The adventurers at 509 Cycles are known for their versatile fat bikes that are designed to handle any trail you throw at them. Drawing from their experience building fat bikes, they’ve designed a gravel bike that offers a similarly wide range of capabilities – the Necessary Evil. The bike is made for road riding, bike packing, gravel racing, and touring, or all of the things you have to do to make it through the year in the Midwest while the trails are drying out. Simply choose between stainless steel and titanium. The featured bike you see here was setup up by the 509 team for a mix of bike packing and gravel riding.

Necessary frame details

509 Necessary Evil509 Necessary Evil

509 Necessary EvilAs mentioned, the Necessary Evil frame is available in steel ($1,000 – 5.1lbs) and titanium ($1,800 – 4lb) frame options. Both are ready for bikepacking with 3 bottle cage mounts, and rack and fender mounts. I do wish there were top tube bolts for a bag – they’re convenient for gravel and bikepacking setups. Upfront, its 44mm headtube is tapered for 1,1/8 – 1,1/2″ steerers. Its seatpost size is 27.2mm.

509 Necessary Evil509 Necessary Evil509 Cycling Necessary Evil

It’s able to fit up to 650×2.3″ and 700x47c tires thanks to its Boost 142×12 rear hub spacing and machined chainstay yoke. We’re currently running 700x42c WTB Resolute tires and still have plenty of room to bump up a size. Brake calipers attach with flat mounts using 32mm bolts.

An ever-so-evil geometry sheet

509 Necessary Evil Geometry

Reviewing the geometry, its relatively short chainstays paired with an aggressive head angle should offer good handling characteristics. While its 170mm headtube – size 57 – shows some characteristics of cross bikes and should offer a low and race-like front end positioning.

Built for gravel

509 Cycling Necessary Evil509 Cycling Necessary Evil

509 Cycling Necessary Evil

We’re running a Sram 1×11 drivetrain with a carbon Force crank, Rival rear derailleur, and an eThirteen TRS+ cassette. Our gear ratio is 40 x 9-46. It’s equipped with mechanical Rival brake levers coupled with TRP Spyre calipers. Rotors measure 160mm in the front and 140mm in the rear.

509 Cycling Necessary Evil509 Cycling Necessary EvilCrowning the front end is a Lauf Grit SL fork. It offers 30mm of travel, a flat mount brake surface, and a 12x100mm thru axle. So far, the Lauf does a good job of reducing road, gravel and trail chatter.

509 Cycles Necessary Evil509 Cycles Necessary Evil

Our Necessary Evil is rolling on an Industry Nine AR25 wheelset and WTB Resolute 700×42 tires. The Resolute tires have a tight tread pattern that stays surprisingly clear even through mud and roll well enough while on pavement.

509 Cycles Necessary Evil509 Cycles Necessary Evil

Wrapping up our build is a Thomson stem and Elite seatpost, Salsa Cowbell handlebar, and a WTB Bolt saddle. The Cowbell bar has some offset to it but it’s the roomiest option if you’re looking to go bikepacking with a bar bag.

509 Cycles Necessary Evil

Our complete build – as seen without pedals – on the 57cm steel frame weighs in at 22.17lbs. 509 achieves this by using 2205 Stainless Steel.

Current state of mind

509 Necessary Evil509 Cycles Necessary Evil

So far the Necessary Evil from 509 Cycles has held its own in muddy conditions. The rear tire gap is ample enough to prevent mud buildup and its relatively short chainstays keep the bike nimble on trails. The somewhat aggressive geometry does remind me a bit of my old cross bike, but I’m upright enough where a long bikepacking trip should be comfortable. To that point, it’s not the fastest rig on roads and it doesn’t have to be. Its Lauf fork eats up the bumps on and off the road while its 42c tires add another layer of suspension. I’m looking forward to how it handles trail riding throughout the fall season and how well it loads down. Check-in for the full review to come!

509 Cycles Necessary Evil


    • FBJ on

      I found warranty is the same as other competitors if not better. 10 Year Titanium, 5 Year Stainless, 3 Year Steel. The frames are proudly made in Taiwan.

        • Dinger on

          Carbon forks are superior and there are plenty of choices. Making a fork with a 1.5″ lower, out of metal will result in an unacceptably high weight for this type of bike.

          Steep-ish head angle, high-ish BB (likely to accommodate 650b). If the chains-tays were shorter, I’d say this was a CX bike.

    • 509cycles on

      We use 2205 Stainless Steel that is double butted on these frames, which does offer the about the same ride quality as chromoly, but rust proof characteristic of TI. I feel that stainless offers a bit stiffer of a ride quality much like TI.

  1. madskills on

    Recently bought this bike out of Wenatchee, WA and I’m so glad I did! It has now become my go-to bike due to its smooth ride that is fully capable of handling all types of terrain.


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