Effects of Adjustable Wheelbase on Kart Chassis

Thanks for your reply @dodo
So, checking if I followed correctly your train of thought, you meant that changing the wheelbase affects only or mainly longitudinal weight transfer (fore/aft) and changing the track width affects only or mainly transverse (lateral) weight transfer?

Remember those statements are only related to weight transfer since that was your original question, but other things are also at play. Increasing wheelbase will increase the leverage that lateral tire forces have on the rotational inertia of the kart, so this is a fancy way of saying it is harder to spin (so you get understeer as a consequence or at least less oversteer).

So when you say “wheelbase affects only longitudinal weight transfer”, that is incorrect. My answer only focused on that particular aspect because it is what you asked about, but that does not mean that is the only aspect to look at.

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Perfect. This is what I was also thinking, I mean, changing the wheelbase will somehow affect lateral weight transfer as well. Thanks for your clarification, but it is still not clear to me the reasons.

This statement above is exactly what I felt when I changed the wheelbase. Actually, I reduced the wheelbase to decrease the understeer and it worked with a consequent reduction in time lap. But, when the track became rubbery, it became an issue and the time lap increased. So my thought was: “Maybe we lost traction or the reduced wheelbase made it to become anchored to the rubber”
This collateral effect of reduced wheelbase makes sense to you?

If the only change you make is moving the rear axle fore/aft, then you are also changing the weight distribution. My previous responses were assuming that CG was not a function of wheelbase, but the reality is that it is unless you manually move the seat or lead around to achieve the original balance. I find it very useful to isolate the original question, but this always has be understood as just a leaping-off point.

Look at it this way. Lets say your CG is 15" in front of the rear axle on a 40" wheelbase. That’s 62.5% rear weight. Now, move the axle forward 2" and make no other changes. The new rear weight will be 65.8%, and the only way to isolate the effect of moving the axle is to move your lead forward to get back to the original 62.5%. Picture an extreme example where you move the rear axle farther forward than the CG, and it’ll pop a wheelie.

Corrected math now.

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Actually, as my kart allows only changes in the vertical axle, I couldn’t move the rear axle position to decrease the wheelbase so I did it in the front axle by rotating 180º both (upper and lower) caster eccentric bushing.