Can you do an episode on frame stiffness? It seems that it is a topic that cyclists are obsessed about. The common school of thought is that when a frame flexes, all the energy to flex the frame is lost. But some of this energy must be returned back to the system when the frame rebounds. I am wondering if you have done any analysis on the actual energy loss when a frame flexes under pedaling forces, and the effects of different frame materials on these losses? Is it even significant or just marketing hype? I am sure this a complicated subject but I would like to hear your thoughts on this subject.
What I would like to see is an episode on shoe stiffness. From a mechanics point of view only the area under your forefoot should be stiff. I don't see how torque is applied from the ankle towards the pedal.
Can you use some form of sensor to measure those losses from vibrations? To "tune" your bike vibrations with different handlebar tyres pressure and so on?
Great video, thanks so much. Question i have is on a velodrome when your riding around the bends is the drag higher on the outside of the bike compared to the inside??
Ever consider revisiting this? Maybe discussing the energy loss as related to Speed of Deformation? Tire compounds have different Hysteresis at different Hz. Figured Silca would highlight the use of Silica in tire compounds in this topic ;-)
Rolling resistance is not just hysteresis in the tyres. The impedance of the bike is just the beginning. Attached to the bike is the rider. Most of the rolling resistance comes from friction between body tissues. That's why the pneumatic tyre - at low pressures as intended by the inventor Dunlop - are much faster than solid rubber tyres. And that's also the reason why wider tyres roll easier than narrow tyres if they are built the same and are run we appropriately different pressures. It's proven to be faster to 28 mm and it's proven not to get slower until 54 mm. Read the Bicycle Quarterly.
Thanks for the knowledge! So if my roads are realy smooth tarmac i get less Roling resistance if i pump higher pressures?! I have a set of tubulars that Max Out at 175psi will that be too much if my local roads are very smooth (i mean they are almost like freshly paved tarmac)
With the latex an butyl ball does this means thath by usin tubeless tyres (thicker casing) vs using latex tubes latex is still faster with the energy return of latex?
For many tires, yes.. the thinner clincher version with latex tube will be faster than the tubeless version. Some technologies, however, are catching up and both the GP5000 TL and Vittoria Corsa Speed TLR are as fast, or faster than their clincher variants with latex tubes.
@18:07 incorrect. 1- An aerodynamic stall isn't a speed thing, it's an angle of attack (angle of the wing chord to relative airflow) thing. 2- Pitch angle isn't necessarily related to angle of attack. 3- You don't need to put an airplane into a dive to recover from a stall, you just need to release back pressure on the stick (which is what primarily controls angle of attack). It gets complicated because there's a relationship between airspeed, angle of attack, and the g-loading on the airplane that can make it a bit hard to conceptualise. Airplanes are cool.
Josh, does the hysteresis of latex increase as it's stretched? In practical terms, would you have more hysteresis with an undersized latex tube compared to a correctly sized tube - using an 18-23mm tube in a 28c tire?
So the hysteresis is related to the material thickness.. so actually the losses decrease as the tube is stretched and the wall thickness is reduced to allow for the stretch. However, this effect is really small and is not worth the reduced puncture resistance loss of the thinner, more elongated tube material. So while using a smaller tube might save 0.02 watts or something like that, it might become 25% more likely to pinch flat, and will also be much less heat resistant under heavy braking.. not worth it in my calculations!
This topic goes to why I've never understood how "super shoe" running shoes can be faster than a shoe with no cushion at all like a racing flat. As close as foam can get to 100 percent rebound, it can never get to above 100 percent. It can't return more energy than was put in. Same goes for carbon plates. Elite marathon runners have such good form that they don't need cushion to run. They would wear racing flats if they were faster but they don't so there must be something to it. PEBAX is more efficient than EVA, but I just can't see how a stack of foam can physically be more efficient than no foam at all.
Since the foot lands slight ahead of the runner when running (sprinting is different), there is a retarding force during foot impact which is absorbed by the body when running in flats, that can be captured in the foam, and then somewhat returned as a propulsive force as the foot rocks forward and the foam recovers. Essentially, the foam is lower hysteresis than the body parts which otherwise absorb these loads. There's a lot of biomechanical stuff they are doing as well, but if you run in these shoes you feel it pretty much instantly and Nike's initial claim of 4% faster has been consistently validated by third parties, there is also great literature showing injury reduction from these shoes.
@@SILCAVelo Oh ok that makes sense. It's the same concept that was controversial about Oscar Pistorius competing in the Olympics because his blades could have an advantage over human legs.
Is there any studies being done on the Hysteresis on wheels? Having read wheel building books I understand that a wheel is also flattens and rebounding as it comes around to the road. How much energy is being lost with stiffer wheels? Say with aluminum spokes or carbon vs steel spokes, and the difference in blades ones to straight gauge and the double butted spokes. I actually had in the late 90’s the Spenergy SPOX wheels with the fiber spokes you could tie into a knot. They where actually really comfortable ride to them but also would flex on sprints and man if you had them on a trainer they would flex enough to rub your brake pads. Anyways I’m curious to the effect wheel material and there stiffness effects the Hysteresis. PS really enjoy your Podcast and the videos
This show is right in my wheelhouse, as a mathematician obsessed with cycling, so I love the occasional math terms like integration. Are there any books (or websites etc) that you would recommend about the math of cycling?
So Bicycling Science by MIT press is pretty good, there is one called Cycling Science that's worth having, and Faster by Jim Gourley is pretty good too.. the challenge for any book on the topic is just keeping up with the technology and also balancing the sort of basic math/science that we talk about here with the stuff people are really interested in which is genearlly 'yeah, but how do I go faster..' The Slowtwitch Forum is a fantastic place to go hang out and participate as so many of the authors of these books as well as the best minds in the industry tend to hang out there and interact with each other which is really cool!
Can you do an episode on frame stiffness? It seems that it is a topic that cyclists are obsessed about. The common school of thought is that when a frame flexes, all the energy to flex the frame is lost. But some of this energy must be returned back to the system when the frame rebounds. I am wondering if you have done any analysis on the actual energy loss when a frame flexes under pedaling forces, and the effects of different frame materials on these losses? Is it even significant or just marketing hype? I am sure this a complicated subject but I would like to hear your thoughts on this subject.
Thanks Joe, and yes, this is in the works for a future episode!
What I would like to see is an episode on shoe stiffness. From a mechanics point of view only the area under your forefoot should be stiff. I don't see how torque is applied from the ankle towards the pedal.
very interesting and explained well. Thank you
Why is Silica so great? Due to Josh's brilliance, certainly. I have several of their products, all are world class best of the best.
Fantastic education. Thank you!
Top tier content 🙌🏼
Excellent explanation of the concept. Thanks for sharing!
Thanks Josh!
Very compelling and detailed Josh. Great primer on the little known world of Hysteresis. An effect that affects us everyday.
Could you guys please work on a chamois with this low hysteresis foam.
+1
Can you use some form of sensor to measure those losses from vibrations? To "tune" your bike vibrations with different handlebar tyres pressure and so on?
Great video, thanks so much.
Question i have is on a velodrome when your riding around the bends is the drag higher on the outside of the bike compared to the inside??
Ever consider revisiting this? Maybe discussing the energy loss as related to Speed of Deformation? Tire compounds have different Hysteresis at different Hz. Figured Silca would highlight the use of Silica in tire compounds in this topic ;-)
Rolling resistance is not just hysteresis in the tyres. The impedance of the bike is just the beginning. Attached to the bike is the rider. Most of the rolling resistance comes from friction between body tissues. That's why the pneumatic tyre - at low pressures as intended by the inventor Dunlop - are much faster than solid rubber tyres. And that's also the reason why wider tyres roll easier than narrow tyres if they are built the same and are run we appropriately different pressures. It's proven to be faster to 28 mm and it's proven not to get slower until 54 mm. Read the Bicycle Quarterly.
Thanks for the knowledge! So if my roads are realy smooth tarmac i get less Roling resistance if i pump higher pressures?! I have a set of tubulars that Max Out at 175psi will that be too much if my local roads are very smooth (i mean they are almost like freshly paved tarmac)
Ok never mind... i just saw episode 0002 and got my answer. Thanks again
With the latex an butyl ball does this means thath by usin tubeless tyres (thicker casing) vs using latex tubes latex is still faster with the energy return of latex?
For many tires, yes.. the thinner clincher version with latex tube will be faster than the tubeless version. Some technologies, however, are catching up and both the GP5000 TL and Vittoria Corsa Speed TLR are as fast, or faster than their clincher variants with latex tubes.
@18:07 incorrect.
1- An aerodynamic stall isn't a speed thing, it's an angle of attack (angle of the wing chord to relative airflow) thing.
2- Pitch angle isn't necessarily related to angle of attack.
3- You don't need to put an airplane into a dive to recover from a stall, you just need to release back pressure on the stick (which is what primarily controls angle of attack).
It gets complicated because there's a relationship between airspeed, angle of attack, and the g-loading on the airplane that can make it a bit hard to conceptualise.
Airplanes are cool.
Josh, does the hysteresis of latex increase as it's stretched? In practical terms, would you have more hysteresis with an undersized latex tube compared to a correctly sized tube - using an 18-23mm tube in a 28c tire?
So the hysteresis is related to the material thickness.. so actually the losses decrease as the tube is stretched and the wall thickness is reduced to allow for the stretch. However, this effect is really small and is not worth the reduced puncture resistance loss of the thinner, more elongated tube material. So while using a smaller tube might save 0.02 watts or something like that, it might become 25% more likely to pinch flat, and will also be much less heat resistant under heavy braking.. not worth it in my calculations!
And when a latex tube decides to go it is usually very fast and dangerous, so don't shave microseconds under-sizing them!
Love the podcast and really like this idea! Please please get a better mic 🎙
This topic goes to why I've never understood how "super shoe" running shoes can be faster than a shoe with no cushion at all like a racing flat. As close as foam can get to 100 percent rebound, it can never get to above 100 percent. It can't return more energy than was put in. Same goes for carbon plates. Elite marathon runners have such good form that they don't need cushion to run. They would wear racing flats if they were faster but they don't so there must be something to it. PEBAX is more efficient than EVA, but I just can't see how a stack of foam can physically be more efficient than no foam at all.
Since the foot lands slight ahead of the runner when running (sprinting is different), there is a retarding force during foot impact which is absorbed by the body when running in flats, that can be captured in the foam, and then somewhat returned as a propulsive force as the foot rocks forward and the foam recovers. Essentially, the foam is lower hysteresis than the body parts which otherwise absorb these loads. There's a lot of biomechanical stuff they are doing as well, but if you run in these shoes you feel it pretty much instantly and Nike's initial claim of 4% faster has been consistently validated by third parties, there is also great literature showing injury reduction from these shoes.
@@SILCAVelo Oh ok that makes sense. It's the same concept that was controversial about Oscar Pistorius competing in the Olympics because his blades could have an advantage over human legs.
Is there any studies being done on the Hysteresis on wheels?
Having read wheel building books I understand that a wheel is also flattens and rebounding as it comes around to the road.
How much energy is being lost with stiffer wheels? Say with aluminum spokes or carbon vs steel spokes, and the difference in blades ones to straight gauge and the double butted spokes. I actually had in the late 90’s the Spenergy SPOX wheels with the fiber spokes you could tie into a knot. They where actually really comfortable ride to them but also would flex on sprints and man if you had them on a trainer they would flex enough to rub your brake pads.
Anyways I’m curious to the effect wheel material and there stiffness effects the Hysteresis.
PS really enjoy your Podcast and the videos
This show is right in my wheelhouse, as a mathematician obsessed with cycling, so I love the occasional math terms like integration. Are there any books (or websites etc) that you would recommend about the math of cycling?
So Bicycling Science by MIT press is pretty good, there is one called Cycling Science that's worth having, and Faster by Jim Gourley is pretty good too.. the challenge for any book on the topic is just keeping up with the technology and also balancing the sort of basic math/science that we talk about here with the stuff people are really interested in which is genearlly 'yeah, but how do I go faster..' The Slowtwitch Forum is a fantastic place to go hang out and participate as so many of the authors of these books as well as the best minds in the industry tend to hang out there and interact with each other which is really cool!
I assume you have seen the spreadsheets by fastfitnesstips? If not check them out, they are right up your street.
"Connect crazyness with women." Hippocrates totally nailed it there.