First, the rebounders that you have to change the springs on every 2 years are not a bad thing. Its not that much more expensive. If the rebounder is 150 dollars cheaper and provides a bounce you like and it costs a dollar a spring, and if you have to change the springs every 2 years, thats 5 times in 10 years and it all costs about the same (that is if its only used by a single person, not a family)

I've found that Needak and the Cellerciser feel very similar for people under 200 pound. The Cellerciser has that extra tier that the Needak doesn't have but most people when they first compare these two, about 50% of the people like one and 50% like the other.
By taking these to the park all these years, I can almost look at a person and guess which one they will like better before they every get on it. The Needak spring gives a deeper bounce that many people associate with a smooth bounce. The Cellerciser has a softer bounce when doing the Health bounce but the Needak has a deeper bounce, giving it slightly fewer bounces per minute.

The 106 gram Cellerciser spring based on people doing the health bounce is most peoples favorite. Note that the 106 gram spring is the metal carbon spring. I've weighed them and some are 108 and some are 109. The dual silver coating is what makes them weight different by the carbon (grey) spring is 106 grams on every spring. I always weight my springs to see if they are all the same tensile strength. If a spring is not double coated with any alloy, they should not weight differently. Cellerciser is the only company that every spring feels the same tension. I put the 110 gram springs all one one and 108 gram ones on another, same exact bounce.
Are lifetime or 2 year springs better?
Jumbo Cellerciser Springs (triple tiered)   106 Grams           Urban springs (standard barrel shaped)

High end (Barrel type ) springs                                           $50 dollar Sporting good store springs (smallest single tiered springs
Needak Springs (Barrel type shaped springs)                           ReboundAir springs (more copper color. Health Bounce rebounder  
                                                                                                    Similar to Lymphaciser as only for Health bounce. Super noisy
Fabric - Really??? Who uses these anymore? Do they still make them?    Bungees - Hexagonal, new type
Consumer notice:

Not all rebounder springs in a rebounder you get weigh the same. 
I weighed each spring to see if everyone of the 36 spring were uniform. What I noticed is that when I weighed each spring after taking them off the rebounder, not all weighed the same. (Note, the Cellerciser has 106 gram springs but the silver alloy that is double layered can make the springs weigh a few grams off on each spring). This is not the same as those that are heavier or lighter from the spring coil, not the coating.

This uneven tension is what makes certain sides of the rebounder feel off and gives the uneven bounce. If one spring loses its tension while others stay firm, this is what I am talking about. Most rebounder springs are not made with high carbon steel so its is more noticeable.

I do promote single or barrel springs for Health bouncing, like the Lymphaciser or the Reboundair. With these the Health bounce is great but the springiness for toning and cardio is lacking. With the  Cellerciser I can do all 3 types of rebounding.

These springs do not adjust as they dont have different tensions in each tier. A heavier person will get a different bounce than a lighter person. Heavy people usually don't like these if doing cardio bouncing but not a problem for lymphatic bouncing. Buying this type of spring can be iffy depending on the weight of the person. I get customer returns when people buy this type for anything other than the Health bounce.

These springs are usually the highest spring grade, the high carbon nickel based steel. Nickel based steel will not stretch out like lower carbon steel. The aluminum springs stretch out the quickest. These are different than tapered springs that look like they have 2 tiers. The tapers are tapers only. The tapered springs which some people called dual tiered springs are the softest with certain types of bouncing as the entire spring is engaged including the tapers. The tripple tiered springs reserve that last taper (the third tier) to be used only when it has to. The Cellerciser spring is tripple tiered and also double anodized coated a spring so it never has to be changed. This coating is the silver coating that is on it that takes away the heat. This is another reason why the Cellerciser spring doesn't have to be changed every two years.
Close up of the Cellerciser spring. Each of the tiers are engaged depending on the persons weight. The new model has digitally tempered springs. They all sound the same when I tap on them with a spoon.

Most springs when I tap them, some sound high pitch and some a lower tone. The awful sounding ones are usually the analog springs. It sounds like a nighmare, like mating condors. Like goose torture.

Note: Some rebounders give 3 g forces, enough to flush the lymph valves but over a longer period of time, not a sudden flush. The health bounce is about repetition. A bungee rebounder, can also give 3 g forces if a person is jumping very high out of the mat but the repetition is slowed and the long deceleration has to come back up "throwing" the person back up instead of a 3.5 inch spring popping the person back up. A good spring for the health bounce will allow the most bounces per minute with the most g force when barely leaving the mat.
What's NEW!
The latest in spring design - Digitally Tempered Springs.
The newest springs on the market are digitally tempering. This allows the air bubbles to go out. Many springs have a bumpy feel but they can put a coating over it to hide this. Voids or bubbles in the lattice of the spring are what cause the spring problems. The more bubbles (voids of air) in the spring changes the sound that they make. With a tuner, you can hear that some springs sound totally different while on a Cellerciser they sound identical due to digital tempering.
Most companies still have the analog tempering which you can tell when you tap on the spring or have a guitar tuner.
ReboundAir has 94 grams springs /19 coils  (4.95 grams per EACH coil)
Needak has 98 grams springs / 20 coils  (4.90 grams per EACH coil)
The Cellerciser has 106 grams springs / 23 coils  (4.61 grams [ Average per EACH of 3 Tiered coils,)
(I'm in the process now of cutting each of the 3 Cellerciser tiers, and getting the gram weight of the belly coils middle, and the 2nd tier and the 3rd tier (tapers on end)
At 36 springs at 106 grams compared to 94 grams, that's 12 extra grams per spring.
432 Gram difference.
Choosing springs for lymph drainage: (see my page on rebounding for lymph drainage)
Bouncing on the right rebounder can help move the lymph from 2 to 14 times quicker than the normal lymph flow rate.  Most people move about 4 fluid ounces of lymph fluid every hour. Inactive people typically move about 1/5 of a ts of lymph per minute. Rebounding helps to move about 4 teaspoons of lymph fluid per minute. 

​Most people only need about 10 minutes of doing the Health bouncing at a time. If on the rebounder that moves 14 times as much lymph than a rebounder that moves closer to 2 times as much, and if the liver cannot process all this waste, sometimes its better to start off with a rebounder that moves less lymph per minute if I plan on jumping for longer times. Its cool to get one that moves the most lymph like on a Lymphaciser but if the body can't handle it then its not good.

The liver can only filter out so much of this waste at time. I do the Health bounce before I go to bed and when I wake up. I find most people get better results when they split the sessions up.
A final world on rebounder springs:
Unless you're a mathematician expert it can be rally hard to pick out the exact springs you want for your weight and bounce type. Some are gonna be too hard and some way too soft. In my opinion the triple tiered springs are usually just right as they adjust for any weight and takes the guesswork out.
Picking out the right springs is just as difficult if you don't know what you are doing a picking out a bungee cord and matching the right size mat to your bounce.

Take my rebounder quiz. It helps!
New Zealand ymphaciser Jumbo Barrel springs
Great for Health bounce only. Nothing else. Jarring if jumping high out of the mat. A+ for lymphatic.
Needak Tapered springs: Great for multi purpose bouncing. 3rd favorite for health bounce. Springs have high initial tension. Very soft at high bounce.
Cellerciser Triple Tiered spring: The 106 gram High carbon steel springs. Most responsive spring. Can be used for up to 350+ pounds.
Rebound Air Barrel spring: Watch the videos to see which springs win the Health Bounce in each weight class. Great for mid weight range.
Match your weight to the gram size of the spring.
Depending on how hard or soft you want the bounce, each spring type gives a different bounce. 

The Cellerciser has 3 tensile strengths in each spring giving making it the most versatile spring. See Cellerciser Page.
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