Mucky Nutz Butt Fender

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I have something of a love/hate relationship when dealing with the elements.

Waterproof shorts have made a significant difference to my riding enjoyment when ‘weather bombs’, the current winter weather nom de plume, have loomed large on the horizon but when it comes to keeping the cack off my crack, mudguards are a necessary evil.


While undeniably functional, traditional mudguards are inevitably a compromise when riding off road. After many years of riding with rear mudguards that clamp on to the seat post, while my buhoochie (that’s Scottish for bottom, for our more genteel readers) was reasonably dry and clear of clart, the ever-present tyre on mudguard bwaaaaaaarrrrrp sound that accompanied the compression of my rear shock and the difficulty that came when trying to mount a rear light on a dropper post when there was already a mudguard attached to it, can only be described as a pain in the arse.

Coupled with the fact that most rear mudguards look gopping on a full suspension frame, I was ready to ditch my old rear mudguard altogether. Fortunately, I suspect that I’m not the only one fed up with such compromises, given the entry of the Mucky Nutz Butt fender into the market.


A family-run business, Mucky Nutz started production of the almost ubiquitous Bender Fender in 2009 and is now arguably one of the major players in keeping your nutz and other parts of your anatomy free from being coated in mud and slop. With the Butt Fender, it’s created a product which – in theory at least – addresses the issues that I have with traditional rear mudguards, as listed above.

The design of the Butt Fender is extremely simple. Constructed from a single piece of flexible moulded plastic, it is basically a flap that attaches to underneath the back of your saddle via protruding tabs on either side of it. That’s it. No Velcro. No annoying little bolts to faff about with and nothing to over-tighten, leading to the inevitable ping of cracking plastic and a frantic search for the superglue. Along the length of mudguard, there are pre-moulded bend points which when folded create a stiffer structure and help to keep the mudguard firmly attached to the saddle.


Fitting the mudguard took only a matter of seconds. While there are easy to follow instructions on the Mucky Nutz website, fitting the mudguard is pretty intuitive. Despite being only a simple interference fit, the Butt Fender has remained rock solid throughout the period of the test, only moving to one side when my bike was leant against a wall. I fitted it to a WTB saddle although it is worth checking your saddle before purchase to ensure that it doesn’t have, as Mucky Nutz put it so eloquently on their website, any daft bits at the back sticking down, such as moulded reflective panels, which can interfere with the Butt Fender.

Extending only 20cm from the end of my saddle, I was initially sceptical of how much protection the Butt Fender would afford but I needn’t have worried. It works. Bloody well too! For something that weighs only a few grams, it has kept my backside clart free with no soggy bottom to speak of. The annoying bwaaaarrp of tyre on mudguard is now a dim and distant memory and there is now space on my seatpost to fit a back light that can actually be seen rather than being obscured.


While I did experience some spray further up my back and on the back of my thighs, it wasn’t that much worse than what I have experienced with traditional bolt-on mudguards. The design means that the clamp for my saddle rails has remained free of dirt, which when it comes to tightening up a loose saddle can be the difference between a five-second job and ages spent fiddling about to clean out hex bolts from accumulated grime. Although the Butt Fender is attached to the underside of the saddle rails, there is still enough space to allow a bolt-on saddle bag to be attached; I’m currently running it with a Lezyne Pod Caddy with no issues.


With the Butt Fender, Mucky Nutz has engineered a solution to the problems posed by traditional mudguards that is simpler, cheaper, substantially lighter but most importantly almost as effective as the competition. Having used it on some frankly filthy rides, I occasionally wonder why the hell nobody else came up with the idea before now. Its discrete looks don’t upset the aesthetic of the bike and the Butt Fender neatly avoids the compromises of traditional designs.


I can’t believe that I am waxing lyrical about what is ostensibly a cheap piece of moulded plastic but then some of the greatest engineering designs are also the simplest. Buy one. Your bahoochie will thank you.

Review Info

Brand:Mucky Nutz
Product:Butt Fender
Tested:by CJ for two months of muddy rides

Comments (0)

    Love the design, but I always end up ripping mine off on really steep technical descents.

    When used with a dropper post on an FS bike, it catches on the wheel on big hits

    Surely it gets in the way when you get off the back of the saddle on steep techy descents? I could see this fouling shorts when trying to get back on the saddle after drops etc. Admittedly this won’t affect all riders… but for me the mudplugger seat stay mounted guard is the ultimate fit and forget solution, mounts nicely just above the tyre without fouling the seatpost, gives comprehensive protection. Don’t fit all FS frames but provided it does fit, it can’t be beat.

    Had a similar thing from a Swedish company. Afraid it snapped after 2 rides. Made my own out of some waste plastic.

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