Is this "normal"?

[Jeff Mulvihill Jr]

I just spent two days testing...
Some background. I'm new, I'm 45 pounds over the weight limit for K1.

Testing on Dunlop SL-4s, a well worn set now...

What was happening: I have a bad oversteer problem, but I think I've determinded why... the rear of my kart is so heavy (or was that my arse?) that my inside is NOT lifting, not even "un-weighting", just stuck down (gotta love gravity). I think that since the inside is planted, when I get back on the power the inside hooks up and since it's on a shorter path, it breaks the outside loose causing oversteer on exit.

Things I tried: (thanks to the help of a fellow karter I did make some progress... my times came down some...) Narrowed the rear track as much as hubs and axle would allow, from 55" to about 52". Raised the tire pressure, from 10 all around up considerably. Believe it or not, my best times were found with fronts a 15 and rears at 25 cold, 17/27 hot. It was FAR easier to drive, less oversteer and my times were getting lower. We messed a little with the front track but that didn't seem to make much difference.

Are the things I messed with "in the right direction" or is this a little weird? I think moving the seat farther forward would help balance it better, NO I haven't scaled the kart... which I should, but I'm going to be changing motor packages, 80 to HPV. And I'll also have a "fit" problem if I move the seat too much... my knee will hit the shifter (yet another reason to get that HPV).

Help everyone?

[Jimmy Moore]

Move the rear back out to 55" and also move the front out all the way. Take the bolts out of the left side stiffener and loosen the bolts on the 3rd bearing. Use short hubs if you've got 'um and try not to go so high with the rear tire pressure, go back to 20 psi if you can. Moving the seat forward will have the most effect and will definetly help alot also, get the seat as low as you dare. Fresh front tires make a world of difference. Beyond that try a little toe out and a little more castor.


[ October 09, 2001: Message edited by: Jimmy Moore ]

[Marc Miller]

Jimmy-

I read that he was having a problem with oversteer, which is a loose condition. With the exception of wideing it back out to 55", everything you told him to do would induce oversteer... what gives?

MM

[Rob Hogenmiller]

Actually I didn't think the advice was totally that bad.

Of the different (4)Manufacturers I've driven widening the front does take away Oversteer. (With the exception of a Margay I rented/drove did the opposite.)

Also lowering the front chassis ride height in the front has helped take oversteer away for me.

Moving the seat forward in my experience would make the Oversteer even worse. I suggest depending on how tall you are moving your seat back to get more grip on the outside rear tire.

To me it doesn't make sense that you could be getting to much grip in the rear (even from the inside) to cause oversteer.

Also it's been my experience that rear tires wear out about 1.5 times the rate of front tires. You mentioned that you were on used tires. The tires themselves may have been help causing the oversteer.

Lot's of other variables but those have been some of my experiences.

Short hubs---- I've found on tight corners the short hubs work better than long hubs, but the long hubs work better on sweeping type corners. (I haven't had much time testing that so don't put to much faith in that.)

[Jeff Mulvihill Jr]

When I messed with the front track, it "helped" but so minimally that it was not measureable, in or out, that lead me to think there was some other problem.

I don't think I'm getting too much grip to cause oversteer, I think there is a conflict between the inside and the outside, the inside is winning and since it's on a shorter path... I TOTALLY guessing there.... nothing else makes sense to me at this point... the fella that helped me out drove it, loved it... he's about 40 pounds lighter than I am... I jumped in NO DIFFERENCE.

Lowering the front cause BAD bottoming... I'll suffer ill handling to save the chassis...

My tires are wearing very evenly, the wear marks are very simliar on all four... I had the exact same handling problems with a NEW set of YGCs in a prior test.

Short hub/Medium Hubs, no difference...

All this lead me to the idea of moving the seat forward, getting weight off the rear. Guess I need to scale the thing to know for sure... I followed my manufacturers directions on seat installation... but not sure those were written for a 220 pound guy... gotta go... gotta get my running shoes on and go work off a few!

Another question, would loosing 25 pounds help my problem (I'm working on that...)? Or does it sound like there is "something" else going on?

[Mike Goebel]

Try leaning forward before you come into a turn and stay there if you can. I did this and the inside picked up nicely and the kart lost almost all of it's oversteer. I next moved the seat forward an inch and also tilted it forward to give me the approximate location of when I was leaning forward. Haven't tested yet with new seat location. Careful I also hurt my rib on one side but that's the cost of real time testing .


Mike G

[John Scott]

quote:

---

Originally posted by Jeff Mulvihill Jr:
I just spent two days testing...
Some background. I'm new, snip causing oversteer on exit.

Help everyone?

---

Jeff
In addition to trying some of the set up comments, I would add that Driving, esp in a shifter, is probably the major cause of corner exit oversteer. Two major things are pinching the entry putting you off line on exit. Second, how you roll on the throttle is important. Many people put an extra spring on the gas pedal to make it easier gently apply power. You might also try to exit in a higher gear, which puts the challenge of carrying more speed in the corner - not a bad thing to try in general.

Good luck and have fun
John

PS: My 80 driver is now in a F2000 and has the same problem...he can spin it by heavy application of the right foot. Amazing thing is that he will admit it

[Roger Miller]

Oversteer and stuck in the rear do not go together.
The important question to ask is *where* in the corner does *what* happen?
Being stuck in the back causes a push or understeer going into the corner, then, new karters are turning so much, that the rear breaks loose in the mid or exit of the corner and it seems like it is loose in back, looking like an oversteer.

So sort that out first, then try to solve the problem. Unloading the rear, picking up the inside rear tire, leaning forward, spreading the rear (some), more caster, depending on the kart wider front, or, narrower front... all of these loosen up the back, decreasing rear grip, allows the kart to turn in better and reduces push.

Then, it should stay stable through the corner not be as likely to break loose going around the corner.

The discussion so far has sounded like a push/understeer going in causing the driver to turn too hard and that breaks the back loose later in the corner.

[Jeff Mulvihill Jr]

Throttle induced oversteer on exit. I'm not getting a "slide" per say, I understand your example, but it seems to be strictly related to getting on the throttle.

John's idea of my "driving" might be a part of the cause. Where I'm getting the oversteer is on slow, tight corners with a "decent" amount of exit room, so hard on the throttle. I know I need to carry more speed in... really "hustling" I still can't make up much, and I know some of that will come with more and more seat time... as well as loosing some pounds...

My times when I "raced" were 8 seconds off pole!! I hate to admit that, but I'm so new that there are more than likely 1000 things that contribute to that. I'm new, I'm heavy (pole was set by a kid who weighed in 3-4 pounds over with a fire breathing motor and I weighed in 47 pounds over stock), I'm stock, I don't understand setup... someone stop me! This oversteer has been a problem since the very first time I drove it at this particular track (as well as one corner in particular at another one), regardless of tires, setup, ambient temperature, time of day, etc. I've been struggling with the "cause"... it is VERY frustrating, I know I'm loosing a bunch of time in other areas but I'm CONFIDENT this is a big loser as well.

Roger, I understand your comment "Oversteer and stuck in the rear do not go together." But my "idea" was that the situation of not lifting the inside might be the cause of the oversteer. The kart trying to use the inside tire's line and not the outside's line. Kind of a cause and effect deal. The outside's "grip" is compromised due to the shorter path of the inside's line. Note this was an "idea"... may be complete BS... but I'm just trying to figure out what's going on...

[ October 12, 2001: Message edited by: Jeff Mulvihill Jr ]

[Jimmy Moore]

Marc,

I misunderstood what he was saying, I thought he ment understeer.

OK, forget everything I said before. Your theory about the inside tire breaking the outside tire loose is not really posible. You need more traction from the rear tires. Lower the pressure to 15psi (you can try 14psi but, at your weight good luck), tighten the left side stiffener, use extended wheel hubs, run your 7.10 tires on 8" wheels, loosen the rear bumper, set rear torsion bar for more flex, use a stiffer axle, tighten the bolts on the third axle bearing cassette, put 2 seat struts on each side, use a softer compound tire, use stiffer wheels. As you go into the turn just turn the wheel once and hold it there through the turn. The more you saw the wheel back and forth the more the rear will break loose.

[Dan Schultz]

Not to sound too harsh, but if you are eight seconds off the pole, I would question if you are driving fast enough to get enough heat in the tires. This would partially explain the oversteer condition (karts oversteer until the tires come in) and why the kart ran faster with unusually high air pressure. Get someone who is more up to speed to try your kart and offer suggestions.

[Roger Miller]

Jeff, let's try this....

Take a pencil, roll it on a flat table, it goes straight. Now, on the back of your kart, you have this thing called a "live" axle. It is solid, like the pencil, the "live" part is the bearing carriers that allow the frame to flex a bit around the axle. Now, when you go into a corner, the inside tire will try to go straight, not turn, and this will cause a PUSH, an understeer. Then, when you crank on the wheel to get the kart to turn, it can and will snap the back loose and seem like oversteer, when it ain't.

Again, the real question that MUST be answered is WHAT is happening WHERE in the corner? You need to carefully understand that before you can do anything. If you think you have oversteer, the back stepping out, but you really have a push on conrern entry, you are going to be trying to fix the wrong thing.

Back when we started karting, I thought we had oversteer, but it was a push going in and a snap spin in the middle or exit from cranking so hard to turn. Have someone watch your hands in a corner. And like was mentioned, have someone up to speed try the kart and see what they have to say.

What is happening when? That is the question.

[Jeff Mulvihill Jr]

Roger,
Thanks for your post. I understand your logic. The places where I'm getting it, I'm actually unwinding the steering wheel for exit, post apex and applying throttle. The oversteer just calls for a lot more unwinding, a lot quicker! I'm VERY careful not to saw the steering wheel, a lot of hours behind a car wheel taught that as well as several schools (racing and kart) so I'm not worried about that... I've got some things to try. As you said, I don't think I REALLY understand what is happening so I don't really know what to apply...

So far what I tried that day... (that didn't seem to do much of anything)
Tire Pressure
Removed the rear bar (back in now and quicker)
Narrowed the rear track
Widened the front track (tried going both ways)
More tire pressure (this helped the most)
Tried shorter hubs, didn't allow any more "narrowing" of rear track. Didn't see a difference.

I'd LOVE to do what Badger suggested... can't find anyone that is 5'10" 225 pounds (without gear on...) at the track...

Jimmy,
I'm not sure what the left side stiffener is... I have a 3 rail kart, don't think I have one??

[John Learmonth]

quote:

---

Originally posted by Jeff Mulvihill Jr:
Roger,
Thanks for your post. I understand your logic. The places where I'm getting it, I'm actually unwinding the steering wheel for exit, post apex and applying throttle. The oversteer just calls for a lot more unwinding, a lot quicker! I'm VERY careful not to saw the steering wheel, a lot of hours behind a car wheel taught that as well as several schools (racing and kart) so I'm not worried about that... I've got some things to try. As you said, I don't think I REALLY understand what is happening so I don't really know what to apply...

So far what I tried that day... (that didn't seem to do much of anything)
Tire Pressure
Removed the rear bar (back in now and quicker)
Narrowed the rear track
Widened the front track (tried going both ways)
More tire pressure (this helped the most)
Tried shorter hubs, didn't allow any more "narrowing" of rear track. Didn't see a difference.

I'd LOVE to do what Badger suggested... can't find anyone that is 5'10" 225 pounds (without gear on...) at the track...

Jimmy,
I'm not sure what the left side stiffener is... I have a 3 rail kart, don't think I have one??

---

Feff, for what its worth, I would try a more rigid axle if I had this problem exiting the corners.

[John Learmonth]

quote:

---

Originally posted by John Learmonth:


Feff, for what its worth, I would try a more rigid axle if I had this problem exiting the corners.

---

That would be Jeff, not Feff, sorry Jeff!!