Setup for one corner?

Matt Clark · Posted: Tue Jun 26, 2012 4:12 am Post subject: Setup for one corner?

So I went out a few weeks ago and had my first day in my kart ('09 Tony kart Krypton) and overall had a pretty damn good day. The engine revved like it should and the chassis seemed to handle well in all areas except for one corner leading onto the straight. I would say it's a medium speed 180 degree corner, it's the last corner before the straight running the track counter clockwise for anyone who's raced there.

The kart seemed to be very loose around this corner for some reason, and it could have a lot to do with how I approached it, but I was wondering what chassis adjustments I should try in order to stabilize it so I'm not sliding at corner exit onto the straight and thus scrubbing speed. I've read some things online that I should maybe try to run the back torsion bar with the flat spot perpendicular to the ground to stiffen it up? Or I've read about ride height in the rear. Dumb question, but how do you move the rear ride height up and down? I'd assume you have to move the bearings which in turn moves the axle?

Another thing is, if the kart seems to be working well in the majority of the track except one corner, would you guys normally still try to adjust for that one single corner? (I'm sure the answer is going to be "try it and see how your lap times go" but just wanted to see). I'd imagine since it's leading onto the straight if I could do something to make it faster there on exit it would more than makeup for some minimal losses in the infield.

Matt

Matt Clark · Posted: Tue Jun 26, 2012 5:46 am Post subject:

I've also read about consciously putting your body weight towards the outside rear wheel, so maybe first session out I can try that since it seems to only occur on one corner, and I'm pretty sure I'd naturally be leaning into the apex of the turn rather than pushing outward.

TJ Koyen · Joined: 03 Oct 2004 Posts: 1461

Sounds like that's the most important corner on the track if it's leading onto the straight, so you will want to be handling well through it.

I don't really setup my kart for one corner per se, but you should definitely be getting through each corner well so if you feel you need something to change the handling, an adjustment might not hurt you anywhere else and help you in your trouble areas.

If it's your first time out, it's more than likely your driving (no offense!). But some quick adjustments to try are narrowing the front track width or softening the front torsion bar, or removing the front torsion bar. These will all give you less front end bite and help get rid of the oversteer. I'd focus on simpler adjustments like these first before messing with ride height and such. And we almost never use rear torsion bars. It's a pretty big change and really is only useful for extreme conditions of low grip.

To really focus in on the issue, try and break the corner down into 3 sections; entry, apex, exit. And determine what the kart is doing in each section. Lots of handling woes are misdiagnosed because the driver doesn't feel a problem in one section of the corner and only feels a different issue in another corner section. For example, oversteer on exit often stems from understeer on entry. The initial understeer causes you to give the kart more steering input and when it finally bites, you've got all this wheel in the kart and it snaps around, sliding the back end. Most drivers only feel the exit sliding so they think they have oversteer. And that'll send you down the wrong tuning path if you're fixing oversteer when really you have understeer.

Your posture in the kart can affect the handling quite a bit. Leaning outwards could hurt or help you though. Maybe the extra weight from you leaning would overload the tire more and give you more sliding, or maybe it would plant the tire and get rid of the sliding. That's an easy adjustment to try.

As a newbie, see if you can tune the oversteer out and go quicker with your driving a bit with different corner approaches and so on to see if it isn't just you. And if you still feel that the kart needs an adjustment, then break the corner down into those 3 sections and determine what it's truly doing. If it's really oversteering, try narrowing the front width a couple spacers. If it's understeering, do the opposite. Half of tuning is finding what your particular style and chassis like, as lots of times, what works for one driver doesn't work for another.
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Matt Clark · Posted: Tue Jun 26, 2012 6:32 am Post subject:

None taken in reference to the driving TJ. Since it was my first time out I was definitely trying different lines through the corner, but unless I went into the corner noticeably slower, it seemed to act the same. It would be planted through the beginning of the turn, then as I transitioned to throttle (I was trying to do the "act like there's an egg under the throttle" trick) at/after apex it would start to break away, leaving me to saw the wheel exiting the turn.

I will say that even though I didn't think I was taking the corner optimally, I wasn't noticeably losing any ground/time to people I was behind, but I was running with Seniors/Masters rotax/tags and I myself would be classed in senior and I wasn't running any lead, so I was probably a bit underweight which I'm sure helped my speed (I actually drafted and passed quite a few (what appeared to be) masters drivers heading into the flat out sweeper after the straight.)

My kart doesn't have the front bar in, but it does have the rear bar in and flat. In your opinion should I take it out completely and see what effect that has?

TJ Koyen · Joined: 03 Oct 2004 Posts: 1461

Peter Zambos · Posted: Wed Jun 27, 2012 7:46 am Post subject:

Hi Matt.
You being on the lighter side it seems, and having a Kypton, which has a thicker outer diameter tubing thus making it stiffer, it seems counter-intuitive to me that you would have the rear bar in at all.

Here's a couple of references for you...

A seat set up guide. Yes, it's for a Kosmic, but, if you don't know already, it's the same chassis with a different color:
http://j3competition.com/downloads/technical/J3_Seat_Setup_Form_v2.pdf

Next, a general set up for the Krypton. I don't know what tires Rotax uses in Australia, so there might be a little variance there:
http://www.tonykartaustralia.com.au/download/krypton-ksx/Krypton%20KSX%20-%20Rotax%20Light.pdf

You want to make sure that your seat is in a good position so that your weight distribution is appropriate. If this is off, every other adjustment is a bandaid solution. Next, T.J.'s totally on point that where you have the most to gain is you and your driving. Even older farts like me have to re-evaluate their lines from time to time.

In terms of adjustments you could look out for, take a look at your camber. Camber is the angle at which your front tires are leaning to the outside or leaning in. Leaning in is called negative camber and leaning out is called positive. I've found that if you don't have enough negative camber, you can float the inside rear tire for way too long on exit, making it difficult to apply throttle. This happens in while entry and apex can feel just fine, with the exit problem being more pronounced in tighter, faster corners. Of course, still focus on the basics and better understand how the kart is working in entry, apex and exit like T.J. said.

Good luck and welcome to karting. Lastly, if you're going to eventually be competing in Senior Max, you may as well bolt on the needed weight now, otherwise a lot of this testing won't be as applicable.
Cheers.

Matt Clark · Posted: Wed Jun 27, 2012 9:06 am Post subject:

Thanks for the info. Peter. I'm planning on getting weight for sure, they just didn't have the scales out on my first day so I didn't know how much to get. I think I'll take out the rear torsion bar and see how that does. I also don't know how much help tires of an unknown age would be in this scenario. I've left the seat in the same position it was purchased, as I bought it off of a guy who is roughly the same size as me and runs (and does well) in FWT. I should be going this Saturday so I'll report back and let you guys know how it does. I appreciate all the advice. I think I've pretty much got the engine info/maintenance down as I've read up before purchasing and while waiting to get a chassis. Now it's tuning the chassis that's the next big hurdle!

Matt

Matt Clark · Posted: Wed Jun 27, 2012 2:45 pm Post subject:

Just went out after work to take out the rear bar and wouldn't you know it I was wrong. The rear bar is out, it's the front that's in. My fault for the mixup! Back to square one now Laughing

Matt

Peter Zambos · Posted: Thu Jun 28, 2012 10:38 am Post subject:

Well, at least that makes more sense, so your issue is now less perplexing. So just focus on your lines and play with the rear track width and you should find improvement.

Matt Clark · Posted: Thu Jun 28, 2012 10:41 am Post subject:

The more I think, the more I believe the tires have a role in this. It seemed later in the day it got more tail happy than in the beginning. This could also be because I was pushing more. Nothing else to do but test different things on Saturday!

Brent Harper · Posted: Sat Jun 30, 2012 6:33 am Post subject:

Take the rear bar out and throw it in the Trash Can... Kart is probably pushing(understeer), you in turn are turning the wheel more and then the fronts grip up and the rear whips around. That is not loose, it is tight and the rear needs to be freed up.
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Nathaniel Dewitt · Joined: 02 Dec 2008 Posts: 109

Turn in a little late let the kart roll through the center of the corner with maybe a very small amount of throttle then just past as your getting to the exit and later than you think start to roll onto the throttle and let the kart go to the side of the track and make sure your smooth on the steering wheel and not trying to force the kart. That corners long and is like an oval turn. If your loose on exit there then you should be loose on exit of the corner at the end of the straight which is usually caused by understeer at the beginning of the corner. As TJ said think about the entry middle and exit of the corner.

Volker Krahn · Posted: Mon Jul 02, 2012 10:32 am Post subject:

Matt Clark · Posted: Tue Jul 03, 2012 1:11 pm Post subject:

Here's a couple of videos from Saturday to visually show:

http://www.youtube.com/watch?v=83uK74hbJRg

http://www.youtube.com/watch?v=qisbxm5eW1M

TJ Koyen · Joined: 03 Oct 2004 Posts: 1461

You need to drive the kart more before you start adjusting. You're not really driving even close to the limits, where the kart is made to work, so you might be chasing a problem that might not even exist. It looks to me like as soon as the back gets a little free you're immediately countersteering hard to keep it from stepping out, which is natural instinct. But the kart will have a little free feeling to it when it's working like it should.

Remember that there should be almost no coasting when you're driving. Get used to the brakes, lock them up a few times to feel how hard you can step on it.

Just go out and drive and get plenty of seat time. Driving is always going to be the first place to pick up time.

And I know you're just trying to not get run over, but don't look back so often. Just focus on looking ahead and visually internalizing the track in your mind.

But yeah, right now I'd just be focusing on getting up to speed with driving.

Your lines didn't look bad for your first time out, just gotta find the limits of the kart.
_________________
T.J. Koyen
OKTANE VISUAL - Custom Helmet Paint & Graphic Design
www.oktanevisual.com
www.facebook.com/oktanevisual
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DB Motorsports
Exprit/Leopard