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The DIY Fat Tire - Erik Kondo

Updated: Jan 19

Wheelchair user pushing on the sand on a ocean beach.
Carsen Beach in South Boston Massachusetts

Summer is here and many people are thinking about going to the beach. Some of these people are wheelchair users. What type of wheelchair wheels will work for them on the sand? Over the years, creative people have come up with different types of beach wheels for wheelchairs. These wheels typically involve some type of wide tire wheel that can be mounted on their wheelchair

It is easy to look at such wheels and assume that it will make dealing with sand effortless. But before you go out and buy expensive beach wheels, it is important to understand the physics of rolling on a beach in your wheelchair. Commercial fat tire wheelchair wheels are available, but they cost more than $500 for a pair.

When it comes to wheels on the beach, you need to remember TRT – Traction – Resistance – Torque.

  • Traction is the “grippiness” of the wheel to the rolling surface. If the wheel spins in place, you will not move.

  • Resistance refers to the things that oppose the wheel from turning. On a flat beach, this is the sand which has to be pushed out of the way of the wheel for it to roll. On an incline, gravity is an additional force that increases resistance.

  • Torque is the force required to rotate the wheel.

These three factors typically affect each other. For example, greater traction usually leads to more resistance which requires more torque. The general idea of having large wide wheels is that you will decrease resistance by rolling over the sand. But it is important to keep in mind that the amount of torque a person can generate is highly dependent upon their physical strength, body positioning, and the manner in which they grip and push the wheels.

In other words, if you have a wide tire wheel, but have trouble gripping the wheel/hand rim and generating pushing power, you may be worse off than using a thinner wheel that is easier to grab. Thus, allowing you to produce more torque.

The DIY Fat Tire

The DIY Fat Tire is a simple and inexpensive method for converting a knobby tire into a fat tire for the beach. The difference is that this fat tire is wider (less Resistance) and easier to grip/push (more Torque) than a traditional knobby/Fat tires. In my opinion, the DIY Fat Tire more functional on a soft sand beach than the commercial options currently available. The photo bellow shows the same size downhill hill tire (Maxxis High Roller 24” x 2.5”) mounted on an off-road handcycle (left) and the same tire setup as a DIY Fat Tire on a wheelchair (right). Notice the difference in width. On soft sand - size matters!

The photo below compares the DIY Fat Tire to a traditional wheelchair knobby tire. Both tires are mounted on 24” (507) rims. The width size difference is quite large.

The DIY Fat Tire is made by purposely not seating the outside tire bead into the rim. When the inner tube is inflated it expands to fill the entire space of the tire. The inner tube is squeezed between the tire and the push rim. The result is a much wider tire. The exposed inner tube on the inside of the wheel is covered with Gorilla tape. The DIY Fat Tire is intended for primarily beach/snow use. Therefore, distances travelled will be relatively minimal and there is less opportunity for the tire to be punctured.

Note. I use 26" mountain bike tires mounted on a 25" (559) wheelchair wheel for typical rough terrain of greater distances and harder packed surfaces. In this situation, I want a pushrim and traditional tire setup.

Some will consider this method heresy and try to tell me why it will not work. But it does. When seating the inner tube, do NOT place the value stem though the rim hole as designed. This position will put excessive stress on the value area as the inner tube expands. Instead, leave the value stem in the middle as shown in the photo below.

The push rim has now been absorbed into the wheel and creates a barrier to hold the inner tube. When pushing the wheel, the user is able to position their palm on the tread and wrap their fingers around the side of the tire and into the soft inner tube. This hand position allows for a very strong grip when needed. This type of grip generates more torque than using either the tire or the push rim of a knobby tire. The beach environment typically has areas of very soft sand, depressions, and slopes which require maximum torque to navigate. I typically wear gloves since the tire tread is very rough.

I am using Thorn Resistant 24x1.9-2.35 Tube Schrader Valve Removeable Core inner tubes ($17). This inner tube is over 4 times thicker (4.3mm) than the standard 1mm that I originally used. It is crazy thick! I have found that regular thickness inner tubes will pop.

In this photo, you can see the evolution from metal push rim to to mounted tire tread to inflated DIY Fat Tire. It is really quick and simple to do. I am fairly certain that this setup will work just as well in the snow as it does in the sand. Note: Since the wheel is sealed with Gorilla tape, I don't think taping the rim is necessary anymore.

Knobby tires typically require an axle spacer and extra long axles to prevent the tire knobs from rubbing against the wheelchair’s sideguards. The DIY Fat Tire uses regular axles because the tire tends to side to the outside of the rim as shown in the photo below. Therefore, there is plenty of space.

To make the DIY Fat Tire:

1. Get two standard 24” (507) wheelchair wheels with rims. (Used should be cheap)

2. Get two thorn resistant 24” x 1.9-2.125 inner tubes.

3. Get two used 24” x 2.4” mountain bike tires with 507 rims. (Used might be free. Worn tread should be fine.)

4. Seat the tire inside bead only.

5. Put in the inner tube.

6. Inflate till firm. Not too much. Remember, heat makes the inner tube expand.

7. Seal the wheel with Gorilla tape to cover the inner tube.

Give it a try. Nothing ventured, nothing gained.

Update - My goal is to go to a new beach and push 1 mile. I have now gone to five beaches. I plan to do as many as I can since I have been avoiding beaches for decades.

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