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Considering the things I've learned about two-wheeled contraptions over the years, bikes like this are making sense to me.

I'm surprised it took so long inasmuch as my second life lies within the dark world of off-road motorcycling, where a smaller diameter rear wheel has been employed for decades.

What are the advantages of a mullet mountain bike? What are the drawbacks? First, the advantages...
  • Some folks appreciate shorter chainstays
  • Lower overall rotating weight
  • Rear axle is lower to the ground -- easier to wheelie & manual
  • I can't say for sure but I expect the mullet configuration offers more nimble handling
Disadvantages...
  • I'm thinking...
  • Still thinking...
  • Okay, here's one. Until mullet is fully embraced by mountain bikers everywhere, you'll be considered an outlier.
  • Wait, is that a disadvantage?
I'll bet others will add to either/both lists.

Some would point out that the rider would need to carry two spare tubes in case they suffered total tubeless failure in one wheel or the other. But actually no they wouldn't. Either size tube will work in either wheel. Trust me, I've done this. While not ideal, it works. I'd carry a 29" tube.

At first I resisted the idea of the mullet. Keep it pure. Accepting the mullet is a paradigm shift for many of us. I love 29" wheels because I'm a big guy and I've found that 29" wheels roll over challenging terrain better. But when it comes to rollover, let's be honest -- the front wheel's size is far more important than the rear wheel's size. I don't believe there's a disadvantage to a 27.5" rear wheel.

What to you think?
=sParty
 

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bipedal
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Currently running 29/27.5+ on both my Stumpjumper and Levo. The handling is a bit slower than 27.5 F&R, but the extra roll-over and traction up front are worth it for the trails I frequent. The big wheel smooths out rocks and ledges and it provides increased floatation and improved steering in desert sand. I also have the sense that the smaller rear tire helps it get around corners a bit quicker than a 29 rear might.

The big front tire slacked out the head angle a bit much so on the Stumpy I reduced fork travel from 150 to 140mm, but on the Levo I was able to just switch the flip chip to the high setting.

You might like it Sparty! No haircut required. ;)
 

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I personally think it's the future. In addition to what you listed, a 650b is inherently stiffer, and lighter than an identical 29er. This means less rolling resistance, and less unsprung mass. It wouldn't surprise me to see them in xc eventually.

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The advantage of the reverse mullet is for the bike manufacturer, since it's easier to put a smaller wheel in a long travel application. Saying a smaller rear wheel has an advantage is like saying a smaller front wheel has an advantage, which doesn't make any sense as long as you can fit them in the bike and the bike fits the rider.


It's not as if 17" chainstays are exactly "short," and it becomes pretty questionable that if you want to go fast that truly short chainstays are what you really want. As you start getting really short, like 16.5", the bike becomes a bit of a handful at high speeds when cornering or when braking when not traveling in a straight line.
 

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The advantage of the reverse mullet is for the bike manufacturer, since it's easier to put a smaller wheel in a long travel application. Saying a smaller rear wheel has an advantage is like saying a smaller front wheel has an advantage, which doesn't make any sense as long as you can fit them in the bike and the bike fits the rider.
Except that the front and rear wheels perform different tasks. Sports cars almost always run different sizes, and motorcycles (the closest motorized analogy to MTB) as well. It's a subtle difference, but if there is a competitive advantage to be gained, it should be explored. Will the average rider notice? Probably not.

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Considering the things I've learned about two-wheeled contraptions over the years, bikes like this are making sense to me.

I'm surprised it took so long inasmuch as my second life lies within the dark world of off-road motorcycling, where a smaller diameter rear wheel has been employed for decades.

What are the advantages of a mullet mountain bike? What are the drawbacks? First, the advantages...
  • Some folks appreciate shorter chainstays
  • Lower overall rotating weight
  • Rear axle is lower to the ground -- easier to wheelie & manual
  • I can't say for sure but I expect the mullet configuration offers more nimble handling
Disadvantages...
  • I'm thinking...
  • Still thinking...
  • Okay, here's one. Until mullet is fully embraced by mountain bikers everywhere, you'll be considered an outlier.
  • Wait, is that a disadvantage?
I'll bet others will add to either/both lists.

Some would point out that the rider would need to carry two spare tubes in case they suffered total tubeless failure in one wheel or the other. But actually no they wouldn't. Either size tube will work in either wheel. Trust me, I've done this. While not ideal, it works. I'd carry a 29" tube.

At first I resisted the idea of the mullet. Keep it pure. Accepting the mullet is a paradigm shift for many of us. I love 29" wheels because I'm a big guy and I've found that 29" wheels roll over challenging terrain better. But when it comes to rollover, let's be honest -- the front wheel's size is far more important than the rear wheel's size. I don't believe there's a disadvantage to a 27.5" rear wheel.

What to you think?
=sParty
Me too on the dark world of off-road motorcycling, although much less of it lately,
unfortunately.
But I think if you were to measure the actual diameter of the inflated tires on a dirt bike, you’d find the front(21” rim) to be really close to the rear(18 or 19”) due to the necessity
of a wider, therefore taller, rear tire to handle
horsepower.
You may remember that Honda tried a 23”
front wheel several years ago—didn’t go over well.
 

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Except that the front and rear wheels perform different tasks. Sports cars almost always run different sizes, and motorcycles (the closest motorized analogy to MTB) as well. It's a subtle difference, but if there is a competitive advantage to be gained, it should be explored. Will the average rider notice? Probably not.

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So what's the "competitive advantage?"

Whenever you're moving, you're fighting rolling resistance, so minimizing that is the biggest "competitive advantage" there is. Big wheels also get hung up a little less, have more grip, all subtle differences that the average rider won't notice, but they're there.

I'm not arguing against doing different things, but different isn't better (or worse) by default.
 

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This sounds like armchair quarterback reasoning. sParty, have you ridden a mullet setup? Own one currently?

I love 29" wheels because I'm a big guy and I've found that 29" wheels roll over challenging terrain better. But when it comes to rollover, let's be honest -- the front wheel's size is far more important than the rear wheel's size. I don't believe there's a disadvantage to a 27.5" rear wheel.

=sParty
Disagree, the rear wheel is where most of your body weight is and it's more likely to get hung up on rocks and roots. It's much easier to unweight the front wheel at will.

I think it may (?) have some useful application in enduro racing, but that's about it. Fitting that you use a 165mm enduro bike as an example.

Disadvantages- smaller wheels get hung up on obstacles, this is accentuated in the rear. Smaller wheels roll slower.

Your point about the rear axle being lower is not valid. Chainstays are plenty short and I don't hear anyone complaining they're having trouble getting the front wheel off the ground. Not to mention the BB height and chainstay length are much bigger factors than rear axle height.

It's a fad, and I'm over it.
 

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I have a B+ Nimble 9.

I put a 29” X 2.6 on the front for one ride. I only noticed slight differences. Not enough to get me excited one way or another, but it was only 1 ride.

I may try it again, may not.


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Lighter weight, stronger wheel, less unsprung weight.

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The weight is a marginal difference and it's not as if 29" wheels are overly weak or flexy...they seem to work ok on the UCI DH circuit.

Bike weight is fun to geek out about, but since we're talking about bikes that require a rider to go, the weight differences are trivial at best. Rolling resistance and grip are far more important, and bigger wheels are better for those things.

It's not just a fad, it's an example of cutting corners and covering it up as something else in order to mislead customers. Martin Maes may be able to kick ass on his GT, but there's no reason to believe he wouldn't be even faster on an actual 29'er, he just happens to be good enough to make up the difference.
 

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The weight is a marginal difference and it's not as if 29" wheels are overly weak or flexy...they seem to work ok on the UCI DH circuit.

Bike weight is fun to geek out about, but since we're talking about bikes that require a rider to go, the weight differences are trivial at best. Rolling resistance and grip are far more important, and bigger wheels are better for those things.

It's not just a fad, it's an example of cutting corners and covering it up as something else in order to mislead customers. Martin Maes may be able to kick ass on his GT, but there's no reason to believe he wouldn't be even faster on an actual 29'er, he just happens to be good enough to make up the difference.
Agreed. That's why I said the average rider would never tell the difference. But, incremental gains are still gains. At the highest level of the sport, they need to chase down every possible advantage.

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Mullet owner here. I also own a 29er.

I notice advantages in both. The 29er rolls faster in the open, while the mullet can “dig” up steep techie single track better. Basically I can get the rpms up quicker on the mullet. However, I find myself having work harder keeping up with 29ers on more open terrain.

The 29er is better on the rough rocky trails. As is mentioned above, the larger diameter wheels soak up the bumps better.

This may be more specific to my bikes, but my mullet has a shorter wheel base which I really like (especially when jumping).
 

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My enduro bike is a mullet, though it’s 26” in the back and 27.5” in the front. No downsides whatsoever. With 2.5” Minions at both ends, the “26” rear actually measures 27”, and the front 27.5”. You can barely spot the difference. The front rolls ever so slightly smoother than with a 26” rim, and gets a smidge more traction. HA went from 65.5 degrees to 65 degrees. Worked well enough this year to get 7 KOMs on Strava DH segments.:)
 

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Discussion Starter · #17 ·
This sounds like armchair quarterback reasoning. sParty, have you ridden a mullet setup? Own one currently?
Kinda. I own a Smash and have multiple wheelsets for it, including 27.5x3. I put the 27.5x3 rear wheel in with a 29x2.6 front wheel and rode it around my street but haven't tried it on trails yet.

But that's not what I'm talking about. I'm talking about a bike that's designed & built as a mullet. With the system I have, I just replaced a rear 29 wheel with a 27.5 wheel. Therefore my chainstays could be shorter &/or I could get more travel out of the same frame with the smaller rear wheel. Mine's not purpose built so it's not optimized.

If I bought a mullet bike, I'd want it optimized to exploit the best advantages of each wheel. Meanwhile one of these days I'll try what I've got just to see if it feels better, worse or indifferent. Nothing to lose.
=sParty
 

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This sounds like armchair quarterback reasoning. sParty, have you ridden a mullet setup? Own one currently?



Disagree, the rear wheel is where most of your body weight is and it's more likely to get hung up on rocks and roots. It's much easier to unweight the front wheel at will.

I think it may (?) have some useful application in enduro racing, but that's about it. Fitting that you use a 165mm enduro bike as an example.

Disadvantages- smaller wheels get hung up on obstacles, this is accentuated in the rear. Smaller wheels roll slower.

Your point about the rear axle being lower is not valid. Chainstays are plenty short and I don't hear anyone complaining they're having trouble getting the front wheel off the ground. Not to mention the BB height and chainstay length are much bigger factors than rear axle height.

It's a fad, and I'm over it.
^ I'm with stupid ^

I wouldn't say there are many disadvantages I just don't see much point. There might be an incremental gain for racing but no practical use otherwise and you lose the roll over of a 29er. I unweight the front wheel over anything that would be an obstical so I want the rear to roll over easier if it isn't so big I need to hop it/unweight.

I ride 27.5 because I like how it corners and jumps which is where the fun is at for me. For general riding I'd prefer 29 but it's not all that big of a difference between them. Maybe mullet would give me something in-between both but it's to small of a difference to care. Geometry and tire choice make the biggest difference in bike feel.

Big disadvantage for me is when the rear tire wears out I move front to rear and a new tire goes on the front. With a new front and mildly worn rear it gives a great balance in corners and I'm not wasting a half worn front tire or riding around with a new rear that stays glued to the trail while the front washes out.
 

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I'm talking about a bike that's designed & built as a mullet. With the system I have, I just replaced a rear 29 wheel with a 27.5 wheel. Therefore my chainstays could be shorter &/or I could get more travel out of the same frame with the smaller rear wheel. Mine's not purpose built so it's not optimized.

If I bought a mullet bike, I'd want it optimized to exploit the best advantages of each wheel.
=sParty
Agreed, the bike needs to be designed to have different wheel sizes. I think a lot of people are under the impression they can just change the front or rear wheel and get the same results.
 
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