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Like an Ass Saver or a butchered water bottle equivalent, the Mucky Nutz Road Butt Fender isn't a a substitute for a full-length mudguard. It's there to stop you getting a soggy chamois. In that respect, it both lives up to its billing and exceeded my expectations.
The Road Butt Fender is a 15g bit of plastic that fits to the saddle rails without tools. The end loops hook under the rails while the 'wings' at the side go over the top. Mucky Nutz say it's "compatible with all standard double steel rail saddles, so long as they don't have any daft bits hanging off the rear". That ruled out four of my bikes: two with saddle rail clamps for seatpacks; one with a saddle-rail mounted CatEye Volt 50; and one with a Rido R-Lt saddle, on which the Fender would fit only droopily. In the end, I put it on a Pinnacle Dolomite... after removing its perfectly good SKS Chromoplastic full-length rear mudguard.
Fitting was fiddlier than I expected. I struggled to get this bit under the rails and that bit over the rails simultaneously. Once in place, though, it seemed secure and didn't budge during the test. So it was considerably more useful than Mucky Nutz's Rear Fender. It was a lot less useful than Zéfal's Swan road mudguard, which provides greater coverage. And for spray protection for club rides, training, or commuting, full-length mudguards obviously outclass the Road Butt Fender.
I've seen pictures of the Road Butt Fender folded up under the saddle when not needed. This seemed liked unnecessary faff to me, given that's it a 15g bit of plastic that sticks out about 20cm from the back of your saddle. Folding it might also put more strain on the fixings where they wedge under/over the saddle rails.
Once the Road Butt Fender is attached, it's awkward or impossible to fit a seatpack, depending on the pack. There are bare rails underneath the Fender, but the side wings bear down on top of them to hold it in place so there's precious little room to play with. My Ortlieb Mudracer seatpacks wouldn't fit; a seatpack that straps to the saddle rails might.
If you've got a bike that won't accept proper mudguards and you don't want to use SKS RaceBlades, Crud Roadracers, or a seatpack, then the Mucky Nutz Road Butt Fender is worth a punt. It's only £6.49. It does what it claims - if that's enough for you.
Bike too racy for proper mudguards? This one at least keeps your bum dry
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Make and model: Mucky Nutz Road Butt Fender
Size tested: n/a
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Mucky Nutz say: "A Butt Fender for road bikes. In most ways it is the same as the standard Butt Fender, with the main differences being it's narrower, designed for the thinner rubber, which means it can be stored under the saddle when not in use."
* Prevents 'soggy arse syndrome'.
* Fitted as close as possible to back face for optimum muck catching.
* Prevents the top of your seat post from getting clogged up.
* Discrete but very effective.
* Possibly the lightest rear mudguard, at just 15g.
* No need for separate fasteners, making it easy to fit and take off.
* Compatible with all standard double steel rail saddles, so long as they don't have any daft bits hanging off the rear. See image.
* When not in use, you can store under the saddle or take off. Simples!
* Easy to clean as it's flexible and opens flat. Simply wipe it and you're done.
Please note: this guard only protects the derrière region.
Tell us some more about the technical aspects of the product?
Material: Customized Polypropylene
Colours: Black (MN0042), White (MN0043).
This rating is purely for 'keeping your chamois dry', which is what it's intended for. As a general purpose mudguard, I'd rate it a 3.
The plastic seems fairly tough.
It's very light indeed.
Dry bum. Rest of me not dry.
You can make something similar yourself, possibly using cable ties, but £6.50 is a fair price.
Tell us how the product performed overall when used for its designed purpose
It does what it claims. I struggled to find any use for it. My non-racing road bikes have full length mudguards, because they're so much better, and when I am racing I couldn't care less about a soggy arse.
Tell us what you particularly liked about the product
Tell us what you particularly disliked about the product
Very limited spray protection. Wouldn't fit several of my bikes. Not compatible with the seatpacks I use. A bit fiddly.
Did you enjoy using the product? No
Would you consider buying the product? No
Would you recommend the product to a friend? If I failed to talk them into getting proper mudguards, yes.
Use this box to explain your score
There's little to choose between this and an Ass Saver.
Age: 45 Height: 1.78m Weight: 67kg
I usually ride: Ridgeback Solo World fixed wheel My best bike is: Planet X Pro Carbon Track. Or Whyte M109
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, cyclo-cross, commuting, touring, club rides, sportives, general fitness riding, fixed/singlespeed, mountain biking