Go-Kart Deceleration - Braking Capability

The braking test for the inter-collegiate competition we’re entering requires the karts to go from a minimum speed of 40 kmph to a stop inside the braking zone of 5 metres. This would result in a deceleration of over 1 g, and many places I’ve seen calculate braking force without reverse calculations tend to consider 1 g as a theoretical maximum deceleration. I have considered a 50 kmph vehicle coming to a standstill in 4 metres for additional safety, which ends up with an even larger deceleration. Are there any limitations which will not let the vehicle achieve this sort of deceleration if the rest of the parameters like piston and mc bores and rotor radius are reverse-calculated considering these conditions?

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The limitation in almost all cases for vehicle’s is tire adhesion to the road.

How do you get round that, softer tires, bigger tires, downforce, lighter weight.

I wonder if it was purely a braking test if performance would be improved by decreasing the tire pressure.

Are the brakes rear only, or front and rear. That will make a huge difference.

Your limitation is generally going to be traction, karts are very over braked. At least racing kart chassis are. Brake pistons, bores etc should not require much if any examination. Find traction, then if you approach thermal or mechanical brake system limits resolve them if you have to.

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I’ve used the friction coefficient between the tyres and the road in the calculations to end up with my force and torque values. Just wanted to see if there was any constraint which would not let it decelerate so quickly. I could attach a few pictures of my calculations if that would be helpful.

Highest G force I have seen karting was a whiteland 4.1G going into the braking zone a few years back. It was exhausting to drive very physical, with rear brakes only I bet 1G is pretty hard to achive.

It’s an inboard braking system with a single disc rotor on the rear axle only.
That’s what I was wondering, what would the system limits be? Theoretically I could get ungodly amounts of force and deceleration, but what limits do I need to look out for while calculation for these values? Currently I have only considered practical constraints like chassis interference, pedal sensitivity and component sizes.

Yeah it sounds pretty unbelievable, but that’s what they’re spitting at us . Also the calculations would give even higher values, and I’m not sure if they’re limited by any other factors.

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There’s a multitude of systems in karting, so there is no clear answer. Just like cars, pads vary, some systems have dual calipers on a single disk. There’s vented and non vented. Ceramic coated and straight steel. The only limit I think I’d be concerned with is thermals, and (Generally) it takes a lot to overheat kart brakes. Like a LOT. You’re not going to overload a typical system on a racing kart in a few stops from 50KPH.

If you have a rear brake only kart, and there is a specific deceleration test that tests only braking, move the seat as close to the rear as you can. You could even work to keep F/R load transfer to minimum by putting seat as low as possible (even below rails if it’s not hitting the ground) and raising the front ride height to provide rake. Depends how extreme you want to go.

The short answer is: (Assuming typical racing karts chassis) The limitation lies in the tires and F/R load transfer, not braking system.

Questions:
I’m curious how you concluded the friction coefficient with how many tires compounds are available. What did you use as a reference?

What kind of a frame are we looking at here? Something self fabricated, or a racing specific chassis?

4.1 G? How exactly did the driver stay in the seat?. If you are a 170# in gear, that means almost 700# that needs to be reacted at the pedals, steering wheel and the inclined lower portion of the seat… LOL I call nonsense. I think you got the numbers transposed…ie 1.4G.

Yeah 4.1 doesnt sounds right. I’d say that would be enough to lift the back wheels off the ground.

230 in the seat, and… poorly… very, very poorly… luckly, my choad took alot of the force with the fuel tank… but in reality its not 4.1 sustained… its peak over a small sector of time… it was honesty crushing pressure… absolutely insane… would come off with tires 3/4 around to the valve stem.

The guy I raced with actually lost the final because he is a bigger guy and itnwas just way to much Gs

I’ve actually done some math on this. You MUST have front brakes to get anywhere close to your target. With rear brakes and a CG above ground, harder decel gives more front weight bias which reduces the force on the rear tires. Using a kart CG and wheelbase, this works out to around 0.6G with a 1.5 coefficient of friction

Edit: just saw this was a 2-year bump

No worries. Still on topic and adds to the conversation