Ask TJ

JIM SILVERHEELS · Posted: Thu Mar 07, 2013 8:50 am Post subject: Ask TJ

TJ, if pushing going into a turn I would want to widen the front end as one option, but if the kart pushes at mid turn I would want to narrow the front end. Is the narrowing of the frontend making the two front tires sit down faster and working together to make more grip? Seems logical but wanted to ask our INHOUSE EXPERT, thanks
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Michael Taksa · Posted: Thu Mar 07, 2013 10:45 am Post subject:

How about slowing down before the turn? Smile

))

Randy Mckee · Posted: Thu Mar 07, 2013 1:14 pm Post subject:

Michael that was funny. We're all guilty of overcooking the turn.

Jim, it's more related to how long the inside rear tire is in the air. A skinnier front will keep it lifted longer so you'll have more rotation in the middle of the corner (assuming your turn-in is good). Doesn't really mean more front grip, just better rotation. I try to tune for timing the lift and drop rather than thinking in terms of grip; though I do catch myself saying front or rear grip alot.

Years ago I read a really good setup manual by Ron Sutton. It deals with the mechanics of weight transfer, timing the lift of the rear tire and how to analyze the rate and duration of that lift to maximize handling for various scenarios (e.g., sweepers verses tight turns). I've also noticed that Aussie guy with all of the excellent setup tutorials (can't think of the site at the moment) often refers to rate of lift. Same idea.

OK, speaking overcooking the turn... too wordy.
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JIM SILVERHEELS · Posted: Thu Mar 07, 2013 1:58 pm Post subject: Randy

Randy, I went and watched the Aussie video and he agrees with what you said. I thought it was the two front tires working together quicker. Learned sumtin today, A wider front end will make the rear inside lift quicker but set it down faster. So, a wider rear track going into a turn prevents an initial push on turn in but sets the inside rear down faster through the turn. Thats why narrowing the rear with mid turn oversteer lets the rear stay in the air longer? thanks amigo
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TJ Koyen · Joined: 03 Oct 2004 Posts: 1414

If you watch the KRacer vids, you'll hear "rate of lift" a lot.

Any time you increase front grip or speed up the rate of lift (widening the front), you're increasing the speed at which the rear sets down as well. A wider front will lift quicker, but set down quicker. Too wide and you risk oversteer or you risk setting down the inside rear too early, giving you exit push.

It's a compromise to find the best balance of lift speed and turning reaction. You might have to sacrifice a little turn-in to get off the corner reasonably.

So Randy basically nailed it.

Don't think about tuning the amount of "grip" you have, always think of it as the rate of lift.
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Jim McMahon · Posted: Thu Mar 07, 2013 2:17 pm Post subject:

Biggest confusion in karting is made with "Grip" and "load transfer". The rate of lift analysis is a very good way of separating the two.
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JIM SILVERHEELS · Posted: Thu Mar 07, 2013 4:47 pm Post subject: TJ

TJ and Randy, got it, knew what to do, but not why.. thanks again.
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Russ Deubel · Posted: Thu Mar 07, 2013 7:34 pm Post subject:

Let me get this straight, I'm loose on exit with 2 spacer wide on each side. If I widen the front it should create a push and cure the loose exit. (Theoretically)

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Russ Deubel · Posted: Thu Mar 07, 2013 7:51 pm Post subject:

Got it,amazing what happens when ya read it the rite way. Thx

TJ Koyen · Joined: 03 Oct 2004 Posts: 1414

Wider doesn't always = understeer on exit.

Wider on front usually = better turn-in, but if you get too wide, it'll lift the inside rear too quickly and set it down almost immediately, causing the kart to sit flat and push off the corner.

Widen the front to get the kart to rotate quicker at turn-in. Narrow it to slow down the rotation.

Understeer on exit caused by an excessively wide front is a case of being way out of the ballpark on your front width. It's a strange side-effect that isn't the norm for what a wide front would do.

The short and sweet of it is, don't try and fix a handling issue (in your case, exit oversteer) with another counteractive handling issue (inducing understeer on exit by over-widening the front track).
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Randy Mckee · Posted: Fri Mar 08, 2013 12:33 am Post subject:

Russ Deubel · Posted: Fri Mar 08, 2013 7:10 am Post subject:

Thx,Randy. Getting the concept.

Chris Livengood · Posted: Fri Mar 08, 2013 8:08 am Post subject:

The guys I've talked to who are good at this no longer talk about oversteer or understeer, they simply talk about lift duration and lift amplitude (using various terminologies). In my experience, these characteristics encompass all of the many handling ailments.
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Jim McMahon · Posted: Fri Mar 08, 2013 9:31 am Post subject: