I have the standard OTK pills, I swapped out the bottom pill from the neutral to standard.
That’s great info! I was visualizing it and it seemed that changing the angle of the bottom kingpin would affect the lean/angle of the front end
If you swapped the bottom eccentric from neutral standard with the arrow facing the front of the kart, then you reduced caster. This would fall in line with what @dodo mentioned, and would raise your front ride height ever so slightly. Sounds like it was enough of a change to make a difference in terms of scraping vs. not scraping.
@CrocIndy thanks again. This setup felt really good, but maybe you can give me some advice on where to go next because I have no idea what happened over the past weekend’s race:
I threw this setup on with 1mm toe out on each side and went racing this weekend. This is the same toe setting I have had on before. The chassis felt really great, I felt like I had just as much grip through the corners as my previous setup but with a more stable rear.
I felt like I could challenge for a podium after the first practice… until I looked at my times… I was a 0.5 seconds slower than before around the same circuit. My previous best was set in March o a 40 degree day. This weekend it was in the 70s and sunny.
I looked at the data from my Alfano and I lose literally all of that time from the exit of the final hairpin of this circuit to the start finish. It is a full throttle run in a 206 with a banked final corner (I marked in yellow on the track map in the screenshot below).
I am thinking I must either have a carb/engine issue or a clutch issue? I am at a loss to explain the lack of pace. It seemed I could keep up well in the tight corners but the others would just walk away on the straights. I also struggled on the start at the drop of the flag.
Things I did before the race - cleaned the carb, cleaned the clutch, changed to your described setup. The tires were the same - Hoosier R60As with three rounds on them - I did not feel that the tires were dead, I had a lot of grip. The engine was not obviously breaking up or performing poorly, it just seems I lacked straight line speed.
I have spare engine that is freshly rebuilt, I may just throw that on for the next race in a week’s time. It is a different circuit but I’m not sure what else to do.
I don’t think its a driving issue, as I can lap very consistently around this circuit.
Any advice on where to look for problems or what to do next?
Red is best lap from yesterday, yellow and green are best from previous race and test:
I cannot speak to the specific set up, but if the kart feels great and is slow off the corner and through the high speed stuff, then you need to free up the rear end (assuming you do not have any engine problems). If you cleaned the carb, an engine does not just lose a half a second like a light switch.
Some data points that make me think the kart is tight (or “bound up”):
- It is a hotter day on a sticky tire.
- It is exit off corner and through high speed stuff that is slow
- Kart feels great (too good!)
Can you attach that alfano file so I can take a look at it? See if there is anything else going in there.
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Thanks @fatboy1dh Could too much grip cause such a big drop-off over such a short lap?
Would be happy to attach the file, but I am new to Alfanos, can I export from the file ADA app?
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I agree with Derek. If the kart feels better and more stable but goes slower, it’s very likely you are bound up in the corner and it’s slow on exit. Hotter temps, a feeling of more rear grip… the math checks out.
Yes, and more. If I’m reading the data correctly, that run from the hairpin to the line is almost half the track in terms of distance.
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So what do you recommend in terms of setup changes?
The next race is at a different track and on MG reds…
And the original setup @CrocIndy explained was for MG Reds, not Hoosiers. 
Probably need to free it up more, especially with the Hoosiers.
I’ve been stuck/bound up and made a small change and cleared over half a second better on lap times.
You can take a few directions on this, unfortunately, and you’re just gonna have to try it.
Do you have test days you can go to?
A.) NEGATIVE CAMBER. Negative can help you free up off the corner.
B.) Rear track width: in your situation, probably a little wider. You may be setting down and reloading the inside rear too early.
Those would be my go-to changes probably in your situation.
What track is this? I’d like to look at a video of a lap.
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I agree with both of these changes. Negative camber helps it roll off corner better at the expense of a little entry/mid-corner front response. Worth a try for sure.
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Thanks @tjkoyen and @CrocIndy I appreciate your input, I felt so lost after that race but what you are both saying makes a lot of sense.
I’ve got no sessions before the next round, only the few minutes of warm-up practice on the morning of the race, so I’m just going to try to make it better. I’m going from the older Hoosiers to fresh MG Reds.
A) I am currently at 3mm positive camber, should I go down to 2 or actually go negative? I like that the front end is responsive.
B) I’m at 52.5 on the rear with 6.0s on. I have the option of 7.1s or 6.0s at the next race, I have brand new sets of both. Would the 6.0s help free up the rear? Should I still increase the track width if so?
Here is the circuit I was at last week but the video is from my previous race there, where I ran the .5 second quicker lap in the Alfano screenshot. I don’t have any footage from the more recent race:
Here is the circuit I am going to next week - it has a lot more higher speed corners but also a very tight double hairpin that will punish too much rear grip. (Vid is obviously not me):
I could understand neutral camber for sharp response before load builds, but he seems to be running a lot of positive which just sounds wrong.
Also, his friction circle is very lopsided which could indicate something asymmetric in the setup, either balance or geometry. Do you agree? The track itself is relative balanced between left and right handers, and I think the cambered right is causing an outer “band” on his circle, but even ignoring that one, his braking and acceleration are all biased off-center, and the general shape is different between left and right.
I am not crazy about the 3mm positive camber, it’s more than I run usually, but camber tends to be a pretty small adjustment and I trust @CrocIndy’s setup. He’s more experienced with that kart and that engine package than I am.
Regarding the friction circle, it looks to me like most of the hard corners are lefts (and there are more of them) and the rights are all fairly soft so I would expect the plot to look offset a bit.
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I’m not just looking at the hard corners. Even the exits of softer corners are scrubbing speed differently between left and right. These arrows point to similar lateral loads, but they are scrubbing very differently. The number of dots is going to be different between left and right because of the number of turns, I know, but if you look beyond that and picture what it would be with the same point density, they are different. You can see these mismatched pairs at other lateral loads as well, they are all over.
The final corner is a banked left-hander, does that explain these readings?
Without being able to step through the data, I am guessing the banking creates that outer “band”. The inner “band” should be more symmetric, but it isn’t. The outer parts of chart are going to be harder to compare left/right, but the center points should be less asymmetric
This is my first year running with the Alfano, I previously had only a Mychron 4, so I am totally new to this level of data. What does this asymmetry mean?
It very well could be related to the camber of the turns, so I am just going off what info is only in this thread. So with all those caveats, I think the balance is off on the kart left/right. Has it been cornerweighted recently? More weight on the right will make it jack easier on lefthanders and harder to jack on righthanders, for example. This can make it feel glued down on some turns and not as bad on others.
I have never scaled this kart.