Suspension in balance bike

[Julian_M]

Please refer to this kiddie 12" wheel balance bike with suspension.

Almost all kiddie balance bike (12" or 14" wheel diameter) don't have any suspension. Only a rare few has it, I found the above china made. I'd like to know the following.

1. In bicycle in general. Rear suspension is to make the tire get in contact with the ground more. But this equates to rider comfort too in all cases? Because I read some articles that rear suspension in bicycle is for maneuverability and not more on rider comfort.

2. In kids balance bike, the kid feet are directly on the floor due to lack of pedals instead of bending the knees when using pedals. So the vibration from bumpy floor can reach the kid more. If there is a suspension in the rear, would the vibration from the floor still transmit to the kid feet and body? If kid feet are on pedals, then it won't transmit, but remember in balance bike, there is no pedal so kids feet step directly on the ground.

3. When comparing to mountain bikes, the suspension is put in different places than the above. Do you consider the above as more of a seat suspension than frame suspension? How do you analyze it mechanically? Why don't mountain bikes use the above configuration too?

Thank you.

 

[Baluncore]

Do you consider the above as more of a seat suspension than frame suspension? How do you analyze it mechanically?

There are three forms of suspension present.

Firstly, the pneumatic tires offer a high frequency vibration and noise reduction to the frame and seat pillar.

Secondly, the seat is about halfway between the front and rear wheels. That reduces the vertical movement of the seat, to half the height of any bump in the road.

Thirdly, when crossing larger bumps, the spring in the frame effectively reduces the amplitude and rate of seat vertical movement.

 

[berkeman]

IMO, don't waste any money or brain cycles on suspension for a kid's balance bike. Wait until they are riding and pedaling big trails with you and need front and back suspension to absorb the bumps and landings.

 

[Julian_M]

There are three forms of suspension present.

Firstly, the pneumatic tires offer a high frequency vibration and noise reduction to the frame and seat pillar.

Secondly, the seat is about halfway between the front and rear wheels. That reduces the vertical movement of the seat, to half the height of any bump in the road.

Thirdly, when crossing larger bumps, the spring in the frame effectively reduces the amplitude and rate of seat vertical movement.

What is the difference if the wheel is 12" vs 14"? Does 14" wheel have suspension characteristic similar to the 12" with suspension?

Also see the image below. The suspension is put differently. What would happen if the 12" balance bike in original message has this suspension configuration?

Or what would happen if the following big adult bike has suspension placement similar to the original message 12" balance bike suspension (see original image)?

 

[Baluncore]

What is the difference if the wheel is 12" vs 14"?

The road will appear to be slightly rougher, because the contact patch of the pneumatic tire with the road will be shorter, so it will average less of the road surface.

Does 14" wheel have suspension characteristic similar to the 12" with suspension?

No. The wheel diameter does not change the geometry of the spring suspension.

What would happen if the 12" balance bike in original message has this suspension configuration?

No difference. The hinge pin is still on the crank axis, so the spring still controls the height of the seat above the ground.

 

[Julian_M]

The road will appear to be slightly rougher, because the contact patch of the pneumatic tire with the road will be shorter, so it will average less of the road surface.


No. The wheel diameter does not change the geometry of the spring suspension.


No difference. The hinge pin is still on the crank axis, so the spring still controls the height of the seat above the ground.

The reason I was looking for suspension for the 12" balance bike was because our enclosed or fenced apartment outdoor flooring uses Clay Brick Pavers like the following:

There is no other place to use the 12" balance bike. We can't use it inside house as the area is small. And we can't use it in the public road, obviously to avoid hazard from cars or other vehicles. Do you call the above bumps high frequency or low frequency bumps? How would bigger tire help and suspension? If I get 14" balance bike without suspension, how would it behave compared to the 12" balance bike with the suspension (as in the image in original message)?

 

[Baluncore]

A balance bike will not be needed for long, see if you can find one second hand, any configuration will do for your yard.

There is no other place to use the 12" balance bike. We can't use it inside house as the area is small. And we can't use it in the public road, obviously to avoid hazard from cars or other vehicles.

If it will only be used in the yard then it does not matter what you get. The pavers are mostly level, so lower the tire pressure slightly if needed to hide any uneven joints. Use the smallest wheels available since that will aid turning in the confined space.

How would bigger tire help and suspension?

For your yard, suspension is quite unnecessary. Bigger tires will make turning more difficult in the small area.

 

[Julian_M]

A balance bike will not be needed for long, see if you can find one second hand, any configuration will do for your yard.


If it will only be used in the yard then it does not matter what you get. The pavers are mostly level, so lower the tire pressure slightly if needed to hide any uneven joints. Use the smallest wheels available since that will aid turning in the confined space.


For your yard, suspension is quite unnecessary. Bigger tires will make turning more difficult in the small area.

I used the following scooter with 5 inches wheel and suspension on the pavers weeks ago and I could feel the bumpiness. So you are saying the bigger wheel of the bike can average more of the surface and hence the bumpiness will be entirely gone? If not entirely gone, the suspension of the bike can help, why won't it?

I ordered the following before and received it but the bearing was knocked out of 12" wheel during shipping and I was waiting for replacement of the wheel. I can sell it after assembled and get the one with suspension pending some computations and mechanical analysis..

It says in the manual it can support 30 kg. In the middle there is a joint connecting the front to the bending mechanism.

I'd like to ask about Nylon Fiberglass. There is glass inside the nylon and it is very strong in tension. So can the joint at right side able to support 30 kg. or is it 15 kg as it is at center? And can 12" pneumatic wheel support 30 kg? How do you compute what is the maximum weight that can be support by a 12" pneumatic tire?

 

[berkeman]

I used the following scooter with 5 inches wheel and suspension on the pavers weeks ago and I could feel the bumpiness.

That scooter has solid rubber tires, so no wonder you felt the bumps! You need pneumatic tires to get that part of the suspension system of a bicycle. What kind of wheels does this new balance bike have? Pneumatic or solid rubber?

 

[berkeman]

BTW, depending on the diameter of the downtube on that seatpost and your kid's inseam, you may be able to get a standard seatpost with suspension built in that will work. That will cushion the ride for the little one. Measure the seatpost downtube diameter and look at suspension seatposts like these:

https://www.cyclingabout.com/best-suspension-seatposts-touring-bikepacking/

The new seatpost and seat are something that you can move to the next few bikes that your kid rides as they grow and graduate to bigger bikes.

 

[Baluncore]

So you are saying the bigger wheel of the bike can average more of the surface and hence the bumpiness will be entirely gone?

The only bumps you felt were when the small hard wheels of the scooter fell into the gap, or crossed the step difference at the gap between pavers. The bigger wheel with lower tire pressure will completely hide that step change from the rider. If the step change was sufficient to cause a rough ride, then you would trip when walking on the pavers, and so you would reseat them, eliminating the problem.

If not entirely gone, the suspension of the bike can help, why won't it?

Spring suspension reduces the shock on the bike frame, and increases the comfort of the rider when off-roading. Spring suspension will only be an advantage when crossing gutters or curbs that might suddenly lift or drop the mass of the rider by more than about 50mm, 2".

Suspension will not help in your yard because the height of the pavers are all about the same. There are no sudden changes in the height of the rider above that level, so the averaging effect of two pneumatic tires will more than suffice to bridge the gaps between pavers.

 

[Julian_M]

That scooter has solid rubber tires, so no wonder you felt the bumps! You need pneumatic tires to get that part of the suspension system of a bicycle. What kind of wheels does this new balance bike have? Pneumatic or solid rubber?

All of the wheels of the new balance bike I mentioned all use pneumatic air pump. Not solid rubber.

I read somewhere that when a child is using pedal, the knees are bent and not touching the ground/road. Whereas when using balance bike without pedal, there is contact of feet with floor that can send shock wave across spine. I am trying to search where I read it again. But if anyone has more details of this, kindly share it. Thanks.

 

[berkeman]

I read somewhere that when a child is using pedal, the knees are bent and not touching the ground/road. Whereas when using balance bike without pedal, there is contact of feet with floor that can send shock wave across spine.

No, that is false. Any road bumps are transmitted to the bike, not to the biker's feet pedaling on the ground. Lordy.

All of the wheels of the new balance bike I mentioned all use pneumatic air pump. Not solid rubber.

Great, so run a little low air pressure in the tires and your kiddo should be be fine.

 

[Julian_M]

No, that is false. Any road bumps are transmitted to the bike, not to the biker's feet pedaling on the ground. Lordy.


Great, so run a little low air pressure in the tires and your kiddo should be be fine.

The kid is 6 years old but overweight. He weights 75 lbs or 34 kg. Kid that age should only be 20 kg.

What is the maximum weight that can be supported by typical air filled 12" pneumatic tires in a bike. I need computations so I can decide whether the tires can support him.

 

[berkeman]

What is the max rider weight for the bike on its datasheet?

 

[Julian_M]

What is the max rider weight for the bike on its datasheet?

Some 12" balance bike lists 80kg. some 30 kg.. that is why I need to know first if 12" pneumatic tire can take more than 30kg. If computations show it allows up to 80kg. Then I can believe some China data sheet which you know are not actually computed by mechanical analysis. They are not Honda but just generic bicycle makers so just estimate it.

 

[berkeman]

He weights 75 lbs or 34 kg.

Some 12" balance bike lists 80kg. some 30 kg..

Then buy the 80kg bike for your son and install the suspension seat post for comfort. Done.

 

[Julian_M]

Then buy the 80kg bike for your son and install the suspension seat post for comfort. Done.

What do you think about Magnesium alloy frame? I heard it is fragile and can just break. I’m also thinking about stainless steel, aluminum or carbon steel body. But the latter quite heavy. And if 12” or 14” wheel size