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Exercise Bikes And Flywheel Weights: Does It Even Really Matter?

exercise bike flywheel weight

If you’ve been searching for an exercise bike lately, you may’ve noticed that the weight of the flywheel is always discussed. If a bike comes with a heavy flywheel, the manufacturer will boast this fact and go into why having a heavy flywheel is better.

The same is true for bikes that come with light flywheels- these bikes will advertise how light they are and why light flywheels are the way to go.

But when it comes down to it- does an exercise bike’s flywheel weight really matter?

Well, if you’re looking for a good workout, then yes, flywheel weight does matter.

Ok, fine, but which is better- light flywheels or heavy flywheels?

The answer to this age-old question will require a little more discussion. Fortunately, this is just the question I’m here to discuss.

In this article, we’ll dive head first into this debate as we look at both sides. After reading, you should know everything you need to to decide for yourself which camp you belong in.

What Is A Bike’s Flywheel?

First things first- all exercise bikes use a flywheel to create the resistance for you to work against. On spin bikes, it’s easy to see the flywheel because it’s clearly visible (it’s the big disc sitting in the front or back of the bike).

This disc is connected to the pedals via a chain (chain drive) or belt (belt drive). As you pedal, the flywheel spins.

If your bike uses a magnetic resistance system, there will be magnets on either side of the spinning flywheel. The resistance is increased by moving these magnets closer to the flywheel (the flywheel is made out of metal, which is magnetic by the way).

Moving the magnets away from the metal disc reduces the resistance.

Magnetic resistance systems are great because nothing actually touches to create the resistance, unlike older school systems that use felt pads and friction- these resistance systems work too, but eventually the felt pad breaks down and has to be replaced.

Regardless of which type of resistance a bike uses, you can see how the flywheel is necessary to create it.

And even though we can’t see the flywheels on traditional upright bikes and recumbent bikes, they are still in there. Most home ellipticals also use weighted flywheels and those systems usually work very similarly to exercise bikes.

Oh, pretty much any flywheel you see now will be “perimeter weighted”, meaning most of the weight is positioned on the outside of the disc.

Marketers love to say that their bike has a “perimeter weighted flywheel”, but in reality, they all do- it doesn’t mean anything.

Ok, we all know what flywheels are and why they’re important to the function of our exercise bikes. Now it’s time to get to the good stuff.

Heavy vs Lightweight Flywheels

heavy vs light exercise bike flywheels

 

Most people, myself included, start with the weight of the flywheel when reviewing an exercise bike. And this is because the flywheel is directly related to providing the resistance and feel of the bike.

And by “feel”, I mean how smooth or fluid it is during its pedal action.

Does the bike offer a continuous, smooth acting pedal action or does it feel choppy or uncomfortable to pedal? The answer to this is largely based on the flywheel.

In order to get a smooth feeling ride, the flywheel needs to build momentum as you pedal. This momentum helps the pedals continue moving throughout your pedal stroke, eliminating any unwanted gaps or pauses between strokes.

Generally speaking, the more momentum your flywheel builds, the smoother your ride is going to be.

There are 2 schools of thought when it comes down to the best way to build this momentum: heavier is better or lighter is better. Let’s discuss each on its own.

Heavy Flywheels

Most home exercise bikes try to increase the flywheel’s momentum by giving the flywheel more weight. A heavier flywheel takes more initial energy to get it moving, but once it is moving, it wants to keep moving longer.

People who are looking to mimic the feel of riding outside usually prefer heavier flywheels because they take more energy to start from a cold start- just like a real road bike.

Think about riding a bike outside- you have to push harder until you get moving. Once you start rolling, it gets easier to pedal (unless you’re going uphill of course).

This is what a heavy flywheel mimics.

Considering most exercise bikes are designed to work with heavy flywheels, it makes sense that going with the heaviest flywheel possible would result in the smoothest ride, right?

Well, not really, eventually it would get to a point where the damn thing was too heavy to get moving in the first place.

Personally, I consider any flywheel over 20 lb to be “heavy”. I think this is a good place to draw a line in the sand and say, “anything heavier than this, is heavy enough to get the job done”.

That said, a lot of bikes these days, especially spin bikes, are coming out with 30 – 40 lb flywheels. Some are even going into the 50 lb range.

Bikes with flywheels this heavy are going to be able to build a lot of momentum as you pedal, which is going to make for a smooth ride.

Of course, when that heavy flywheel gets moving, it’s going to be harder to slow it down too (something to keep in mind if you have achy joints).

So, when it comes to flywheels and building momentum, it makes sense why heavy flywheels would be preferred- the extra weight simply builds more momentum, which helps keep those pedals moving seamlessly.

So then what’s the deal with luxury bikes like the Keiser M3i which is famous for its 8 lb flywheel?

Light Flywheels

There are a few manufacturers who are producing amazing spin bikes that run smoothly by using a light flywheel.

Keiser and their M3i is the most famous example, but there are others too that are trying to mimic what Keiser has mastered (like Sunny and their SF-B1709).

The key to making a light flywheel successful is in the speed at which it spins.

I think I mentioned earlier that there are 2 ways to increase momentum in the flywheel as it spins- you can make that flywheel heavier or you can make that flywheel faster.

Increasing the speed at which the flywheel is spinning is also going to increase the amount of momentum it builds, which is going to create that fluid pedaling motion which we are looking for from a quality bike.

In the case of Keiser, I’m pretty sure I read somewhere that the flywheel spins 11x for every full pedal stroke- that’s crazy fast.

Keiser was able to create this fast flywheel system through the design of their gears that produces such a high gear ratio. The result is a very fast flywheel, which wouldn’t be possible if the flywheel was heavy.

Unlike heavy flywheels, lighter ones don’t take as much energy to start or stop. This is great for achy or sensitive knees, but it might not mimic the feel of a road bike as much as a heavy flywheel bike does.

Bikes that successfully utilize a light flywheel system can create a very comfortable riding experience, but it’s all about the speed at which that flywheel is spinning.

Which brings me to an important point- just because a bike has a light flywheel doesn’t mean it’s optimized for increased flywheel speed.

There are plenty of exercise bikes out there that are geared the same way as traditional heavy-flywheel models, but come equipped with light flywheels.

These bikes are not going to provide the same feel as a bike like Keiser that is designed specifically to use a light flywheel.

In other words, some bikes use a light flywheel to save cost; others use a light flywheel on purpose.

Final Thoughts

Ok, exercise bikes come in all shapes and sizes. They all use a flywheel of some sort and these flywheels can be heavy or light.

Great- but which is better?

I wish I could provide a cut and dry answer to that question, but it all depends on what you’re looking for.

Something you should keep in mind, is that most home exercise bikes are designed with a system that would benefit from a heavier flywheel.

Keiser is an obvious exemption because they’ve designed a light flywheel system that works wonderfully. And there are other brands out there trying to copy their success.

But in order for a light flywheel to work as well as a heavy one, it has to spin much faster- if the bike isn’t designed to get that flywheel moving fast enough, the resulting workout experience will suffer for it.

Another thing to consider is that going with a heavy flywheel is a usually a much more budget friendly way to go.

Keiser is awesome, but it does cost $2k. Let’s be real, not everyone is working with that kind of budget.

So if you’re working with a tighter budget, I’d recommend going with a heavy flywheel system.

If you’re looking for a spin bike, but are dealing with arthritis in your knees, you may be better off with a light flywheel that doesn’t require as much effort to start and stop (light flywheels tend to be a little less “jarring” on the joints as well).

I know I’ve been referring to spin bikes a lot throughout this article- this is because flywheel weight is usually associated most with these bikes that are designed for high intensity workouts.

But flywheel weight is an important consideration for upright and recumbent bikes too, especially if you’re looking for a bike that can provide a more strenuous workout.

Just like spin bikes, upright and recumbent bikes that utilize lighter flywheels will likely be significantly more expensive. The fact is, increasing flywheel weight is the most affordable way to provide a smooth ride.

Ok, I feel like I’m starting to ramble on a bit here, so I think it’s time for me to sum things up:

When it comes to flywheel weight, I think heavier is the way to go for most of us. It’s a pretty safe bet that an exercise bike with at least a 20 lb flywheel is going to provide a fairly smooth ride. These bikes tend to be more cost effective than advanced bikes that properly utilize a light flywheel.

Alright, that’s all I got for now. I know that’s about as clear as mud, but ultimately it really does come down to personal preference.

I’d love to hear what you think about the topic. Leave a comment and let’s get the discussion going.

 

 

 

 

Will

19 Comments

  1. Hi, I am looking to get a spin bike mostly for medium-intensity cardio workouts, but nothing too intense. I am choosing between a bike with a 29-lb flywheel and magnetic resistance versus a 40-lb flywheel with felt friction resistance. Both are belt drive. Do you think the 29-lb flywheel would be too light? Would the convenience of magnetic resistance and less upkeep compared to the felt resistance be worth the lighter flywheel? Thanks in advance!

    • Hey, great question. I think 29 lb is definitely heavy enough to provide a great workout, especially for moderate intensity workouts. Personally, I’d go with the lighter flywheel and magnetic resistance (I’m not much of a fan of felt friction). The magnetic system will help add to the overall smoothness of your rides and not having to worry about the felt pad breaking down is a huge perk.

  2. I’ve read comments that the Keiser is harder on your joints. Two factors, Q factor is large on the Keiser and the lighter flywheel doesn’t supply enough inertia on the upstroke. Apparently it also gets choppy at higher speeds. I like the design/weight of the Keiser but worry as I have knee issues.

    • At around 200 mm or so, the Q factor on the Keiser is a little wider than some, but I think they did that on purpose. Keep in mind, a narrow Q factor is only beneficial to some- it all depends on your body shape and size. If you have a narrow pelvis/hips, you may benefit from a smaller Q factor, but if you don’t you might actually benefit from a wider one. Honestly, most of us probably wouldn’t notice the difference between a few millimeters here or there. And if you have bad knees, I would think the lighter flywheel might be beneficial for ya too- it’s going to put less stress on your joints to get it started from a cold start (and make it easier to stop). And I haven’t heard many complaints about the smoothness of the Keiser M3i- the flywheel builds momentum through speed of revolution instead of using added weight. Elite cyclists can probably tell the difference, but I’m not sure your average recreational rider could. Either way, I don’t think the Keiser would really be any harder on your knees than any other spin bike. The best way to tell for sure with that Q factor would be to take one for a test spin. PS- they have a 30 day return policy if it’s uncomfortable. Hope that helps!

  3. HI, my ortho doc is suggesting I get a bike. Ride, ride and keep riding and moving that knee he says! I had a complete tear of ACL back in August and trying to rehab w/o surgery. No arthritis in knees but have a lot of overall joint pain. I also need to lose 20lbs. What would be the best bike for someone like me ?Thanks:)

    • Sorry to hear about your knee. You’re safest bet would be going with a recumbent bike- they’re the lowest impact and are the same kind of bikes you’d find in a therapy clinic. Recumbents are a good way to keep that knee moving like your doc wants. And since they’re so low impact, it should be pretty comfortable for ya. And if you get a nice one, you can still get a pretty intense cardio workout on one. Not sure what kind of budget you’re working with, but I like Sole and Spirit as brands. Diamondback’s are also great. They all offer heavy-duty machines that are easy to use. Here’s my recumbent bike guide if you wanna check it out. Hope that helps and good luck with that knee!

      • Hello there,

        what are your thoughts on the Yesoul S3? I was wondering if that also counts in as a good flywheel bike with only 7,5kg and magnetic resistance. I’m not sure if it’s the right thing for me. I’m looking for a medium workout, 2-3x per week 45 min cardio sessions.

        • Hi, I’m not familiar with that bike, but I checked it out. A 7.5 kg (or 16.5 lb) is quite light for an indoor cycle, especially for one that’s going for around $500. The weight capacity for the S3 is really low too, so I think you can do a little better for that price range. Depending on what’s available in your area, you might want to check out the JOROTO X2 (it’s on Amazon)- it goes for around $400 and comes with a 35 lb flywheel and a 300 lb weight limit. If your budget allows, Schwinn’s IC3 could also be a good option: for about $650, you get a 40 lb flywheel, a 300 lb weight capacity, and a nice warranty. Hope that helps and thanks for reading!

  4. Hello, I have my eyes set on this bike. It has a 25lb flywheel, and a maximum weight limit of 330lbs. I’m around 270lbs and I need to lose weight. Is this a good enough flywheel weight for me to lose at least 100lbs or anything?

    • Yeah, I think a 25 lb flywheel is heavy enough to feel smooth during workouts and also heavy enough to provide enough resistance to get a great workout. Good luck with your weight loss journey!

  5. I’ve got a NordicTrack R35. The wheel is not smooth. There’s a gap when you pedal a full turn and it’s like starting over. Jerky a bit. It has a 25 lb wheel or so. How is it that it’s not smooth? I’ve tried the Schwinn IC4, Bowflex C7, Velocore and a Pro form cx 10. All heavier wheels and totally fantastic smooth. I’ve ordered the Sole R92 as it’s compatible with Zwift and others but it has a 20 lb wheel so I’m thinking it’ll be bad too. I’m wanting a recumbent bike with a smooth wheel that works good with Zwift etc.

    • Hmm, sounds like that R35 might have a malfunction or something not working correctly, because a 25 lb flywheel is definitely heavy enough to provide a smooth feel. Have you contacted NordicTrack’s customer service? If not, that would be my first suggestion, although don’t expect going through their customer service to be an easy process. The R92 is an awesome bike and that 20 lb flywheel should feel just fine. Don’t let your bad experience with the R35 make you think you need heavier than a 25 lb flywheel because you don’t (personally, I prefer Sole products to NordicTrack anyway). I hope your experience with your R92 is better and I’d love to hear what you think about it when you get it. Good luck!

  6. I’m currently shopping for bikes and man is it frustrating. There are so many choices and I’m going out of my mind. I came across the Sunny brand model that has the 7.36lb aluminum flywheel. It’s in my price range I’ve been looking at but the flywheel weight is throwing me off. When riding a bike on the road my knees definitely start to hurt after about 20 minutes or so and after reading your article I’m thinking I should go with this one instead of the Schwinn or other Sunny models with heavier flywheels. Have you heard anything about this model and if it performs well with the light flywheel?

    • Hi, yeah I’ve heard of the SF-B1709- you can actually check our review of it out here. I think it’s a pretty solid choice for the price. If you commonly have knee pain with riding, the lighter flywheel might not be a bad idea- it’ll definitely make it easier to start and stop, putting less stress on your knees in both cases. Sunny is a pretty trusted budget brand too and they do a nice job with their indoor cycles. User reviews for this bike are very positive as well. Overall, for the price, I think it’s a pretty good option.

    • Hmm, I’m afraid I’d need a little more info than that to provide any assistance. You might want to check out some of my buyer’s guides for info on the different types of exercise bikes.

  7. Hi, I have arthritis in one knee and cartilage year as well as some ligament laxity – any bikes you would recommend? I have ridden bikes outdoors for years in my 20s (daily about 20+miles/daily commute) with the same existing knee problem and had no knee pain. Any suggestions much appreciated. Many thanks

    • As long as riding an outdoor bike doesn’t aggravate your knee problems, you should be fine with riding any style of exercise bike. Indoor cycles replicate the experience of riding a road bike the most, so if that’s what you’re going for I’d recommend an indoor cycle (aka spin bike), especially if you’re looking for a bike that can provide a great workout. These bikes come in a wide range of prices and features, so it really depends on what you’re looking for. Here’s a link to my spin bike guide that might be helpful. Take care and thanks for reading!

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