Skinny full-sus or plus hardtail for the UK National Endurance Champs?

We race both at the 24hr Relentless Exposure mountain marathon, which is as tough as it sounds

Wrapped around the lower slopes of Scotland's Ben Nevis at the end of October, the Relentless Exposure event lap is a serious block of climbing and big grin/big risk descending. I’m going to be racing around it eight times (that’s 88km / 54.5 miles with 2,760m / 9,056ft vertical) and mostly at night as part of two teams of four blokes old enough to know better. Sounds like the ideal place to let a couple of XC freaks out to play.

  • The course: A superb but very demanding 11km (6.8 mile), 345m (1,132ft) lap including elements of the World Cup XC course and even the last drop of the DH course. Ridden eight times over 24 hours
  • Horse one: Cannondale Scalpel-Si Black Label with Lefty Carbon 2.0 100mm travel fork, Shimano XTR Di2 gears and brakes, Enve bar and Enve rims on Chris King hubs with Schwalbe Racing Ralph Evo Snakeskin 29x2.25in tyres
  • Horse two: Open One+ with RockShox RS-1 120mm travel fork, SRAM Eagle XX1 gears, SRAM Level Ultimate brakes, USE Vyce bar/stem and custom DT Swiss X551 rim/SRAM hub wheels with WTB Ranger 27.5x2.8in tyres
  • The equipment goals: Minimising cumulative fatigue and maximising speed on a brilliant but brutal, mostly rocky, wet and dark race lap

If using the term ‘freaks’ sounds like I’m being harsh, then the curious looks I was getting around the race paddock definitely confirmed that both arrows in my quiver were causing a stir, and marked me out as either very lucky or very rich.

This year's version is the least black version of the Cannondale Scalpel-Si Black Inc we've seen, but it's still a stealthy predator
This year's version is the least black version of the Cannondale Scalpel-Si Black Inc we've seen, but it's still a stealthy predator

The Cannondale Scalpel-Si Black Label is an off-the-peg full-suspension XC bike — albeit a very high peg at £9,500 / $12,790. With Cannondale’s unique Lefty single-legged fork, and other eccentric aspects, it’s definitely a distinctively different option to the large number of super light, but essentially very similar carbon fibre, full suspension bikes available from mostly European brands. To add an extra comparative spark, it’s loaded with a full Shimano XTR Di2 electric shift suite.

Open's stunning sub-1kg One+ frame deserves a suitably golden build up from SRAM, RockShox, DT Swiss, USE, KS, Fabric and WTB
Open's stunning sub-1kg One+ frame deserves a suitably golden build up from SRAM, RockShox, DT Swiss, USE, KS, Fabric and WTB

The Open Pro+ has a 990g frame that would make an ideal basis for a conventional ultralight 29er hardtail. However, as it’s one of the few frames in that category that can also take a 27.5x3.0 plus tyre, I couldn’t resist experimenting to see how a bit of low-pressure pneumatic float would compare to ‘proper’ hydraulically-damped suspension and small volume 29er tyres. And what else could I use to help me soar through the Scottish mountains than SRAM’s XX1 golden Eagle transmission?

Full sus or full plus?

The plus tyre Open was all about going with the flow
The plus tyre Open was all about going with the flow

With no time to pre-ride the course after a long drive north on the Friday, and setting up our pit on Saturday morning, the first lap is a blind charge. This seems like a smart time to deploy the extra tyre insurance and bail-out gear (32x50T rather than 32x40T) of the Open. 

Some seriously steep final climb pitches are the perfect place to open the Eagle’s wings, while rock sections certainly make me glad of the big 2.8in wide footprint of the High Grip compound front tyre. Pre-event testing I’d done on the rolling resistance of the tyres seems to be confirmed by the ease with which it dispatches the fire road sections too.

Despite less grip and less communicative brakes than the Open, I manage to squeeze another 7secs out of the descent

Despite doubling back for a bottle that got shaken out on the roughest descent, I catch my marker man Sam from our other team around the halfway point. I can’t shake him on the snaking second climb or the groomed berm descent to the finish, but a lap of 39.44mins is a decent opening innings for me.

There’s no plus tyre bar showboating round the opening car park corners as I launch the Scalpel into my second lap, and sudden slips from the harder compound 29x2.25 tyres nearly deck me a few times before I back off my traction expectations. The impressively sensitive Lefty and progressive 100mm of rear travel keep the Cannondale hooked up under power though.

It’s also much smoother and consistently poised over bigger rocks and lumps than the Open as I trigger through to gear 11's top-out, and a “beep” from the Di2 tells me that I’m maxing my speed potential on every descent too. Having already ridden the boulder sections of the first technical descent once, the 69.5-degree head angle and fork precision help me pick and stick better lines, and there’s no bottle ejection issues either. 

Despite this lap feeling significantly quicker, I reel in Sam’s 1:26min lead at almost the same point as the first lap. The difference this time is that the clean-rolling 29er tyres and better first half pacing mean I kick past him and open up nearly a minute's gap on the less technically challenging second half of the lap and I clock in 56 seconds faster than the previous lap.

Stiff, light and puncture friendly, Cannondale's Lefty fork is a racer's favourite for very good reason. The current damping is the best in its 17 year history too
Stiff, light and puncture friendly, Cannondale's Lefty fork is a racer's favourite for very good reason. The current damping is the best in its 17 year history too

With the previous rider on our team puncturing, Sam has a seemingly unassailable 5:13min lead when I grab the timing chip, I figure the Cannondale is the best chance I have of chopping down the deficit. Even with smaller tyres the plush Lefty helps offset increasing fatigue compared to the firm damping of the RS-1 and I work my way steadily through a field that’s now spread out round the entire lap. 

Unbelievably I catch sight of Sam just near the top of the final climb, digging deep to playfully stick a bar plug into his thigh just as it levels out onto the short stretch of summit fire road. Despite less grip and less communicative brakes than the Open, I manage to squeeze another 7secs out of the descent to bank a 41.07min lap.

Tortoise and the hare

It's a hell of a lot easier setting out on another lap when the course is a proper beaut
It's a hell of a lot easier setting out on another lap when the course is a proper beaut

By the time I start my next lap (the first of a properly dark pair), our team is actually 2:12mins up on Sam’s, and while that 40-tooth lowest sprocket on the Cannondale needs some proper grunting up a couple of sections of the course, I’m feeling cocky as I nip past the last few riders on the highest climb, loop through the weird little tunnel by the marshal point and pile into the descent.

Within a few metres, one of the curses Sam has undoubtedly been muttering translates into a rapidly deflating front tyre for me, presumably from a rock strike I didn’t even feel. Even worse, by a stroke of genius the C02 cartridge in my inflator is already empty so there’s no chance of a quick reseal. On the silver lining side, the Lefty means I can unseat the tyre, fit a tube and get pumping without removing the wheel, but Sam has laughed a long way off into the distance before I’m back rolling again.

The amount of zombies wobbling round the course make Day of the Dead decorations totally appropriate
The amount of zombies wobbling round the course make Day of the Dead decorations totally appropriate

Clattering around in pursuit on extra ‘just-in-case’ pressure, rider traffic seems heavier too. At roughly halfway through the race there are significantly more cyclozombies wandering about all over the place, making polite overtaking difficult as trails get wetter and the temperature drops noticeably. A double lap means I should temper my pace, but I’m determined to try and get our team back within sight of our adversaries. 

High gearing means I’ve got no option but to hammer the climbs either, even if jabs of cramp are starting to flash up my legs on the steepest sections. I’m still turning it up to 11 on the Di2 display at every opportunity though and by taking some serious ‘wrong side of the tree’ risks on the swooping wooded singletrack sections, I somehow claw my way onto Sam’s wheel by the start of the final climb. 

I fumble down the final descent in a mess of snot, tears, sweat and dribble, but elated to be back on par

I’m absolutely in bits from the effort of getting there though and I can barely steer let alone add torque into a gear on the climbing turns. It’s the mark of a true gent that Sam kindly coaxes my carcass to the top though and I fumble down the final descent in a mess of snot, tears, sweat and dribble, but elated to be back on par.

It’s a short-lived position for our team though, with his rear wheel badly dented from the first puncture, Ryan takes out the Scalpel for his double lap only to blow the front tyre again. Worse still, he runs the full length of the main descent in search of an Allen key before realising he doesn’t need to take the wheel off to repair it. Funny in retrospect, but a clear indicator of how fused your brain gets at 1am in the morning when you’ve been flat out for five laps already. 

With the Cannondale proving that its ability to gain a minute a lap comes at the cost of potentially losing five times that to the Open, it’s the plus bike that becomes my failsafe option for the next double lap. That massive 50 tooth rear sprocket gets a fair amount of use too, emphasising just how seamlessly the whole set up works compared to most wide ratio (44T+) cassettes. 

While the tracking is vague, the inline stiffness of the RS-1 and superlative control of the Level Ultimate brakes combine with the fatter, stickier tyres to make descending a lot less nerve-wracking too. That means while I’m sodden from a couple of cloud bursts and the laps are my slowest (45:56 and 47:04) so far, I actually feel better when I clock in at the finish of my laps than at the start.

Final furlong

No you keep the chip, I don't want to ride another bloody lap
No you keep the chip, I don't want to ride another bloody lap

With no real chance of catching our friendly adversaries or improving our current 4th overall/2nd in vets position, I’m pondering bike choice for my final ‘death or glory’ lap. In an ideal world I’d have had a set of custom lightweight 29er wheels built for the Open as well as the plus wheels or just fitted/bought a fork that didn’t need a Predictive Steering front hub. 

Every cleaned climb feeds into a crescendo of dead horse flogging that would mean a jail term from the Jockey Club

With the right tyres, that would have dropped overall weight by around a kilo to a road bike-like 8kg overall. Even a tougher/bigger front tyre to puncture proof the Cannondale might be a shrewd move, but to be honest I can’t be bothered to change it. With my body teetering on the edge of total cramping collapse, having an excuse to stop and throw in the towel would actually be welcome.

I attack the climbs with a similarly suicidal approach, expecting my tendons to coil up round my butt like broken springs every time I stand out of the saddle to stamp the Cannondale cranks round. Somehow the soup of exhaustion, endorphins and euphoria swilling round me mean that every cleaned climb feeds into a crescendo of dead horse flogging that would mean a jail term from the Jockey Club. 

It uses big shifter paddles rather than neat buttons, but that gear selection window leaves no doubt that Di2 is all about the digital
It uses big shifter paddles rather than neat buttons, but that gear selection window leaves no doubt that Di2 is all about the digital

With nothing to lose I keep it pinned on a course I now know inside out, buoyed up by glances at the Di2 display telling me I’m two or three gears higher than I was on my last Cannondale night lap. I’m weaving past the wrecks of singlespeed soloists, shouting kudos to marshals and have-a-go heroes alike with my last scraps of breath. 

It’s now that I really appreciate the amount of race experience that’s gone into the Scalpel too. The specific 55mm offset on the fork keeps the steering feeling immediate despite a more-stable-than-average (for XC) baseline geometry. A van loading incident put the remote front and rear lockout out of commission, but the default suspension tune balances pedal efficiency against trustworthy traction so well that we don’t miss it. 

While the SRAM stop-and-go package of the Open or a conventional XTR group will save £2,500 / $3,000 (as well as some weight) on the same Scalpel rolling chassis, 24 hours with Di2 has definitely made us appreciate the faultless shifting quality more. I charge the last few hundred meters to the top of the final climb and wring the last few watts out of my wrecked body to see that number 11 on the Di2 display one last time, then hang on for a whooping, hollering, tyre sliding, hacked line plunge into the famous Fort William arena. 

Somehow I’ve bloody made it and as I ride through the tunnel under the downhill track, barely miss the barriers and frenziedly fish out my timing chip to stop my lap time, I’m a rolling-eyed, ruined-leg wreck. Having just clocked my third-fastest lap of the race, it’s been well worth digging deep though, even if Sam’s already over the line and waiting to shake my hand.

Lessons learned

It takes true grit to finish a Scottish 24hr and a fair amount of that grit is taken intravenously
It takes true grit to finish a Scottish 24hr and a fair amount of that grit is taken intravenously

It’d been ages since I’d raced a 24hr event, but Relentless has such an excellent course and atmosphere that I can’t wait to do it again. That said, there are definitely some things I’d change and I recommend you do the same:

1. Make sure any spares are actually useable, so check your C02 cartridges are full and your tubes fit your rims — my valves were only just long enough.

2. Use a bottle cage you can trust. A handful of grams can’t compensate for the lost time and frustrated rage of having to stop and run back up the trail for your bottle.

3. Plus-sized tyres are great for playing and roll well in the rough, but they come with a significant weight penalty which makes it slower in repeated acceleration situations on technical XC courses.

4. Whatever format you choose, tougher tyres might be worth the extra weight if they shrug off punctures that cost you minutes.

5. Tech can be unreliable. We accidentally ripped the lockout hose out of the Lefty and only managed to glue it back together and bleed the system less than an hour before the start. We also ended up with a single-ring set-up after Cannondale’s mechanics couldn't get the front shifter and mech of the Di2 system to play ball before sending the bike.

6. Unique isn’t always user friendly either. The RS-1 and Lefty forks both required specific and rare front wheels that you’re not going to be able to find replacements for in a hurry. The asymmetric Ai rear wheel of the Scalpel is a potential spares issue if you have a problem too.

7. Believe in your ability. 24hr races are an awesome opportunity to find out what you can really do if you really push yourself to the limit. Even after years of racing, that last lap at Relentless was certainly an eye-opener for me and I’ve been enjoying a cardio confidence reset for months since.

8. Pick your team mates on character, not just wattage. We had a brilliant time in the pits with the constant banter of two deliberately closely matched teams of mates and we’re still laughing about it now. A finely honed athlete in a fury is no fun to be with.

Guy Kesteven

Freelance Writer, UK
Guy started filling his brain with cycle stats and steaming up bike shop windows back in 1980. He worked the other side of those windows from '89 while getting a degree in “describing broken things covered in mud" (archaeology). Dug historical holes in the ground through the early '90s, then became a pro bike tester in '97. Guy has ridden thousands of bikes and even more components the world over since then and can remember them all in vivid, haunting detail. Can't remember where the car keys are, though.
  • Discipline: Strict sadomasochist
  • Preferred Terrain: Technical off-piste singletrack and twisted back roads. Up, down, along — so long as it's faster tfhan the last time he did it he's happy.
  • Current Bikes: An ever changing herd of test machines from Tri bikes to fat bikes and everything in between.
  • Dream Bike: His Nicolai Helius AM custom tandem
  • Beer of Choice: Theakston's Old Peculier (not Peculiar)
  • Location: Yorkshire, UK

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