Late Model problem

Justin Wilson

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Running Pro Late Model at Nashville and our LR keeps getting smaller through race and after race the stagger is all out of whack because of it. Been in racing a long time and never had this happen. Anyone have an suggestions or solutions
 

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You mean when you measure your tire after a race it is physically smaller than what you measured before the race started? Then you must be leaking air somehow. During the race the tire heats up, which makes it more pliable - and also the air pressure in it goes up, so air can leak more easily.

I suspect a bad valve stem, and it's a cheap easy part to replace to see if that cures the problem. Although first I'd use a valve stem core tool to make sure that the valve core is fully seated but not stripped, and I'd pull the core out to make sure that the little O-ring on it looks good. We once had a leaky core because we assumed that all cores are the same, and hadn't paid attention to swapping them between different brand wheels. And of course you'd want to check for dirt that might have gotten into the valve stem while pulling the core out and replacing it. Look for cuts or even weak places on the valve stem itself - racing contact can leave small cuts and abrasions. We've had them crack where the stem meets the part that seals against the wheel - both at the top of that seal where the stem ends, and also its bottom side that contacts the wheel.

I'd also carefully look for dings in the tire bead seating area all around the rim (inside seat too). If you decide to change the valve stem then I'd clean the bead seats and look for pits from rust. Finally, if you're running a bead lock on that wheel I'd make sure that it and its mating surface are flat and that all of the bolts are torqued correctly.

You could have a small hole somewhere in the tire, or around a plug you've put in. Any sidewall blemishes due to racing contact are suspect. The old spray it with soapy water trick might find it, if you over-inflate the tire by about 10 to 15 pounds (or a little more than what you normally expect to pick up during a race). That much over-inflation should not permanently grow your tire as long as you're only keeping it that high for the few minutes it takes for spraying it to reveal a leak.
 

Justin Wilson

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Yes it is smaller than our measurements before the race. Second race in a row it has happen. I appreciate the feedback and will look into it! This past race it was both left side tires
 

kyle18fan

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Tires commonly get smaller when rubber wears away
 

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Tires commonly get smaller when rubber wears away
Well sure, but tread wear only causes small size decreases - 32nds of inches. This is an experienced racer, so he should be well aware of it.

Tires grow while they're hot, and usually you can measure it if you hurry to measure before they cool back down. That can be difficult at dirt tracks, though, since it's easy to drive through water or mud before you get to your pit. But even cooled tires should not measure smaller than where they started, unless you dunked them in ice water for a while.
 

kyle18fan

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Well sure, but tread wear only causes small size decreases - 32nds of inches. This is an experienced racer, so he should be well aware of it.

Tires grow while they're hot, and usually you can measure it if you hurry to measure before they cool back down. That can be difficult at dirt tracks, though, since it's easy to drive through water or mud before you get to your pit. But even cooled tires should not measure smaller than where they started, unless you dunked them in ice water for a while.

There are only so many things that can cause this issue
 

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There are only so many things that can cause this issue
Yep. I think there is something else going on too, so I'm talking with him hoping that I ask the right question that will ferret it out.
 

kyle18fan

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Yep. I think there is something else going on too, so I'm talking with him hoping that I ask the right question that will ferret it out.

Ask the resident race car expert .......... I will call him up.

HEEEEEEYYYYYYYYYYYY @aunty divePlease give this fellow some expertise, I will owe you one

If he can't help you, you can't be helped :salute: watch him though, he is a Canadian with an attitude
 
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kyle18fan

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Never have I seen a tire get bigger when rubber disappears, I have only been dealing with tires for about 6 decades, so certainly you will tell me I am wrong.
 

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Never have I seen a tire get bigger when rubber disappears, I have only been dealing with tires for about 6 decades, so certainly you will tell me I am wrong.
You are wrong. Have you ever worked on a race car?
 

kyle18fan

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You are wrong. Have you ever worked on a race car?

Yes, there isn't much I haven't worked on. Half a million dollar loaders to mini bikes ......... a worn tire is shorter than a new one it only stands to reason. So ... in all my years of experience, any worn tire I ever saw was shorter than a new replacement. Next you will tell me that the worn knobby on my MX bike is taller than a brand new one.So instead of answering the OP's question, you have to pick out my statement. My statement clearly says " commonly " and in my world, that is how it works. Ever put a new inside dual on a semi with a worn outside ? guess which one has the load. Now if your race car tires are different, so be it. Help the op out
 

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If you start your pressures at 12 pounds on the left
Yes, there isn't much I haven't worked on. Half a million dollar loaders to mini bikes ......... a worn tire is shorter than a new one it only stands to reason. So ... in all my years of experience, any worn tire I ever saw was shorter than a new replacement. Next you will tell me that the worn knobby on my MX bike is taller than a brand new one.So instead of answering the OP's question, you have to pick out my statement. My statement clearly says " commonly " and in my world, that is how it works. Ever put a new inside dual on a semi with a worn outside ? guess which one has the load. Now if your race car tires are different, so be it. Help the op out
Let me educate you. if you start with 84 inches on the right rear and 83 on the left, what is your stagger? BTW we are talking Pro late model like the OP said. Answer this and I will help you.
 

kyle18fan

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If you start your pressures at 12 pounds on the left

Let me educate you. if you start with 84 inches on the right rear and 83 on the left, what is your stagger? BTW we are talking Pro late model like the OP said. Answer this and I will help you.

Sounds like an inch to me. Now educate me on why my sons worn out motorcycle tire is shorter than the matching replacement. The op asked for help, in my world worn out tires get smaller
 

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Sounds like an inch to me. Now educate me on why my sons worn out motorcycle tire is shorter than the matching replacement. The op asked for help, in my world worn out tires get smaller
So, if you start your right rear at 20 psi which got you 84 inches , then you start your left rear at 12 psi that got you 83 inches that gave you an inch of stagger right?
 

kyle18fan

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So, if you start your right rear at 20 psi which got you 84 inches , then you start your left rear at 12 psi that got you 83 inches that gave you an inch of stagger right?

Are you helping the op or boosting your ego ? what about that worn semi tire and that worn knobby, those are " common " to me. Late model tires aren't my thing, apparently they are yours ..... so help the op
 

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Are you helping the op or boosting your ego ? what about that worn semi tire and that worn knobby, those are " common " to me. Late model tires aren't my thing, apparently they are yours ..... so help the op
yeah thats what Im trying to do but you are giving him info thats wrong. No way you start a tire on the left at X and it gets smaller. Heat and friction say otherwise. Your " knobby tire" doesnt even remotely compare to a racing slick.
 

kyle18fan

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yeah thats what Im trying to do but you are giving him info thats wrong. No way you start a tire on the left at X and it gets smaller. Heat and friction say otherwise. Your " knobby tire" doesnt even remotely compare to a racing slick.

If you pay attention, I asked for a race car expert to help the man, the info I gave him clearly said " commonly " as in my world. So I will stick with what I know, you are the race car tire guru. Now can you please help the op ? Good grief, lets disregard my comment. I didn't throw in any comment on heat or increased pressure, my comment was on rubber that had worn away ... disappeared. I measure tires at a given pressure
 

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If you pay attention, I asked for a race car expert to help the man, the info I gave him clearly said " commonly " as in my world. So I will stick with what I know, you are the race car tire guru. Now can you please help the op ? Good grief, lets disregard my comment. I didn't throw in any comment on heat or increased pressure, my comment was on rubber that had worn away ... disappeared. I measure tires at a given pressure
I did pay attention, You said "Never have I seen a tire get bigger when rubber disappears, I have only been dealing with tires for about 6 decades, so certainly you will tell me I am wrong

So I did.
 

kyle18fan

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I did pay attention, You said "Never have I seen a tire get bigger when rubber disappears, I have only been dealing with tires for about 6 decades, so certainly you will tell me I am wrong

So I did.

Ok, now did you help the op ? And everything I said applies to tires that are common to me, that is why I asked a race car expert to help the op ! did you help him yet ? Something tells me you are going to keep blowing up my alerts and that you aren't going to help the op at all ..... other than to smart off about getting somebody that can read a tape o_O
 

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Ok, now did you help the op ? And everything I said applies to tires that are common to me, that is why I asked a race car expert to help the op ! did you help him yet ? Something tells me you are going to keep blowing up my alerts and that you aren't going to help the op at all ..... other than to smart off about getting somebody that can read a tape o_O
Yeah, I helped him at the start, said get someone who can read a tape.( really should) Then I answered your response with a "no" then you went from there. So each time I responded.
 

kyle18fan

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Yeah, I helped him at the start, said get someone who can read a tape.( really should) Then I answered your response with a "no" then you went from there. So each time I responded.

Well thanks for helping the fellow, I am sure he appreciates the detailed approach you took to diagnosing his problem. Now I am going to go back to my tires that get smaller when they wear out, hopefully you will go back to your tires that get bigger when they wear away .... and everybody will be happy :salute:
 

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Well thanks for helping the fellow, I am sure he appreciates the detailed approach you took to diagnosing his problem. Now I am going to go back to my tires that get smaller when they wear out, hopefully you will go back to your tires that get bigger when they wear away .... and everybody will be happy :salute:
I think I did help him. In the 30 plus years of racing Ive never had a left rear lose circumference without a puncture or a leak of some sort. Also never had a left rear that didnt gain pressure and size unless we had a failure. Thats racing 101 stuff. He might be a young dude so he/she can start from the bottom up.
 

kyle18fan

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I think I did help him. In the 30 plus years of racing Ive never had a left rear lose circumference without a puncture or a leak of some sort. Also never had a left rear that didnt gain pressure and size unless we had a failure. Thats racing 101 stuff. He might be a young dude so he/she can start from the bottom up.

Did that right rear grow because the tread wore off .... or because heat increased the pressure ?
 

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Did that right rear grow because the tread wore off .... or because heat increased the pressure ?
First of all he was talking about the LR, but to humor you, the RR will gain circumfernce because of heat. Why do you think we start our pressure low?
 

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First of all he was talking about the LR, but to humor you, the RR will gain circumfernce because of heat. Why do you think we start our pressure low?

You didn't answer my question, I am familiar with tire heat and increased pressure. I asked you if that tire grew because rubber wore away. The reason I asked, is because when I see a worn tire and measure it, it is smaller than a new tire with all the tread on it. I am specifically asking if a tire grows when it wears ... pressures being a constant, lets say 20 pounds and room temperature. Measure that tire, cut off a quarter inch of rubber and measure again.
 

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You didn't answer my question, I am familiar with tire heat and increased pressure. I asked you if that tire grew because rubber wore away. The reason I asked, is because when I see a worn tire and measure it, it is smaller than a new tire with all the tread on it. I am specifically asking if a tire grows when it wears ... pressures being a constant, lets say 20 pounds and room temperature. Measure that tire, cut off a quarter inch of rubber and measure again.
The tire grew because of heat and friction.
 

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And btw, we arent talking about a static tire, the tire is moving and gaining heat. Why are you confused about this?
 

kyle18fan

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And btw, we arent talking about a static tire, the tire is moving and gaining heat. Why are you confused about this?



I am not confused, I understand that when rubber wears away a tire gets smaller, which is what I have been saying all along.
 

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I am not confused, I understand that when rubber wears away a tire gets smaller, which is what I have been saying all along.
Has nothing to do with a pro late model tire (Goodyear,Hoosier,McCreary,General etc..) hence the reason I said "no" which you engaged in further discussion.
 

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Of course a tire gets physically smaller when its tread wears away. But for racing tires that's a small amount - typically measured in 32nds of an inch. Certainly not the roughly 3/4 inch that the OP has told me in PM that his tires are shrinking. While kyle18fan is technically correct about tires getting smaller due to wear, late model racing tires do not have the big knobs that dirt motorcycle tires have. If the OP's tires were wearing about 3/4 of and inch then they'd be worn through the cords and blown out (long before they reached 3/4 inch).

On the other hand, Spotter22 is confusing stagger change with tire wear, then goes off on a tangent about stagger changing due to tire growth while racing. While Spotter22 is correct that stagger can (and often does) change that way, this is not what the OP is telling me he is talking about (in PM). The OP is aware of tire growth and its effects on stagger while racing. That's why he is mystified about how his left side tires are shrinking instead of growing.

I am trying to work with the OP on how his tires are measuring so much smaller after a race. Maybe it is a measuring problem. If not I haven't thought of any other reasonable explanation except for leaks. In my racing past I have had tires leak (mainly due to valve stem problems) that didn't show up while the tires were sitting in the pits - these tires had to build up more pressure (due to racing) to get them to leak, and then they leaked enough to show lower pressure than I originally set them to. So far the OP has measured "normal" pressures (in PM, and I'm trying to get him to define his "normal" for me). So I believe we also have a terminology disconnect too.

By the way, even though it's common practice to measure stagger by measuring tire circumference, the long accepted engineering defined way of measuring stagger is actually via tire diameter. Stagger is defined as the difference in heights of two tires; height = diameter. But since diameter and circumference are related by a constant (pi) you can get away with measuring circumference. I too like measuring circumference since it is easier to do and thus can be more accurate. But be careful when comparing stagger with somebody to make sure they are calculating it the same way that you do. I used to write my stagger notes with my numbers corrected to diameter (dividing my circumference measurements by pi) and when asked I'd divulge those numbers - I got cussed at by some people who just used circumference numbers, and who accused me of divulging "wrong" numbers when actually I was giving them engineering numbers that were about a third of what the circumference numbers alone would yield. LOL
 

kyle18fan

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Of course a tire gets physically smaller when its tread wears away. But for racing tires that's a small amount - typically measured in 32nds of an inch. Certainly not the roughly 3/4 inch that the OP has told me in PM that his tires are shrinking. While kyle18fan is technically correct about tires getting smaller due to wear, late model racing tires do not have the big knobs that dirt motorcycle tires have. If the OP's tires were wearing about 3/4 of and inch then they'd be worn through the cords and blown out (long before they reached 3/4 inch).

On the other hand, Spotter22 is confusing stagger change with tire wear, then goes off on a tangent about stagger changing due to tire growth while racing. While Spotter22 is correct that stagger can (and often does) change that way, this is not what the OP is telling me he is talking about (in PM). The OP is aware of tire growth and its effects on stagger while racing. That's why he is mystified about how his left side tires are shrinking instead of growing.

I am trying to work with the OP on how his tires are measuring so much smaller after a race. Maybe it is a measuring problem. If not I haven't thought of any other reasonable explanation except for leaks. In my racing past I have had tires leak (mainly due to valve stem problems) that didn't show up while the tires were sitting in the pits - these tires had to build up more pressure (due to racing) to get them to leak, and then they leaked enough to show lower pressure than I originally set them to. So far the OP has measured "normal" pressures (in PM, and I'm trying to get him to define his "normal" for me). So I believe we also have a terminology disconnect too.

By the way, even though it's common practice to measure stagger by measuring tire circumference, the long accepted engineering defined way of measuring stagger is actually via tire diameter. Stagger is defined as the difference in heights of two tires; height = diameter. But since diameter and circumference are related by a constant (pi) you can get away with measuring circumference. I too like measuring circumference since it is easier to do and thus can be more accurate. But be careful when comparing stagger with somebody to make sure they are calculating it the same way that you do. I used to write my stagger notes with my numbers corrected to diameter (dividing my circumference measurements by pi) and when asked I'd divulge those numbers - I got cussed at by some people who just used circumference numbers, and who accused me of divulging "wrong" numbers when actually I was giving them engineering numbers that were about a third of what the circumference numbers alone would yield. LOL

When I set up a bicycle computer, I put a mark on the tire and one on the floor, then I push the bike until that mark hits the floor again ....... then measure the distance between the marks and enter it into the computer. Beats fiddling with a tape on a narrow tire :D I only stagger if I have been drinking :salute:
 

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Of course a tire gets physically smaller when its tread wears away. But for racing tires that's a small amount - typically measured in 32nds of an inch. Certainly not the roughly 3/4 inch that the OP has told me in PM that his tires are shrinking. While kyle18fan is technically correct about tires getting smaller due to wear, late model racing tires do not have the big knobs that dirt motorcycle tires have. If the OP's tires were wearing about 3/4 of and inch then they'd be worn through the cords and blown out (long before they reached 3/4 inch).

On the other hand, Spotter22 is confusing stagger change with tire wear, then goes off on a tangent about stagger changing due to tire growth while racing. While Spotter22 is correct that stagger can (and often does) change that way, this is not what the OP is telling me he is talking about (in PM). The OP is aware of tire growth and its effects on stagger while racing. That's why he is mystified about how his left side tires are shrinking instead of growing.

I am trying to work with the OP on how his tires are measuring so much smaller after a race. Maybe it is a measuring problem. If not I haven't thought of any other reasonable explanation except for leaks. In my racing past I have had tires leak (mainly due to valve stem problems) that didn't show up while the tires were sitting in the pits - these tires had to build up more pressure (due to racing) to get them to leak, and then they leaked enough to show lower pressure than I originally set them to. So far the OP has measured "normal" pressures (in PM, and I'm trying to get him to define his "normal" for me). So I believe we also have a terminology disconnect too.

By the way, even though it's common practice to measure stagger by measuring tire circumference, the long accepted engineering defined way of measuring stagger is actually via tire diameter. Stagger is defined as the difference in heights of two tires; height = diameter. But since diameter and circumference are related by a constant (pi) you can get away with measuring circumference. I too like measuring circumference since it is easier to do and thus can be more accurate. But be careful when comparing stagger with somebody to make sure they are calculating it the same way that you do. I used to write my stagger notes with my numbers corrected to diameter (dividing my circumference measurements by pi) and when asked I'd divulge those numbers - I got cussed at by some people who just used circumference numbers, and who accused me of divulging "wrong" numbers when actually I was giving them engineering numbers that were about a third of what the circumference numbers alone would yield. LOL
Im not confusing anything. I was crystal clear on why a left rear wouldnt be smaller after a race and throwing his stagger off unless it was leaking. Crystal clear, you can write another essay on it if you want but what I said it 100% correct.
 

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Im not confusing anything. I was crystal clear on why a left rear wouldnt be smaller after a race and throwing his stagger off unless it was leaking. Crystal clear, you can write another essay on it if you want but what I said it 100% correct.
Sorry, I meant that you were confusing the OP's issue with your argument with kyle18fan. Didn't mean that you were wrong.

By the way, if you don't like long explanations then don't read them.
 

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Sorry, I meant that you were confusing the OP's issue with your argument with kyle18fan. Didn't mean that you were wrong.

By the way, if you don't like long explanations then don't read them.
Trust me, I did the readers digest version. Good luck with your research on a shrinking tire
 
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