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Old 04-12-2015, 08:16 PM
wims wims is online now
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Rim width vs disc speed

I once read that disc speed was determined by a discs rim width. Generally it goes rim width - 10mm = disc speed. So a disc with a rim of 19mm would be rated speed 9. However, when I looked at a few of my discs I found that this general formula does not hold up. Take for example the Roadrunner, it has a speed of 9, but the rim is only 18mm wide. It's only 1mm tho, so it's not a biggie. Same with the PD, it's a speed 10, but the rim is 19mm. But the real oddball was the Underworld. It's rated speed 7, but the rim is "huge", 19mm wide.

What makes the Underworld a speed 7 when it got such a wide rim, relatively speaking? How come it's rim is wider than that of the Roadrunner, yet it's rated two whole levels below it?
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Old 04-12-2015, 08:34 PM
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JedV JedV is offline
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I'm by no means an expert on this, but I understand that there is no set system in place for those numbers. Therefore you'll see variation between brands. Speed is a relative term, and relates to how hard and with how much spin the disc should be thrown to get the advertised glide, turn and fade.

Aside: Innova's flight ratings are different from Westside when it comes to turn and fade. Dynamic Discs uses. 5 as a decimal place on turn and fade.
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Old 04-12-2015, 08:35 PM
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kevdiv48 kevdiv48 is offline
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Quote:
Originally Posted by wims View Post
What makes the Underworld a speed 7 when it got such a wide rim, relatively speaking? How come it's rim is wider than that of the Roadrunner, yet it's rated two whole levels below it?
Different manufacturers have slightly different rating systems. Don't take the ratings verbatim.
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Old 04-12-2015, 09:03 PM
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Stardoggy Stardoggy is online now
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That, and more than just rim width determines a disc's speed. It's physics, man.
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Old 04-12-2015, 09:22 PM
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joshtrum joshtrum is offline
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I posted a thread maybe a year or so ago to try and bring rationality to flight ratings. There is no rationale. If a disc is rated 6/5/-2/1 and it flies like that, that's as far as you should
Question. Trust me when I say this is not a road you want to try to go down. Just drive you mad
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Old 04-13-2015, 10:56 AM
charris414 charris414 is offline
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bigger rim typically means a faster cruising speed. however, it takes a significantly larger amount of snap (aka acceleration) to get the disc up to that cruising speed and achieve the advertised flight (glide, turn, and fade). if you don't get the disc up to that speed it'll act more overstable than it would for a "big arm." And if you exceed the cruising speed you'll get the funky torquey/roll-over.

smaller rims are technically slower, but they're also much easier to accelerate up to their cruising speed.
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Old 04-13-2015, 11:57 AM
hugheshilton hugheshilton is online now
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Disc speed is not physics, it's just marketing. Lots of people try to create imaginary ways in which the "speed" rating of a disc is physics, but none of the supposed interpretations have any real physics behind them. Hint: physics involves actual, measurable numbers. How do you turn a speed "9" into numbers that can be measured against a speed "10" (in terms of release speed, angular velocity of spin, off axis torque, etc.)? Nobody knows because the speeds are just made up numbers. Heck, we can't even come to any agreement on why discs fly the way they fly.

I pointed out in a thread quite a while ago that in loads of Innova's discs (esp the newer ones), the rim width does not actually match the speed. I got booed down; apparently a lot of people on here don't believe the rim widths posted in the PDGA specs are correct anyway. One of these days I'm going to buy some calipers and actually measure the rim widths on all my discs to see if the PDGA specs are correct or not. Until then, it's just something silly to argue about on internet forums.
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Old 04-13-2015, 12:01 PM
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zendragon zendragon is online now
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While many companies use rim size as the speed in general, there are definitely other factors. The XXX is a great example. It's got a wider rim, but blunter nose that slows it down with more wind resistance, so it's rated at a 7 speed by most.

But mostly, speed is a marketing term and not necessarily accurate in terms of actual disc flight.
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Old 04-13-2015, 12:16 PM
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crd 81 crd 81 is online now
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If someone is able to get a disc up to its cruising speed and is able to really see how those discs fly, then they can make judgments on the speed/rim-width correlation. For example, if they throw a Valkyrie, PD, TD, or any other disc in the 1.9 rim-width category around the same distance, then they should be able to label the distance of the 1.9 rim-width with a certain amount of consensus. Granted, certain discs are going to require different lines to achieve their distances base on their stablities even if they are within the same rim-width category. Still a consensus on distance and speed can be achieve, in my opinion.

Based on that, if a disc is in the same rim-width category as the ones being tested and if they are either beyond or below the consensus of the measured distances, then you can say that one is flying below or beyond their "speed" class. There are certain exceptions like discs that are made to be very overstable (which will fly shorter) and those that have more glide (which will fly longer).

Using the general consensus of distances of said discs, I believe that discs that fly longer than their rim-width category are usually more desirable than those that fly shorter.

TL;DR: I think using the rim-width to judge the speed of discs is good as long as people can get the discs up to speed.
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Old 04-13-2015, 01:35 PM
hugheshilton hugheshilton is online now
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Quote:
Originally Posted by crd 81 View Post
TL;DR: I think using the rim-width to judge the speed of discs is good as long as people can get the discs up to speed.
So I *think* you just said that the "speed" of a disc is no accurate representation of the actual distances you can get out of it (which I agree with) because some discs with a certain rim width fly much farther when given the same amount of power than others with the same rim width.

What you didn't say is that some discs handle power well beyond their "speed" rating and others can't handle even the amount of power of most discs within their "speed" rating. A lot of pros can throw Destroyers around 500 feet on a good rip. If they gave most Vulcans the same rip, they would be instant rollers, no matter what angle they released them on. But the Vulcan is a "faster" disc so it SHOULD be able to handle more power than a Destroyer according to some people's definition of the "speed" rating. Given that it's a speed 13 and its inbounds flight chart, one would think a Vulcan had the potential of going around 440 feet when thrown with the correct (fast) arm speed on the right line, but my experience is that this will never happen even with very clean form (unless it's used as a roller or in a heavy tail wind).

So a Destroyer can handle much MORE power than most speed 12 discs whereas a Vulcan can't handle as much power as most speed 13 discs. Therefore, my conclusion is that "speed" ratings based on rim widths are actually pretty useless for judging how much distance you'll get out of a particular disc.

And that's not even mentioning all the variations you get in dome and PLH within the same mold, especially in larger rim widths. I'm sure someone on here will point out that they own a freak overstable Vulcan that is more OS than most Destroyers and can be thrown 500+ feet.

Larger rim widths are generally more aerodynamic with less drag, especially when the rim is more pointy and the profile is lower. More aerodynamic discs can cut through the air faster; however, they also seem to have the potential to turn over more. Thus, the increase in aerodynamics must be combatted by increasing the dome or with higher PLH (having the rim stick out farther of the bottom of the disc) which I think increases drag and makes the disc more stable. This paragraph is complete conjecture on my part and probably most of it is either over simplified or an incorrect guess.
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