The simple, strap-on Ass Savers Win Wing MTB now delivers wider fat-tire coverage to tame the rain, mud, and even dust spray off your mountain bikes’ rear tires. Not only does it keep your backside cleaner, it also protects your dropper post seals, meaning smooth saddle drops for longer with less maintenance. And again, it’s both light and affordable.

We’ve been testing the new Win Wing MTB out on the trail for the best part of a year. And while I don’t use it for every mountain bike ride, whenever its especially wet or muddy out, I always reach to strap one on whatever bike I’m riding that day…

Ass Savers Win Wing MTB strap-on rear mountain bike fender (Photos/Cory Benson)

Since Ass Savers first launched their gravel Win Wing fender, I was already strapping it onto XC bikes to keep my butt dry and my dropper post stanchions & seals protected from mud flung off the rear tire. Now there’s finally a bigger, wider Ass Savers Win Wing MTB, made just for mountain bikes. And now it will clear up to a 29 x 3″ tire.

Initially, Ass Savers started development of the wider MTB version to target adventure riders and bikepackers that wanted to keep themselves and their gear from getting sprayed and covered in mud. Remember, a lot of bikepacking saddle packs are waterproof. But it’s still a pain to get in and out with all your gear, from a muddy bag.

So ultimately, they saw how many regular mountain bikers also would appreciate a simple, lightweight, durable, and low-cost rear wheel fender. To keep the rider dry and preserve dropper post function. Who services their dropper post like they’re supposed to, anyway!

So the wider Ass Savers Win Wing MTB project became strap-on rear fender for all mountain bikers. And that meant it needed more adjustability

What’s new?

Compared to the gravel version, which can already officially clear up to a 700x60mm (29 x 2.3″) tire, the new Win Wing MTB has clearance for up to a 29 x 3″ mountain bike tire. Plus, it has a much longer and wider fender blade for added coverage. The new blade is ~42cm long x 11.5cm wide across its midsection (vs. 39x10cm for the gravel version) to wrap even the biggest MTB tires.

Because the fender blade is longer (and thus a little heavier) and because it will see more rough terrain off-road use, Ass Savers also made the new Win Wing MTB’s wishbone mountain bracket thicker and stronger.

Then, since there’s more variability in mountain bike seatstay angles from hardtails to full-suspension bikes, the MTB fender’s wishbone legs’ length is adjustable with 3 heavy-duty snap tabs to position the bracket directly over the top of your tire for best mud protection. And you can now adjust the blade angle itself +/-15° for a nice & functional flat installation.

How does it work?

Ass Savers designed the new Win Wing MTB’s Tangential Coverage to sit just above your tire to catch most rear wheel spray where it originates at the tire.

works best when the wishbone is located at the top of the tire, with just 1cm of clearance between the tire and the fender bracket.

adjust the legs of the wishbone to align its top directly above the rear axle, then…

make sure to fold the flat fender blade along all the pre-scored marks to get the proper curved shape, and lastly…

adjust the fender blade angle to be horizontal or tipped slightly upwards for max ass saving performance

And don’t worry about getting it stuck in the rear wheel when you pick up trail debris or a bunch of sticky mud. The anti-jam wishbone layout flexes forward, away from the tire if something sticks in your rear wheel. And then, in most cases, it’ll just spring back into place.

Tech details

• easy-to-install & quick-to-remove mountain bike rear fender
• fits 26-29″ wheels and tires up to 3″ wide
• adjustable-length glass fiber-reinforced black polyamide (nylon) wishbone bracket
• 50% recycled 0.9mm thick polypropylene black fender blade with various printed designs
• +/-15° blade angle adjustment
• black thermoplastic polyurethane (TPU) dual-duty feet & attachment straps (includes frame protection stickers)
• fits narrow steel seatstays up to boxy carbon or alloy stays
• 100% made-in-Sweden in ISO14001 sustainability-certified factories
• 114g total claimed weight (mine actually weighs 116g)

Review: Stay clean(er) with Ass Savers’ Win Wing MTB fender

I’ve been testing the Win Wing MTB since last spring, for year-round trail riding. And it does a great job of keeping you cleaner than without a fender. It’s no full-coverage fender, for sure. But, even as the backs of my legs and most of the frame still get sprayed with water, mud & trail muck… the seat of my pants, my saddle, and my dropper posts stay MUCH cleaner!

(Even when installed a bit further from the tire than it should be.)

I don’t have it fitted for every ride, but I’ve mounted these things to almost a dozen different mountain bikes & eMTBs in the past year. And it’s totally my go-to for any mountain bike ride I expect to be rainy, wet, or especially muddy.

I’ve generally been able to keep it in the single shortest leg setting and just quickly adjust the blade angle for pretty much all full-suspension bikes – less than 30-second swap from bike to bike. Or for swapping to a hardtail, I’ve made the legs one position longer – a more involved change that takes a couple minutes, which I do with a tire lever because of the tight, secure snap-together fit of the legs.

Riding Impressions and Takeaways

I’ve ridden this thing on some really rough and steep enduro terrain. And I experienced no problems with its secure fit or durability. My closest call was catching it on my butt on an exceptionally steep descent when I slid far back over the rear wheel. But even then, it caught the seat of my pants, pulled out of the way without restricting my movement, and snapped safely back into place when I got back over the bike.

The fender does move up and down more on the mountain bike than it did on a gravel bike, unsurprisingly riding with it over proper drop and through rock gardens. But the biggest impact I’ve encountered is small tire rub marks inside the fender, that happen without even noticing it on the bike.

While some mountain bike riders might not love the look of having a rear fender, I don’t mind it.

If you have the all-black one, frankly, it kind of disappears once on your bike.

It’s my feeling that a small fork arch fender is an absolute minimum necessity, no matter where you ride. And if you ride in wetter conditions, there are plenty of bigger front fender options to pick from. But a rear fender is just as useful. Yet, options remain limited. I’ve tried plenty. And they either lack real protection (like Ass Saver’s own original Big clip-on saddle fender) or are overly complicated, bulky, and heavy.

This Ass Savers Win Wing MTB is just 116g. It’s easy to put on & take off, yet stays put over pretty challenging terrain. And it actually blocks a lot of mud & spray before it gets to you or your dropper.

Ass Savers Win Wing MTB – Pricing, options & availability

The Win Wing MTB is available now directly from Ass Savers with free global shipping, and in-store in dealer bike shops worldwide. The new strap-on rear mountain bike mud guard sells for 33€ in all-black Stealth. Or for 1€ more you can pick from a couple more stylish options like the beige Detour dots or the colorful purple & pink ROKS design that I have fitted to my mountain bikes now.

Ass-Savers.com