Understable Vs Overstable Discs: Stability Explained

In an attempt to stay (relatively) sane, many people picked up disc golf during the pandemic to get outside and stay active. If you've ever found yourself in a disc golf store confused by lingo like "understable vs overstable discs" then you've come to the right place.

Being able to visualize what the disc will do before you buy it will arm you with knowledge on the course and ultimately help you build a great bag!

The bottom line:

• Understable discs generally are usually better for beginners, and when thrown with a flat release, will go right with a RHBH (right-handed backhand) throw.
• Overstable discs are sometimes referred to as "beefy" and are used by more veteran players and those facing headwinds; will fade left with a RHBH throw.
• Stable discs will have a consistently neutral flight path and tend to fly straight when thrown flat.

This video I made explains it pretty simply: 

What Is Disc Stability?

Simply put, disc stability refers to the disc's tendency to either fly straight, fade to the left, or turn to the right after it is released from a player's hand.

As a disc spins, depending on the amount of air above or below it, will apply either downward or upward forces on the disc's nose (front of the disc), therefore affecting the disc's flight characteristics.

There are a lot of other variables that affect a disc's stability, but the easiest way to learn about what a disc will do before you even throw it is to check out its unique flight ratings. (Here's a nifty article explains flight numbers really well.)

Back in the '90s, Innova Discs created the four-number flight designation as we all know it. It's been adopted by most disc manufacturers to give players the ability to visualize how their different molds will look in flight.

Keep in mind, it's not an exact science, and your mileage may vary from disc manufacturer to mold and model.

Understanding Flight Ratings

The four numbers stamped on the disc that will help you understand its stability are Speed, Glide, Turn, and Fade. For example, an Innova Sidewinder's flight numbers are: 9 | 5 | -3 | 1 

They will always be shown in the order of S/G/T/F and are based on standard RHBH throws.

Speed

Current speed ratings range from 1 to 15. This number denotes the rate of speed at which the disc flies through the air. We'll save you the nitty-gritty details about aerodynamics... for now. For instance, a sharp-edged distance driver will fly at a much faster speed than a thicker-edged midrange disc.

Glide

This number tells you about the disc's ability to instead of falling during its flight. Discs with a high amount of glide are great for new players because of their ability to produce more distance with less effort.

Current glide ratings for discs range from 1 to 7. Disc golf manufacturers assign glide ratings to their discs to indicate their potential for distance. With a range of 1 to 7, a higher rating suggests the disc is more likely to travel further (for beginners), allowing players to select the best disc for their level of experience.

Turn

This number refers to the disc's tendency to turn to the right at the earliest high-speed portion of its flight when it is at its fastest. Turn ratings range from +1 to -5, with +1 indicating it is highly resistant to turning over, while -5 means there is a big tendency for the disc to turn in the direction of its original spin.

Fade

Ranging from 0 to 5, the "low speed fade/low speed stability" describes the disc's tendency to go left at the end of its flight when it has lost a majority of its speed. (Think about it as the opposite of Turn.)

A rating of 5 means the disc will have a strong impulse to turn in the opposite direction of its spin. So for a RHBH throw, that means to the left.

What Part Of The Disc Affects Stability?

We could nerd out about the magic of gyroscopic forces all day, but we'll give you the short version.

 Basically, when there is an upward or downward force on the front of a disc (also known as the nose), it actually affects the area that is 90 degrees from the front. So if you've thrown your disc RHBH, the right edge of it will have pressure. And vice-versa.

Here's a video that explains it much better we can:

So what does this mean?

Depending on the disc's mold, some are made, for example, where more air will pass over the top of a disc (thrown RHBH a.k.a in a clockwise direction), so the nose is made susceptible to more downward force. Therefore the right edge of the disc is affected and goes downward and it will turn right, making it understable.

If you were to make the same throw with a disc that was created so more air passes under it than over it, the right edge would go upwards due to the pressure and the disc will be considered overstable.

Ta-da! Now you know what makes a disc turn while in the air.

Other factors that affect a disc's stability are the rim width and parting line height (PLH), which we'll get into next.

Big Rim Energy

As we mentioned before, the weight that goes into the rim during the manufacturing process will affect how the disc flies. The rim width is also colloquially known as "wing length." The measurement of the wing length is taken from the outer edge of the disc to the underside of the flight plate.

Distance drivers with higher speeds will have very large rim widths.

PDGA's maximum rim width currently sits at 2.6cm.

With a thicker rim for a player to grasp, more plastic means more concentrated weight near the edge of the disc, which helps keep the disc spinning in the air for longer.

This increased capacity for distance is what gives drivers their mass appeal. It will require more arm speed to kickstart the spin (a.k.a the snapping motion of your throw) but will continue to fly longer. These high-speed discs do require excellent technique, which is why they aren't recommended for beginners.

The PDGA has a list of approved golf discs for play along with comprehensive specifications for disc manufactures when they create their molds.

How Parting Line Height (PLH) Determines Stability

When a disc is manufactured, plastic blends are injected into a mold where the disc is allowed to cool slightly. As this happens, the plastic will shrink- and depending on the type of plastic, the edges could stay relatively flat or they may continue to shrink further inward as it cools, creating a "dome" effect.

The separation line on the nose of the disc is called the parting line. In general, a higher PLH demonstrates less shrinkage during the manufacturing process, meaning less turnover. A lower PLH indicates more shrinking, and therefore more turnover.

Does Beating A Disc In Affect Disc Stability?

When disc golfers talk about seasoning or "beating in" their discs, they're talking about how discs become more understable after hitting trees and taking damage.

What does that mean?

Basically, the PLH gets pushed down and warped, therefore changing the disc flight characteristics to be more understable.

As painful as it is to hear your brand new disc unwillingly high-five a tree or sign (we've all been there), some pros actually prefer certain discs that are beat in to a sweet spot of their liking. And once your disc is beaten into the preferred stability, you'll never want to let it go!

What Is An Understable Disc?

Understable discs tend to be lighter in weight and will have a tendency to turn to the right during its flight.

In general, understable discs will also have a higher glide rating than overstable models. Because of their lighter weight, these discs will not serve you well in windy conditions.

What Is An Overstable Disc?

An overstable disc will have a higher tendency to fade to the left at the end of it's flight. These are great discs for advanced players, because they are more reliable and can be used in the wind

Overstable Vs Understable: When To Use Them

A handy trick for determining whether or not a disc is understable or overstable is to add the last two numbers in the flight rating together. For example, "-1+3" would result in +2.

If the outcome is a positive number, the disc can be classified as overstable. If it's negative, then it is considered understable. An equation resulting in a 0 would indicate a stable, straight flying disc.

Depending on the scenario you're facing, knowing which disc to use is imperative - which is when knowing this formula will come in handy.

When to Use An Overstable Disc

Overstable discs typically are utilized by advanced or intermediate players who have considerable power and need their discs to dependably fade to the left. 

These discs will also be used in windy conditions because they are more likely to fight the wind and hold their flight pattern. They offer excellent control and work nicely for getting around corners and obstacles.

Some disc golfers use overstable discs for rollers, downhill shots, flex shots, and are some of the best discs for overhand tomahawk throws.

When To Use An Understable Disc

Understable discs have the potential for a lot of versatility. Along with generally being easier to throw, they're also very generous with giving extra distance while requiring less arm power. Because of this, they are great for beginners.

The understable nature of the disc will keep the flight path straighter for a little longer which can give you some sweet added distance.

Pros also utilize understable discs for specialty shots when they're in a tricky position and need a shot to keep turning right without fading. When you've mastered the ability to carve out different shots with an understable disc, you can perform other highly effective shot types such as long anhyzer shots, hyzer flips, and backhand rollers.

What Stability Is Best For Beginners?

Generally, understable discs are the best option for beginners with lower arm speed because they are simply easier to throw farther. Because these discs require less power and less release accuracy, they are more forgiving and give newer players more distance.

The downside of throwing an understable disc is that the high glide can negatively affect accuracy. Because an understable disc will have less torque resistance, if thrown too hard, the disc may flip over and hit the ground early as well.

If you notice that your understable discs keep landing farther and farther to the right, then it might be time to try a stable or overstable disc. Then with some practice, you can work towards building a bag that has a mix of everything you might need out on the disc golf course!

Popular Understable Discs

Axiom Paradox (5, 4, -4, 0) This understable midrange can be used as a teaching tool for beginners or a utility disc for advanced disc golf players.

Innova Mamba (11, 6, -5, 1) With a high turn rating, this disc can be used for shaping long turnover lines.

Innova Leopard3 (7, 5, -2, 1) A popular choice for fairway drivers, this understable disc has excellent glide and is useful for players of every skill level.

Discraft Avenger SS (10, 5, -3, 1) Beginners will find this disc comfortable and accessible to work on shaping their shots.

Popular Overstable Discs

Innova Destroyer (12, 5, -1, 3) The Destroyer is popular with forearm throwers with loads of power. It's a reliable beast in headwinds!

Discraft Nuke (13, 5, -1, 3) Considered one of the most popular maximum distance drivers in the world, the Discraft Nuke is able to maintain its fast speed for a long time.

Prodigy X2 (13, 4.5, 0, 4) This consistent overstable distance driver can be found in many players' bags.

Innova Wraith (11, 5, -1, 3) The Wraith is popular with both backhand and forehand throwers. Players of all abilities will enjoy more glide and solid distances.

Axiom Panic (13, 4, -.5, 3) This useful, beefcake of an overstable disc is beloved for its ability to hold hyzer lines and fight big headwinds.

There’s no right or wrong way to build a bag. Ultimately, what feels good to you is dependent on learning how your discs fly by practicing different shots and angles in various wind conditions. Learning about disc stability is the first step, but nothing will ramp up your progress faster than getting out there and throwing!

Looking to add some plastic to your bag? Check out our tasty collection of disc golf discs for sale in our shop!

Read More:

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