6 Awesome Design Features of the GRIT Freedom Chair

6 Awesome Design Features of the GRIT Freedom Chair

Nov 5th 2021

We like to think of the GRIT Freedom Chair as the best of beauty and brains: it's visually appealing and efficiently engineered, and it took years of dedication, multiple prototypes, and a lot of feedback from wheelchair riders to get here. Read on to learn about six surprisingly awesome design features of the GRIT Freedom Chair!

Awesome Design Features of GRIT Freedom Chair, stronger axle: two people use stack of weights to test the frame and axle

1) The axle is 2x stronger than normal wheelchairs

Wheelchair riders know the frustration of bent axles! We want our GRIT Freedom Chair riders to be able to move beyond the pavement with confidence, so we spent months engineering an axle that's twice as strong as what you'd find on a regular wheelchair.

The GRIT Freedom Chair axles are 15mm in diameter, compared to the 12.7mm (half an inch) diameter that's standard on most wheelchairs. Because the strength and stiffness of an axle is proportional to the diameter to the fourth power (d^4), this diameter increase results in a much stronger axle!

We tested them by repeatedly dropping the chair off an 11 inch curb, at an angle so that it only landed on a single wheel, with over 300 pounds of weight. The axles survived with flying colors!

Awesome Design Features of GRIT Freedom Chair, built-in suspension: disassembled GRIT outdoor wheelchair

2) The suspension is built into the frame and wheels

Suspensions are more and more common on mountain bikes, but they aren't really well suited to most wheelchairs: they're heavy and expensive, they make it hard to know exactly where your center of gravity will be, and worst of all, they tend to steal power out of every push stroke (watch the suspension of some off-road chairs as a rider uses them, and you'll see what I mean).

They do, however, have some advantages, especially on rough terrain. Without a suspension, chairs can feel stiff and rides can be full of exhausting vibrations.

We wanted to give our GRIT Freedom Chair riders the comfort benefits of a suspension, without any of the downsides. How did we do it? We threw engineering at the problem! The GRIT Freedom Chair's steel frame absorbs vibrations from the wheels, limiting what gets transmitted to the rider. The front wheel is made out of industrial-strength rubber, and has holes in it to help it absorb the shocks of bumps on the trail. Lastly and most importantly, we designed the seat supports out of sheet metal and made it flexible in just the right places, to help absorb the jostles of riding off road.

Awesome Design Features of GRIT Freedom Chair, change gears: person sitting in off-road wheelchair holding tops of levers

3) You can change gears more easily than on a bike

We wanted to give GRIT Freedom Chair riders the benefits of changing gears, without any of the extra cost and complexity of derailleur systems. To accomplish this, we designed the lever system to allow the rider to slide their hands up and down the bars. This gives riders the same range in gearing as a typical mountain bike system (3:1) without any complicated knobs or buttons.

Awesome Design Features of GRIT Freedom Chair, change gears: person sitting in off-road wheelchair holding bottoms of levers

Pushing at the top of the bars gives the riders a lot of torque (50% more than regular wheelchairs), making it easy for them to climb hills and roll over grass, mud, and even sand. Pushing at the bottom of the bars requires more effort, but lets riders push the levers a lot farther each stroke. This makes the chair go faster, about 80% faster than regular wheelchairs on flat ground, and without any extra effort.

4) The front wheel absorbs bumps and adapts to riding conditions

Wheelchair casters get beat up by average riding conditions, and off-road most casters don't have a chance. We designed the GRIT Freedom Chair front wheel to survive extreme riding conditions and to give riders a comfortable, safe, and effortless ride on a variety of different terrains.

The first thing new riders notice about the GRIT Freedom Chair front wheel is how big it is -- at 8.75" diameter it's twice as big around as regular wheelchair casters. And that means that it's a lot less likely to get stuck. It rolls right over bumps, rocks, branches, grass, and sand. It's solid rubber, which is great at absorbing vibrations and means you'll never have to worry about punctures. The holes in the wheel help to reduce weight and also allow it to deform (and spring-back) when you hit big obstacles. Think of it as a built-in shock absorber!

The shape of the wheel itself is important too. If you look at the wheel from the front, you can see that it's got a triangular cross-section. This means that on smooth ground, only a small part of the wheel touches the ground, reducing friction and making it easier to push the GRIT Freedom Chair. On soft ground, more of the wheel contacts the ground, giving it a wide contact area to keep it from sinking in. The front wheel gives great performance whether on pavement or sand!

Awesome Design Features of GRIT Freedom Chair, customizable and repairable: standard bike wheel & parts used in GRIT all-terrain wheelchair

5) It's designed to be customizable and repairable

Here at GRIT, we're tinkerers. So naturally, we encourage our GRIT Freedom Chair riders to tinker with their chairs: to add accessories, swap out components, change the gearing, or make repairs.

We ship every GRIT Freedom Chair pre-drilled with extra mounting holes so that it's easy for you to add your own straps and accessories. The steel frame is easy to weld to (if you're so inclined), and we'll work with you to help you design your own add-ons.

Most importantly, every moving part on the GRIT Freedom Chair is an off-the-shelf bike part. No special fasteners or proprietary interfaces. Your local bike shop has everything you need to customize or repair your chair.

Awesome Design Features of GRIT Freedom Chair, rust-proof: whole frame of rugged GRIT wheelchair with powdercoat and zinc plate protection

6) The lightweight steel frame is rust-proofed

We designed the GRIT Freedom Chair frame out of high strength steel. This lets us use thin tubes, resulting in a frame that's lighter than most off-road wheelchairs (even those made out of aluminum). Even better, steel frames are much less likely to crack than aluminum frames, meaning you can ride your GRIT Freedom Chair longer, and in more extreme conditions, than the competition.

One concern with steel is that it can rust, so we attacked this head on. Instead of painting the GRIT Freedom Chair, we powder coat it. This is a much more durable solution -- it's more scratch resistant, thicker, and it looks better. As an extra layer of protection, we zinc plate each chair's frame, inside and out. So you never have to worry about your chair rusting!