Weight's effect on go karting lap times.

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Manoah2u
Manoah2u
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Re: Weight's effect on go karting lap times.

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something that adds significantly in karting, is weight distrubution. Many, and really, many people who go out karting
do not position themselves correctly while cornering. They tend to position themselves in a 'motorcycle' pose;
corner to the righ; lean to the right. corner to the left, lean to the left. this is correct for motorcyclists, not for karting.

The goal is to have the most grip in the outer wheels - if you lean to the inside wheels, you tend to bring the balance
to the left, thus the weight pressure to the inner wheels; causing these to get the most grip, but this has the result that
the inner wheels have the tendency to 'press' or 'steer' the kart into understeering.
When you instead shift your weight to the outer wheels of the corner;
thus; corner to the right, lean to the left, corner to the left, lean to the right, then you shift the weight balance to
the outer wheels causing them to get the most grip and steering the car 'inwards'.

BTW, allthough the experience is fun and good, tire screeching is a killer for laptimes. You'd want to minimize tire
screeching, and minimize track distance. Taking the corners as tight as possible with the most speed possible.

Obviously material depends significantly. I've had blazingly good laptimes at a indoor kart centre here, then took another heat in another kart [despite it being the same model] and i could not come close to my previous laptimes, despite having clear runs.

And btw holy topic-revival batman!

good to see the search function is used though 8)
Dumpster sounds so much more classy. It's the diamond of the cesspools.

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rscsr
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Re: Weight's effect on go karting lap times.

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Manoah2u wrote:...
I don't quite get where you are getting this from.
As far as I understand, rubber has qualitatively the same characteristics on a kart tire and a race tire. So the coefficient of friction lowers with increasing vertical tire loads. Therefore you want to have the center of mass as far inside as possible (to counter the moment due to the centrifugal acceleration) (have look at oval cars, like Whelen Series). This is also the main reason why you want the center of mass as low as possible (to keep the vertical forces on the inside and outside tires as close to each other as possible).

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Tim.Wright
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Re: Weight's effect on go karting lap times.

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The reason for doing this in a kart is not primarily to reduce load transfer but rather to lift the inside rear wheel off the ground otherwise it will create a huge understeering moment due to the lack of a differential.

If karts had differentials, there would be no reason to do this.
Not the engineer at Force India

Manoah2u
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Re: Weight's effect on go karting lap times.

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rscsr wrote:
Manoah2u wrote:...
I don't quite get where you are getting this from.
As far as I understand, rubber has qualitatively the same characteristics on a kart tire and a race tire. So the coefficient of friction lowers with increasing vertical tire loads. Therefore you want to have the center of mass as far inside as possible (to counter the moment due to the centrifugal acceleration) (have look at oval cars, like Whelen Series). This is also the main reason why you want the center of mass as low as possible (to keep the vertical forces on the inside and outside tires as close to each other as possible).
Tim.Wright wrote:The reason for doing this in a kart is not primarily to reduce load transfer but rather to lift the inside rear wheel off the ground otherwise it will create a huge understeering moment due to the lack of a differential.

If karts had differentials, there would be no reason to do this.
there you go.

+ personal experience. Have you even driven a kart? You'll be surprised on how much positive effect leaning 'to the outside' has to a kart. Much less slippery sliding.

It has thus nothing to do with the rubber compound. And proof that in theory stuff might sound reasonable, but in real
life total different results come forward.

I'll suggest you'll go ahead and run a kart just to see the effect. It's really significant, no matter whether you are experienced or 'first timer'. It'll feel a bit awkward at first but once you get comfortable with it you'll improve laptimes
and overtake other participators with ease.
Dumpster sounds so much more classy. It's the diamond of the cesspools.

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mertol
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Re: Weight's effect on go karting lap times.

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Some theory:
From the equation a=F/m you can see that the acceleration decreases when u have more weight. However having more weight also increases the grip of your tires as they have more vertical load so you can use more force. In the turns the force is increased naturally because of the weight and when stopping you can apply more brakes but once you floored the gas you can't extract anymore force. So in theory the biggest loss for heavier drivers would be on the straights.

autogyro
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Re: Weight's effect on go karting lap times.

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Tim.Wright wrote:The reason for doing this in a kart is not primarily to reduce load transfer but rather to lift the inside rear wheel off the ground otherwise it will create a huge understeering moment due to the lack of a differential.

If karts had differentials, there would be no reason to do this.
Absolutely Tim.
Interesting to postulate whether the benefit of applying weight to the outside front tyre to lift the rear inside tyre achieves a better result with a driver heavier than the lightest available?
Given the chassis flex being the suspension it would be difficult to quantify the 'best' driver weight.

Blanchimont
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Re: Weight's effect on go karting lap times.

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What about the weight distribution of the driver. Take two drivers with the same weigth, but the first one has heavy legs while the second one has a heavy upper body(or a heavy helmet). In the case of the second driver the load transfer is bigger and should make it easier to lift the inside tyre.

One thing i've often heard is that on a very wet track, heavier drivers actually benefit from the higher tyre loads. Can any (semi-)professional kart driver confirm this?
Last edited by Blanchimont on Tue Jan 20, 2015 11:50 am, edited 1 time in total.
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autogyro
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Re: Weight's effect on go karting lap times.

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Blanchimont wrote:What about the weight distribution of the driver. Take two drivers with the same weigth, but the first one has heavy legs while the second one has a heavy upper body(or a heavy helmet). In the case of the second driver the load transfer is bigger and should make it easier to lift the inside tyre.
Hmmm, helmet ballast?

Blanchimont
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Re: Weight's effect on go karting lap times.

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Why not train your neck muscles on track? :mrgreen:
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tuj
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Re: Weight's effect on go karting lap times.

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weight plays a massive role in karting times. I'm on the bigger end and it sucks to go against these little guys.

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mertol
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Re: Weight's effect on go karting lap times.

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autogyro wrote:
Tim.Wright wrote:The reason for doing this in a kart is not primarily to reduce load transfer but rather to lift the inside rear wheel off the ground otherwise it will create a huge understeering moment due to the lack of a differential.

If karts had differentials, there would be no reason to do this.
Absolutely Tim.
Interesting to postulate whether the benefit of applying weight to the outside front tyre to lift the rear inside tyre achieves a better result with a driver heavier than the lightest available?
Given the chassis flex being the suspension it would be difficult to quantify the 'best' driver weight.
I don't think chassis flex is required to lift the rear tire. Karts have ackerman steering geometry combined with high caster angles for that.

autogyro
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Re: Weight's effect on go karting lap times.

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I don't think chassis flex is required to lift the rear tire. Karts have ackerman steering geometry combined with high caster angles for that.
A heavy driver will act in two ways.
More weight to transfer but also more weight to keep the rear wheel on the ground by preventing chassis flex in the right direction.

hawkus81
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Re: Weight's effect on go karting lap times.

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Alright I've got a question for you guys, I usually consider myself pretty quick in the go-karts. I've got a few trophies and medals for 1st places among friends and work competitions etc but this one person has come along that seems to be consistently faster than me.

The only thing I can put it down to is weight he is 70kg and i'm 85kg.

Our times:
Me: 38.251 (3rd fastest time of the week) @ 85kg
Him: 37.921 (1st fastest time of the week) @ 70kg

Difference 0.33 seconds

The track is 700m long and reasonably flowing with 2 hairpins and the karts are 9HP 270cc 4 strokes so nothing fancy.

My question is weight adjusted who is faster? Is 15kg worth 0.33 seconds in a lap? My gut feel it would be, I consider our skill levels be very very close... in fact probably almost the same.

Normally I'm quick enough that weight doesn't matter but this guy has about the same skill so I can't beat him on skill alone :/ Damn skinny people!

Image
Last edited by hawkus81 on Tue Jan 27, 2015 6:36 am, edited 1 time in total.

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AnthonyG
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Re: Weight's effect on go karting lap times.

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Tim.Wright wrote:The reason for doing this in a kart is not primarily to reduce load transfer but rather to lift the inside rear wheel off the ground otherwise it will create a huge understeering moment due to the lack of a differential.

If karts had differentials, there would be no reason to do this.
This would so hard explain why I post my fastest times just before I walk out sick with my muscles giving up.
Now I just need to find a way not to get carsick when leaning on the outside and I'll be the new Senna.
Thank you really doesn't really describe enough what I feel. - Vettel

jz11
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Re: Weight's effect on go karting lap times.

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having driven a lot of those hobby carts, any and all comparison between two drivers in 2 different carts is pretty much impossible, because you will never know how "old" is the "other" frame, very big impact carts ability to turn - "rubber" tubes, usually from straightening the chassis after crashes, prevent the "differential" in the rear to work (too much flex = no lift on the rear inside tire), nor you know front caster/camber settings (again - direct impact on the "lift differential"), and then there are those lawnmower engines with unknown power curve

the only way to compare anything and get somewhat reliable data is for 1 driver to drive the same cart and add ballast, see how he does

and not only side to side leaning matters, front/rear as well, especially in wet with "slicks", that being said - leaning is sort of "next level" for hobbyists, beginners and mediocre drivers will benefit much more if they try to keep their posture as steady as they can, and focus on braking/steering