The Fox Mainframe Helmet is a Sweet Deal Priced at $90 [Review]

For mainframe

There was a time when affordable gear stood out to tell all of your friends what your mountain bike budget looks like. This sweet Mainframe MIPS helmet from Fox looks decidedly similar to their Speedframe Pro lid, and your buddies will have to pay close attention to know that it cost $89.95. The Mainframe’s mostly solid colorway is available in black, white, blue, red, and whatever we’re calling that neon yellow hue that’s still around for some reason.

The main differences between those two Fox helmets are that the hard shell doesn’t cover the EPS foam at its lowest edge on this one, leaving it to scratch and dent as you toss it around. The Mainframe also has a fixed visor so there’s no place to place your goggles or glasses while climbing, and the Speedframe has larger frontal vents to let the wind in. The more expensive helmet also uses a Fidlock clasp on the chin strap that’s easier to use with gloved or numb hands than the classic trident buckle on the Fox Mainframe.

The Mainframe offers all of the usual fit and adjustability features. A ratcheting ring that squeezes your skull can be angled between several different positions to tilt the shell where you like it and re-fit to accommodate hair growth or haircuts. With a 61cm dome circumference, I wear a size large and there’s plenty of space for more hair or a larger head to squeeze inside the shell.

The chin strap isn’t designed to fit long faces or low-slung ears. I have a massive head that’s fairly oblong and the triangular straps that are designed to fit around the ear don’t make it to the bottom of mine. Not even close. I tried sliding the lower plastic piece rearward and tilting the shell back a bit, to no avail. While this misfit isn’t a huge deal it’s also not wildly comfortable. If you have a longer face you may want to try the mainframe on before purchasing.

Fox Mainframe

Inside, the Mainframe padding is similar to most modern half shells with a soft washable layer covering the EPS across the front half. At 420g for the size large, the helmet feels really good while riding, with every bit as much comfort as the higher priced model. The MIPS insert is quieter than they were a few years ago, though it may still present the usual hair slicing and tangling issues. My hairs are too short to confirm or deny that variable.

Ventilation in the Mainframe is slightly less than the Speedframe, and it’s still quite good. It doesn’t have the brow openings up font, but the four large holes under the visor do a solid job of moving air through. The internal tunnels that allow air to flow from one vent to the next are shallower in this helmet, and it may get a little steamy on warm summer climbs. I’ve ben testing it in cold and crappy conditions here in Bellingham, Washington, and the ventilation is more than enough to keep my head dry while climbing quickly.

Fox Mainframe

My main gripe with the more expensive Fox Speedframe Pro is that they used a white chin strap that turned to a shade of “gross” in short order. The black strap on this lid should keep its good looks all season so its wearer can spend more time with grips in their hands instead of holding a tooth brush and laundry soap.

Check out our mountain bike helmet buyers guide and our picks for the best mountain bike helmets.

Party laps

  • Good price given the level of protection
  • Relatively lightweight (418g for size large, tested)
  • Decent ventilation

Pros and cons of the Fox Mainframe MIPS Helmet.

Dirt naps

  • Not for long faces or low ears
  • No glasses or goggle storage
  • Fixed visor