Why Is The Flywheel Weight Important For Spin Bikes?

Why is flywheel weight important for spin bikes zoomed on flywheelWhen you look at spin bikes on the internet there is a lot of talk about the importance of the flywheel weight. Its’ weight is one of the main differences between a standard upright exercise bike. It seems to be accepted that the heavier it is the better it is.  But why?

The flywheel is a big wheel usually situated at the front of the bike. It is perimeter weighted to give it more momentum.

As you turn the pedals the flywheel turns. It is connected to the pedals by way of a chain or belt drive. The heavier the flywheel is, the harder it is to get turning and once you have it turning the longer it will take to slow down because of the momentum that has built up – it carries on turning after you’ve stopped pedalling.

This arrangement was first introduced in the 1980s. It gave you a similar riding experience indoors to the one you have when riding an outdoor bike.

Without the weight of the flywheel it is too easy to pedal and the wheel stops turning as soon as you stop pedaling which is not what happens when you ride a bike.

Outdoor Bikes And The Flywheel

When  you start pedalling on an outdoor bike you have to push hard to get started and when you have got it moving the bike will continue to move on its own when you stop pedalling. On an outdoor bike your bodyweight is providing the weight you push against and gives the bike the momentum. The bike continues to move forward when you stop pedaling.

This is the experience that a heavy flywheel provides for the user on an indoor bike. The feel is much more natural and it won’t feel like the effort is too easy or you are riding in the wrong gear.

Natural Smooth Ride

The flywheel also provides a more fluid cycling motion. Without the weight of the flywheel, pedaling is more jerky and is more of an up and down motion which can add pressure on to your joints and can make you more susceptible to injury.

With a light flywheel you are constantly adjusting your pedalling speed. The pedals will speed up on the down stroke and then slow down as you move round the bottom and top of the pedaling cycle. This is because there is no weight to keep them turning and so they will slow down quickly.

A heavy flywheel can also smooth out any irregularities that might be caused by the friction on the resistance pads not grabbing the wheel evenly due to poor adjustment or wear.

What Weight?

The weight that the flywheel begins to be heavy enough to givee these benefits on a spin bike is around 30 lbs where the cycling motion becomes fluid and natural. As the flywheel gets heavier the motion becomes more smoothed out but it gets harder to get it started and it takes longer to slow or to stop the flywheel.

The heaviest flywheel I have seen on a bike is 66 lbs and this is really for the very seasoned trainer who is in training for endurance events.  It makes getting started more demanding and much more effort is required to stop.

Most spin bikes are in the range of 30 lbs to 50 lbs and for most people this range is fine for providing them with the smoothness and workout they want.

One disadvantage of heavier flywheels is that they cost more to make and that adds to the overall cost of the spin bike as well as making the bike heavier which can be a problem when you come to move even with the transport whells

The big benefit of the heavy flywheel is the natural and smooth riding motion that gives a better and more efficient riding experience. This helps to prevent injuries to your joints that could come from the choppiness of the up and down motion which is due to changes in speed that happen when you have a light flywheel in particular when out of the saddle pushing against the resistance.

But what about bikes such as the Keiser M3i with a light flywheel. It only has an 8 lbs flywheel and that is at the back of the bike rather than at the front.

Despite the light flywheel it still produces a smooth and natural ride and most customers give it top marks. It uses a different approach to getting the momentum needed by increasing the speed the flywheel is turning than on traditional spin bikes.

This additional speed produces the same feel (of momentum or kinetic energy) for the customer when riding the bike as the heavier flywheels with the usual chain or belt drive configuration. It has a much larger pedal belt wheel giving a higher gearing ratio.

It has the momentum to keep the pedals turning so they don’t slow too much to help keep a cycling motion while pedalling and prevent an up down motion. It does come at a cost with you not getting much change from $2000 (there are a number of other qualities to the bike including belt drive, magnetic resistance and it looks great too).

The important thing is that both approaches is they provide a fluid natural ride when you are working out or training.

It can be done by weight or speed – as a general rule to get the required momentum a heavier flywheel is a more economical than the faster flywheel.

30 comments for “Why Is The Flywheel Weight Important For Spin Bikes?

  1. Felix Kronabetter
    March 6, 2018 at 7:00 pm

    Thanks! Very useful info…

    • Paul
      March 7, 2018 at 6:53 pm

      You’re welcome. That’s great to hear. Thank you.

    • Mrs Wendy Sanderson
      April 14, 2021 at 7:25 am

      This is a great informative web site – helped us pick the right bike and understand how they work. Thank you for your great information!

      • Paul
        April 14, 2021 at 5:38 pm

        That is fantastic to hear. Thank you. It’s great it helped you in picking the bike that is right for you.

        • ashish garg
          May 5, 2021 at 5:48 pm

          Can U Comment on Magnetic Resistance bs Friction Resistance Bikes
          and also
          Precor Spinning Bike Perimeter Wheel front flywheel va Matrix CXC Bike Rear Light Flywheel Magnetic Resistance

  2. Tristell Santa Cruz
    March 31, 2018 at 6:16 pm

    Very good details between the weight differences, helped me make my decision which spin bike to purchase!

    • Paul
      September 3, 2018 at 5:36 pm

      Thank you. Great to hear it helped.

  3. Heelai Shinwari
    April 11, 2018 at 4:04 am

    Hi. I have the Schwinn Perimeter Weighted Flywheel and I need help connecting it. I cannot find the spot where that turns it on.

    • Paul
      June 1, 2019 at 1:11 pm

      I’m not sure I understand the question and I’m very sorry for delay in seeing and responding to your question. Hopefully you got it sorted.

  4. Yolanda
    July 25, 2018 at 4:15 am

    Awesome info. Exactly what i needed to know

    • Paul
      August 23, 2018 at 4:11 pm

      Thank you, I’m glad you found it helpful

  5. Vernon Pye
    September 16, 2018 at 1:01 am

    Is a 13.2 lbs flywheel to light for a home bike?

    • Paul
      December 6, 2019 at 7:12 pm

      It depends on the type of bike and what your exercise goals are.

      As a general rule for indoor cyclies and spin bikes it is too little to give a natural smooth ride similar to an outdoor bike but the Keiser M3i is one exception. You probably want at least a 30 lbs.

      On upright bikes they can be that weight but there isn’t the same requirement for someone to train as intensely as you can on a spin bike/indoor cycle.

  6. Ronny
    October 30, 2018 at 9:28 am

    Very handy info. Thanks for taking the time to explain to people.

    • Paul
      May 28, 2019 at 5:26 pm

      You’re welcome – great to hear this.

  7. Alex
    January 24, 2019 at 7:20 am

    What about Keizer mi3?

    • Paul
      June 3, 2019 at 6:12 pm

      Hi, you can read my review on the bike here.

    February 22, 2020 at 1:53 pm

    So, I have a “OLD” probably 20+ year stationary bike. My wife and I want to upgrade but there are so many options. We want something that can be used for a casual spin but also hold up to out of the saddle spinning. My wife is fun sized, 5′ 130lbs and I am 6’1 220lbs. Is there a good check off list to go by?

    • Paul
      February 22, 2020 at 2:16 pm

      Our compare page may help you. It lists all bikes reviewed. It includes a guide to height range, price, style (indoor for spinning). You can find the comparison pay here. It’s not a check list you can tick off but it is a good start. (I believe.) If there is anything more you’d like to know, please let me know in the comments below.

  9. Sven
    March 30, 2020 at 7:22 pm

    Your site provides the information I was looking for. As someone else said, thank you for taking the time to provide this wealth of information. I am an advid rider am looking for a bike that will challenge me.

    • Paul
      March 30, 2020 at 7:43 pm

      It’s great to hear that. Thanks for your feedback on the site. Hopefully, you’ve found the information you need to find the bike you are looking for. If not, please let me know.

  10. CamSam
    May 15, 2020 at 9:25 am

    Hi – Thanks for your article! I’m comparing a 11kg flywheel with a belt drive and magnetic resistance, vs a 20kg flywheel w/ chain drive and friction resistance. Which do you think is the better bike?

    • Paul
      May 15, 2020 at 7:05 pm

      Hi – it’s great to hear you like the article. Assuming these are the same style exercise bike and are an indoor cycling bike /spin bike then:

      For a spin bike / indoor cycling bike an 11kg (approx 24 lbs) flywheel is on the light side unless it has a similar set up to the Keiser M3i which only has approx 4kg flywheel (8 lbs). If you are wanting to do indoor cycling workouts and stand up on the pedals at various intensities and resistance then I’d go for the 20kg flwheel (44 lbs).

      The friction resistance vs magnetic resistance will make a whooshing sound and require some maintenance to keep it working optimally.

      The chain drive vs belt drive the chain drive will have a clinking sound and need lubricating and tightening from time to time vs the low maintenance and very quiet belt drive.

      It can come down to your fitness goals, type of cardio exercise you want to do, the style of bike, cost of the exercise bike as well as flywheel weight, drive type and resistance type.

      I hope this helps you in choosing between your bikes. If you have any other questions please let me know and I’ll help where I can.

  11. Susan WOOLDRIDGE
    September 2, 2020 at 11:26 am

    I am 73 years old and have decided to try an exercise bike as my feet are not great for walking. I have read all your comments about the fly wheel weights but still not sure which to choose. I would like to pay around £120 – £150 and have something fairly sturdy but pretty basic with a seat back and not too heavy as I will need to move it myself. It is my legs that I want to exercise rather than a full workout. Perhaps you can help me.

    • Paul
      September 2, 2020 at 8:05 pm

      You may want to look at recumbent or semi-recumbent exercise bikes rather than a spin bike (designed to be similar to an outdoor bike and don’t have back support) as they have back support. You are in a more of sitting down position with your leg out in front of you rather than below you. Two bikes you may want to consider are, looking at the reviews (I’ve not researched in detail) in the UK near the price range and have transport wheels to help with moving around, Sunny Health & Fitness SF-RB4616 weighs 27 kg and the skandika Foldaway X-1000 Plus Fitness Bike weighs 16.5 kg.

      I hope this is of help and good luck.

  12. Adam
    January 27, 2021 at 2:55 pm

    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!

    • Paul
      February 1, 2021 at 7:31 pm

      You can still get a good smooth natural feel with a lighter flywheel (e.g. Keiser M3i Bike <9 lbs but you pay a premium price for it). It depends on gearing ratio etc. Check the reviews to see what people say about the cycling experience. For moderate workouts it shouldn't be an issue.

      In using a felt resistance bike there is a little more noise and maintenance involved but not prohibitive by any means, If you just want to get on your bike with minimal checking then magnetic resistance is the way to go.

  13. Fiona O Connor
    February 8, 2021 at 4:53 pm

    Hi, thanks for the information. I have attached links to 2 bikes below and was wondering which ones you think is the best? 1 has an 18kg flywheel and the other has a 5kg flywheel, both magnetic belt driven bikes. I like to get up and cycle and follow fitness classes when I am on the bike.

    18kg flywheel: https://www.mcsport.ie/collections/exercise-bikes-76/products/hit-fitness-g8-indoor-cycling-bike-hit00235

    5kg flywheel: https://www.mcsport.ie/collections/exercise-bikes-76/products/hit-fitness-s12-spin-bike

    • Paul
      February 9, 2021 at 7:48 pm

      Hi, These are 2 bikes I’m not familiar with.

      The G8 is listed on the site you link to as magnetic resistance but in their brochure it is listedas having friction resistance. Looking at the pictures it could be either. I’ve asked the supplier to clarify.

      The G12 flywheel is light and I can’t see how they get the inertia in the wheel to help provide smoothness and fluidity in the pedaling motion. It doewsn’t appear to have the gearing ratio that the Keiser M3i has. I’ve asked the supplier about this too.

      Sorry I don’t have an answer for you. When I get a response I should be able to help further.

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