Home Forums Chassis & Handling Tire Stagger for chassis tuning

This topic contains 11 replies, has 7 voices, and was last updated by  Gary Lawson 1 year, 1 month ago.

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  • #9573

    Bob Baldwin
    Blocked

    At what point on tuning your chassis do you pay attention to playing with tire stagger ?

    I would think the Compound hardness plays into the equation

    Would like comparisons between Sprint and RR

    In this case I am referencing MOJO tires NOT exactly a Softer Compound compared to others

    #9626

    TJ Koyen
    Participant

    We always measure our tires to make sure they’re close to the same circumference. If there’s a big difference, we put the bigger tire on the outside.

    You can’t really tune with stagger unless you lathe the tires or something so it kind of just is what it is.

    #9641

    Ray Lovestead
    Participant

    TJ – have you found many tires that were really out of bed?  I could see being concerned with a rear tire that was 0.5-1.0″ different in circumference than the other side.  But I haven’t come across to much of a difference to warrant a concern.

    Bob – I do know guys that buy lots of tires and match them up by size.  But I don’t know anyone who staggers them.  But if you did want to, you could put larger diameter tire on the outside rear wheel.

    Ray

    #9683

    Bob Baldwin
    Blocked

    Ray  : I would think you would want both rear tires as close to the same circumfrence as possible . Though you could play around with air pressures to make up slight differences . I talked to a guy a few weeks ago at Go Pro in NC. He was insisting that if a Sprint track as example has 10 turns 7 left  3  right you ALWAYS put the larger tire on the right side . I tried to get him to explain his rationale of thinking and I was NOT buying his answers .

    To my way of thinking you would be upsetting the Balance of the kart , Perhaps even making it HARD to lift the inside rear tire on cornering . Maybe even affecting Castor Camber ?

    #9684

    TJ Koyen
    Participant

    Ray,

    Yeah we do run across tires that are off by a fair bit sometimes. Some brands are more inconsistent than others. Anything more than .25″ and you can feel it on track. The kart will pull to one side.

    Bob,

    Just like a sprint car, you run a larger outside tire to help the car turn left on an oval. Though karts work a bit differently, that’s the principle that’s being applied. If you have a bigger tire, putting it on the RIGHT side will help the kart turn left. I wouldn’t adjust air pressures to make up circumference differences either. That’s a pretty integral part of chassis tuning. That’d be like running an extra torsion bar to help straighten your bent frame.

    What makes you so skeptical of this guy telling you to put the larger tire on the outside? What rationale do you have for putting it on the inside? Would you not also be upsetting the balance of the kart? And how would it affect caster or camber? Just trying to follow your train of thought.

    #9691

    Bob Baldwin
    Blocked

    TJ : To some degree I can understand all OTHER racers in Oval track events WANTING to have Stagger in Right rear to help the racecar turn left . Though in karts with a solid axle we as karters  have a different set of chassis tuning paramaters to go by .

    I probably should have added that in his explanation to me he mentioned that EVEN if the 2 rear tires were same circumference around he would add a pound or 2 of air to make the right rear bigger

    To that extent I guess he MIGHT be correct Though at WHAT point do YOU see a measureable difference ? Again I am NOT sure What his Geomety setting were on the front end

    Using the example stated above 7 left turns 3 right turns I would think you would be foolish to put the larger rear tire on the left side .

    Let me ask you 2 questions :

    1. Is it NOT better to have the rear tires as close as possible in size to Balance out the settings on a kart ?

    2. Does having a right rear 1/2 inch + circumference or larger have an effect on the front end geometry ?

    I honestly don’t know the answer to the question I posed .

    #9693

    TJ Koyen
    Participant

    You want your rear tires to be the same size. I wouldn’t add air either to induce stagger because like I said, tire pressure is a pretty important tuning tool.

    So to answer your questions:

    1. Yes, you want equal rear tire circumferences.

    2. I’m sure it has a negligible effect since you’re changing the rake of the one side. But you won’t feel the difference. It isn’t really quantifiable.

    Bottom line for me is, I don’t want stagger in the rear tires, but if there is some, I put the bigger tire on the outside and don’t adjust tire pressure to fix stagger.

    #9706

    Eric Alexander
    Participant

    Bob – Either you misunderstood the guy at GoPro Motorplex or he’s in the weeds.  You are correct that using that theory – and all things being mechanically perfect – he’d want the staggered tire on the LEFT side for that course.

    Also as you most likely know by now, TJ is a great source for information.

    Regarding tuning with air pressure:  I “once upon a time” scaled my kart to find it had a slight twist resulting in a higher diagonal weight.  At the time I thought I’d see what air pressure changes did to effect that.  I balanced the kart using air pressure, then went out – ran 10 laps or so – and blistered the rear that was on the heavy side.  Rookie mistake.  I’d never blistered a tire before, nor have I since.  But what I learned was use tire pressure to fine-tune the handling, not compensate for a mechanical imbalance.  Better to address the mechanical issues with mechanical solutions in order  to get your tires where you can fine-tune the handling.  In this case, measure the tire circumferences and match like-measured sets together.

    I will say this, I’ve had very good results running different pressures left-right depending on the number and direction of turns.  At GoPro Motorplex, I start with .5 pound more cold pressure on the right (Bridgestone YLBs).

    #9785

    Tim Koyen
    Participant

    Eric is right on the mark.

     

    And with regards to running slightly different pressures on one side or another to compensate for a track that has substantially more turns one way, that is also very common.  A lot of people will even their tire pressures out right when they come off the track hot, which effectively offsets them to compensate for one side or tire being worked more than the other(s).

     

    And just to echo what was said by many, I would NEVER induce a stagger condition by increasing tire pressure.

    #9792

    Bob Baldwin
    Blocked

    Eric / TJ : Well put I understand what you are saying about evenly matched circumfrence on the rear . Honestly the only time we ever used Kart scales was when the Kart was brand new we went to  OGP hired a tuner for the day did the seat placement and LEARNED some important lessons on Kart Geometry . Pretty much proceeded to try to learn the rest as we went along . other than Tech I don’t recall ever moving the seat again based on what the scales were saying . Probably a mistake on our part . did a lot on rear wheel base and front end Geometry .based on notes but that was about it .

    Not sure WHY but I recall making the above changes and the LAST thing we would decide to do on the check list and notes was WHERE to set the Air Pressures at .

    TJ: you are also correct about trying to “INDUCE ” a stagger if for NO other reason than SAFETY Purposes .

    #9840

    Valentin Yakimenko
    Participant

    There are ways to increase or decrease stagger. Visit your local dirt track! For example: take harbor freight torch, and a tire that is bigger out of two. Take out valve steam and heat the tire from senter out but do not heat the side walls. And it is best done while tire is on axle or freespending hub. So you rotate the tire while heating. You will see tire shrinking in. Stop. Take it off and deep it in bucket with cold water but keep valve steam out of water. Let it cool of put valve steam back in air up. And check. If you want to grow a tire, add extra 5-8 lbs of air and while spending around heat the side walls. Lett cool of on its own. Let some air out and check. Hope that helps.

    #9923

    Gary Lawson
    Participant

    Some of you sprint guys are probably reading Valentin’s post thinking he is nuts but he is absolutely correct on how to easily shrink and grow a tire. Some tires are harder than others to grow based on construction. A Burris or dunlop are very easy to stretch a tire 1/2″ just by inflating it to about 50 pounds. Others like bridgestone are nearly impossible to grow more than an 1/8″ without using heat/ice bucket.

    In regards to how stagger can be used in sprint kart it is pretty much useless. The reason why is because karts have so much caster and turns are generally so tight that the inside tire is unloaded very much or completely off the ground. In oval racing the driving barely turns the wheel and they don’t run more than 12 degrees caster typically. Couple that with how the inside rear can have as much as 175 lb of preload that tire will never be completely unloaded. The stagger is used to help turn the kart in the corner and the increased weight on the left rear helps the kart drive off the corner with more speed.

    In sprint racing, like TJ said any more than approximately a 1/4″ the kart will pull excessively down the straights. A 1/2″ difference in stagger, front or rear, will cause the corner weights to be off by as much as 10 lbs in the front and rear.

    Also, an oval kart typically runs 1 1/2″ front stagger and 1″ rear.  This much stagger naturally puts negative camber in the entire right side of the kart and positive camber in the left side.

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