Lets bring this back to the top. I have an embarrassing thing to admit, I made a front bar change on my kart last weekend in a “Monkey see, Monkey Do” situation and it made the kart better, but I’m still not sure I understand exactly WHY it made it better.
I’ve never played with front bar before ever…kart is an '18 OTK and I’ve left the flat blade in the flat position the whole time I’ve owned it. I’ve always made my adjustments with width, caster, etc and felt like I could get it to a comfort zone for me, pace at my local clubs was always fine after adjustments here and there.
This past weekend at a new track I got to where I felt the kart was comfortable. I was chasing the rear in a few spots but in my opinion those situations were flat sliding, which I’m rationalizing now was actually NOT flat sliding which is embarrassing that I’m interpreting the problem with the chassis incorrectly. Anyone that’s ever observed me in my kart has always mentioned it looked like my kart was not jacking as it should be and in the past I’ve added caster to make it jack more which has made it quicker.
Anyhow, back to this past weekend struggling for pace and notice everyone on OTK’s is running the gold (softer) front bar. Nothing to lose I get the gold front bar and throw it on there and what do you know it makes the kart quicker and I’m not chasing the rear nearly as much in the areas I was previously. I thought it was going to plow understeer making that change and it really didn’t make the front feel much different at all.
So in analyzing this after the fact…I wasn’t really flat sliding from lack of jacking was I? I must have been overwhelming that outside rear? Softer front bar reduces jacking even further right so it’s going to stay even flatter but carry whatever lift is created for longer allowing it to release off corners better?
To be quite honest I was at an impass when I made that change. I wanted to put a second seat stay on or put neutral caster pills in the kart…both of those would have made it worse not better based on the results from the front bar.
I guess as I type this the conclusion is…how do I diagnose overwhelming a tire vs. flat sliding moving forward??? Is there a tell tale sign of one vs. the other? Reading the tires?
A tire that’s sliding will basically look the same regardless of why it’s sliding, so that diagnoses method is out when you’re trying to figure out what that why is.
Always break the corner down into its three parts; entry, apex, exit. If the slide is happening at entry, you’re likely jacking too much weight. If it slides at apex, you’re getting close to the kart being good, but you’re still overloading the rear tire at max lateral load. If it slides at the apex-to-exit transition, it can be assumed you have understeer-to-snap-oversteer.
My experience is that flat-sliding from lack of weight jacking is fairly rare. It does happen, but it’s more likely that the kart will just be flat and scrubbing and binding, not sliding if you aren’t jacking enough weight. Most of the time, if your perception is the kart is flat-sliding, you are overloading that outside rear tire.
In my torsion bar testing this year, my experience was that the stiffer bar helped the kart turn in snappier, but it also set that inside rear down quicker and actually provided more rear grip at apex and exit. When I went to the stiff bar, I went faster. Then I tried the front bar softer again, but went max caster to see if I could get the same level of turn-in, without the negatives of the kart being stuck on exit. That’s exactly what happened; the max caster made the kart drive into the corner better (not quick as twitchy as the stiff bar), but also held the inside rear up in the corner longer. I went even faster that session.
My point is that maybe the stiff bar got you halfway where you wanted to be at. Softer bar with caster might’ve gotten you even more time.
That’s where I’m confusing tuning. I always though adding caster would only help on entry and once you got to apex with more caster it would set down quicker not slower…I probably should have tried the centering pills at one point but I ran out of test sessions and went with it. Appreciate the input here to help me rationalize how you can get different ways of getting the same amount of lift but with different behaviors on exit to aid in other areas
Guess I should elaborate a little more. I’m not saying caster will set down slower, necessarily. I’m saying it will be more possible to carry the lift longer with the caster compared to the front bar. A kart with neutral caster will still be slower loading and hold the wheel up for longer in the corner. But if we are looking at front end adjustments, I’m saying caster > stiffer bar when talking about duration of lift.
I always think of the frame as a spring. If you stiffen a spring, it will snap back quicker when released. So if you stiffen the front bar, the inside rear will snap back down quicker when released. Now looking at caster the same way. Caster is not stiffening the spring. But it IS allowing the spring to be “pulled back” further. So you get the bigger initial movement in lift, but it isn’t as prone to snapping when loaded up.
Obviously a kart frame is far more advanced than a simple spring and there are other factors at play, but I think that analogy sort of captures it in an easy to visualize way.
Caster will probably want to set the rear down earlier, but if you are able to hold the wheel steady and keep that flex in the frame, it isn’t going to want to snap down like a stiff bar will. A neutral front-end kart will still be more progressive in its loading, but sometimes caster or a stiffer front end is a necessary evil to get it to turn.
I’ll add to this. I went softer on my bar trying to remove front “grip”, from metal to nylon, on my Compkart. Hoping to remove front grip and get rid of some apex to exit oversteer. If anything oversteer was the same, but I was lacking turn-in and couldn’t get the kart down to apex as easily. Makes since as I’m reducing front grip, but I saw no appreciable difference in the rear? Beginning to think I’m chasing this problem from the wrong direction.
Video for reference, really struggled through Turn 3 and 4 and was sawing at the wheel trying to keep the rear end under me.
now I’m really confused. I swore the flat blade bar in either position was stiffer than all the round ones…
from the setup guide:
Flat bar adjustable: horizontal position “standard”: Vertical = very stiff
Round bar, Chrome = Soft
Round bar, Silver = Medium
Round bar, Gold/Brown = Hard
picture of the bars
The standard setup is the flat bar in horizontal position. The flat bar is the stiffest of all
torsion bars. Note that the round torsion bars requires round fixing clamps.
Softest seat Compkart makes. I was a bit fast on initial steering input to get the kart pointed in, but I think I was compensating for the softer front end.
I did the same thing on my compkart last Wednesday, completely removed the silver round bar. Chassis seems much more compliant into the corner. Doesn’t seem to hammer me around as much.
It seems so simple to me, the front end is attached to the backend.
More bite in the “rear end” tends to feel like less bite in the “front end”. It’s pushing because you’re getting too much rear bite. The front end and the backend are part of the same kart. They work together.
Knowing that, if you put the bore in, and you get a push, quite possibly the bar is taking bite out of the front end. Not the other way around. Makes perfect sense to me.
TJ is correct. It’s always been my experience that when you place a stiffer front bar in it will also make the front end bite more. Depending on what your kart is doing it can sometimes balance out your kart if your having a slight push. If you have access to a lathe you might try making your own for a lot less money than it cost to by one from a kart shop. You can purchase the material at Graingers. They also give specs on the Tensile Strength which will give a few choices on stiffness. I’ve made my own for some time now and can be a life saver. Below is a link to the material. It’s worth a try. It does make a difference.
In a time of desperation once, we took a Sawzall to the round tubing on our old KartLift to make a super stiff front bar in the middle of a race weekend.
I’m good with the theory of what I did now, but I’m still failing to properly understand where the OEM OTK flat bar falls in the spectrum of hard to soft.
turned vertically it’s the stiffest bar possible correct? But it was stated here that the gold round bar (stiff) is actually stiffer than the flat bar is in the horizontal position. Where does the flat bar at horizontal compare to the rest of the round bars.
Couldn’t you just move the flat bar at varying angles to get any desired effect if it’s softer than gold in one position and stiffer than gold in another? Why various bars if you could just use the flat bar in an array of different positions and get the same result?
