MIXED WHEEL MANIA! – FIVE BIKES TESTED TO SEE IF MIXED WHEELS REALLY BRING THE PARTY
What benefits do mixed wheels really offer out on the trail?
Mullet bikes have been an interesting trend to follow in recent years. The mixed-wheel-size setup has become more popular among certain manufacturers and is the preferred setup for several racers on both the enduro and downhill circuits. Being that this is a potentially simple conversion for many riders, it’s also something we see riders experimenting with on their own, sometimes as a way to adjust geometry to suit the needs of the trail, but often just to reap the benefits of the smaller, lighter rear wheel. Is the trend here to stay? Is it something you should try on your own bike? Generally speaking, we have found that most bikes not designed for mixed-wheel conversions do not work well. There is often—but not always—a detrimental compromise to some aspect of the bike’s geometry. We picked a few bikes made for the conversion and even one that was not, just to see what the hype is all about and what differences it made out on the trail.
A BIT OF MULLET HISTORY
Mixed-wheel size bikes likely go back to the beginning of cycling itself, but the modern mountain bike mixed-wheel bike predates even the mainstream adoption of 29er wheels. Cannondale offered the smaller sizes of its SM700 with 26-inch front and 24-inch rear wheels in 1988 then Specialized would follow years later with its Big Hit model. This setup was popular for freeride bikes, as they were thought to be particularly stout and strong for hucking. Trek also toyed with the concept with their 69er single-speed, a bike dreamt up by legendary rider and racer Travis Brown. The innovative concept combined a 26er rear wheel with a 29er front. More recently we’ve tested mixed-wheel bikes from Foes Fabrication. Their Mixer bikes have been offering this concept since 2016. When we tested that first Foes, we concluded, “The chainstays are slightly longer, and the taller front end takes some time to get used to. That said, though, the handling is supremely confidence-inspiring.” With that proof of concept in mind, we set out to see if one of our favorite test bikes from last year could benefit from a Mullet makeover.
SPECIALIZED STUMPJUMPER EVO ELITE ALLOY
We reviewed this bike here. It sits squarely in the trail bike category, with enough travel to ride tough terrain and still feel efficient enough to climb back to the top under its own power. We chose the EVO for this experiment because Specialized makes it particularly easy to do. They offer an aftermarket shock link that corrects the geometry for the smaller wheel. The aluminum Mullet link sells for $79 and is available direct from the Specialized website. It comes with bearings installed and is ready to go; all you need is a 27.5 wheel and tire to complete the package. Installation takes about 15–20 minutes for an experienced mechanic and is likely not too technical for even a relatively new home mechanic to handle.
This Stumpjumper EVO Alloy has geometry that’s on the aggressive side for the trail category with a 64.5-degree head angle, 475mm reach (S4 size) and 76.9-degree seat angle in its standard settings. With its chainstay-mounted flip chip and optional head cup, the EVO has six completely different geometry options available to the rider in minutes to suit just about any type of riding preference. Specialized makes this conversion ultra-easy with an interactive geometry finder on its website that allows you to see the geometry changes with and without the mullet setup.
The Stumpjumper uses a conventional suspension linkage with a combination of aluminum bolts and washers holding it all together. The procedure only requires Allen wrenches to perform. Simply remove the old one, swap over the spacers, being sure to orient them the same way they came out, and torque everything down to spec. Always take care when working with the linkage bolts of any suspension bike. They are often made from lightweight materials that can be easily damaged by over tightening. They are also often expensive to replace and hard to find. You can usually find torque spec on the manufacturer’s website.
With our initial setup complete, we noticed the bike felt altered, with a slightly more rearward weight bias, and slightly more sag in the rear shock. We added 10 psi to compensate, and hit the trails with roughly 20-percent sag in front, and 25-percent sag in the rear. With the slight rearward bias, the climbing position is slightly changed, although not very advantageously. The slightly smaller rear wheel still hooks up well. The Stumpy EVO is no slouch climber, but it’s no lightweight, either. The smaller rear wheel allows you to accelerate up and over things slightly quicker.
Cornering is where you’ll notice a big difference at first. The mullet conversion makes a change to the balance point and means you feel like you have more bike in front of you than you did before. It also feels like the rear wheel is tucked underneath the seat more, which gives a quicker, more responsive cornering feel. With the mismatched wheel sizes, though, it can feel like the front end can’t quite keep up with the speed of the rear in some instances. At a minimum, it will require some time to get used to the changed handling.
The 27.5-inch wheel rolls over things relatively well still. However, the 29er version of this bike feels like it will plow through things easier in general. The main advantage of this mullet setup came with an increase in what we’d describe as “flickability” down the trail. With the Mullet link-corrected geometry, there’s no worry about the geometry being “choppered out,” as the smaller rear wheel is accounted for. The bike becomes more quick-feeling, and looks for the playful lines on the trail more easily.
The rear suspension felt like it tended to use travel more quickly with the Mullet link compared to the stock. Riders who feel like they blow through travel with this new setup will need to add volume spacers to their shock to help it resist bottoming better.
It seems much of the real payoff is felt while jumping on this bike. The EVO went from mild-mannered trail bike to “searching for anything to jump off” mode. With the rear end tucked underneath the seat more, the rear end tends to come off the ground more easily. This is not to say that the mullet upgrade will magically make you a better jumper; it won’t. Rather, it gives the feeling that the rear wheel just lifts off the ground more often than when it was a 29er back there. This trait slightly reduced the stability of the bike on descents we plowed through before, but we found ourselves flicking to different lines with this setup anyways. The only downside to this setup when jumping came when we landed hard, which exaggerated the shock’s tendency to blow through its travel. Riders looking to utilize the Mullet link setup for days in the bike park should take note.
The Mullet link gave our EVO a noticeably different personality, at least from the rear shock back. With the geometry corrected, the long front end we came to know and love for its stability and rock-plowing ability remained, but with a more lively rear end that could pop off things more easily. We would go so far as to call this setup somewhat “unbalanced,” but in a somewhat positive way. While the setup took some getting used to, it had real benefits for making the bike more jumpable and playful feeling on the trail. While we’d still prefer the stock 29er setup for most days, the Mullet link setup certainly has its place. While the new setup has some drawbacks for overall balance and stability, riders looking to “bike-parkify” their EVO may have found the secret ingredient.
KONA PROCESS X
MBA assistant editor JJ Squires recently talked about his Process X in “Writers’ Rides”. In that article, he wrote about how he’s ridden his Process X in mullet form primarily throughout the bike’s life and has only recently switched back to a 29-inch rear wheel. The Process X is specifically designed to switch between a 29- and 27.5-inch rear wheel with a flip chip on the seatstays. They’re even labeled by wheel size! This allows a seamless change between the different wheels without affecting the geometry of the bike at all, or that’s the idea. As a result, he didn’t have to change anything to feel comfortable.
The reason for riding a 27.5-inch rear wheel so much this past year was because he rode so much bike park in New Mexico. He found the mullet setup to be more comfortable on jumps, specifically when trying to whip and enjoyed the way he could toss the bike into corners more quickly. He, being a slightly shorter man at 5-foot-10, also enjoyed the advantage of a smaller wheel on steep terrain as the tire wouldn’t bite his butt as often. The disadvantage of the smaller rear wheel was on mellower XC trails or big climbing days. The efficiency and rollover of the 27.5-inch wheel compared to the 29-inch wheel was much lower, which brought more fatigue on bigger days in the saddle.
The main advantage of the mullet setup on the Process X comes when jumping or riding down steep tight trails. The mullet setup is not necessarily faster, but it makes it more fun, and that’s the reason we ride, isn’t it?
ROCKY MOUNTAIN ALTITUDE POWERPLAY
This bike is Rocky Mountain’s enduro-oriented electric-assist model and we reviewed it here. Rocky Mountain released an MX mount that alters the front shock mounting location to raise the back of the bike and compensate for the height lost with the smaller wheel. This aluminum mount simply bolts onto the Altitude and Altitude Powerplay models and costs $136. The link does lower shock-rate progression from 40.3 to 36.1 percent on the Altitude and from 45.5 to 43.4 percent on the Altitude Powerplay. According to Rocky Mountain, this mount will increase travel while also lowering the rate curve so you might have to increase shock pressure or go up in spring rate to achieve proper sag and suspension feel. It’s also worth noting that you can only use positions one through five on the Altitude’s Ride 9 chip positions due to seatstay brace and seat tube interference constraints.
Our first mixed-wheel MX Link swap took place at Mammoth Mountain’s bike park after a few laps in 29er mode to get acquainted with the trails. The shock mount took about 10 minutes and is a simple bolt-on affair. We kept it in the exact same position—1 on the Ride 4 adjustment, the slackest setting. We did have to add air to the shock to achieve proper sag.
Out on the trail the bike felt identical in terms of ride height and general front-end steering response, but there was a whole new feel to the bike. Even though the wheelbase is almost identical, the bike suddenly felt much shorter overall but particularly in the rear end. It snapped through Mammoth’s bermed corners easier and faster than with the 29-inch wheel. Rear-wheel traction also seemed to be enhanced and easier to predict. The front end feels lighter, too, and easier to loft over rocks and ledges. And while jumping the bike, it seems a bit more flick-able and easier to whip the back end around than before.
The only place that the mullet setup seemed to suffer was in the chunky rock gardens where the rear wheel had a tendency to hang in holes and square edges more than before. On the flip side, the bike felt more confident while navigating the steep rock slabs on Velociraptor, a pretty steep and gnarly DH trail. It was easier to stay in what felt like the bike’s sweet spot balance-wise in the tech. Overall, we preferred the mixed-wheel setup in the bike park.
Back on home soil, that same setup worked equally well. We were climbing more with the lack of lift access; there was little to no downside there. It did reveal what is perhaps the biggest drawback on this bike with going mullet—a reduction in top assist speed of one mile per hour. Since the bike’s speed sensors are on the rear wheel, Rocky Mountain could have allowed its dealers to reprogram the new wheel size into the system but feared riders abusing the adjustment to squeeze more speed out of the 29er setup. According to Rocky Mountain, allowing its system to be hacked in this manner opens them to a fine of up to $30,000 per bike sold in the EU. The rider, shop and distributor are also each liable for $30,000 per bike.
While it is just one mile per hour, we noticed it enough to swap back to 29 inches for longer, faster rides. Since it is so easy to swap, we go mullet for self-shuttle DH trail laps and general park riding.
GIANT TRANCE X
Giant’s Trance X is the only bike in this group test that starts as a 27.5-inch bike and is not officially convertible. Our long term review can be found here. In this case, we simply swapped out the 160mm-travel Fox 36 fork and 27.5-inch front wheel for a 160mm-travel Marzocchi Z1 coil fork and 29-inch front wheel. We chose this fork for a few reasons: the first was its ultra-supple coil spring, but the other and more important feature is the ability to internally adjust travel in 10mm increments. Since the Trance X has flip chips in the shock’s linkage, we can compensate at the rear end as well.
To start, we did not adjust the fork’s 160mm travel. We put the bike’s flip chips in the high setting and rode. The feeling was immediately different. The bike’s stance felt similar from an overall balance perspective but the bottom bracket felt a touch higher. This bike is already pretty low so this was not detrimental to overall handling. The front end is a bit slacker feeling with more wheel flop than before, likely due to the change in trail that comes with the larger-diameter wheel. Steering response became way slower, but stability and predictability are much higher in return. Places that made the bike feel nervous, like bombing through rock gardens at speed, were replaced with far more confidence. Even though we went down in width from a 27.5 x 2.6-inch Maxxis Assegai to a 29 x 2.5-inch version of the same tire, traction seemed better, and it tracks through soft surfaces more predictably, too.
On the flip side, some of us missed the flickable, playful nature of the 27.5-inch front end. We could easily cut tight inside lines with the smaller wheel where the larger one forced us wider. Acceleration seemed slightly slower with the bigger front wheel, too. Later in testing, in an effort to lower the bike, we put the chips back in the low setting and backed the fork’s spring preload all the way out. Even though the bike became slacker than ever, it just worked and worked quite well. The preload trick scrapped our plans to internally lower the fork.
In the end, the mixed-wheel Trance X is a different bike than in standard form, and it quickly became a staff favorite. Would we say it’s better? Better at going fast, yes. More fun and playful? No, it’s a trade-off, but the resulting mixed-wheel package is good enough that some wrecking crew members think Giant should have made this bike in Mullet form in the first place.
VITUS ESCARPE 29 AMP
This bike is the first full-carbon bike in the Vitus’ lineup and we reviewed it here. The Escarpe 29 AMP comes with 29-inch wheels front and back, and though Vitus doesn’t specifically mention mullet compatibility on their website, we were told it is an option with the flip chip flipped into the high mode. All we did to this bike to make it a mullet was flip the chip into the high mode and swap the components to a 27.5-inch rear wheel. With that done, there wasn’t much more to do to make it feel comfortable.
The Escarpe is already a bike that feels light on its feet; even as a 29er the handling is sharp. Once we threw on the 27.5-inch wheel, the handling got even sharper. Tight corners were sought after and welcomed at full speed, and throwing it sideways on a jump was second nature. We can’t go without mentioning the ease of popping into a manual or wheelie either. With that said, our weight was shifted rearward ever so slightly, specifically noticeable on the flatter sections or when standing up to pedal. We could’ve combated this by lowering the stem, but we didn’t because we were having so much fun playing off the back end.
All who rode the mullet version of this bike began secretly scheming how they might add it to their own garage, but it’s not without its faults. The 27.5-inch rear wheel enhanced the descents but was of no help on the climbs. Not to say it was a hindrance on most climbs, but we just felt slower climbing long fire roads. Tech climbing remained about the same with no traction lost with the smaller rear wheel.