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Specialized Fuse Expert 6Fattie review

22 Aug 2017

A monster-tyred trail machine that's ideal for high-mileage off-road missions

Cyclist Rating: 

Specialized believes the trail-focused Fuse could see riders abandoning skinnier tyres in favour of this ultra-modern and versatile fat bike design.

Its huge balloon tyres sit on 27.5in diameter rims. However, their enormous volume means their external circumference is almost the same as on larger 29in wheels.

The result is a bike that can roll over everything in its path, providing the sort of grip and comfort previously associated with full-suspension designs.

The frame

The Fuse’s radical diamond chainstay design consists of a unique split-bridge piece behind the chainset that links the bottom bracket to the chainstays.

Its purpose is to accommodate both the Fuse’s massive tyres and broad hub without unduly extending the chainstay length.

With this accomplished, it extends back to meet the uncommonly neat forged dropouts.

These self-contained pieces house the internally mounted brake calliper along with the removable derailleur hanger and thru-axle.

The short, tapered head tube uses concealed bearings, resulting in a very low and clean-looking front end.

Just behind this are the ports for the internally routed cables to activate the dropper post and derailleur, while the rear brake line runs underneath the down tube.

All in all, the Fuse presents itself in an extremely composed and self-contained way, something nicely off set by the loud colour scheme.


SRAM’s GX 10-speed groupset has one less cog than you might hope for, but this isn’t noticeable on the trail, partly due to the relatively small 30-tooth single front chainring.

You might spin out on smooth downhills but will be less likely to run out of gears heading upwards.

The shifter and derailleur combine to shunt the chain with an authoritative clunk, which is welcome when the going gets rough.

Specialized’s own Stout brand crankset sports a large diameter PF30 alloy spindle, and sits in a chunky bottom bracket shell.

With enough power to easily stop the bike with a single finger, the SRAM DB3 brakes still lag slightly behind Shimano’s in terms of all-out power.

Finishing kit

Dropper posts are an MTB innovation that allow you to lower your saddle height on the fly, giving you more room to manoeuvre when descending.

The Fuse’s unbranded dropper post provides 120mm of up and down shift to the saddle, operated by a switch on the bars.

For all but the tallest riders, this will accommodate maximum pedalling efficiency at one end, while still allowing the user to move the saddle out of the way when tackling steep, technical descents.

The extremely short stem and wide, flat bars are what you’d hope to see on a bike with such a fun disposition.

Contact points are very much a personal choice. Thin and agreeably tacky, we liked the grips along with the thinly padded saddle.


Specialized’s huge Ground Control tyres are supported by equally broad WTB Scraper double-wall rims which lend their massive width a gently rounded profile.

This helps to allow the rider to lean the bike over at almost unimaginable angles without sliding.

Both are ready to go tubeless which, given the hefty weight of a three-inch wide inner tube, should also speed them up.

However, although these are good tyres, we didn’t find quite as much grip as we were hoping for.

Rolling on a sealed cartridge front hub and a more basic loose-bearing rear, a minimalist 24 and 28 spokes respectively mean the wheels ditch weight without noticeably giving away any stiffness.

On the trail

On-road, the tyres are a drag. However, the second you’re away from the tarmac the transformation is remarkable.

The ability to roll over everything is a revelation. And it’s not just on rough terrain that the bike feels efficient – once up to speed, the baggy tyres don’t feel like a hindrance.

Rubber aside, the bike performs like a modern trail hardtail, with the handling and location of the contact points all feeling familiar.

At a full three inches wide, the tyres don’t soft-pedal the Fuse’s credentials as an out-and-out fatty.

Their huge size provides equally huge grip and cushioning. Run at far lower pressure than seems advisable, initially the amount of squish is a litt le disconcerting, although the grip and comfort are immense.

The contact patches smother the ground, allowing you to lean the bike over at ridiculously acute angles through corners, while their volume eats up bumps and keeps the bike in contact with the ground.

Thankfully, they also confounded our expectations that such enormous tyres would be slow to accelerate or laborious to drive forward.

The result is a ride that’s more akin to piloting a full-suspension bike than a hardtail.

Once we’d grown accustomed to the way the extra volume affects the handling, the geometry helped put us at ease.

It’s pretty much perfect for general trail duties, with a slight bias towards ragging around, but still with the ability to cover ground efficiently.

Ideal travel

The Manitou Magnum Comp fork offers 120mm of travel, which feels spot on – enough to soak up most bumps without feeling mushy, and does so in a controlled way.

The black coloured stanchions look cool and reduce friction, while its backward arch design is stiff , allowing for purposeful steering.

At 740mm wide, the bars provide enough leverage to make the most of the robust fork.

With the frame carrying most of its length in the top tube, the stubby stem keeps steering direct and the rider’s weight centred.

Braking is fine – you’ll need to find a long descent before you start hankering for more stopping power.


Frame: Designed for huge tyres but still very neat looking. 9/10
Components: 1x10 groupset is great for most trail-riding duties. 8/10 
Wheels: Huge tyres give the bike the feel of full suspension. 8/10 
The Ride: Progress is fast and smooth over all terrain. 8/10


The Specialized Fuse Expert 6Fattie is a monster-tyred trail machine that soaks up the bumps and is ideal for high-mileage off-road missions. 


Fork travel: 120mm claimed/120mm measured
Seat tube: 434mm/438mm
Top tube: 609mm/600mm
Reach: 420mm/420mm
Stack: 619mm/620mm
Head tube: 100mm/100mm
Head angle: 67 deg/67.5 deg
Seat angle: 73 deg/72.5 deg
Chainstay: 430mm/430mm
Wheelbase: 1140mm/1130mm
BB drop: 58mm/58mm


Specialized Fuse Expert 6Fattie
Frame M4 Premium Aluminium forged disc mount, 148mm thru-axle dropouts, Manitou Magnum Comp forks w/ 120mm travel
Groupset Shimano GX, 10-speed
Brakes SRAM DB3 Trail
Chainset Stout XC Pro, PF30, 30t
Cassette Custom Sunrace, 10-speed, 11-40
Bars Specialized Stout XC, flat bar
Stem Specialized XC, 3D forged alloy
Seatpost Tranz X, Dropper Post, 120mm travel
Wheels WTB Scraper i45 double-wall, 45mm wide, tubeless compatible
Saddle Body Geometry Henge Comp

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