Change tire set effects setup

T

thebigo

Member
Here's a strange one. I scaled the kart in the shop with tire set "A" then switched to tire set "B" and got a drop in cross by 5%. Tire wear is very close.
Set "A" Maxxis pnk/blu
LF - 5 psi 32.5"
RF - 6 psi 34"
LR - 5 psi 32.5"
RR - 8.5 psi 34" (psi to maintain 34")
Front 45%
Left 58%
Cross 65%

Set "B" Maxxis pnk/blu
LF - 9 psi 32.5" (psi to maintain 32.5")
RF - 9 psi 34" (psi to maintain 34")
LR - 4 psi 32.5" (psi to maintain 32.5")
RR - 8.5 psi 34" (psi to maintain 34")
Front 45%
Left 58%
Cross 60%

All the time with the driver in the kart. Thought a wheel is not on properly or something else. I repeated the exercise by putting set "A" then Set "B". The results were within 0.1 % not negligible enough. Are the pressures effecting the tire wall spring rate? What else could be explainable?
 
Set the air at either 5 lb rights and 4 lb lefts, or 5 lb lefts and 6 lb rights regardless what pressure you race at and scale, then note your numbers and go from there. As mentioned you need to size your tires ahead, just adding air to read what you need is not an option as pressure changes effect handling to much to do that.
 
My mistake is thinking that as long as the tire is the proper size, the pressure is dictated by the track condition. I usually mix and match tires that start with 5 psi on the left and 6 psi on the right and 32.5" & 34" respectively. Obviously my way of thinking is totally wrong.
ABR#69 - No I DO NOT race on those pressures. Most of the time I finish the night with 4 - 5 lefts and 5 - 6 rights but no more than 1 psi split.
Kj26 & racing promotor - I have to do a better job of stretching or shrinking to achieve the size. I found I have to do it every time we race on some tires. I have 4 sets to play with, about 1/32 or less in thickness.
 
This post is winded so please bear with me.
I have been trying different air pressures at room temp and in a home made hot box, I can sustain 250 degrees tire surface. But I very seldom get exactly what I plan. Some tires do not keep the pressure longer than 24 hours. Those leak very slow around the mold markings such as the date stamp or serial number. I use the hot box on them to make them grow. Sometimes I let them air cool or dunked in ice water. The results are not consistent.
The ones that hold psi I pump them 1/4" over the wanted size. Ex. race size of 34", pump it 34 1/4" room temperature and leave it for about a week. Then drop the psi to 6, wait about an hour and check the size, Sometimes it works, but most of the time it shrinks again. It's frustrating because I feel I'm doing it wrong.
The one that leak down in a day, I use the hot box by growing it by 1/4" and when it grows another 1/8", i.e. 34 3/8" I dunk it in ice cold water. Most of the time it works, but I have to repeat the process the next time we race. I only have 4 sets to play with. I do consult with the top runners, but I can't retain everything they tell me in such a short time. They are busy with other peeps and yet never refused to help out. It's just me, at 75, I have to write everything down and follow instructions.
Having said that, what is the proper way to grow or shrink tires? For what it's worth I do internal prep the Maxxiss every 4 weeks as per instructions. I read many a post but never in detail in it's entirety. Maybe there is no single procedure. Do I need more tires to pick and choose?
 
thebigo said:
My mistake is thinking that as long as the tire is the proper size, the pressure is dictated by the track condition. I usually mix and match tires that start with 5 psi on the left and 6 psi on the right and 32.5" & 34" respectively. Obviously my way of thinking is totally wrong.
ABR#69 - No I DO NOT race on those pressures. Most of the time I finish the night with 4 - 5 lefts and 5 - 6 rights but no more than 1 psi split.
Kj26 & racing promotor - I have to do a better job of stretching or shrinking to achieve the size. I found I have to do it every time we race on some tires. I have 4 sets to play with, about 1/32 or less in thickness.
Click to expand...
Once the races are over and the tires are washed, I'll add 10# air to the Rights and pull the valve core from the LR. The LF hardly ever changes so I never pay attention to it. That helps to keep the rights from shrinking & the LR growing.
 
thebigo said:
This post is winded so please bear with me.
I have been trying different air pressures at room temp and in a home made hot box, I can sustain 250 degrees tire surface. But I very seldom get exactly what I plan. Some tires do not keep the pressure longer than 24 hours. Those leak very slow around the mold markings such as the date stamp or serial number. I use the hot box on them to make them grow. Sometimes I let them air cool or dunked in ice water. The results are not consistent.
The ones that hold psi I pump them 1/4" over the wanted size. Ex. race size of 34", pump it 34 1/4" room temperature and leave it for about a week. Then drop the psi to 6, wait about an hour and check the size, Sometimes it works, but most of the time it shrinks again. It's frustrating because I feel I'm doing it wrong.
The one that leak down in a day, I use the hot box by growing it by 1/4" and when it grows another 1/8", i.e. 34 3/8" I dunk it in ice cold water. Most of the time it works, but I have to repeat the process the next time we race. I only have 4 sets to play with. I do consult with the top runners, but I can't retain everything they tell me in such a short time. They are busy with other peeps and yet never refused to help out. It's just me, at 75, I have to write everything down and follow instructions.
Having said that, what is the proper way to grow or shrink tires? For what it's worth I do internal prep the Maxxiss every 4 weeks as per instructions. I read many a post but never in detail in it's entirety. Maybe there is no single procedure. Do I need more tires to pick and choose?
Click to expand...
It sounds to me like you really need to invest in a couple new sets. Leaking tires are not helping your cause, how old do you think your current sets are ?
 
Roll Speed Dynamics told me to keep my rights pumped up to 34.5 when not being raced. they typically measure 34 with the correct tire pressure.
Patrick looks after more tires than most.
 
I agree with Patrick, all our Maxxis have to be 34.5 or sometimes higher to measure 34-34.250. And, this is week to week, if left below this they will shrink. So once the races are done, you should air them back up. Usually I'll just shoot air in them after racing then I'll measure them at the house Sunday to ensure they stay. Burris aren't as bad, I usually put 10-20lbs in them and leave them and they stay correct. Vega have always been my most consistent tires.

Stretching, I wrap them in tire warmers and air them up to about 34.750 or 35 and let them sit and cool, drop the air then they'll usually be very close. But, I still have to let them stay around 34.5 while not in use to keep them there.
 
My apology but I'm afraid I don't know you by name.
Kj26 - Age of tires. 2 sets 2019, 1 set 2020 and 1 set 2021. I get them from the top runners. Between two racers.
"J'-remy & ABR#69 - I store mine at 34.25" for the rights, LR with no air and LF at 3-4 psi, but if LF shrink I store them at 32.12. And usually leave all tires as they were raced and check them next day when I take them out of the trailer. But it sounds I should be doing this sizing at the end of the night before I leave.
I'm going to try 34.25 for the rights and see what happens.
 
thebigo said:
This post is winded so please bear with me.
I have been trying different air pressures at room temp and in a home made hot box, I can sustain 250 degrees tire surface. But I very seldom get exactly what I plan. Some tires do not keep the pressure longer than 24 hours. Those leak very slow around the mold markings such as the date stamp or serial number. I use the hot box on them to make them grow. Sometimes I let them air cool or dunked in ice water. The results are not consistent.
The ones that hold psi I pump them 1/4" over the wanted size. Ex. race size of 34", pump it 34 1/4" room temperature and leave it for about a week. Then drop the psi to 6, wait about an hour and check the size, Sometimes it works, but most of the time it shrinks again. It's frustrating because I feel I'm doing it wrong.
The one that leak down in a day, I use the hot box by growing it by 1/4" and when it grows another 1/8", i.e. 34 3/8" I dunk it in ice cold water. Most of the time it works, but I have to repeat the process the next time we race. I only have 4 sets to play with. I do consult with the top runners, but I can't retain everything they tell me in such a short time. They are busy with other peeps and yet never refused to help out. It's just me, at 75, I have to write everything down and follow instructions.
Having said that, what is the proper way to grow or shrink tires? For what it's worth I do internal prep the Maxxiss every 4 weeks as per instructions. I read many a post but never in detail in it's entirety. Maybe there is no single procedure. Do I need more tires to pick and choose?
Click to expand...
As to the rolling internal every month, where are you racing ?
 
I have been told if you store them in a trailer, or any place that gets real hot (or I would assume cold) it is very hard to maintain tire size. The air pressure is fluctuating in the extreme conditions.
 
Surveyor said:
I have been told if you store them in a trailer, or any place that gets real hot (or I would assume cold) it is very hard to maintain tire size. The air pressure is fluctuating in the extreme conditions.
Click to expand...
Ya, that's why I take them out the next morning. I get home after midnight and too tired to empty the trailer.
 
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