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Softride/Beam bike Rolling Resistance

 

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devashish_paul

Apr 4, 12 19:34

Post #1 of 33 (3741 views)
Softride/Beam bike Rolling Resistance Quote | Reply

....need to only lift some of the rider, not all the rider for each bump on the road, resulting in less tire deformation.

According to the old softride website: http://www.softride.com/..._adv/resistance.html



This is actually in line with my results at Ironman Canada, (in 6 years in the 90's my times were similar, but the one year I rode with a softride, my time was 10 minutes faster)....some of that is aerodynamics, but what they say makes some sense.


cervelo.com (P3) |infinitnutrition.ca | bushtukah.com
Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


(This post was edited by devashish_paul on Apr 7, 12 17:41)


Broken Leg Guy

Apr 5, 12 18:41

Post #2 of 33 (3641 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

The TitanFlex site used to have a chart like that too. Can't seem to find it on the current site. I love my TF!


Formerly DrD


Epic-o

Apr 5, 12 19:41

Post #3 of 33 (3606 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

But they don't say how they modified the rolling resistance to obtain that table...

3 seconds/km due to rolling resistance it's impossible


BICYCLE DESIGN AND + http://cds-0.blogspot.com/




Jiowa

Apr 5, 12 19:54

Post #4 of 33 (3595 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

Interesting, so on a bad road, not only does a beam bike feel more comfortable but it decreases the rolling resistance. Nice!




Running is a gift.


devashish_paul

Apr 6, 12 9:44

Post #5 of 33 (3494 views)
Re: Softride/Beam bike Rolling Resistance [Epic-o] [In reply to] Quote | Reply

It would be interesting to see how they got the data. My data points where 5xIMC with rigid bike generally 10-15 min slower than with the beam bike. 1xWildflower with beam bike 7 minutes faster than the 2 times with rigid bike. The wildflower result is actually more significant, because of the rough road and the time I did it with beam bike I was no where close to the biking fitness the 2 times without beam bike. Unfortunately, i don't have powermeter data to back this up, just race times and we know they are variable, but I think the hypothesis that they present is sound because the road has to deflect a smaller percentage of the rider's weight than with a rigid bike, leading to less tire deformity.


cervelo.com (P3) |infinitnutrition.ca | bushtukah.com
Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


Greiffster

Apr 6, 12 11:18

Post #6 of 33 (3464 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

<<but I think the hypothesis that they present is sound because the road has to deflect a smaller percentage of the rider's weight than with a rigid bike, leading to less tire deformity.>>

The problem with the hypothesis is that it is only half the equation. The beam is loaded and effectively reduces the force between the road and the tire as the bike rolls over the bump. Yes, for a split second. What Softride doesn't mention is what happens after that. The beam will "unload" its compression and effectively add that force to the weight of the rider, for another split second. During this time, you will increase the tire deformity and subsequent rolling resistance. Its a wash.



jeffp

Apr 6, 12 12:32

Post #7 of 33 (3431 views)
Re: Softride/Beam bike Rolling Resistance [Epic-o] [In reply to] Quote | Reply

this!!

we made up an impossible model and then passed it off as science. see, um, these 30-40w of rr, well with this bike, they are 0-10. gotcha, makes sense


Damon

Apr 6, 12 13:37

Post #8 of 33 (3406 views)
Re: Softride/Beam bike Rolling Resistance [Greiffster] [In reply to] Quote | Reply

Quote:
The beam will "unload" its compression and effectively add that force to the weight of the rider, for another split second. During this time, you will increase the tire deformity and subsequent rolling resistance.
This is only true if loss due to tyre deformation is linear, which it isn't. You lose more energy from one deep deformation than from two shallow ones.
Why? The tyre carcass deforms more on large impacts, and a tyre loses energy each time it stretches and returns to a position (it's not a perfect spring, it has hysteresis). The most efficient system varies the deformation of the tyre as little as possible.
So suspension is better for rolling resistance.


Jiowa

Apr 6, 12 14:06

Post #9 of 33 (3387 views)
Re: Softride/Beam bike Rolling Resistance [Damon] [In reply to] Quote | Reply

Damon wrote:
Quote:
The beam will "unload" its compression and effectively add that force to the weight of the rider, for another split second. During this time, you will increase the tire deformity and subsequent rolling resistance.

This is only true if loss due to tyre deformation is linear, which it isn't. You lose more energy from one deep deformation than from two shallow ones.
Why? The tyre carcass deforms more on large impacts, and a tyre loses energy each time it stretches and returns to a position (it's not a perfect spring, it has hysteresis). The most efficient system varies the deformation of the tyre as little as possible.
So suspension is better for rolling resistance.

True. Just need to find a really bad road to test this on.




Running is a gift.


trail

Apr 6, 12 14:44

Post #10 of 33 (3375 views)
Re: Softride/Beam bike Rolling Resistance [Damon] [In reply to] Quote | Reply

>The most efficient system varies the deformation of the tyre as little as possible. So suspension is better for rolling resistance.

Two points.

You seem to be making the assumption that the efficiency of the tire deformation is less than the efficiency of the beam deformation. You're simply transferring the deformation from one spring system to another (And one of those spring systems is far more directly linked to my scrotum, so I'm not sure I want the high frequency deformation transferred from tire to beam. Running a supple tire that handles those deformation well seems, empirically to be both comfortable and efficient.

And second, I question whether the beam system is an efficient "impedance matching transformer" for high frequency "bumps" relative to other frame based suspension, such as the fork and stay system. Cervelo, for one, seems to have puts its money into the stay system on the R5 and its predecessors.


(This post was edited by trail on Apr 6, 12 18:36)


Tom A.

Apr 6, 12 15:34

Post #11 of 33 (3359 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

devashish_paul wrote:
...but what they say makes some sense.

No. It doesn't.



http://bikeblather.blogspot.com/


Jiowa

Apr 6, 12 16:44

Post #12 of 33 (3329 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

Beam deforms instead of tire, reducing rolling resistance. That makes sense.

Now I don't know if it's true but I'm guessing it is but I doubt it's as big as they claim.

15 watts per wheel sounds reasonable to me, so assuming 30 watts per tire and a beam reduces this by 10 watts that would save about 10 minutes over 112 miles. Of course, reducing the rolling resistance by 33% is probably impossible.

If the beam does help it's likely to be about 1 watt or less.




Running is a gift.


Tom A.

Apr 6, 12 17:29

Post #13 of 33 (3316 views)
Re: Softride/Beam bike Rolling Resistance [Jiowa] [In reply to] Quote | Reply

Jiowa wrote:
Beam deforms instead of tire, reducing rolling resistance. That makes sense.


No. It doesn't.



http://bikeblather.blogspot.com/

(This post was edited by Tom A. on Apr 6, 12 17:45)


Jiowa

Apr 6, 12 17:34

Post #14 of 33 (3310 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

Tom A. wrote:

No. It doesn't.

Does too.




Running is a gift.


jeffp

Apr 6, 12 17:44

Post #15 of 33 (3305 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

see Tom, you are missing that the beam is an anti-gravity system. it takes your weight off the wheels so the tires never have to deform. If we weighed you and your beam bike together at say 180lbs, once you got on it, that would magically become 20lbs as your weigh towuld vanish from teh system, cuz da beam is taking it anti throwing it into som ecosmic wormhole.


devashish_paul

Apr 6, 12 19:13

Post #16 of 33 (3280 views)
Re: Softride/Beam bike Rolling Resistance [trail] [In reply to] Quote | Reply

Read carefully what Damon said. I would tend to agree that the tire is less efficient in dealing with deformation at high frequency than the beam (I suppose it depends on beam design). I am not sure you have ever ridden a beam bike but it is far more comfortable than any rigid bike I have ever ridden....the closest has been the Airfoil pro and even then it's no match of the beam.

Tom I believe the entire premise is that the beam is much more efficient at dealing with high frequency vibration than the tire. This is where the gains are supposed to come from, allowing you to ride with higher tire pressure without the Crr loss that is associated with high tire pressure in the real world.

Again this is old softride data. Those bikes were always fast. I am not sure how much came from better aerodynamics than bikes with seat stays and dowtubes and how much was from purported rolling resistance savings.

To the person saying that the bike + rider weight remains unchanged, you are correct. But the bike + rider weight only come into play when you have to move the bike plus rider vertically to deal with road vibrations. If you just need to move the bike (vertically), but not the rider, then would the total weight associated with tire deformation not be less (the rider is not vertically displacing, only the bike)?


cervelo.com (P3) |infinitnutrition.ca | bushtukah.com
Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


trail

Apr 6, 12 19:23

Post #17 of 33 (3265 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

 >If you just need to move the bike (vertically), but not the rider, then would the total weight associated with tire deformation not be less (the rider is not vertically displacing, only the bike)?

I don't think it would be less. Assuming completely undeformable tires and a perfectly efficient beam suspension, (zero energy loss and zero rider displacement) the energy required to deform the beam would exactly equal the energy to actually lift the rider. E.g. the effective force of tire-to-road would remain the same.

You may gain comfort, but not efficiency. There is no free lunch.


That's not to say that comfort itself couldn't account for performance differences (if you buy the numbers).


devashish_paul

Apr 6, 12 19:35

Post #18 of 33 (3259 views)
Re: Softride/Beam bike Rolling Resistance [trail] [In reply to] Quote | Reply

I think the entire premise is that the beam is better at dealing with high frequency vibrations than the tire ( the tire uses up more energy than the beam does is dealing with high frequency vertical displacement). That's why it would be nice to measure with a powermeter, because it takes the entire comfort thing out of the equation. Of course, it does not remove the aero savings from beam bike vs the previous generation of ridig bikes, so for all we know the saving were not at all from the rolling resistance front, but everything to do with the aero savings.


cervelo.com (P3) |infinitnutrition.ca | bushtukah.com
Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


Tom A.

Apr 6, 12 19:47

Post #19 of 33 (3249 views)
Re: Softride/Beam bike Rolling Resistance [devashish_paul] [In reply to] Quote | Reply

devashish_paul wrote:
Tom I believe the entire premise is that the beam is much more efficient at dealing with high frequency vibration than the tire. This is where the gains are supposed to come from, allowing you to ride with higher tire pressure without the Crr loss that is associated with high tire pressure in the real world.

If you truly believe what you wrote above, then you have a complete misunderstanding of the sources of rolling resistance in a bicycle tire and how the pneumatic tire construction acts as the most "efficient" suspension you can get.

In short, you WANT the tire to take up the deflection because it can actually RETURN the energy (most of it...minus tire internal losses) back to the road surface in the trailing half of the contact patch. Use a tire with low internal losses, and "Voila!", you have low rolling resistance on ALL surfaces. Remember, it's the "torque arm" caused by the difference in energy absorbed in the leading half of the contact patch and the energy returned in the trailing half of the contact patch that is the source of rolling resistance.

In contrast, any energy that makes it "past" the tires (e.g. if they are too stiff) cannot be returned to the road surface as the tire does. It needs to be dissipated somewhere...either in the rider, or in a damper of some sort (i.e. read "beam"). That energy needs to be supplied by YOU to keep going forward. Sure, you may have actually reduced the rolling resistance of the tire by stiffening it up, but the total "resistance to forward" motion is overall higher.

Take a read again through my ST articles on "Tires and wheels...", "What's in a Tire", and "What's in a tube". They're in the Tech section.



http://bikeblather.blogspot.com/


devashish_paul

Apr 7, 12 17:41

Post #20 of 33 (3162 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

Thanks Tom, that is a helpful explanation. I'll go have a look!


cervelo.com (P3) |infinitnutrition.ca | bushtukah.com
Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


Jiowa

Apr 7, 12 23:05

Post #21 of 33 (3121 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

So how much energy is lost by a bike moving vertical due to bumps in the road? Let's say like going over train tracks.

And would the dampening caused by a beam when going over the train tracks make a difference in the loss in energy? I'm guessing it does. What say you?




Running is a gift.


Damon

Apr 8, 12 12:06

Post #22 of 33 (3049 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

Thanks for the clear explanation Tom.
It's not quite true however that
Quote:
any energy that makes it "past" the tires (e.g. if they are too stiff) cannot be returned to the road surface as the tire does.
Consider: If the whole bike goes up a hill, then it has accumulated energy that is released going down a hill. The same thing happens at a much smaller scale too, over road bumps. Even small ones. Energy that goes past the tyre can be returned.

Not all of that energy does make it back to the road - some energy is lost every time the rider is jiggled (because the rider's body isn't a perfect spring). That energy comes from rolling resistance.
If you can find a way to reduce load variation on the rider, then you will have lower rolling resistance.

As [Trail] points out, that suspension system needs to be a more efficient spring than the human body, otherwise you would lose just as much energy. Looking at some of my flabby riding buddies, that's probably not too difficult a task..


Tom A.

Apr 8, 12 16:51

Post #23 of 33 (2999 views)
Re: Softride/Beam bike Rolling Resistance [Jiowa] [In reply to] Quote | Reply

Jiowa wrote:
So how much energy is lost by a bike moving vertical due to bumps in the road? Let's say like going over train tracks.

And would the dampening caused by a beam when going over the train tracks make a difference in the loss in energy? I'm guessing it does. What say you?


I say you should be bunny hopping those train tracks anyway ;-)



http://bikeblather.blogspot.com/


Tom A.

Apr 8, 12 16:51

Post #24 of 33 (2997 views)
Re: Softride/Beam bike Rolling Resistance [Damon] [In reply to] Quote | Reply

Damon wrote:
Thanks for the clear explanation Tom.
It's not quite true however that
Quote:
any energy that makes it "past" the tires (e.g. if they are too stiff) cannot be returned to the road surface as the tire does.

Consider: If the whole bike goes up a hill, then it has accumulated energy that is released going down a hill. The same thing happens at a much smaller scale too, over road bumps. Even small ones. Energy that goes past the tyre can be returned.

Not all of that energy does make it back to the road - some energy is lost every time the rider is jiggled (because the rider's body isn't a perfect spring). That energy comes from rolling resistance.
If you can find a way to reduce load variation on the rider, then you will have lower rolling resistance.

As [Trail] points out, that suspension system needs to be a more efficient spring than the human body, otherwise you would lose just as much energy. Looking at some of my flabby riding buddies, that's probably not too difficult a task..

I was referring to energy in the frequency spectrum of road roughness...



http://bikeblather.blogspot.com/


tdstegner

Apr 8, 12 17:29

Post #25 of 33 (2963 views)
Re: Softride/Beam bike Rolling Resistance [Tom A.] [In reply to] Quote | Reply

I'm thinking that the difference in energy lost has to do with the direction of the forces acting on the wheel. With a supple tire, a bump causes the tire to deform, with force vectors going up and back. On the "back" side of the bump the tire returns to it's original shape causing forces down and forward - returning most of the energy to the bike's forward movement. With a stiff tire, the force encountered with a bump is directed through the wheel directly to the bike moving all of it (bike and rider) almost straight up. This causes the bike to move up vertically. When it comes down. there is very little force in a forward direction, it's all vertical in a downward direction... I'm also thinking that a beam doesn't store much energy in a horizontal direction. When a beam absorbs energy from forward motion, it's changed to vertical and forward energy is lost. Thoughts?
Is this just restating what you have already said?


.

Sometimes you're the hammer - sometimes you're the nail...

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