“Mullet” Bikes….What’s it all about?

What the heck is a “Mullet” bike? It’s a party in the back, business in the front, of course. What this means for a mountain bike is a 27.5″ rear wheel with a 29″ front. The “Mullet” moniker stuck because 27.5″ wheels are regarded as more nimble and playful, and 29″ wheels are regarded as faster, but perhaps less fun according to some riders.

Sorry, that is getting close to entering a wheel size debate here. Our stance? 29″ wheeled bikes are fast, and fun. 27.5″ wheeled bikes? Also very fun, and fast. Neither is going away, and both work really well. We have been fortunate to ride a lot of bikes over the last decade in both wheel sizes. 29″ wheeled bikes drastically improved recently, and dating back to about 2017 began to adopt geometry other than strictly for XC riding. This is when 29ers became “fun” and not just all about speed and “business.” The Kona Process 111 was the first to push the boundaries on geometry a 29er could have, with a “long, low, and slack” shape, and a attitude ready to party.  It was said to be the first 29er that “didn’t feel like a 29er.” The new 2020 Kona Process 134 now takes this bikes place in the lineup. Over the last couple years, some of our staff fully switched to riding 29ers as more brands followed the trend and made “shreddy” enduro and trail 29er bikes with more travel. However hopping back on 27.5″ wheeled bikes more recently reminded us how they are not slow, and are really fun.

Then something new popped up at the end of 2018. Union Cycliste International (UCI), the governing body of all cycling racing announced the removal of a rule that had long been in place regarding wheel size on bikes used in races. They would now allow MIXED wheel sizes, meaning the front and rear wheel could be of different sizes, whereas before they were required to be identical front and rear. All of a sudden, a handful of downhill and enduro racers started racing with 29″ front wheels, and 27.5″ rear wheels, and winning races or getting on podiums on these bikes. The main reason appeared to be shorter riders could get out behind the bike in an aggressive downhill position with less fear of hitting their bottom on the big 29″ rear wheel. More and more riders below 6 feet tall started adopting this “mullet” configuration throughout the summer of 2019, and boom: it was a trend, and it was winning.  The benefits are better traction and rollover from the front end, with the rear remaining nimble quick to accelerate, and out of the way on steeps and jumps. Martin Maes from the Enduro World series, Laurie Greenland, Danny Hart, Troy Brosnan and others have all raced aboard “Mullet” bikes during the 2019 race season.

Is this the bike industry forcing another new standard down our throats? Not necessarily. The UCI rule change is the biggest reason, alongside the rapid improvement in technology and components that pro racers have access to.

Can you just slap a 29er wheel and fork on the front of your bike and call it good? Not necessarily. Think about how it would change the geometry of your bike: the front end would be raised compared to when the 27.5 wheel and fork are installed. This slackens the head tube angle, AND the seat tube angle, and raises the bottom bracket height. A more slack seat tube angle is ok, but higher BB and slackened seat tube do not help the bikes performance, and cause the bike to feel a little funny. Trust us, we tried with a Marin Hawk Hill. It rode ok, and showed us there are some sweet benefits to the Mullet configuration, but it wasn’t perfect, because the bike was not designed to accomodate these changes.

So many pros are getting away with it because they have full time mechanics setting their bikes up each race, and they have access to all kinds of expensive bits and goodies from component manufacturers who want their product on the race scene.  Mostly we’re talking about components that allow changes to geometry, to correct for raising the front end with a 29″ wheel. Eccentric bottom brackets to again lower the bb height, and angle-set headsets to correct for the 29″ changes as well. This allows the pros to have a bike with more or less the correct geometry, but a mullet configuration.  Also, they are pros, and are very good at riding bikes and can compensate for the changes to their bikes geometry. More downhill riders are adopting this than enduro riders, and this is because geometry changes from adding a 29″ wheel and fork to a bike originally designed as a 27.5 bike are more noticeable while climbing than descending, and most notably while seated and pedalling.  

This is why we say the Mullet Marin Hawk Hill (or “Hawk Zone”) we put together this summer wasn’t perfect, especially while seated and pedalling.  It had a slacker head tube, seat tube, and raised BB all at once. It felt a little hard to push the front wheel along, a little wobbly, and did not have a good seat tube angle for pedalling.  However, on rolling terrain, it was sweet. It carried speed like a 29er, but was easier to turn the pedals and accelerate with the smaller wheel, and also felt more nimble. There was also ample butt to rear tire clearance when getting rowdy.

So how do we make it perfect?  Well Guerilla Gravity has a solution.  This brand encourages tinkering with your bike set up, and will sell their frames to you configured a number of different ways, including Mullet configurations.  Their made in the USA carbon frame has a really cool reach adjust feature in the headtube, allowing for riders to change the reach of their bike by 10mm easily. These reach adjust headset cups also make use of a 14mm stack spacer below the headtube above the fork crown on their 27.5” wheeled bikes, and a zero stack spacer on 29” wheeled bikes.  This screams “Mullet,” because if you take the Shred Dogg or Megatrail, swap the spacer for the zero stack one, and put a 29” wheel and fork on, you have not drastically raised the front end. Play with fork travel, handlebar height, and ride on!

The “Secret Menu” on Guerilla Gravity’s website offers two mullet configurations: the Trail Dogg (Shred Dogg/Trail Pistol combo), and the MegaSmash (Megatrail/Smash Combo).  We put together a Trail Dogg recently and took it on the Ferrins trail in Jackson, and were really impressed. It was the best of both worlds with the small rear wheel and big front wheel: rolled fast, kept momentum, climbed well, rolled over obstacles, cornered well, and thanks to changing the spacer under the headtubt to the zero stack spacer from the Trail Pistol 29er, the geometry of the bike was still in the sweet spot.  Some measurements we took on our Size 2 (medium) Trail Dogg in the 130mm “Trail” rear travel mode, with a 130mm 29er fork were: 342mm BB height, 605mm stack height, 64 degree head tube angle, and most importantly for a trail bike: 76 degree effective seat tube angle. These numbers are on par with most new trail bikes out there, and only 4-5mm higher in BB height and stack than the stock “Shred Dogg” 27.5 front and rear configuration, so not a huge change.

So, are Mullet bikes replacing 29ers and/or 27.5 bikes?  No. Are they a cool concept, and fun to ride? Yes, when frame design allows.  Will everyone prefer them? Maybe not. But will you see some Wheel Wranglers staff with personal Mullet bikes from Guerilla Gravity next year?  Most definitely, and we expect to see other brands jump on board too. The key is just to figure out a way to maintain “normal” geometry.

We will even rent you a Trail Dogg mullet bike if you’re interested.  Book now and add it as an extra when you book a Shred Dogg for a $10 setup fee. Trail Pistol, Shred Dogg, Trail Dogg, and 2020 Kona Process 134s available now and all fall 2019!

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