Kart pulls???

[Michael Taksa]

My Kart wants to go straight on all the turns, even if the wheels are turned, I either have to slow down to almost a standstill, or yank the steering wheel so hard that it starts to spin... Is this what is known as a pull??? No Idea on alignment, 97 Haase Cr125 shifter, with rear tosion bar.
What to do?
Thanks.

[Jean Stafford]

Mike:

What you are describing is what the Stock Car boys call tight. By this they mean the back of the car is so tight that the front end "pushes", or understeers.

If you are experiencing an understeer, there could be several things you might try.

1. Incrase caster, the amount the wheels are trailing the spindle, a little at a time. This should transfer, or shift, more weight, and allow the rear wheel on the inside to lift slightly.

2. Narrow up the rear end.

3. Lower the front tire pressure, or up the rear. The first should make the front stick better, the latter should lessen the "push"

4. Play with the softness of the axle. Most mfg's. have a selection of axle stiffness.

5.Move the wheels out on the front. This should also transfer more wieght.

All of these things I've mentioned have loosened my Kart up, each in it's own little bit.

You didn't mention what class you run, and horsepower has an effect as well. More is better, just ask anyone..

Just for your info, I run a Yamaha KT-100 in Masters Class, about 12 Hp, and an old Margay Syncro-Blade Chassis. I have noticed another thing you might try, and that is move the weight around. If you are adding weight, keep it on the seat. I found this to be the key to get my chassis to handle, not well, but controlable at least.

Good luck, and if all else fails, go to the Hasse Dealer and get his input. He's probably running the chassis, and has a good idea of what it likes.

[Randy Mckee]

Michael,

I often end up with the same condition, and consequently burn-up front rubber. Try some of the suggestions Jean presented. Also check-out the Tech page on the web site: http://www.ekartingnews.com/tech/010325chassisset.html However, I've noticed that every chassis reacts differently to setup changes. Some karts do exactly the opposite of what you'd expect. With this in mind, experiment with various setup changes and keep good notes.

Also, keep in mind that each chassis change can make a huge difference; try to change just one thing at a time. Do some laps and experiment. Also, keep and eye on the stop-watch after each change. The kart might feel a bit better after a significant adjustment, but you could actually be running slower laps. The clock will tell the truth, not your gut.

Best of luck...

[ August 07, 2001: Message edited by: Randy McKee ]

[Tim Pappas]

You will find that it is worse in one direction or another depending on the Earth's rotation. Sometime this happens in an East/West direction and sometimes it is North/South. It is the opposite south of the equator. Thats why the toilet swirls clockwise north of the equator and counterclockwise down south. It is the same thing with your kart. If you are at a track that has turns predominately against the Earth's rotation, then the best thing to do is to change the direction of your tires. Instead of mounting them with the arrows going forward, point the arrows towards the back. That should solve the problem.

[Marc Miller]

Tim and I don't always agree... but when we do, it is magical.

And this moment... is better than any David Copperfield special ever aired on national television.

Thanks Tim.

Marc

[Gary Kozuma2]

quote:

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Originally posted by Michael Taksa:
My Kart wants to go straight on all the turns, even if the wheels are turned, I either have to slow down to almost a standstill, or yank the steering wheel so hard that it starts to spin... Is this what is known as a pull??? No Idea on alignment, 97 Haase Cr125 shifter, with rear tosion bar.
What to do?
Thanks.

---

Hello Mike,

One of the most important tools I've ever bought for karting is a front end alignment tool. It's a version of the exact toe style. Cost about $115. Until you know what your alignment (caster, camber and toe in/out) is, along with your weight distribution, you'll be burning up tires and getting frustrated. Your description sounds pretty extreme to me. How much air did you say you have in those tires?

My recommendation is to take it to a kart shop or hook up with someone at your local track. I had a CRG that was doing the same stuff. Had 2 problems, one was weigh balance and the other was too much toe in.

Gary K.

[Michael Taksa]

I'll try to respond to all of you at once.
First of all THANK YOU.
Class: 125cc shifter.
Track is the same all the time: OVRP.
I've only been there two times, and it is pretty far from me, so I don't spend much time there.... I would like to set - up as much as I can before hand.
I did make one change and I think that is what brought this on... I moved the tie rod ends on the spindle side back to the original holes without adjusting the toe... The reason I did this is because they were mounted to a piece that was welded to original spindle and did not look safe to the guy who did the imspection. I will adjust the toe next. Is 1/16'' out pretty much the standard? I also have spacers on front wheels and can move them out more. On caster/camber I am not sure I can do the adjustments. I don't have any extra pills, and I don't know what is there now. I can work on the weight distribution and tire pressure.
Thanks again, hope to race against you at some point.

[John Learmonth]

quote:

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Originally posted by Michael Taksa:
My Kart wants to go straight on all the turns, even if the wheels are turned, I either have to slow down to almost a standstill, or yank the steering wheel so hard that it starts to spin... Is this what is known as a pull??? No Idea on alignment, 97 Haase Cr125 shifter, with rear tosion bar.
What to do?
Thanks.

---

Michael,
It’s called an ‘understeer’, AKA a ‘push’. Does it understeer from the moment you turn the wheel, or does it turn in OK but then understeer?

Assuming it understeers from turn in, the problem could be too little front weight, clapped out front tyres, too little weight jacking effect (the mechanical effect caused by the inside front wheel lowering and physically lifting the inside rear wheel), or not turning the wheel sharply enough. I would suspect inadequate jacking effect to be most likely, but any of the above could also be contributing or causative factors.

How wide is the front end, and do you know how much caster you have (a lot or a little)? Low caster is OK (in fact I think it’s great), but with low caster you need to have the scrub radius (the distance from the king pin axis to the contact patch at ground level) quite wide.

Caster and scrub radius together create the weight jacking effect, and a greater degree of either will increase jacking. High caster will generally cause excessive tyre wear though, because it causes a lot of camber change as you steer the front wheels, usually causing excessive inner tread wear, but sometimes wearing the outside of the tyres as well. Uneven tread wear is always a symptom of not using the tyre tread to it’s full potential (IMO).

Don’t be tempted to use high caster and wide scrub together, it will tend to tear up the front tyres and make the kart difficult to drive smoothly.

If it turns in OK but understeers quickly after then you’re probably failing to keep the inside rear contact patch unloaded. This could be too much rear weight, or the chassis waist being too rigid. If the tyres aren’t good then you may just not be producing enough ‘G’ force to keep the inside rear unloaded (ie to flex the chassis enough). If this is the case then the chassis will force the IR back to the track and both rear wheels will ‘push’ the front end.

Toe in wouldn’t help either.

If the weight is too biased to the rear, then it won’t matter much what the front end geometries are doing.

There’s a brilliant article elsewhere on this site to do with front end geometry, have a read of that. I hope it helps.

[Chad Hartzell]

Everyone- this is my first official post regarding chassis help in 4 years. It has taken a while for me to get enough confidence in what I do to share with others. Feel free to critique my ideas…

Here are some ideas for you regarding the Haase:

(1) Definitely check your toe. I prefer zero toe for my Haase Mizar, but it depends on the track. If OVRP has a lot of tight / twisty corners, the toe out may help some, but it gives a little more rolling resistance on the straights. (2) Take the rear torsion bar out. This will give you less bite in the rear. (3) You can also check the axle stiffness. You should always know this simply for your own information. The softer the better based on your description. (4) If your chassis model has the front torsion bar, try placing that in (keep the rear out) and see what that does. It will stiffen the front end, giving you more bite. (5) Is the rear axle in the "up" or "down" position? I placed the axle in my Mizar in the "up" position to induce a looser condition in the rear. (6) I have no shifter experience, but could the front / rear brake bias cause any problems if there was too much in the rear? (7) What are the condition of your tires? The reason I ask is that on my Haase I practiced with old fronts and it was worthless to even be on the track the push was so bad. (8) Have the checked the frame for being straight? (9) Is your seat too far back?

Regarding the caster / camber pills, I would work with the adjustments that are on your kart prior to adding another element into the mix. Hope this helps…

[Michael Taksa]

Ok. Thanks all.
I will work on my weight distribution and toe next. Then If that has no effect I will try other things.

[Scott McFadden]

A useful tip is to check your front-end settings with the kart on a level floor with the driver sitting in it. Toe and chamber especially will be much different than on the stand. Once you have a good setup on the floor you can record your data for subsequent set-up on the stand. It is also interesting to take note of how your chassis reacts to front end weight changes. You can see this by, for example, stretching your tape measure across the front discs and simultaneously sitting on the front bumper. Karts I’ve checked have all tended to move toward toe in as weight is increased. So what you say?….remember there is a substantial weight-shift forward under braking especially on a kart with front brakes.

Also for not too much money, a couple of 10" magnetic spirit levels and a tape measure will give you surprisingly good setup capabilities by using your front disks as the measuring points (assuming they are not floating ). I also bought a couple of $10 bathroom scales to check weight distribution. (help you save for your next set of tires or go faster pipe).

A useful on-track test is to lean forward in the seat to see if that helps or hinders, as a quick way of determining if more weight forward will help.

[John Learmonth]

quote:

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Originally posted by Scott McFadden:
A useful tip is to check your front-end settings with the kart on a level floor with the driver sitting in it. Toe and chamber especially will be much different than on the stand. Once you have a good setup on the floor you can record your data for subsequent set-up on the stand. It is also interesting to take note of how your chassis reacts to front end weight changes. You can see this by, for example, stretching your tape measure across the front discs and simultaneously sitting on the front bumper. Karts I’ve checked have all tended to move toward toe in as weight is increased. So what you say?….remember there is a substantial weight-shift forward under braking especially on a kart with front brakes.

Also for not too much money, a couple of 10" magnetic spirit levels and a tape measure will give you surprisingly good setup capabilities by using your front disks as the measuring points (assuming they are not floating ). I also bought a couple of $10 bathroom scales to check weight distribution. (help you save for your next set of tires or go faster pipe).

A useful on-track test is to lean forward in the seat to see if that helps or hinders, as a quick way of determining if more weight forward will help.

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All karts will change camber because of driver weight, some less, some more. I’ve seen as much as 12mm of camber change (almost ½”), which is VERY substantial. Typically you would see about half this change, but this is still quite significant as it relates to your handling and tyre wear, especially considering that the outside front will gain ADDITIONAL neg’ camber when the steering is turned (caused by caster angle).

All karts (that I’ve measured) change toe to some degree (always gaining toe-in), but not all will change enough to worry about (if the change is less than .5mm then I wouldn’t worry too much). But I’ve seen as much as 4mm of toe change (about 3/16”, again considering the small diameter of kart tyres, a very substantial change), but about 2mm of toe change is more typical (again, still quite significant).

Scott is quite correct, the only way you can know what you’re camber and toe settings really are is to actually measure them with the driver in position, and you can record the change due to REMOVING driver weight in order to be able to re-create the driver seated settings on the stand. But be careful, any wear in your rod ends or king pin bearings will make this inaccurate.
I don’t think it’s any accident that many manufacturers are advising the use of varying degrees of ‘static’ toe-out and pos’ camber. However, the ‘dynamic’ toe and camber changes caused by weight will vary ON THE SAME KART depending on driver weight, weight distribution, scrub radius, and even caster angle and KPI (which will change when you adjust camber angle). So any recommended factory settings can only be an approximation of any changes you will see on your kart.

To REALLY know how much your weight affects your alignment, you really need to align it with your bum in the seat! Anything else is just a guess. These changes can be measured using conventional alignment methods, but with some degree of difficulty. There are at least two products (perhaps more) that make measuring one or both toe and camber changes simple, accurate, easy and quick. Among these are the Pro-K-Laser and the ZTB Chassis Alignment System (which is my product, so please read my comments with this in mind).

[ August 10, 2001: Message edited by: John Learmonth ]

[ August 10, 2001: Message edited by: John Learmonth ]

[ August 10, 2001: Message edited by: John Learmonth ]

[John Learmonth]

quote:

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Originally posted by Randy McKee:
Michael,

I often end up with the same condition, and consequently burn-up front rubber. Try some of the suggestions Jean presented. Also check-out the Tech page on the web site: http://www.ekartingnews.com/tech/010325chassisset.html However, I've noticed that every chassis reacts differently to setup changes. Some karts do exactly the opposite of what you'd expect. With this in mind, experiment with various setup changes and keep good notes.

Also, keep in mind that each chassis change can make a huge difference; try to change just one thing at a time. Do some laps and experiment. Also, keep and eye on the stop-watch after each change. The kart might feel a bit better after a significant adjustment, but you could actually be running slower laps. The clock will tell the truth, not your gut.

Best of luck...

[ August 07, 2001: Message edited by: Randy McKee ]

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Randy, on the whole only making one change at a time is generally good practice, however this doesn’t always hold true as some changes will need to be accompanied by another change in order for the benefit of the first change to be realised, and for the first change to not actually make things worse (even though it may be what you needed to do).

My favourite example of this (but there are others too) is the interdependency of caster and scrub radius settings. Many people have tried increasing front track width (which also increases scrub radius) and found this one change to be truly terrible, so tend to avoid using wider scrub settings. After all they’ve made only one change (which is accepted wisdom) and it was bad, but a wide scrub will only work with a low caster angle (usually).

They’ve made an advantageous change, without making another change needed to make it work. If they’d made two changes at the same time (ie lessened caster as well as increasing scrub) then it’s very likely that they would have found a handling and lap time improvement coupled with improved front tyre wear (I know this is a sweeping statement, but I’ve generally found it to be true).

It isn’t good to wear the fronts significantly more than the rears, despite what ANYONE may tell you. This is always a sign that you have a significant problem. Many people seem to accept excessive front tyre wear as a karting fact of life, but it need not (and should not) be so!

I keep beating on this drum, but high caster angles cause excessive tyre wear and promote overheating of the rubber (caused by the excessive ‘steered’ camber changes caused by high caster angle), which is why less caster is generally a better way to go, but only if you increase scrub (of course depending on what actual range of caster adjustment is possible on any particular kart, some karts having less and some more, and keeping in mind that you can have too little caster). This is because lessening caster lessens weight jacking, but increasing scrub gets it back again (without affecting camber change).

Having said that, unless you have at least some understanding of any major interactions between two adjustments, making two changes at a time is one of the most confusing things you can do. Making two changes simultaneously will multiply the possible (side) affects of the changes you make.

With karts, not many adjustments actually change only one thing. Most adjustments will have multiple affects. An obvious example being a change in rear track width, which will change the ‘overturning moment’, alter the rear ‘spring rate’, alter the rear geometric ‘roll’ / ‘roll stiffness’ ratio, alter the mechanical roll stiffness, alter axle oscillation, alter the effectiveness of the weight jacking effect, alter any braking or torque induced rear toe change etc. etc.

Some changes caused by an adjustment will be minor and some will be major, but even if you make only one change it can often be difficult to know exactly which effect of the change actually resulted in any improvement or deterioration in handling, lap times or tyre wear.

I agree a kart that is easy and comfortable to drive can sometimes be slower than a kart that is harder and less comfortable, but this is by no means always the case, most of the time the opposite is true (in my experience), but this might be more of a reflection on my level of skill!

[Larry Ferguson]

Anyone of you consider the fact that he might have his brake bias adjusted all the way forward? If this is the case, I know for a fact that it's not going to turn in very well (Just ask my kid what I did to him at Streets of Willow this year! Oops!) Take a look at the brake adjustment.

[Michael Taksa]

Larry, that was the case, it eliminated the lock-up somewhat, but the kart still does not turn in well. Anyone can tell me the "normal" toe setting?