Moving the seat forward to achieve better weight distribution

Right now I’m 51%-39%, would like to get closer to 42% at the front. I have two 3kg lead weights attached to the bottom front of my seat, one on either side. I have a large fuel tank which I fill roughly 3/4 full.

I removed one of the 3kg weights and placed it between my pedals, and I barely achieved 40% on the front. There really isn’t any room for this much lead at the front of my kart anyway.

Without going and drilling holes in my seat only to find out not much difference was made, could I expect any significant change moving my seat 10-15mm forward?

I can tell a difference between a full tank an empty one, so CG is pretty much the biggest tuning tool you’ve got. 10mm might not sound like much, but you are moving something like 75kg

Some karts are more sensitive to seat movement. Also it depends on how far you are off the optimal seat location. I would stop worrying about holes in the seat and move it. Moving weight to the front is ok for a temporary test or solution but it does increase the polar moment of inertia of the kart, which theoretically increases the resistance to rotation. 15 mm should make a difference.

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@Kakarot I just noticed your math isn’t mathing. What is your current CG? 51+39=90, so are you currently 61/39?

I made a quick sheet and got a change from 39% to 40% front weight when moving 3kg. Then, I moved 70kg forward by one tenth of the wheelbase and went from 40% to 44% front weight.

Assumption: You and your weighted seat are roughly half the mass of the kart. Lets say the total is 400 lbs for this exercise.

If you put the seat exactly between the front and rear axle. You would have 50-50 weight distribution (if the frame was symmetric), 200 on each end.

If you put the seat directly over the rear axle, you could have 75% rear weight at max, 300 on rear and 100 on front.

so that means that from the middle position to the rear axle is a theoretical 25% weight distribution change and that distance is around 500 mm. That works out to about 1 percent weight change per 20mm of seat movement.

Hope that makes sense and helps.

Whoops. Yeah, 61/39.

Thanks for the replies. There’s 50mm from the front lip of my seat to the bars that hold my fuel tank. I wouldn’t want to be hard up so thinking 20-30mm shift forward max is all I can do. Sounds like by your math the most I can achieve is 40.5% to the front. Suppose it’s better than 39%.

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If you can move your pedals forward some, that will help.

Did you try putting the kart on the scales pointing the opposite direction? This will help rule out any issues with the scale. I have seen them in use at the track without being level. This an affect the accuracy. Same with tire pressure.