Pressure splits

Marcis71

Member
If I scale my kart with 6 PSI in all 4 tires or scale it with 6/5 to the exact same percentages, is there a handling difference? Does the pressure split itself make a difference or just if you make the split after setting the kart up?
 
Scaling it both ways then choosing one and making everything match 100 % same would show no handling difference ( that would be noticeable ) on track, I suppose some math wiz could show difference on paper, making the pressure change then race on track is where it would show up.
This debate might be popcorn worthy.
 
Scaling it both ways then choosing one and making everything match 100 % same would show no handling difference ( that would be noticeable ) on track, I suppose some math wiz could show difference on paper, making the pressure change then race on track is where it would show up.
This debate might be popcorn worthy.
All I'm going to offer, is, consider changes to size and shape of contact patch with pressure change.
 
Only responding because it's been awhile since a thread had a good debate.
I have considered what you point out in saying it would only show up while raced in my line of thinking, that slight contact patch difference should not mean squat on the scale pad, remember he's saying make all adjustments MATCH 100%, Am I missing something !! Or are you basically Agreeing ?
 
So, what difference does the pressure change make on track?
Why?

No one races scales. Lol
 
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So, what difference does the pressure change make on track?
Why?

No one races scales. Lo(
Opening up the split frees the kart up.
Increases size, less contact patch, less rolling resistance, to name a few.
I would not agree NO one races scales, some over think it !!
 
Where are the best paying scale races?

To some, just need to know that it changes things. Some want to know why.
Overthink, maybe.

Can't do better, if you are content to do what everyone is doing. Someone looked for the information you are using.

Bottom line, all, repeat, all chassis changes affect, wait for it,
The size, and shape, of the contact patch.
Jmo
 
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I'll add another thought.

The only thing securing your kart to the track are four small contact patches.
Manipulating those, and the traction availabe, is chassis tuning.
 
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I'm not trying to overthink this I just don't understand what the actual difference is by running split pressures. I've always been of the opinion (possibly the wrong opinion) that the more air in a tire the freer it rolls so I've always ran the most I could get away with, I just want to know why people run splits. I see it being a tuning tool but if all is equal would more air pressure be faster?
 
Sorry I did not mean to imply you were over thinking it as I know guy's that do, you had a legit question.
I was hoping to see more debate on the original topic, not just what making pressure changes does.
 
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You both missed the point.

Even though you reset percentages, the size and shape of the contact patches changed.

On all 4 tires.

And that is just sitting still. (Racing scales)
 
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That contact patch isn't only going to be affected setting still... it has changed when it hits the track too. ;)

I think splits do affect handling, even with all other numbers being the same. Normal split has the RS tires a PSI or 2 higher than the lefts, this would make the sidewalls stiffer (more air) and in turn less rolling resistance but also less side bite. My sons Prowler is very picky about pressure splits. Every time I've tried running no split (same in all 4) It tightens up and locks the kart down. We put the usual 1psi split back in and the kart responds well.
 
You both missed the point.

Even though you reset percentages, the size and shape of the contact patches changed.

On all 4 tires.

And that is just sitting still. (Racing scales)


I should know better (my time is too valuable for some debate)....BUT :)

How much does the psi change the profile? What brand of tire are we talking about?
When cutting a tire using a template, I see very little (ie .001" = one thousandths of an inch = way smaller than the width of a human hair) when adjusting air pressure by 2 psi. It isn't until you reach around 15 psi in a tire that you effectively change the profile (ie balloons out the center of the tire.) Recognizing that dirt racers will never see that high of PSI, why is it that you think that a real, although minute, profile change (if it is even measureable at all) would affect the handling? Furthermore, when running very low psi (ie 4-6 psi) in kart tires with the sidewalls pulled out as much as we do, and 350-400 pounds pushing them down onto scale pads changes the profile dramatically more - then consider how they deflect under loading on the track (ie acceleration, cornering, lateral g-forces, etc.) I think we would be really splitting hairs (literally) on a pound or two changing the profile being the reason that the kart handles differently.

No doubt that air pressure splits affect handling, but I feel that the tire profile (at the pressures that we race at) has very little to do with that change in handling.

I think of psi affecting the spring rate of the tire moreso than the contact patch. That IS something measurable.

Personally, I think too many racers race on scales -- Gone are the days of a guy being able to set up a kart by the seat of his pants. Instead we see guys plugging in "factory" set-ups and then wonder why they can't hit their behinds running up "norf" on our black dirt oval tracks and floppy sidewall tires.


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
just using these numbers for simplicity sake.

Consider a lr tire with 100# sitting on.
5 psi pressure

By definition, the contact patch must be 20 square inches.

Increasing pressure to 6 psi, contact patch must be 16.667 square inches.
17% less contact patch area. should make a noticeable difference.
 
I should know better (my time is too valuable for some debate)....BUT :)

How much does the psi change the profile? What brand of tire are we talking about?
When cutting a tire using a template, I see very little (ie .001" = one thousandths of an inch = way smaller than the width of a human hair) when adjusting air pressure by 2 psi. It isn't until you reach around 15 psi in a tire that you effectively change the profile (ie balloons out the center of the tire.) Recognizing that dirt racers will never see that high of PSI, why is it that you think that a real, although minute, profile change (if it is even measureable at all) would affect the handling? Furthermore, when running very low psi (ie 4-6 psi) in kart tires with the sidewalls pulled out as much as we do, and 350-400 pounds pushing them down onto scale pads changes the profile dramatically more - then consider how they deflect under loading on the track (ie acceleration, cornering, lateral g-forces, etc.) I think we would be really splitting hairs (literally) on a pound or two changing the profile being the reason that the kart handles differently.

No doubt that air pressure splits affect handling, but I feel that the tire profile (at the pressures that we race at) has very little to do with that change in handling.

I think of psi affecting the spring rate of the tire moreso than the contact patch. That IS something measurable.

Personally, I think too many racers race on scales -- Gone are the days of a guy being able to set up a kart by the seat of his pants. Instead we see guys plugging in "factory" set-ups and then wonder why they can't hit their behinds running up "norf" on our black dirt oval tracks and floppy sidewall tires.


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com

All that is insignificant until you place the load on the tire.

Measure the axle centerline height change ,fully loaded with only a 1 psi change.

Now, consider the dynamic changes, all the way around the track.
 
Some will argue the tire sidewall construction makes a difference.
Dynamically, yes. Statically, no.


A balloon at 5 psi with 100 pounds on it will have the same contact area as any tire with the same 5 psi.
 
just using these numbers for simplicity sake.

Consider a lr tire with 100# sitting on.
5 psi pressure

By definition, the contact patch must be 20 square inches.

Increasing pressure to 6 psi, contact patch must be 16.667 square inches.
17% less contact patch area. should make a noticeable difference.
On track yes, on the scales NO.
 
On track yes, on the scales NO.
I'm not sure what your argument would be?
The original post was resetting to same scale number, would there be a handling change?

If a 1 psi change to the left side creates a negligible change to scale weights, then the lf and lr changes cancel each other, for the most part.

Contact patch, both statically, and dynamically, is what makes the handling difference.
 
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