Weird weights on the scales?

VR88

New member
Just pick up my first tag kart (used 2015 tony kart). It fits me well and is track ready. I tossed it on the scales for a check and it looks pretty well balanced. However I noticed when I turn the wheel it loads the same side rear. That is something 100% foreign to me. When I turn right I would expect the LR to see more weight not the RR. Can someone help me understand this dynamic? Thanks.
 

alvin l nunley

Premium User
The whole point for lots of caster is to unload the inside rear wheel. Does it do the same thing turning left or right? Do you use electronic scales? They could be hooked up backwards!
 

VR88

New member
The whole point for lots of caster is to unload the inside rear wheel. Does it do the same thing turning left or right? Do you use electronic scales? They could be hooked up backwards!
Yes does same thing turning both sides. Scales were double checked because I expected the caster to unload the inside. Cant wrap my head around why it loads the inside.
 

paulkish

old fart
Caster's cranked to the front?

Front spindle assemblies were each bolted to the wrong side?

don't know
 

sundog

Member
Forget the scales for a moment, see if the side you're turning to is "actually" loading or unloading. Easier to check without the driver in. Jack up the front and see if the inside front wheel is going lower.
 

alvin l nunley

Premium User
Yes does same thing turning both sides. Scales were double checked because I expected the caster to unload the inside. Cant wrap my head around why it loads the inside.
It's not possible, you turn left or right, the inside wheel gets lighter. There's no other possibility if everything is correct on the kart. Or the scales are wrong! It's one or the other, I guarantee you.
Prove it to yourself; turn the wheel hard left or hard right. Lift the inside rear wheel, then lift the outside rear wheel, tell me which one is heavier.
 

paulkish

old fart
ackerman

just winging it not being able to visualize it but might some ackerman change how it lifts if you turn the wheel a lot?
So it might depend on if he's turning it more then would be turned when in use???????????????
 

Pete_Muller

Moderator
The whole point for lots of caster is to unload the inside rear wheel. Does it do the same thing turning left or right? Do you use electronic scales? They could be hooked up backwards!
Al,

I thought I might have mentioned this here before ---- caster alone will do nothing for loading/unloading. It's a combination of caster, kingpin inclination and scrub radius that jacks the weight. How stiff the waist of the chassis is will also effect the actual amount of measurable change.

PM
 

Bob Evans

Grumpy Old Admin
Staff member
Just pick up my first tag kart (used 2015 tony kart). It fits me well and is track ready. I tossed it on the scales for a check and it looks pretty well balanced. However I noticed when I turn the wheel it loads the same side rear. That is something 100% foreign to me. When I turn right I would expect the LR to see more weight not the RR. Can someone help me understand this dynamic? Thanks.
Add physical weight to the LR, and see which corner it shows up on. Is the RF showing increased weight when you turn right?
 

alvin l nunley

Premium User
Al,

I thought I might have mentioned this here before ---- caster alone will do nothing for loading/unloading. It's a combination of caster, kingpin inclination and scrub radius that jacks the weight. How stiff the waist of the chassis is will also effect the actual amount of measurable change.

PM
All my research must be wrong. All my experience with building kart's must be wrong. All my drawings must be wrong. I was convinced I was right, but I guess not. Still, the KARTS I built handled just fine.
 
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sundog

Member
KPI alone will make both wheels load or go down turning left or right. When you add caster then the inside wheel will go down and the outside wheel will go up. Of course you need scrub radius for any of this to happen. If you only have caster the inside will still load but the outside will go way up.
 

alvin l nunley

Premium User
If you had no caster at all, just kingpin inclination, when you turn the wheel, left or right, both wheels go equally. That action raises the front end a small amount. If you had no kingpin inclination, just caster, when you turn left or right, the inside will goes down and the outside will goes up. It also raises the front end. A car doesn't need caster, it uses kingpin inclination, in fact there was a time when they put in negative caster to make it easier to stear. A kart uses a solid rear axle, versus a differential like cars have, so unlike a car, a kart needs to get the weight off the inside rear wheel in order for it to turn. Because kingpin inclination causes both tires to go down the same amount when turning left and/or right, if you didn't have caster, you would go straight at the end of the straightaways. My personal experience, with my "homemade" Mako shark, which had no kingpin inclination, was that the kart handle just fine, in fact, better than most.
Now I've been told that, because Sprint karts are different from LTO karts, this innovation does not apply, but for the life of me, I can't figure why!
I'm old, and my shoes are too tight, and my feet hurt, and I like it. (Dana Carvey) I love that guy.
 

alvin l nunley

Premium User
I find it hard to understand how people can argue for the necessity of kingpin inclination when there have been karts, mine included, that have been built and raced and handled just fine without it.
 
I find it hard to understand how people can argue for the necessity of kingpin inclination when there have been karts, mine included, that have been built and raced and handled just fine without it.
Al, how long ago was this? Technology and understanding of it has come a long ways in more recent yrs. These chassis manufacturers have done a lot of R&D on chassis design before sinking in their money.
Then please tell us how much hands on experience you have with this in the last 20 yrs.
 

alvin l nunley

Premium User
Then please tell us how much hands on experience you have with this in the last 20 yrs.
"Hands-on"? None! But in the previous 20 years, quite a bit. Now let me ask you; how much experience have you had building karts in the last 20 years? I'm especially interested in your experience with karts that had no kingpin inclination! Understand I don't care if you built them or not!
 

Pete_Muller

Moderator
Al,

I believe what SoCo Tire is pointing out is that chassis, tires, weight, wheels, spindles, and axles have all changed pretty dramatically over the last couple of decades.

If your experience with a "kart that worked really well" was on Goodyear Bluestreaks or Carlisle tires, on a kart that was 36" wide and weighed 115 lbs.... well, things have dramatically changed. I suppose a valid question would be: did you ever try to change the front end on the kart you built to incorporate any kingpin inclination? To be perfectly honest, back a long time ago, I think one of the reasons we didn't see KPI was because the chassis and the spindles were easier to build without it.

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