Are footpegs superior if you don't pedal?

[Hummina Shadeeba]

trail would be a hinderance to grip while turning

One of those things you see first hand and never learn why?

I don’t have a reason to believe increased trail would be a cause of less control or less traction and just a hunch and was hoping someone had an answer. I don’t see anything on the web supporting that.


Related to center of mass: “ The farther forward (closer to front wheel) the center of mass of the combined bike and rider, the less the front wheel has to move laterally in order to maintain balance.[35] Conversely, the farther back (closer to the rear wheel) the center of mass is located, the more front wheel lateral movement or bike forward motion is required to regain balance. This can be noticeable on long-wheelbase recumbents, choppers, and wheelie bikes.[36] “.
Another reason recumbents are hard to ride I didn’t realize

https://en.m.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

 

[speedmd]

I don’t see anything on the web supporting that. Maybe the contact patch becomes a worse shape.

Here is some more data on the topic. Flop would be the search term.

https://rolobikes.com/pdf/rolo-wheel-flop.pdf

 

[speedmd]

Related to center of mass:

Interesting looking at weight imbalances. This article covers a bit of the tradeoffs on the topic and a good read. https://cyclingtips.com/2018/11/the-geometry-of-bike-handling-its-all-about-the-steering/

Played with the inverted pendulum a bit more. Went with a 4 foot piece of rod with drill chuck on one end with the same diameter shaft on the back end. Balance point is just over a foot from the heavy end. I suck at balancing it either end up when I move around. Find that I have to start darting around a few steps much sooner once the heavy side up starts moving around to have any chance at balancing it. It does sit relatively steady when standing put balancing. With the light end up, it definitely rocks around quicker and moves a bit further before I can bring it back to balance and while moving I can walk more normal and change pace and direction and maintain control about as well (poorly). I will play with it one more time in a few days to see If somehow I develop skills thinking on it.

 

[speedmd]

Given the low weight bias of most light weight bikes and low power ebikes have vs the rider, the riders position has the major impact on center of mass - location, and on its influences to steering and overall vehicle trajectory and control. Many riders are many multiples the weight of their rides. Even heavier rides are dwarfed by the mass of their riders. Certainly there are many variables to discuss on steering, geometry, BB height and the like but they should be linked to new threads IMO. Have at it.

With the question of foot pegs vs pedals, I am thinking the most significant question is, do pegs allow more range of rider motion thus allowing more influence of their mass moving-placement over the machine. Is it easier for one to move their mass forces closer to where it can have max benefit and as needed. Quickly thinking about this, it seems to me that pegs have more latitude on placement- location than a crank set and would allow loading on either side with more freedom than a crank-pedals that are setup to pedal efficiently. Thoughts?

Given that foot controls like moto brakes and shifters are not used on most of the low power ebikes, multiple peg positions are also possible. Looks like a fresh area of exploration IMO.

 

[BalorNG]

trail would be a hinderance to grip while turning

One of those things you see first hand and never learn why?

I don’t have a reason to believe increased trail would be a cause of less control or less traction and just a hunch and was hoping someone had an answer. I don’t see anything on the web supporting that.


Related to center of mass: “ The farther forward (closer to front wheel) the center of mass of the combined bike and rider, the less the front wheel has to move laterally in order to maintain balance.[35] Conversely, the farther back (closer to the rear wheel) the center of mass is located, the more front wheel lateral movement or bike forward motion is required to regain balance. This can be noticeable on long-wheelbase recumbents, choppers, and wheelie bikes.[36] “.
Another reason recumbents are hard to ride I didn’t realize

https://en.m.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

Not all of them. My FWD bent has 70% front weight bias actually, and CG is pretty close to head tube... but yea, barring direct input to balance corrections (leans, differential bar leaning/wrestling) that are much tricker than most realise (one should be an acrobat to do trackstands on a non-fixed-gear bike) and/or *all wheel steering* the closer CG to steered wheel the better.
Here is a good article on this subject:
https://www.motorcyclespecs.co.za/model/yamaha/yamaha_morpho_ii.htm

There is also frame stiffness to consider!

 

[speedmd]

Cool concept bike.

As far as pegs vs crank-pedals, it's looking to me at least, for a given wheel base and steering geometry setup, it boils down to the influence the dynamic mass loading (Riders movement- positioning) has over the static mass loading (Bikes CG-moment of inertia) and how this balance changes as the pair change trajectory. As far as what would be superior, that would be determined as mentioned before, and somewhat different if its a trials bike or streamliner.

 

[ebike4healthandfitness]

As far as pegs vs crank-pedals, it's looking to me at least, for a given wheel base and steering geometry setup, it boils down to the influence the dynamic mass loading (Riders movement- positioning) has over the static mass loading (Bikes CG-moment of inertia) and how this balance changes as the pair change trajectory. As far as what would be superior, that would be determined as mentioned before, and somewhat different if its a trials bike or streamliner.

Using the pegs to shift bodyweight (e.g. knee almost touch ground in a corner on a motoGP bike) lowers center of gravity of the rider-bike pair which in turn lowers the amount of lean angle needed.

 

[speedmd]

Nice!

 

[Chalo]

Using the pegs to shift bodyweight (e.g. knee almost touch ground in a corner on a motoGP bike) lowers center of gravity of the rider-bike pair which in turn lowers the amount of lean angle needed.

That's less about lowering C of G and more about shifting it over to one side of the bike centerline.

 

[BalorNG]

Cool concept bike.

As far as pegs vs crank-pedals, it's looking to me at least, for a given wheel base and steering geometry setup, it boils down to the influence the dynamic mass loading (Riders movement- positioning) has over the static mass loading (Bikes CG-moment of inertia) and how this balance changes as the pair change trajectory. As far as what would be superior, that would be determined as mentioned before, and somewhat different if its a trials bike or streamliner.

Amen!

 

[speedmd]

Using the pegs to shift bodyweight (e.g. knee almost touch ground in a corner on a motoGP bike) lowers center of gravity of the rider-bike pair which in turn lowers the amount of lean angle needed.

That's less about lowering C of G and more about shifting it over to one side of the bike centerline.

It's well accepted to have a host of bennies. If the rider in not trying to drop as close to the pavement as possible, he is surely doing a pretty bad job at hiding it. The tires work better with the bike a bit more vertical as does a pencil eraser working much better when the pencil is closer to vertical. Contact patches are reported to be very different. Also helps keep the bike off the ground.

From a loading standpoint, how else could one lower their CG if not to get off the saddle and drop off the side of the bike that is in their way? The high side is not a viable option. The bike wants to stand up on its own. Loading it this way also puts more of their mass load more firmly directed toward the contact patch without going through the bikes suspension which would also help keep the metal bits off and rubber on the road.

 

[Chalo]

Point is, it makes no difference how close the rider is to the contact patches to realize the benefits you're talking about. It only matters how far over from the bike centerline. ebike4healthandfitness keeps going back to the assertion it's better to have the rider lower in the chassis, when that doesn't help.

 

[ebike4healthandfitness]

Point is, it makes no difference how close the rider is to the contact patches to realize the benefits you're talking about. It only matters how far over from the bike centerline.

Lowering the center of gravity does matter.

Here is something written by a motoGP engineer:

https://www.bennetts.co.uk/bikesocial/news-and-views/features/racing/why-do-racers-dangle-their-leg

"To understand cornering dynamics, we must first appreciate that cornering is a balancing act. Basically speaking when riding around a corner at speed we are keeping the cornering and gravitational forces in equilibrium. These forces act through the combined (motorcycle & rider) centre of gravity. When we hang off we effectively move the centre of gravity closer to the ground and towards the inside of the corner which, for a given speed, requires less roll angle to balance out these forces. This allows the motorcycle to remain more vertical and on the fatter part of the tire giving us more grip."

 

[Chalo]

It's not the height of the CoM, it's the angle. If the rider were sticking 10 feet off the top of the bike, but at the same angle, he could turn just as hard. Why is this difficult for you to get?

 

[Hummina Shadeeba]

higher c of g requires more angle.

More so the rider seems to be getting inside to reduce that angle instead of low.
https://lifeatlean.com/how-getting-lower-creates-body-position-issues/

 

[Chalo]

higher c of g requires more angle.

I don't think that's true, and I can't identify any mechanism by which it would be that way.

Same wheelbase, same steering geometry, same tires, same speed, same lean angle as projected through the CoM, you get the same turn radius. The tires and steering can't possibly know how far away the CoM is, but only what the angle is.

 

[speedmd]

higher c of g requires more angle.

I don't think that's true, and I can't identify any mechanism by which it would be that way.

Same wheelbase, same steering geometry, same tires, same speed, same lean angle as projected through the CoM, you get the same turn radius. The tires and steering can't possibly know how far away the CoM is, but only what the angle is.

Its basic trig. Force of gravity on the rider times the horizontal distance from the patch C-line. Higher up, is a shorter horizontal distance. The lower the angle of the rider the greater the force will be assuming he can stay on. :lol:

Now back to, pegs vs pedals. Do pegs allow for more of these acrobatics (range of motion - loading)

 

[Chalo]

higher c of g requires more angle.

I don't think that's true, and I can't identify any mechanism by which it would be that way.

Same wheelbase, same steering geometry, same tires, same speed, same lean angle as projected through the CoM, you get the same turn radius. The tires and steering can't possibly know how far away the CoM is, but only what the angle is.

Its basic trig. Force of gravity on the rider times the horizontal distance from the patch C-line. Higher up, is a shorter horizontal distance. The lower the angle of the rider the greater the force will be assuming he can stay on. :lol:

Staying on is indeed an issue. But "gravity" in this case is the combined vector of static gravity and centripetal force. The force of angular acceleration here is indistinguishable from gravity, and the combination of both is what must align angularly with the CoM. The distance from contact patches to CoM doesn't matter, only the angle.

 

[speedmd]

higher c of g requires more angle.

I don't think that's true, and I can't identify any mechanism by which it would be that way.

Same wheelbase, same steering geometry, same tires, same speed, same lean angle as projected through the CoM, you get the same turn radius. The tires and steering can't possibly know how far away the CoM is, but only what the angle is.

Its basic trig. Force of gravity on the rider times the horizontal distance from the patch C-line. Higher up, is a shorter horizontal distance. The lower the angle of the rider the greater the force will be assuming he can stay on. :lol:

Staying on is indeed an issue. But "gravity" in this case is the combined vector of static gravity and centripetal force. The force of angular acceleration here is indistinguishable from gravity, and the combination of both is what must align angularly with the CoM. The distance from contact patches to CoM doesn't matter, only the angle.

Please do the math and show us. Basic torque equation. Free body dia will work. Don't try to wiggle out of it by confusing the issue with centripetal forces and not show us where-how it adds up. BTW, Gravity does not change direction until you travel well around to a different side of the globe. :wink: Save that one for your youtube channel.

 

[Chalo]

The angle marked "COM" represents the combined vector of gravity and centripetal force. If your center of mass isn't along that line, you're on your way to either a highside or a lowside fall. The angle is the same under the same conditions, no matter how tall you are or how tall your bike is.

Here's an iconic picture of the late Jobst Brandt:

He was a very tall man. But he didn't have to lean more steeply for the same turn than a shorter man would have.

 

[Hummina Shadeeba]

i can lean off my bike while going in a straight line and the bike angle will change of course. i can do the same while in a turn and change the angle of the bike. with the rider leaning to the inside the bike is going to stay more upright. it may have the same forces to make the bike slide either way but if its not leaning over maybe the tire patch is more concentrated and more pressure and less likely to slide.

 

[Hummina Shadeeba]

https://www.fxsolver.com/browse/formulas/Lean+angle+due+to+a+tire+thickness+of+a+bicycle
i see thickness of the tire as a variable in lean angle but does the angle matter if more angle doesnt necessitate less grip? it seems theyre leaning over more so to keep the ideal tire patch: https://www.fxsolver.com/blog/2015/06/03/motorcycle-leaning-angle/

 

[Chalo]

The more moto dingdongs lean, the harder they can corner. But at some point the pegs and other parts will drag on the ground and pry the tires away from full contact. So they heave their cricket-sized asses overboard to keep leaning farther without ditching their bikes into the gravel. At that point I don't think it's about optimizing contact patch or anything else; it's only about cornering harder, faster.

So if you're an idjit, study those dudes. If not, then treat your bike and yourself with respect. Ride within your limits, and your bike's.

 

[Hummina Shadeeba]

i think folks including myself are trying to understand the science behind it more than anything else.

regardless of where the center of mass is on the bike, high or low, its the same force and turn angle, but at some point before you get to the point of the bike hitting the ground the tire patch is going to change shape and be elongated and now its the same force over a larger area and the tire is effectively harder and less grippy, no? Or you have a super round tire, like they do, so the shape of the contact patch stays more so the same when leaning. It seems they lean to keep the bike more upright and keep the roundest tire patch on the road possible.

 

[Chalo]

To address the original question more directly, there's one major trick that pedals have in their favor over pegs. Pedals can be placed with the outer pedal down and the rider's weight on the outer pedal in a turn. This creates a kind of suspension that isn't in line with the chassis of the bike, and tends to keep the tires planted on the surface when bump forces are strongly across the chassis rather than in line with whatever mechanical suspension is available.

Weighting the outside peg has the same general effect, but it's less pronounced due to the fixed location of the peg. So when used correctly, pedals offer better adhesion of the tires to the surface than pegs. Any peg that's placed low enough to offer comparable dynamic suspension when turning in one direction will tend to contact the ground early when the bike is turned in the opposite direction.