Sunday Morning crew chief

Cutting the tires isn't for the purpose of sizing -- you size tires by mounting them and stretching or shrinking them with heat/cold.
Take the valve core out of your left rear and place the tire in the sun until it is hot. The put it in the freezer for a bit. That'll shrink it some. Repeat if necessary to get desired stagger you want.
I don’t have a freezer with this much space. Is it OK to use an ICE bath to quench the tires?
 
Opens have surplus HP that can break the tires loose at any moment....they almost always run less stagger than stock class karts.

Cutting the tires isn't for the purpose of sizing -- you size tires by mounting them and stretching or shrinking them with heat/cold.
Take the valve core out of your left rear and place the tire in the sun until it is hot. The put it in the freezer for a bit. That'll shrink it some. Repeat if necessary to get desired stagger you want.
Thank you for the feedback. I read in an older thread that you were cutting tires for a customer at for Ben Hur at a specified OD in order to have proper stagger at Hur. This was where I got the comment from. Maybe not an ideal situation.

So yesterday we went back to Rockport. I spent Thursday, Friday and Saturday morning preparing tires. Mostly adjusting tires OD in order to have some variation once we got to Rockport. (1/10th mile with 50’ Radius) basically giving the kart a solid baseline setup from multiple TritonJr teams. (The setups were all similar)

I used high pressure, sunshine, zero pressure and freezers to my stagger set.

last night it was warm, wet and HUMID.
Practice our stagger was
Front 1.5”
Rear 1.31 ( 1 5/16)

I also had sets for the rear set at
1.25” & 1.43”. Plan was to use practice as a baseline and adjust.

with no prep on the tires we were better than we’ve ever been there. Plan was to use the same set for the heat race. While waiting I put 13 pounds in the right side and emptied the left side. As we staged I adjusted the tire pressure to race psi. Started outside 2nd row and by turn one was in 2nd place and running strong. First three laps running with the kid that won the previous week. Midway through the heat you could see the kart tightening up. So much that we hit the wall exiting T2 and spinning. However, still ran 2nd place and pulled away from the other karts.

Immediately washed the tires and measured stagger.

finished the race with 1.0” of stagger. Before the feature all three sets of tires had returned to a size that put us at a stagger disadvantage. I ended up moving my FR tire to the back.

ran the feature with
Front 1.25”
Rear 1.125”

..... feature was a blood bath of ten karts. Ran up to 3rd and was involved in 4 cautions.

How do I grow and shrink tires and get the sizes to stick? Yes
 

CarlsonMotorsports

Premium User
You don't cut tires to stagger them. Not sure what was said or misunderstood there, but that's not how it is done.
Sizing is done during mounting with tire rings. If additional sizing needs to happen, then you use air pressure & heat/cold alternating for stretching and shrinking. There are several threads on this forum that cover that pretty well.

Sizing them before going to the grid may have helped for the first few laps, but that will go away quickly as the tires go back to their previous size. Just like a rubber band -- tires have elasticity and will return to their previous size if the band/webbing inside the tire isn't stretched too. 13 psi will not stretch a tire -- it may help maintain the size during the week, but that won't be enough pressure to stretch that belt in the center of the tire. It also takes time -- generally not something you do at the track -- although if you get there early enough, you can throw your tires out in the sun before they are used and get "some" benefit from that.
Proper preparation (in the shop during the week) will make a race car consistently fast on the track. This includes tire sizing.

For prep -- it sounds like from previous discussions, the tires are simply over prepped, and that backing off of your prep program has allowed the prep to work it's way out over time and heat cycles, freeing the kart back up. Prep can be very helpful most of the time, but it can also become a crutch, or a hindrance if you use too much of it. A little prep can make the driver feel like a hero -- a lot of prep can flat lock the car down and make him look like a zero.
 
You don't cut tires to stagger them. Not sure what was said or misunderstood there, but that's not how it is done.
Sizing is done during mounting with tire rings. If additional sizing needs to happen, then you use air pressure & heat/cold alternating for stretching and shrinking. There are several threads on this forum that cover that pretty well.

Sizing them before going to the grid may have helped for the first few laps, but that will go away quickly as the tires go back to their previous size. Just like a rubber band -- tires have elasticity and will return to their previous size if the band/webbing inside the tire isn't stretched too. 13 psi will not stretch a tire -- it may help maintain the size during the week, but that won't be enough pressure to stretch that belt in the center of the tire. It also takes time -- generally not something you do at the track -- although if you get there early enough, you can throw your tires out in the sun before they are used and get "some" benefit from that.
Proper preparation (in the shop during the week) will make a race car consistently fast on the track. This includes tire sizing.

For prep -- it sounds like from previous discussions, the tires are simply over prepped, and that backing off of your prep program has allowed the prep to work it's way out over time and heat cycles, freeing the kart back up. Prep can be very helpful most of the time, but it can also become a crutch, or a hindrance if you use too much of it. A little prep can make the driver feel like a hero -- a lot of prep can flat lock the car down and make him look like a zero.
That’s the point we are at. Tire program tells us to wipe during the week, so we do. I sometimes feel we are over prepped
 

CarlsonMotorsports

Premium User
That’s the point we are at. Tire program tells us to wipe during the week, so we do. I sometimes feel we are over prepped
It's pretty easy to over-prep, especially with some of the harsher chemicals.
Our prep program is designed to be simple --
more wipes = more bite,
less wipes = less bite.
It doesn't get much easier than that.
The problem lies in inexperience and comfort.
The crew doesn't have a large data base to look back at for notes on different track conditions, temperatures, kart counts, etc. Meanwhile, the new driver "feels" like the car is hooked and he's feeling like Superman able to put the car anywhere he wants on the track. Prep can definitely hook a car up -- and then the driver wants "more" of that "feel." Soon thereafter, everyone's scratching their heads wondering why the engine got hot and the kart wouldn't get out of it's own way when it was absolutely glued to the track and would go wherever the driver placed it, (ie locked down.) With our sorely underpowered stock class karts, you don't dare make a kart "stuck" like that. It has to lightly "dance" on top of the track to keep from lugging the engine down.
The best way to learn is experience - which costs time and money.
 
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