Weight vs lap times

Do you know if with the KA100 engines you can change them back and forth between restricted and non restricted for junior and senior or is however you get the engine how it stays?

The only difference is the header, so you should be able to just swap the headers from junior to senior I believe. I know people who have done it, just not sure if there is a different way engine builders build a junior vs. senior engine to optimize performance.

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Do you feel comfortable moving to seniors? Don’t base it on your friends in the class, base it on your comfort level and ability.

I understand that weight is the enemy of longitudinal acceleration but (up to a point) the friend of lateral acceleration.

First, am I right?
second, how can we use the excess weight we’re sometimes stuck with, to our advantage?

Thanks :pray:

If weight was perfectly in the center of the kart or the COG of the kart then this would be easier to generate an answer for…the issue of course is that is not true.

For longitudinal acceleration, where the weight is at maximum is also a factor - same with (-)acceleration (braking). This is why adjusting the rake of the chassis, seat position, or height of driver can affect this parameter. However, especially in a kart, this effect is considerably (at least to the driver) less than the effect on lateral acceleration.

No two drivers in the same kart, with the same seat position will progress through a corner exactly the same. This is because no person is built exactly the same as any other person - no suit is the same, or helmet, or tire even, lap to lap. Sure, minor differences don’t matter to most of us, but significant ones will - how tall a driver is, their body type, and overall weight of course. Even if drivers weigh the same, where their mass is concentrated can vary significantly.

Some drivers could move the seat forward or back, but you can’t change the driver in weight or body type (think rower vs marathon runner). Generally karts that have a higher percentage of front weight tend to be more aggressive in steering than those with weight further back. To similar extent, although displayed in a different outcome, drivers that sit at different heights affect the handling drastically- all these affects agnostic of the drivers actual weight.

Ultimately, a driver that weighs more transfers more weight in the kart while cornering or while accelerating or braking. That might not be a positive necessarily though, as we can’t chop up a driver into 5lb increments and move it around the kart. No matter how you slice it -heh- a lighter driver does have a fundamental advantage at all times, even in a regulated min weight category because more mass is available to shift about the kart to optimize performance compared to a heavier compatriot.

Excess weight in a driver is tricky to view as an advantage - again you can’t move it around where you want. But, lots of heavier drivers make it work. A heavier guy higher up might have an advantage cornering in the rain for example, or set way low it could theoretically help in a gripped up situation if your competitors are taller and bulky chested (or have fat heads) - shades of gray.

In a concession kart you can’t move the seat around, aside from forward or backward, or perhaps by adding seat padding. In these cases heavier drivers may want to try and shift weight forward to help keep excess weight off the rear axle and tires to minimize chassis hop.

I wouldn’t say that I feel uncomfortable but it is a little daunting. To this point I have only ever raced against juniors but I am definitely build more like the seniors. I’m about 30 pounds heavier and 6 inches taller than everyone else in the class.

At the end of the day I just want to race in the class that I can be most competitive in, so that is what I am trying to decide now.

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Thanks for your thoughts Eric.

“… because more mass is available to shift about the kart to optimize performance compared to a heavier compatriot.”

You’re referring to ballast here?

You’ve talked a bit about the height of the driver in the seat. I wonder if I should try a seat cushion again to test the effect of raising the COG on unloading the inside rear.

My answer to a weight disadvantage is to use the slight grip advantage it confers to do less accelerating than the other guys.

Appreciate your thoughtful answers.


Yes, referring to ballast such as Lead weight. I’ve seen people use batteries on a non-tag chassis before though and get away with that as well…which in retrospect not sure is ok…but anyway…

Yes! A seat pad or cushion is a great way to try a COG change to see the effect, either below or behind the driver we’ve done both before prior to moving a seat…

I like your thought on doing less accelerating than the other guys, but the question would be exactly where is that disparity occurring. Especially on a rubbered-in track, more grip may not be ideal!