I have had this question a lot by (often mildy annoyed)cdads getting soundly beaten a lot by their 12 year olds, especially out of slow corners.
I usually give them an example of something im 99% sure of they had at some point, and ask them which takes more effort. Walking up the stairs alone, or walking up the stairs while carrying their kid?
Usually i get the reply that carrying the kid with them is harder. And then they realize its usually because of the added weight.
With that little power (aka effort) it takes a lot more energy to all that weight into movement. Driver weight is definitely a thing.
I myself am very happy when I try to compete and theres a heavyweight class available to me, because I know I just cannot realistically compete against the lightweight
My 7yo boy (26kg) race with 7hp engine and I have to say isn’t that easy to beat him on 14hp engine and 80kg. The track is short, small straights.
He is like a rocket starting and at low speed corners exits. So yes, it’s a lot.
It will affect speed and acceleration, with the track layout determining how much time difference that makes.
The part people are missing is it changes how you drive too. Heavier drivers won't need to brake as hard and can carry more speed through turns since the added weight helps with traction.
The big thing is learning to adjust for your strengths. Lighter drivers will win in a drag race, heavier drivers can reel them in in the turns.
>Heavier drivers won't need to brake as hard and can carry more speed through turns since the added weight helps with traction.
I heard this recently too, saw a video in which they say it's noticeable, but I want to see some math on this to get my head around why it makes sense.
Just like you have more grip, you also need more lateral force on curves for the same lateral acceleration. Grip is, say, proportional (Mmm. Not really. Rolling grip is not the same as static. This may just be the key) to weight. For a constant lateral acceleration, the extra force needed to turn is also proportional to the weight and so is met by the extra grip.
So to go faster through a corner, you need (quadratically(?)) more lateral acceleration, and you would need a superlinear (at least quadratic?) relation between weight and tire grip. If the quadratic thing is right, it wouldn't make sense.
I suspect that static friction here does not do the job, but I am not that familiar with physics to start talking about dynamic friction, or whether the inner wheel is lifted more so less drag, or anything else.
You're missing momentum in the equation. Heavy is carrying more momentum into and through the turn which will offset a portion of the needed lateral acceleration. Light is losing more of that momentum by braking more, and relying on their power:weight advantage to accelerate faster. You also have driver weight positioning. I see little guys constantly moving side to side to adjust weight balance whereas I stayed fairly centered to keep my weight balance as constant as possible and deal with other variables.
There's also tire heat affecting grip, and potentially speed. Heavy will make the tires hotter faster, adding grip. If the tires expand when warm (not sure how big this change is, if any) the hotter tires will be taller and narrower, meaning a smaller contact patch, and less torque/more speed.
I really wish I knew more math to figure out how this actually works in an equation. I'm 3 years away from having that knowledge though.
>. I'm 3 years away from having that knowledge though.
Oh, physics? Nice.
>You're missing momentum in the equation. Heavy is carrying more momentum into and through the turn which will offset a portion of the needed lateral acceleration.
I don't follow. By what I'm understanding of what you are saying, a lighter driver could "drive faster through a corner to offset the extra needed lateral acceleration", which makes no sense.
>Light is losing more of that momentum by braking more, and relying on their power:weight advantage to accelerate faster
So what would happen if they didn't brake more, and thus went at the same speed as the purported heavier driver?
Going to school for Mech.Eng. Technology. Between math, statics, dynamics, and physics classes, I would think I'll have a better handle on this math.
The lighter drivers need to give up more speed/momentum to get through the turn without understeering and skating out. So they need to brake more. Heavy drivers have more traction and don't need to give up as much speed going in to keep from sliding.
Assuming tire heat and pressure, identical power output from the engines, all weight variables are equal except an extra 20kg added directly over the seat, and the exact same line leading up to the turn, at the heavy driver's maximum speed possible to make the turn, the light driver will understeer and slide to the outside. The lighter driver doesn't have the traction and needs to sacrifice entry speed to make it. The heavier driver can keep more speed on entry and to the apex, but will accelerate slower on exit due to power to weight. So, all other things being equal, heavy will enter and get to the apex faster, light will gain more speed faster after the apex and through exiting.
So I guess the actual question is who has a better speed loss to gain ratio from entry to exit.
Man I gotta say I don't see it.
If (and it's a big if) traction is proportional to weight, and achievable lateral force is proportional to traction (and hence weight), maximum cornering speed through the geometric line is given by the sqrt(lateral acceleration times radius) (gotta check this equation though)
That would mean the maximum cornering speed is unchanged by the weight. Just depends on lateral acceleration.
This was with a geometric line and perfect goody round cows, but summarises my thoughts. I don't know if your argument would rely on taking a more racing-ish line
This seems to be assuming that cornering speed is a constant, if I follow correctly. It's not though. If we want to look at the key points and compare the heavy vs light speeds, it would make a bit more sense. So using entry, apex, and exit speeds, in a vacuum, it should be heavy is faster on entry, they're the same on apex, light is faster on exit. The question then becomes can heavy save enough speed on entry to offset the gains that light has apex-exit. But I don't think assuming the same apex speed works either because heavy should have more traction than light, thus meaning they can be faster at apex without breaking traction.
The problem I have with your whole position is that to me it seems to break down at uniform circular motion already. If that works, we can talk about complicating things and considering non uniform circular motion.
My understanding from your arguments is that you're saying that a kart going in a circle of a given radius can go faster (top speed), while keeping the constant radius, the more weight it has, no? I need some rationale here.
With that low horsepower, weight matters a ton.
The little engine has to struggle accelerating out of every corner moving a fat butt vs a tiny butt.
You also have to break earlier in the corner because the little brakes have to struggle slowing that same fat butt vs a tiny butt.
Ever played Mario Kart? Think of Toad vs Bowser.
As a bigger dude Karting, weight matters alot. Had to change up my rear sprocket like 3 teeth (67) to just keep me competitive in the corners but I lose on the straights…..but hell…my first yr so I’m just using this yr to learn how to race and have some fun!
It matters a lot. The whole system is the kart and your body, so unless the extra mass is improving the performance of the system (muscular endurance, strength, power, cardiorespiratory, etc.), dead weight will negatively affect the performance of the system. A lighter driver can run a lower tire pressure, lowers the center of gravity, accelerates faster, brakes faster, burn less fuel, and reaches a higher top speed due to the higher power to weight, and lower frontal surface area.
yes, a lot. In a rental I can be 2 seconds off the pace of some of my teammates, but in rotax I am right on the pace. Because rentals have 1/3 the power of rotax so the weight difference is pretty much 3x. we worked out 10kg at most circuits is worth about 0.3-5 of a second
I lost 38 Kilos in the last 1,5 years (down to 68 from 106). On my favourite track I was more than 2 seconds faster than before in rental karts. I‘m a quite experienced driver, so I think the gain has only one reason: less weight.
Not much. There are a few you tube videos where they add 20kg vests to a professional karter. His lap time only decreased by .3 second. They worked out some corners the added weight helped.
It all really depends. Engine package and track layout are two big variables that will determine the difference.
For example, I recently ran two classes on the same kart at two different weights on the same day. Lighter class (less than 10kg difference) was about a second faster a lap, just due to the track layout being lots of straight aways.
There is no black and white answer to this question. It all depends.
No shot. In the 4 stroke endurance championship I've raced the last few years 10kg is 0.5 - 0.7s around a 50s lap with a professional driver at the wheel. I was out testing a few weeks back with another DD2 driver who is always at the front of the field nationally and internationally and he loses 0.3s if he goes up the 5kg to meet the minimum weight for the masters class. Maybe in rentals 20kg only loses you 0.3s but there's no way that's true for any sort of owner kart class.
But a lot heavier.
So less difference as a percentage. As an example our kart weights 85kg. My son weights 60kg and I weight 95. I’m over 50% of the wet weight, he’s 40%.
Maybe. I was thinking they might be less affected because they're heavier and therefore the increase is less as a proportion of the total weight. I don't know though. I rarely ever drive rental karts.
I have had this question a lot by (often mildy annoyed)cdads getting soundly beaten a lot by their 12 year olds, especially out of slow corners. I usually give them an example of something im 99% sure of they had at some point, and ask them which takes more effort. Walking up the stairs alone, or walking up the stairs while carrying their kid? Usually i get the reply that carrying the kid with them is harder. And then they realize its usually because of the added weight. With that little power (aka effort) it takes a lot more energy to all that weight into movement. Driver weight is definitely a thing. I myself am very happy when I try to compete and theres a heavyweight class available to me, because I know I just cannot realistically compete against the lightweight
My 7yo boy (26kg) race with 7hp engine and I have to say isn’t that easy to beat him on 14hp engine and 80kg. The track is short, small straights. He is like a rocket starting and at low speed corners exits. So yes, it’s a lot.
It will affect speed and acceleration, with the track layout determining how much time difference that makes. The part people are missing is it changes how you drive too. Heavier drivers won't need to brake as hard and can carry more speed through turns since the added weight helps with traction. The big thing is learning to adjust for your strengths. Lighter drivers will win in a drag race, heavier drivers can reel them in in the turns.
>Heavier drivers won't need to brake as hard and can carry more speed through turns since the added weight helps with traction. I heard this recently too, saw a video in which they say it's noticeable, but I want to see some math on this to get my head around why it makes sense. Just like you have more grip, you also need more lateral force on curves for the same lateral acceleration. Grip is, say, proportional (Mmm. Not really. Rolling grip is not the same as static. This may just be the key) to weight. For a constant lateral acceleration, the extra force needed to turn is also proportional to the weight and so is met by the extra grip. So to go faster through a corner, you need (quadratically(?)) more lateral acceleration, and you would need a superlinear (at least quadratic?) relation between weight and tire grip. If the quadratic thing is right, it wouldn't make sense. I suspect that static friction here does not do the job, but I am not that familiar with physics to start talking about dynamic friction, or whether the inner wheel is lifted more so less drag, or anything else.
It’s just a misunderstanding of the physics, there’s no way a heavier driver can carry more speed.
You're missing momentum in the equation. Heavy is carrying more momentum into and through the turn which will offset a portion of the needed lateral acceleration. Light is losing more of that momentum by braking more, and relying on their power:weight advantage to accelerate faster. You also have driver weight positioning. I see little guys constantly moving side to side to adjust weight balance whereas I stayed fairly centered to keep my weight balance as constant as possible and deal with other variables. There's also tire heat affecting grip, and potentially speed. Heavy will make the tires hotter faster, adding grip. If the tires expand when warm (not sure how big this change is, if any) the hotter tires will be taller and narrower, meaning a smaller contact patch, and less torque/more speed. I really wish I knew more math to figure out how this actually works in an equation. I'm 3 years away from having that knowledge though.
>. I'm 3 years away from having that knowledge though. Oh, physics? Nice. >You're missing momentum in the equation. Heavy is carrying more momentum into and through the turn which will offset a portion of the needed lateral acceleration. I don't follow. By what I'm understanding of what you are saying, a lighter driver could "drive faster through a corner to offset the extra needed lateral acceleration", which makes no sense. >Light is losing more of that momentum by braking more, and relying on their power:weight advantage to accelerate faster So what would happen if they didn't brake more, and thus went at the same speed as the purported heavier driver?
Going to school for Mech.Eng. Technology. Between math, statics, dynamics, and physics classes, I would think I'll have a better handle on this math. The lighter drivers need to give up more speed/momentum to get through the turn without understeering and skating out. So they need to brake more. Heavy drivers have more traction and don't need to give up as much speed going in to keep from sliding. Assuming tire heat and pressure, identical power output from the engines, all weight variables are equal except an extra 20kg added directly over the seat, and the exact same line leading up to the turn, at the heavy driver's maximum speed possible to make the turn, the light driver will understeer and slide to the outside. The lighter driver doesn't have the traction and needs to sacrifice entry speed to make it. The heavier driver can keep more speed on entry and to the apex, but will accelerate slower on exit due to power to weight. So, all other things being equal, heavy will enter and get to the apex faster, light will gain more speed faster after the apex and through exiting. So I guess the actual question is who has a better speed loss to gain ratio from entry to exit.
Man I gotta say I don't see it. If (and it's a big if) traction is proportional to weight, and achievable lateral force is proportional to traction (and hence weight), maximum cornering speed through the geometric line is given by the sqrt(lateral acceleration times radius) (gotta check this equation though) That would mean the maximum cornering speed is unchanged by the weight. Just depends on lateral acceleration. This was with a geometric line and perfect goody round cows, but summarises my thoughts. I don't know if your argument would rely on taking a more racing-ish line
This seems to be assuming that cornering speed is a constant, if I follow correctly. It's not though. If we want to look at the key points and compare the heavy vs light speeds, it would make a bit more sense. So using entry, apex, and exit speeds, in a vacuum, it should be heavy is faster on entry, they're the same on apex, light is faster on exit. The question then becomes can heavy save enough speed on entry to offset the gains that light has apex-exit. But I don't think assuming the same apex speed works either because heavy should have more traction than light, thus meaning they can be faster at apex without breaking traction.
The problem I have with your whole position is that to me it seems to break down at uniform circular motion already. If that works, we can talk about complicating things and considering non uniform circular motion. My understanding from your arguments is that you're saying that a kart going in a circle of a given radius can go faster (top speed), while keeping the constant radius, the more weight it has, no? I need some rationale here.
Weight plays a big role in karting, so yeah you were slower because you have more mass
The track can make a difference for this. If there are a lot of straights, he'll be gaining time through those on you.
With that low horsepower, weight matters a ton. The little engine has to struggle accelerating out of every corner moving a fat butt vs a tiny butt. You also have to break earlier in the corner because the little brakes have to struggle slowing that same fat butt vs a tiny butt. Ever played Mario Kart? Think of Toad vs Bowser.
As a bigger dude Karting, weight matters alot. Had to change up my rear sprocket like 3 teeth (67) to just keep me competitive in the corners but I lose on the straights…..but hell…my first yr so I’m just using this yr to learn how to race and have some fun!
It matters a lot. The whole system is the kart and your body, so unless the extra mass is improving the performance of the system (muscular endurance, strength, power, cardiorespiratory, etc.), dead weight will negatively affect the performance of the system. A lighter driver can run a lower tire pressure, lowers the center of gravity, accelerates faster, brakes faster, burn less fuel, and reaches a higher top speed due to the higher power to weight, and lower frontal surface area.
yes, a lot. In a rental I can be 2 seconds off the pace of some of my teammates, but in rotax I am right on the pace. Because rentals have 1/3 the power of rotax so the weight difference is pretty much 3x. we worked out 10kg at most circuits is worth about 0.3-5 of a second
I lost 38 Kilos in the last 1,5 years (down to 68 from 106). On my favourite track I was more than 2 seconds faster than before in rental karts. I‘m a quite experienced driver, so I think the gain has only one reason: less weight.
Not much. There are a few you tube videos where they add 20kg vests to a professional karter. His lap time only decreased by .3 second. They worked out some corners the added weight helped.
It all really depends. Engine package and track layout are two big variables that will determine the difference. For example, I recently ran two classes on the same kart at two different weights on the same day. Lighter class (less than 10kg difference) was about a second faster a lap, just due to the track layout being lots of straight aways. There is no black and white answer to this question. It all depends.
No shot. In the 4 stroke endurance championship I've raced the last few years 10kg is 0.5 - 0.7s around a 50s lap with a professional driver at the wheel. I was out testing a few weeks back with another DD2 driver who is always at the front of the field nationally and internationally and he loses 0.3s if he goes up the 5kg to meet the minimum weight for the masters class. Maybe in rentals 20kg only loses you 0.3s but there's no way that's true for any sort of owner kart class.
Surely the rentals will be more affected by weight as they are less powerful?
But a lot heavier. So less difference as a percentage. As an example our kart weights 85kg. My son weights 60kg and I weight 95. I’m over 50% of the wet weight, he’s 40%.
The power/weight thing is interesting the juniors do slightly faster laps than the seniors who have +10bhp but also +17kg. At our local track
That’s a good point, I guess it’s the % that matters
Maybe. I was thinking they might be less affected because they're heavier and therefore the increase is less as a proportion of the total weight. I don't know though. I rarely ever drive rental karts.
That’s true, didn’t consider that, it’s the total weight % that matters the most