Do clip ons actually change weight distribution?

465 Views 18 Replies 9 Participants Last post by Mike, 2 d ago

BlurpleGatorade

Discussion Starter · 9 d ago

Boring physics question incoming. I've been trying to research this topic but all I can seem to find is people saying yes or no without explaining why. This is purely out of curiosity as I've already decided that I love the sportier riding position of my new clip ons and I doubt knowing the answer would make me any faster. I'm gonna setup a scenario to eliminate any outside factors.

So in this scenario we have two bikes that are exactly the same except one has clip ons and one has handlebars. They are ridden by the same rider who grips both the clip ons and the handlebars with the same amount of pressure. Lets assume for now that the rider is not resting on the tank in either configuration and is sitting on the same spot on their seat (also same amount of pressure on the footpegs). Essentially all that has changed is that the rider is a little more leaned forward with the clip ons.

Since the rider still has the same amount of weight resting on the same spot on their seat, wouldn't the weight distribution be the same? This is what I've been thinking since I've read that when you stand up on a bike and put all your weight on the footpegs it actually lowers the center of gravity of the bike (despite the fact that the center of gravity of your body is higher when standing) because the place where your weight is actually resting is lower than when you're sitting. If anyone has any good links for stuff to read on the subject that would be awesome.

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Das Chicken

· #2 · 9 d ago

Why guess? Measure it for yourself! Put one wheel on a scale, lift the other to the same height, get someone to balance the bike for you while you sit on it in a riding position. Measure the other wheel, then change bars/clip ons and repeat.

BlurpleGatorade

Discussion Starter · #3 · 9 d ago

Das Chicken said:
Why guess? Measure it for yourself! Put one wheel on a scale, lift the other to the same height, get someone to balance the bike for you while you sit on it in a riding position. Measure the other wheel, then change bars/clip ons and repeat.

Man thats tempting. Unfortunately I switched to an upper triple from an S and I'd have to drill it which I'd rather not do. Might be worth it though...

VFR4Lee

· #4 · 9 d ago

I'll guess yes. If you lean forward to the clip ons, more weight is on the front than if you sit up and beg.
I put a LSL handlebar conversion on my old 5th gen VFR. I sat up more straight and got my feet down on the ground better than before. Which was unexpected, and not really related, but........ Maybe helps a bit.

1neeto

· #5 · 9 d ago

I think it’s the perceived feel of pressure on the handlebars. Leverage. With clip-ons, it’s easier to put fast and precise inputs because it takes less energy to do so. Also it’s easier to put too much pressure if you rest too much weight on your clip-ons like new riders tend to do. It is also easier to load the front end because of said leverage. With handlebars, you’ll have a more stable and planted feel because your weight is resting nicely on the seat and pegs. It will require more effort to achieve the steering responsiveness you get with clip-ons, because it’s not as easy to load the front when your body weight bias is more centered. I guess what I’m trying to get at is that while in your hypothetical situation the weight distribution might be the same, when it’s time to add inputs to the front end, they will feel different because of the leverage.

I doubt I answered your question so my apologies.

Sent from my iPhone using Tapatalk

Reactions: 1

Bastak

· #6 · 8 d ago

BlurpleGatorade said:
Essentially all that has changed is that the rider is a little more leaned forward with the clip ons.

This changes the rider's centre of gravity.

BlurpleGatorade said:
If anyone has any good links for stuff to read on the subject that would be awesome.

Motorcycle Dynamics by Vittore Cossalter

Reactions: 2

ziffusion

· #7 · 8 d ago

Bastak said:
This changes the rider's centre of gravity.

The point made in the OP was that the center of gravity will not change because of the lean.

BlurpleGatorade said:
I've read that when you stand up on a bike and put all your weight on the footpegs it actually lowers the center of gravity of the bike (despite the fact that the center of gravity of your body is higher when standing) because the place where your weight is actually resting is lower than when you're sitting.

I think OP is saying that if mass behaves this way (acts through the point of contact) - then that hasn't changed because of the lean. Someone with better physics chops will have to chime in on this.

ziffusion

· #8 · 8 d ago

Das Chicken said:
Why guess? Measure it for yourself! Put one wheel on a scale, lift the other to the same height, get someone to balance the bike for you while you sit on it in a riding position. Measure the other wheel, then change bars/clip ons and repeat.

nah - we are all theoretical physicists here.

Kiwi Rider

· #9 · 8 d ago

Absolutely it changes weight distribution. When racing you keep your weight forward to keep weight on the front wheel for cornering grip. (The side bonus of this is it makes your profile more aerodynamic.)
One of the techniques taught at Level three of the Cali SBK school revolves around shifting your weight distribution on the bike to the assist cornering. At the point beyond the corners apex when your getting back on the gas and the bike wants to run a wider line you lean your weight even further forward and off the inside of the bike ('kiss the mirror' is the memory tool they use) to apply more weight to the front half of the bike. This compresses the front suspension more which shortens the wheel base and sharpens the steering rake angle, both of which help the bike run a tighter line.

Reactions: 1

Bastak

· #10 · 7 d ago

3

ziffusion said:
The point made in the OP was that the center of gravity will not change because of the lean.

Rider's COG moves with the rider. Lean back, lean forwards, lean sideways, shift back in the seat, shift forward in the seat, etc. Rider's COG is in a different position with each movement. Rider's COG would be in a different position in each image below (handlebars vs clip-ons vs aggressive clip-ons). Motorcycle COG stays the same. Combined COG moves with rider movement. With clip-ons, combined COG is further forward.

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ziffusion

· #11 · 7 d ago

@Bastak

Those are nice pictures of various sitting configurations. They say nothing about how each changes the COG of the entire system (rider+MC) though. And intuitively, it does look like the COG should change (to me, too).

But the OP is suggesting that the way physics works is that an attached mass acts through its point of attachment - and the overall COG of the bike will not change so long as the point of attachment of the mass (i.e. the rider's ass attached to the seat) does not change.

BlurpleGatorade

Discussion Starter · #12 · 7 d ago

Thanks for the replies everyone! Love those pics Bastak and thanks for the explanation. I'm curious as to what specifically causes the change in combined COG. Obviously in the pictures above the riders COG would be different for each picture but their points of contact are the same. What I'm thinking at this point is that maybe with the more upright riding position you don't have to put as much pressure on the footpegs to keep your torso from falling forward, so when you lean forward farther and have to keep a higher pressure on the footpegs it moves your weight forward. I never took that many physics classes though so I might have a fundamental misunderstanding. Let me know what y'all think.

(also I definitely need to get a copy of motorcycle dynamics, its on my list as soon as I finish my second read of Twist of the Wrist 2)

Reactions: 1

ziffusion

· #13 · 7 d ago

BlurpleGatorade said:
What I'm thinking at this point is that maybe with the more upright riding position you don't have to put as much pressure on the footpegs ... I never took that many physics classes.

That is an excellent observation. There is more than 1 point of attachment. Maybe you should've taken those physics classes. You seem to be good at this

Reactions: 1

Skywalker67

· #14 · 7 d ago

ziffusion said:
But the OP is suggesting that the way physics works is that an attached mass acts through its point of attachment - and the overall COG of the bike will not change so long as the point of attachment of the mass (i.e. the rider's ass attached to the seat) does not change.

I guess you're missing one fundamental point.
The rider is attached to the bike in 3 different points: footpegs, seat and handlebar.
If the rider bends forward onto the handlebar, part of his weight is shifted from buttocks/feet to hands, therefore there is less weight in the centre of the bike, and a bit more on the front.

Reactions: 1

ziffusion

· #15 · 7 d ago

Skywalker67 said:
The rider is attached to the bike in 3 different points: footpegs, seat and handlebar.

Yes - correct. I was missing that entirely. I realized that when @BlurpleGatorade mentioned the footpegs.

Bastak

· #16 · 7 d ago

BlurpleGatorade said:
Thanks for the replies everyone! Love those pics Bastak and thanks for the explanation. I'm curious as to what specifically causes the change in combined COG. Obviously in the pictures above the riders COG would be different for each picture but their points of contact are the same. What I'm thinking at this point is that maybe with the more upright riding position you don't have to put as much pressure on the footpegs to keep your torso from falling forward, so when you lean forward farther and have to keep a higher pressure on the footpegs it moves your weight forward. I never took that many physics classes though so I might have a fundamental misunderstanding. Let me know what y'all think.

(also I definitely need to get a copy of motorcycle dynamics, its on my list as soon as I finish my second read of Twist of the Wrist 2)

From a static perspective, if you're sitting on a bike that is not moving (no horizontal forces). Let's assume it's on stands. As Skywalker pointed out, your feet are resting on the pegs, your butt is on the seat, and your hands on the handlebars. This is to counteract the downward force of gravity which is applied at your COG. The point where the COG acts is the sum of all gravitational forces acting on the rider's body - it's a simplification so we don't have to consider all the individual elements. It moves with you.

You could choose to sit on the seat, no hands on handlebars, feet off the pegs (100% of reaction force applied at the seat)... Or you could choose to impress the girls and do a handstand on the handlebars (100% of reaction force applied at the handlebars)... To remain in static equilibrium, you must resist the downward force of gravity somehow. You decide how you want to do it and you decide how to distribute it between those three points.

When you decide to do a handstand on the handlebars, you've now moved your COG directly over the handlebars, so the downward gravitational force is applied in a straight line directly over the handlebars. You are resisting that force at the point where your hands make contact with the bars. This means more weight is applied to the front of the bike and less to the rear.

So think of COG as the theoretical point where the downward force of gravity acts - by moving around on the bike, you change where the downward force is theoretically applied. Then you decide how to resist that downward force. As others have pointed out, clip-ons help direct more weight to the front of the bike. Also consider that in a sport riding position, when leaning, the outer leg is in contact with the tank which also resists the force of gravity... But that's getting into a whole new chapter and introducing many other forces and complexities....

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Bastak

· #17 · 7 d ago

@BlurpleGatorade here's the best image I could find online showing rider COG (right), motorcycle COG (left) and combined COG (middle). All else being equal, if the rider hangs off more, the rider COG moves more to the right, motorcycle COG stays where it is and combined COG moves to the right as well (to a lesser degree than rider COG).

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Kiwi Rider

· #18 · 6 d ago

Bastak said:
@BlurpleGatorade here's the best image I could find online showing rider COG (right), motorcycle COG (left) and combined COG (middle). All else being equal, if the rider hangs off more, the rider COG moves more to the right, motorcycle COG stays where it is and combined COG moves to the right as well (to a lesser degree than rider COG).

Yep and its the same principle with regard to forward/aft weight transfer when changing to clip ons from a handle bar set up. There - question answered!

Reactions: 1

Mike

· #19 · 2 d ago

Yes, big time.

Friend had a fast, modded R1. He put an LSL bar kit on and it was almost unridable.

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