We all like freedom of choice, right? Whether it’s the little things in life, like a latte instead of cappuccino, or the big things like who gets to run the country. And that extends to bike geometry too. Sure there are bikes with zero adjustment that are great. But why not build in the same degree of adjustability that most brands use when developing a bike into the final product? Well, that’s exactly what the Specialized Stumpjumper Evo Elite Alloy and Trek Fuel EX 9.7 XT Gen 6 both offer.

Specialized Stumpy Evo Vs Trek Fuel EX

And it’s not just the degree of adjustability that makes this such a good head to head test. Both bikes are 29ers that are designed for aggressive trail riding, both are from the biggest brands in the bike business and both are discounted right now, which makes them really good value if you’re looking to buy one of the best mountain bikes. The Trek Fuel EX 9.7 XT Gen 6 is £4,175 and the Specialized Stumpjumper Evo Elite Alloy is £4,399.

Geometry adjustments

The Specialized Stumpjumper Evo Elite Alloy has six different baseline geometric combinations. There’s the adjustable head angle with three settings, that uses a second offset top bearing race that simply drops into the head tube. One direction for +1.25º, flip it round for -1.25º. The frame also has flip-chips in the chainstay pivots that simultaneously adjust the chainstay length and BB height, so you can change the weight distribution of the bike too.  You have long and low, or short and high, where the chainstay length changes by 5mm.

A second upper headset insert with the Stumpy Evo for adjusting the head angle by +/- 1.25º

Not to be out done, the new Trek Fuel EX 9.7 XT Gen 6 also has adjustable headset cups. But it requires a little more work than the Specialized as you have to knock the standard cups out and press in the +/-1º offset cups, which are sold separately. So not really a trail side adjustment then. But that’s not the only way to fine tune the head angle and ride quality of the Fuel EX. Mino link flip chips in the rocker link also adjust the head angle by 0.5º and change  the BB height by 8mm. So again, you have six unique geometry configurations. On paper it’s a draw, but factor in the Specialized’s more user-friendly head angle adjustment, and the ability to play with weight distribution, and it’s round one to the Stumpy Evo. 

Mino Links at the seatstay/rocker link junction of the Fuel EX offer trailside geometry adjustment

Geometry side-by-side

To bring you the the most accurate geometry, we measured the bikes in our workshop, rather than simply listing the manufacturers’ claimed geometry. Both bikes are in the stock settings so the Trek has the Mino Link in the low position with the standard headset cups. The Specialized also has the zero offset headset insert fitted, with the flip chips in the chainstays in short/high position. Both bikes were measured with our Maxxis control tyres fitted, which keeps the bottom bracket height comparable.

Frame construction and weight

While both bikes have similar degrees of adjustment, they use different frame materials. The Trek Fuel EX at our chosen price point is a full carbon frame construction, including the rocker link, and the complete bike weighs 15.52kg (34.22lb). At this level the Specialized frame is a full aluminium construction, and the weight of the bike creeps up to 15.99kg (35.25lb).

Sharp lines of the full carbon frame make the Trek Fuel EX 9.7 Gen 6 eye catching

Suspension design and travel

The Stumpy Evo uses Specialized’s signature four-bar design and a Fox Float X Factory shock to deliver 150mm rear travel. Paired to the frame is a four-way adjustable 160mm Fox 36 Factory fork. That’s 10mm more travel front and rear than the Trek Fuel EX. The Fuel EX also uses Fox suspension components, but you get a less sophisticated 36 Rhythm fork and Performance level Float X shock. That’s the price you play for having a lighter carbon frame, right?

Specialized takes a unique approach by up-speccing the alloy Stumpy Evo frame with Fox Factory suspension

Integrated down tube storage

If you want to ride without a pack, but don’t want to risk getting stranded in the back of beyond without any tools or food, then you’ll be pleased to know that both bikes get integrated down tube storage. Specialized’s SWAT door is substantially bigger than Trek’s BITS internal storage though, which makes it that much easier to fish a snack, or tool, out of the frame.

The original and still the best: Specialized’s SWAT door in the down tube lets you carry essentials in the bike, rather than on your back

Drivetrain: SRAM Vs Shimano

There are differences in the drivetrains too. Specialized is firmly in the SRAM camp with a 12-speed GX Eagle transmission. Where the shifter pod and OneUp dropper remote integrate perfectly with the Matchmaker camps on the SRAM Code RS brakes. 

SRAM’s GX mechanical drivetrain is still the benchmark for shifting performance

Trek has gone with a Shimano drivetrain. In this instance a headline grabbing XT derailleur and 12-speed SLX shifter and 10-51t cassette. Both drivetrains are mechanical, which helps stop the price of the bikes getting out of hand. And while we could not get the Shimano shifter to marry perfectly with the SRAM DB8 brake lever clamp, the brakes on the Fuel EX are actually first rate. 

We’ve been super impressed by the light lever action and ample stopping power of the SRAM DB8 4-piston brakes

Performance

In terms of the suspension response, the Trek felt balanced front and rear, as both felt open and free. But that meant rapid changes in the pitch of the terrain or sudden direction changes caused the bike to seesaw a little too much. Which is why we ended up running the fork and shock harder than ideal. With more adjustable dampers, say Fox Performance Elite, we could have wound on low-speed compression damping and restored stability that way.  The only way you going to get that on the Fuel EX though, is by spending more money.  Which is why we’d like to see Trek offer a higher specced alloy bike at the same price, even if it meant that would be a little heavier.

The Trek Fuel Ex 9.7 Gen 6 takes flight. But we’d like to see a better fork, or one with more damping adjustment, to really take it to the next level

For maximum performance and tunability then, you need adjustable geometry and adjustable damping. And the Specialized Stumpy Evo Elite Alloy has both in spades. And even if you’re not into tweaking settings, geometry and weight distribution, the baseline settings on the Stumpy Evo will get you 90% of the way there. For riders looking for that final 10% though, the Stumpy Evo Alloy won’t disappoint. Stretch it out for maximum speed and composure, or tighten up the angles and proportions to make it more playful and nimble, the choice is yours. Factor in all the adjustability of the Fox Factory suspension and it’s a tweaker’s paradise. Never before has this level of performance and adjustability been available at such a competitive price. Which makes the Specialized Stumpy Evo Elite Alloy the bike of choice for the discerning trail rider that wants maximum performance. 

The Specialized Stumpy Evo Alloy Elite is the ultimate all-rounder. There’s nothing this bike can’t do well

Conclusion

Having adjustable geometry on a trail bike is really useful. In fact, we’d argue that it’s of most use on a trail bike, simply because trail riding means different things to different people. Love techy, rocky climbs and need lots of pedal clearance? Stick the BB height adjustment in the high position and keep those cranks spinning. Live for the descents and suffer fire road climbs just to get to the fun stuff? You’ll probably want the slackest head tube insert to stretch out the front centre and slacken the head angle for maximum stability at speed. 

With adjustable geometry and adjustable suspension components, the Specialized Stumpy Evo Alloy Elite is the Swiss Army knife of trail bikes

The pricing and intended use are both of these bikes are really close, but there are distinct differences in approach. Trek has splashed out on a lighter full carbon frame, and has had to fit Fox Performance level suspension to bring the Fuel EX in on budget. Specialized has done the opposite. Opting instead for an alloy frame and then ploughing the associated cost savings straight back into Fox Factory level suspension components, which in this instance, has clearly paid off.