parts that work for me. It has enabled me to build the bike I want for my needs, conditions and geography. I don't have to settle for the specifications dictated by Cannondale.

Now, £3,000 / €4,199 / $4,500 is a lot to pay for a frameset – especially when the standard Topstone Carbon 4 as a complete bike is only £2,800.

In its favour, the Lab71 frameset is lighter, sharper and better-looking than the standard frameset.

Cards on the table, I’m a huge fan of the Topstone. In its standard guise, it’s a brilliant gravel bike – light and agile enough to be raced, yet comfortable enough to be an epic multi-day ride. It’s got all the fixtures and fittings to carry everything you’ll need too.

What makes Lab71 different?

Lab71 is named after a combination of Cannondale’s advanced development lab at its Connecticut headquarters and the year the company was founded, more than 50 years ago.

Cannondale’s road bike product manager, Sam Ebert, remains tight-lipped about the exact nature of the upgrades to the construction over the cheaper Hi-Mod carbon layup, saying only: “The new Series 0 carbon construction found on the Topstone Lab71 makes use of cutting-edge materials and processes rarely seen in the bike industry due to their complexity and cost.

"This advanced fibre and nano-resin composite has exceptional tensile and compressive strength properties, which allow Cannondale engineers to achieve more with less material.”

The result, on our scales, is impressive – with the total frame module (frame, fork and seatpost) weighing in at 1,727g.

• Frame: 1,080g, painted, size large with all hardware inc. thru-axle
• Fork: 485g (including 6x bottle boss bolts) 
• Post: 162g including bottle boss bolts (x6)
• Extras: seat binder, thru-axless, headset and Cannondale’s Hollowgram SL carbon seatpost (all included in the £3,000 price tag)

That’s a saving of more than 160g over the ‘standard’ carbon Topstone – not exactly a hefty frameset in the first place, especially when considering its pivoted rear end and 30mm of suspension travel.

In comparison, BMC claims the elastomer-infused 20mm-travel URS weighs in at 1,050g in a size medium (unpainted, with no hardware). You can add 1,250g for the dedicated 20mm-travel fork for a total of 2.3kg.

The Lab71, in large, with a 40mm-travel Cane Creek Invert CS fork weighs in at 2,350g with the steerer cut, and includes the headset and hardware.

Even though the Lab71 has been lightened, it hasn’t been compromised. It has 45mm tyre clearance, triple bottle bosses, top tube bento box mounts, triple-anything mounts on the fork, mudguard mounts, full internal cable routing, a SmartSense port (or toolkit recess) and a threaded BSA 68mm bottom bracket shell.

I could do without the fork mounts and SmartSense port, but some may well appreciate their inclusion.

The key feature of the Topstone is the back end and its Kingpin suspension system. The design maximises compliance in the seat tube with a pivot design, and of that 30mm of travel, only 25 per cent (7.5mm) is at the rear axle. That means the seat tube effectively acts as a leaf spring, combining with flex zones in the seat and chainstays and a maintenance-free pivot point that holds everything together.

Cleverly, the leaf-spring design is proportional to the size of the bike, and when you compare the width of the thinnest section of the seat tube on the small to the extra-large, the difference is marked – 16mm on the small and 28mm on the XL.

The tube cross-sections change according to size and the laminate design also changes. This means stiffness is scaled to deliver a consistent experience whatever the rider's size.

Cannondale Topstone Lab71 geometry

The Topstone Lab71's geometry is the same as the standard Topstone Carbon – and that’s a good thing. The 71.2-degree head angle is relaxed compared to a drop-bar road bike, but not as extreme as more trail-orientated gravel bikes such as the Rondo Mylc.

This is paired with an effective 73.1-degree seat angle and, on my large test frame, a sporty endurance-like 610mm stack and 402mm reach. The fork offset and my choice of 40mm tyres give a trail figure of 62mm. 

This puts the steering squarely into stable territory rather than road race bike quickness. It's ideal for the variety of terrain you’ll find on gravel adventures. Its closest rivals in this middle ground between race and trail geometry are our current Gravel Bike of the Year, GT’s Grade Carbon LE and Giant’s latest Revolt.

Build your own

As good as the range-topping Topstone Carbon 1 RLE is, it’s not the build I was looking for with a 2x SRAM Force AXS groupset, SmartSense lights and a carbon seatpost. Costing £8,000, it weighs 8.9kg in a size large.

SRAM’s most affordable electronic groupset, I think it’s the best option for a bike that, let’s face it, is going to get bashed and smashed around.

Aside from using Apex, I’ll admit to having gone for quite a premium build.

I’ve opted for an Easton cockpit with the EC90 ALX carbon bar and EA90SL stem. I had the bar on a test bike recently and was impressed – I like the subtle flare, measuring 44cm wide from hood to hood and 48.3cm at the drops.

I also like the profile of the bar across the tops, along with the 80mm reach and compact 123mm drop. The bar's 232.2g weight is impressively light, as is the 137.1g for the stem (including an out-front mount). Easton’s tacky tape fills out the front end and I’ve added a set of SRAM’s wireless blips to the underside of the bar tops.

At the back, I couldn’t resist going for a RockShox XPLR Reverb dropper post (75mm-drop version). I’ve tried a few gravel bike dropper posts recently and found I use them all the time, although it's not exactly essential. The Reverb’s wireless electronic activation makes it the best of the current gravel dropper crop. It doesn’t come cheap, however.

The post is topped with Cannondale’s Line-S carbon saddle, a name that may sound familiar to some. Cannondale has relaunched the popular Fabric range of saddles under its name, and the Line-S Pro is one of my favourite short saddle designs – tipping the scales at 181g. Its short shape is easy to move around on, it has ample padding and its squat shape suits me perfectly.

The Topstone rolls on Cannondale’s all-new G-SL27 carbon gravel wheels. These have a 27mm-wide internal hookless rim, a DT Swiss 240 rear hub and Cannondale’s own hub shell with DT internals up-front. They weighed in at 1,325g a pair on my scales and I’ll be testing them thoroughly in the coming months.

Wrapping the G-SL27s are Tufo’s Swampero gravel tyres, which tip the scales at 439.9g each and are protected by a liberal amount of Continental tubeless sealant. Tufo was legendary in the tubular tyre cyclocross days and these are my current favourite gravel tyres for adverse weather conditions.

The drivetrain comprises a 42-tooth chainring and an 11-44 (HG-compatible) 12-speed cassette.

My complete build, including a pair of Time ATAC XC 6 pedals (290g), two Cannondale side-entry bottle cages (92g) and a Cannondale Set-Off Flat kit (249g) strapped to the down tube storage bracket, tips the scales at an impressively light 9.07kg.

Or, without pedals and accessories, like an off-the-peg Topstone Carbon RLE, it's 8.439kg – 461g lighter on the scales and considerably cheaper with a saving of £899.04

Cannondale Topstone Lab71 ride impressions

On longer rides, the Topstone Lab71 is pure class; the lightened and tightened frameset feels road-bike responsive and stiff on the tarmac. It’s just as rapid when you head off-road, yet feels superbly composed, stable even.

On the wide gravel roads of Salisbury Plain, the Topstone Lab71 feels every inch as quick as pure gravel race bikes, such as BMC’s Kaius and Factor’s Ostro Gravel. It bests those bikes easily when it comes to comfort.

Usually, when a frameset is made lighter, it means more reliance on high-mod fibres, which are lighter, but the trade-off is increased stiffness. That's not something you necessarily want from a gravel bike. Cannondale, though, has done a great job of maintaining the Topstone’s characteristics while cutting weight.

The rear-end compliance is subtle but superb. It never gave a suggestion of uneven movement at the saddle – even when powering along seated and in the drops, and pushing the pedals hard.

The back end’s smoothness is a good match for the front end, which is firm but never tooth-rattlingly hard, and only adds to the overall impression the Lab71 gives. It’s a bike built to go fast off-road, but one that’ll happily cruise too, and you’ll be comfortable in either camp.

Venture further off-road onto trails and singletrack, and the geometry is well suited to handling twists, turns, roots and rocks. The relatively slack, 71.2-degree head angle stabilises the steering and the seat tube angle is effectively a steep 73.1 degrees.

However, it measures up at 71.9 degrees because of the leaf-spring like shaping. The 62mm trail adds to the stability of the steering and it makes the Lab71 a bike I’m more than happy taking on trails usually reserved for mountain bikes.

My build choices work well here. SRAM’s Apex AXS shifts quickly and accurately. The brakes may not be on a par with the latest ergonomic advances of the new Red XPLR AXS, but they haven’t let me down. The Easton bar is a great shape, not too overtly flared, but comfortable on the tops, hoods and drops. The Easton tape was great, but was superseded by Lizard Skins' thickest 4.2mm tape when I recently switched the fork to the Cane Creek Invert CS.

The Cannondale wheels are light for a gravel wheelset, and they’ve proven themselves well. Like many carbon wheels, the freehub internals are from DT Swiss and run with the brand's characteristic smoothness. At £1,600 a set, they are a good rival to similar wheels from more established brands.

I’ve recently used the Lab71 as the test bed for Cane Creek’s new Invert CS fork. This stiff upside-down design with 40mm of travel is a great match for the Lab71’s Kingpin back end. Helpfully, the Invert CS' matt-black finish is a perfect match for the Lab71’s front end. It adds expense and a net 765g to the complete bike weight (up to 9.204kg with pedals and accessories in place).

The Lab71 has performed superbly in all conditions and all terrain, but it's not without its niggles. The rubber bungs in the fork-leg mounts tend to fall out. I'd expect better from a premium frameset such as this.

The net effect of creating what is now essentially a full-suspension gravel bike has been marked. I’m much more confident taking the Lab71 onto more extreme terrain with the dropper post – and that includes seriously steep technical descents. It also added a layer of smoothness on all gravel surfaces and it's now a bike that's more forgiving and less fatiguing on big days out.