Trail braking in low horsepower kart

briggs206

(TJ Koyen) #21

Are we talking about trail-braking or power-braking?

Seems unusual that an engine would overheat and be damaged by simply braking later…


(Eric Gunderson) #22

@tjkoyen I’m talking about power braking, so I apologize for not making that clear. When I was growing up that’s how the term trail braking was presented to me, which is I know now not the technical term.

Either way, it’s a chronic problem with a lot of 206 racers to power brake as you say.


(Mike Clark) #23

Davin, Reread what I asked.

How does an engine applying load to an axle with a brake on it affect the opposite end of the kart if front has no brakes. Brake cancels engine to some extent and the axle exerts one load. So the axle is either applying no load, an acceleration or deceleration load. All the inputs go to the rear axle. There is only 1 load for accel/decel and it comes from the rear. So the weight transfer is a result of the load axle applies whether it 3/4% max accel or 100% max accel minus 25% accel from being on brakes as well.

Same with “loading and unloading at the same time doesn’t really help you.” the tire only sees the net result of the load. If you load a tire 100 and unload it 30 it is loaded 70 whatever units you want.

I brought up brake balance because it would matter on a kart with front brakes. Then you could load opposite ends with brakes and throttle. I don’t see how that works on a single brake kart.

I have always viewed trail braking as trailing off the brake as you add steering.
100 brake/0 steering
80 brake/20 steering
50 brake/50 steering
and any other combo
Basically the more steering, the less braking and vice versa
That way you always use the tire at the limit of combined steering and braking. More prevalent in cars. Plus in a car you have suspension and more dramatic weight transfer.


(Mike Clark) #24

I would think power braking would not be good for the clutch either.


(Aaron Hachmeister) #25

I understand what you’re saying. If an engine is applying 12 in-lbs of accelerating force to the axle and the brakes apply 6 in-lbs of decelerating force, the overall force acting on the axle is 6 in-lbs accelerating. Davin is correct if we are talking about 4 wheel brakes or something more complicated than a kart. In a kart you are correct, it would have the same effect as just applying 6 in-lbs of acceleration force to the axle.

However, this will really wear down your brakes, clutch, and engine. Like Eric said, you’re running the motor under a higher load and it will eventually cause the engine to burn a hole in the piston (ask me how I know that). Brakes are being engaged at a high speed while not slowing down the kart, and the clutch is being worked to still try to accelerate the engine while the axle is resisting that acceleration. Trail braking is only useful in really specific circumstances, typically higher speed turns.

My thoughts on trail braking in general for single speed lower hp karts essentially follow the thought that it is all about maintaining momentum through the corner, and getting on the gas as early as possible. As a result, trail braking to the apex ends up using space in the corner that you could be accelerating through instead. I could brake in a straight line, turn in, and get on the gas before the apex, starting to roll onto the gas pedal just after turn in, to really lengthen the amount of space that I can use to accelerate out of.

This is very general and as turns become more complex and situations change the theory adjusts as well. If you are racing in a pack and someone is trying to pass you, you could try to brake later and eliminate their opportunity to make a pass under braking going into a corner. This reduces your exit speed however, so it depends on what turn is coming after the corner you are in. If you have a very long straight ahead, it may be better to leave the opportunity to pass under braking open so that you can maximize your speed down the straight and possibly get them back before you even get to the next corner as they will be compromising their exit speed in the action of passing you.

If the corner is sharper and/or doesn’t have as long of a straight after it, you may want to normally trail brake into it since even though you may have a lower exit speed, you could still set up the following turn to maximize that exit speed and make up time there. The time you lose on exit by trail braking may be negated because you are carrying more speed for longer coming into the turn. A good example here is turn one a Road America, a tight chicane after a long straight. Watch the video here and you can see how they are braking much later than you would if it was just the right hand turn followed by a straight, and how late they are getting back on the gas because there is still the left hand portion of the chicane to navigate before the following short straight https://youtu.be/pnsfYIDt9EU?t=423.

I usually tell my friends “To go fast, you want to get on the gas early, which means you need to be slowed down early. However, you still want to brake as late as possible. So basically just brake early, but as late as possible. Easy, right?” After that they start to understand how much more difficult and different racing is from generally driving a car.


(James McMahon) #26

Clutch doesn’t care unless you’re doing it to the point of making it slip.


(Davin Roberts Sturdivant) #27

In a general sense, deceleration forces affect the vehicle similarly , regardless if you have rear brakes or front. When I say braking force, I mean the loading that goes to the front of the kart when you decelerate. ( I guess you could think about it as the vertical and horizontal loads on the tire.)

Also with the weight shifting thing, karts shift weight much more quickly, and it feels less pronounced than a car because of lack of springs, suspension, where you’re sitting in car etc, but it’s still happening.

It’s just the loading on the tire happens faster.

Regardless, my opinion is to avoid using gas and brake at the same time, as often as possible to reduce conflicting front/rear weight loads.

When you’re trail braking, you’re already asking the tire to handle braking/ forward weight shifting under deceleration and some turning, so giving it power at the same time can easily overload a tire’s grip.


(Mike Clark) #28

Davin,
I have no issues on not using brakes and gas at the same time. I think it is no advantage and some disadvantage I was just looking for clarification on the is point as it pertain to a low HP kart. I assume 1 rear axle brake. (No fronts)
Weight transfer, trail braking and all that I get and we agree on.
I am just questioning your statements like this:
“Regardless, my opinion is to avoid using gas and brake at the same time, as often as possible to reduce conflicting front/rear weight loads.”
It is one front/rear weight load on a single brake kart. It may be dynamic and rapidly changing, but it is coupled. So if the load always totals 100 how is there a conflicting front / rear weight load. What is a conflicting load? 60/60? how does that happen? Remember 1 brake, so you are playing front brakes against rear power.

“When you’re trail braking, you’re already asking the tire to handle braking/ forward weight shifting under deceleration and some turning, so giving it power at the same time can easily overload a tire’s grip.” Power and brake cancel on the axle, the way I see it. So the load is just a single load on the rear tire in respect to power and brake on the contact patch. If you add power you are reducing the braking, which lowers the force. If you add too much brake or power alone you can exceed the limit.
The load on the tires contact patch from corner and accel or decel is cumulative to just a force and vector. That either exceeds the limit or it doesn’t.

My fundamental premise:
Two opposing forces can not exist from braking and power on a live axle single brake kart at the tires contact patch at the same time.


(Aaron Hachmeister) #29

Clutch wear was more of a Yamaha thing, I’m not sure if that can be an issue in 206 or not. I know in low stall clutches it shouldnt be an issue, but 206 has a rev limiter at 6,100 RPM I believe? That means if the clutch engages at 3,500 RPM which I think is accurate because every search I’ve found says between 3,000-4,000 RPM engagement clutch slip could be a possibility.


(Mike Clark) #30

Aaron,
I think what you wrote is a very good assessment.
A decreasing radius comes to mind as an example if where trail braking could be used effectively. It is almost sure to get you if you come in to fast and don’t start fixing it early enough.

Question for you and TJ and all.
Do you differentiate between late braking and trail braking? If so what is the difference?

I have my definition of the difference.


(Mike Clark) #31

3,600 seems to be what most feel is the magic number.

I see power braking as being hard on the whole driveline from engine to rear sprocket.
My take is just reduce the throttle by as much as you would be taking away with the brake.


(TJ Koyen) #32

Trail-braking would be ‘trailing’ the brake into the turn-in, late-braking would still be basically straight-line braking.

You could conceivably brake extra-late for an overtake and really diamond the corner off so that you’re still applying almost all your braking in a straight line, but then really rotating the kart hard at mid-corner.


(Ted Hamilton) #33

With any deceleration, weight transfers forward. It doesn’t matter if that’s because the engine goes from full throttle to half, or if brakes are applied equivalently. Brakes tend to be able to make that transfer happen more quickly…