Unweighting inside rear through high speed, wide radius corners

Chassis Setup, Tires & Handling Forum
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I drive a 2019 Kosmic OTK chassis in LO206 Sr at 370lbs. Our track (Mac Track in Mcminnville, OR) has a section of fast “esses” which I am really struggling to get my kart comfortable through. They are (or should be) flat out and it is a series of fairly wide radius corners.

Here is an aerial view:

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The section I am referring to is at the top center of the image. The track is ran both directions. I feel pretty good through them in the CCW direction because they are a bit slower speed coming out of the top half of the oval. In the CW direction, that back straight builds up quite a bit of speed before entering the esses with the wide right, wide left, tighter right and tighter left series.

What I am struggling with is oversteer from apex to exit through the last three corners (left, right, left). Once you go too deep on one, the entire series is messed up so it’s a big impactful mistake.

I’ve played around with my chassis setup but I’m new to karting so I was hoping to get some advice for things to try. Current setup: two small spindle spacers up front, 2mm tow out, stock caster, neutral camber, medium height front and back, stock oval torsion bar in flat position, one extra seat stay per side, 1390mm rear width. I’m a tall guy at 6’2" so I would think I’d have no issue jacking weight?

I think I have a okay understanding of chassis tuning at a high level. To better unweight the inside rear, I need to increase weight jacking. That would normally involve: widening the front, increase caster, stiffen torsion bar, or narrow the rear. However, I feel like the front end of my kart is already “VERY” pointy. As I understand those adjustments, they would further increase the “pointiness” of the front end which I don’t necessarily want to do. In fact, it sometimes feels like the front pulls the rear around into oversteer at times.

I tried stiffening the torsion bar a touch which made the esses feel slightly better but the slower corners felt like the rear was setting down too quickly. It made the binding / bog on exit worse than it already feels so I took that adjustment back out. I tried a touch of negative camber to see if freeing up the front would help but I really don’t drive well with understeer and it was slower. I was thinking next time out, I should widen the front and narrow the rear. I guess I am just looking for some guidance on which direction I should be going next time I go out. Other drivers can keep their foot down through all four corners and I believe I am losing a lot of time having to lift slightly as to no induce oversteer and mess up the whole series of corners. I was also seeing my right rear tire coming in with the highest hot pressures after a session. As the layout was clockwise and most of the corners are right handers, I feel like that pointed to scrubbing / not lifting it enough somewhere.

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It isn’t uncommon to have a kart that is slightly too free in fast stuff but good in slow stuff for vice versa. Can be hard to find the balance sometimes.

If the kart is too oversteery in fast stuff, you’re generally going to want to sliiiiightly reduce front bite, but it has to be a very small adjustment. The kart isn’t really jacking weight in a fast corner because you never put enough wheel in for long enough to get the inside rear unloaded. So it probably isn’t an issue with how the kart is jacking weight, especially since it’s good in the slow corners.

Your front is already a bit narrower than stock so I would leave that. Otherwise that was my first recommendation. The negative camber is a small adjustment and should help. If you don’t like how that felt, you could also go for a bit less toe-out to get the front to be less pointy. You could try widening the rear a tiny amount too. It may be a driving technique issue as well. Do you have video showing the issue?

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Interesting! Thanks as always for the feedback. While they are fast corners, they also require quite a bit of direction change from the exit of the previous corner to setup the entry of the following corner. So, I feel like there should be quite a bit of energy building up in the chassis through each corner to unweight the inside rear. What I can feel is that the first slight right hander is no problem flat out. Then following left hander, I need to lift slightly not because of losing the rear at turn in, but rather because otherwise I lose the rear at the apex to the exit. Once that happens, I have to catch the oversteer which pushes me deep on the exit and I run out of time to setup for the following right hander.

I have footage from this weekend. I have not had time to cut it all together for a youtube upload but I have a link to the raw footage in my GoPro cloud storage which should work: Heat 1 - 9/19/23 | GoPro

Probably want to jump ahead to 6:00 for the first time through that section without being right behind someone.

Rewatching the footage, I feel like my inputs are quite minor and smooth but I could be way off. That is something that I have consciously been working on. Re-watching it sometimes looks like I get oversteer at turn in as well in a few spots. Definitely open to admitting it is the archer not the arrow if you see anything I’m doing wrong!!

10:08 is probably the best time through there this session.

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It looks like you are entering too low and apexing too early to start the section and then paying for it through the esses.

You might be defending from another kart here, I’m not sure, but it looks like you are not setting up most of the corners in the lap and turning in early quite often. In some cases where there is oversteer, there is still 5 feet of track on the exit or so that you could play with without forcing the kart down and causing it to slide. Like if you look at 10:00 or so, you’re driving in the middle of the track approaching that section, so you’re already setting up poorly for it and going to have to force the kart down on that exit to get set up for the next left, meaning a larger swing of force when you’re switching directions. You’re half to one kart width lower than the kart in front going into that section.

I would also note that if you are going to have to lift for the section, whether you want to or not, you’re better off lifting before the turn to set the kart up and then power through the apex rather than turning in, realizing you’ve got too much speed on, and then having to lift and drop the lateral force (and inside wheel) in the middle of the corner, which will upset the kart and could cause oversteer as well. You always want to be on power before apex so that you can manage the loud and not shock the kart with any inputs halfway through the corner.

I would try some different things with the driving first. Whenever there is one section that is giving you issue, you should first try to change your driving style through there rather than the kart. The kart is a constant and should be fairly balanced the whole track if it’s good in one section. If there is one corner or section giving you issue, it’s probably something you’re doing there as a driver.

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Yeah in some ways it is probably hard to examine the driving technique during a race because it isnt always clear when someone is all over your rear. I had a driver attacking for most of the race until he bump passed me when I go long off the track out of the corner prior to the back straight…So the reason I am in the middle of the track on both straights is because of that.

I feel like I am usually pretty good with the racing line so this is probably a bad example. However, this is my first season so there are so many technique things left to polish! It is nice to hear that it is probably a technique thing more than a chassis setup issue. I’ll be trying to clean that line up next time we run clockwise!

Could I get a pulse check on the tuning approach if the line is cleaned up and I’m still having the oversteer issue? Sounds like a touch of negative camber would be the the first thing to try. Second would be less toe. Widening the rear seems like it might impact the jacking in the slow corners though so I’d probably want to avoid that I’d imagine unless nothing else is working.

The handling issue I’ve had with this kart the entire time in so many corners is turning in feels good and then I get snap oversteer from mid to exit. Slowing down my hands helped but its still a common issue I have with this baseline setup. I could just be over driving the corners as well…

Thanks again!

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I would take caster out if having oversteer at the apex on the fast stuff

If you have trouble staying on the same line as the fast guys are running = cant steer without the back stepping out - you have too much rear lift

Lean harder to outside on the slow stuff to deal lack of caster

didnt watch the video :wink:

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EDIT:
I left out this important bit; sometimes what appears to be a handling/setup issue can actually be a driving issue.

Watching the video, I get the impression that you are perhaps ‘looking for lap time’ on the entry of some corners just a little bit too much. You need to arrive at the apex with an amount of speed/energy that is in harmony with the turn, your line, and your chassis setup. When you do this, the energy in the outside front tire crests in the desired location (at the tire’s optimal grip/load/slip angle level), causing the kart to rotate (or really complete the rotation), which transfers that energy to the outside rear tire, and then, in accordance with your setup, sets the inside rear tire down.

If you arrive at the apex with too much speed (even a tiny amount too much speed) the ‘extra’ energy on the front tire slightly overloads it (which delays the cresting of energy, rotation, and the rest of the cornering process). The increased slip angle (from the beyond optimal energy/load) tends to both make the kart drift off line slightly, and delays the rotation (and typically this delay translates into a more energetic -faster- rotation).

If you carry too much speed into a corner that leads into additional corners, then the issue can cascade, and become amplified in each corner. Anyway, maybe watch back your video and see if you can pick out corners where you might have carried a touch too much speed to the apex.

BTW, I now this because I do it all the time in sim… even though I know better. :roll_eyes:

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Watching the video, it looks like you are overdriving the entry of the esses, which isn’t necessarily causing the sliding, but certainly doesn’t help the issue. Ideally, you would want to hit the curbs in turns 6 and 7 to enter the sequence, then get the kart to the middle of the track before turning in for 8. This would let you take a wider line and help you set up the next corners better, which could also help stop the kart from sliding as much on exit. Something that might help is to drag the brake and keep the throttle on, which would help limit rotation and stop some of the snap oversteer you are getting.

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My experience early on is when this happened the kart was actually understeering a little on entry, grabbing, then snapping loose. So you might work on changes to increase turn in a little

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Thanks for the feedback everyone! I really appreciate the experience you all have and your willingness to help a new guy figure things out!

Here is my onboard from qualifying so that you can see my lines without the factor of having to defend in a race: https://youtu.be/7z_aY_Lp1kw?si=NzdSDthc5TWu37LR

Based on the feedback here and rewatching the video, I have noted a few things:

  • TJ’s comment about lifting at the corner entry instead of through the apex is something I see myself doing and need to work on. On the best laps, I am hearing that I am lifting earlier and getting back on the throttle closer to the apex which seems to keep the kart more settled on the exit. This advice really clicked with me and will keep it in mind next time!

  • Brennan is super quick at this track and the videos I’ve seen of him driving reflect the feedback he is giving here! Brennan, I did notice that you take the curb in turn 7 and take an earlier apex through there compared to what I was doing. This seems to let you get to the middle of the track for T8 way better like you said! I will give that line a try next time! Thanks man!

  • The comment about over driving the corners makes sense and is something I know that I do too often. Slow in, fast out right? I think I just get the importance of momentum in the low HP class of 206 too much in my head. When I am thinking about my braking points and corner entry, often I am more focused on carrying speed through the corner rather than ensuring my entry speed isnt compromising the corner and exit. I definitely feel comfortable on the brakes and trying to take corners as fast as possible but I think I need to refocus that and force myself to backup some key corners. Need to remember smooth is fast.

  • I still feel that there could be some chassis adjustments to be made, though I understand technique is more important. I’ve just rarely felt comfortable with the handling of my kart. It often feels like the front end is overly sensitive (“pointy”). While I really don’t enjoy driving with understeer, it sometimes feels like I have amazing turn in grip initially, but then as the kart loads, the rear washes out. That forces me to counter steer which sets the inside rear down and then I bog badly on corner exit. Rewatching the footage focused on my hands, I see a lot of corners where I make an initial steering input and then immediately have to counter steer. I’m no expert but it looks like my hands are moving very small amounts and are not too jerky so I’m not sure what else to do. Based on this feedback, it could just be because I’m carrying too much speed into the corners? Thoughts on moving my tie rods up closer to the steering column to reduce the steering rate on my OTK?

  • I see myself driving a defensive line way too much. There are a number of situations across all the sessions where I would have been better served by just driving the racing line, tucking in behind someone and not compromising my lap to defend. I’ll work on that.

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