PSI offset

ggodwin

Member
What is the purpose of PSI offset?
It seems like everyone runs a softer Left side. What is the theory behind this?

Obliviously it’s going to help the cart turn left to a degree, but doesn’t it also provide some resistance for weight to transfer?
 

Damelot85

Member
I have been wondering the same, I prefer my kart with straight up the same all the way around I found it better, on asphalt that way and when I ran dirt I was the same.

Can you perhaps explain What changing pressure on the LF and LR what might be changing in way the kart handles? i.e what would more or less air in the LF change or when would you add or remove air from the LR?
 

JanGaLanG

Member
We race with no prep tires my theory has been to run the least amount of pressure I can in my tires 2.75 L and 3.75 R. Small bullring no momentum tracks.
 

ggodwin

Member
We race with no prep tires my theory has been to run the least amount of pressure I can in my tires 2.75 L and 3.75 R. Small bullring no momentum tracks.
But the question is why so psi-offset? I do it but it’s because everyone else does it.

I don’t know why we do it. I assume we turn better. But, I also watched a clone medium and clone heavy driver who does not win both features recently and he’s on 4psi/4psi.

So I’m asking the group why we do it.
 

ggodwin

Member
It's about several things, spring rate, rebound, weight transfer.
Our tires are not only springs but they are shocks as well
Weight transfer is really something that I felt would be a reason. Does an even offset allow “too much” weight transfer? Is that even possible? I’ve always figured the more weight transfer the better.
 

"J'-remy

Member
I tend to adjust my air more front and rear to deal with push loose situations. your right sides are taking most of the load around the corner. more air in the rights deals with all the transfer . but roll speed can be gained through increasing air in all 4 not just the rights. you should experiment with what works best for you. I run more psi than most
 

XXX#40

2A supporter
Weight transfer is really something that I felt would be a reason. Does an even offset allow “too much” weight transfer? Is that even possible? I’ve always figured the more weight transfer the better.
Even air gives it a head start to transfer, making its quicker.
Yes depending on other settings it can allow too much, too soon.
 

XXX#40

2A supporter
I tend to adjust my air more front and rear to deal with push loose situations. your right sides are taking most of the load around the corner. more air in the rights deals with all the transfer . but roll speed can be gained through increasing air in all 4 not just the rights. you should experiment with what works best for you. I run more psi than most
You can accomplish quick info by running different air in all tires, and something you can throw at it in a hurry, it's still a band aid
 

Damelot85

Member
You can accomplish quick info by running different air in all tires, and something you can throw at it in a hurry, it's still a band aid

So if the kart seems better with even air psi, what is the “band aid” covering?

And would it always be faster if the chassis was adjusted differently and then run with split psi?
 

XXX#40

2A supporter
So if the kart seems better with even air psi, what is the “band aid” covering?

And would it always be faster if the chassis was adjusted differently and then run with split psi?
Several things, too much LS%, too low VCG, low RF caster, not enough bite in RS tires.

8 times out of 10 it'll be faster with split and the chassis correct, but there's times you have to get out of the box, ie. Reverse air split to make the chassis force bite
 
Spring rate...and to a lesser extent ride height affecting tilt and VCG.
Going up on air is just like installing stiffer springs on a suspended car.
Obviously there are times that you want a lot of split (ie high grip,) and times that you want less split (ie low grip.)
Again, there's no "one size fits all." Some chassis, some drivers, etc do better with different amounts of pressure split.

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paulkish

old fart
Many many years ago now JWD offered us the three basic rules of tires:

Match the hardness of a tire to how abrasive the track. More abrasive, harder tire.
Match sidewall stiffness to how hard the track. Harder track, stiffer sidewall.

and... Match air pressure to track grip. Less grip, less air pressure.

That's it about tires and what to do in a nutshell.
The rest is about how circumstances change and fine tuning to prevent or fix on track problems big and small.
__________________________________________________

Now I'll throw in my odd logic on it bringing in 1 and 1 to get 3 as usual:.

Some logic to throw into the mix.
4 wheel drift means your left side tires have given out and the right side tires can't hold all the weight and grip expectations on them, by themselves, so you drift out to the right.

Left front tire give out and the right front tire can't hold all the weight put to it, so you push.
Left rear tire gives out and the right rear tire can hold what it needs to hold, so your loose.

That stuff together and air split is to help left side tires hold grip longer because in general less air matches up with less grip.
And you get the less grip because in general turning moves weight to the right off the left side tires.

Since the thoughts in this are about the fronts then fine tuning can come in to either free the right front up letting the left front loose grip faster/sooner or tighten the front up with less air trying to help hold grip at the left front longer.

Lots and lots of things we talk about on here all the time to fix problems or go faster are bout controlling when a left side tire weakens it's grip and how much grip it looses when you need it to loose grip.

... or it ain't because this is just IMHO and ain't necessairly right anyway. ... :)

So air split is just one way of many ways to control the amount of grip at the left side tires and in turn control the load on the right side tires to put them as close as possible to be running at their limit of grip, ... to be fast.

edit: That IMHO is the purpose. The why you need to do it is endless. ... :)
 
Good points, Paul.
I'll throw this out there for you to chew on though...
With high cross kart set-ups, the LF is barely touching the track. I've seen karts carry the LF the entire way around the track - ie it is not gripping the track at all and the kart is fast, certainly not pushing.
 
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