New tire for 2021

DanicaFreak

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https://www.nascar.com/news-media/2019/08/16/nascar-goodyear-targeting-2021-for-new-tire-in-cup-series/

Goodyear has been working with NASCAR on plans to introduce a new tire in the Monster Energy NASCAR Cup Series in 2021. Instead of the 15-inch tires currently used, the targeted size of the new tire is 18 inches and the change would coincide with the introduction of the Generation-7 vehicle.

The impetus behind the change, according to Goodyear’s Director or Racing Greg Stucker, is to help make the cars look more like the ones a customer would drive off the showroom floor.
 

DanicaFreak

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a bigger tire should increase gas mileage right? Reduce transmission RPM,,,
 

Spotter22

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The circumference of the new tire will be the same as the old ones - give or take an eighth of an inch.

The difference is in the aspect ratio and because of that, the spring rate.
I wonder what the rate gain will be at the same air pressure? Of course I'm assuming gain in the rate instead of losing considering the sidewall will be a couple inches shorter
 

aunty dive

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I wonder what the rate gain will be at the same air pressure? Of course I'm assuming gain in the rate instead of losing considering the sidewall will be a couple inches shorter
Good question. Test, test, test.

Yes, the spring rate of every tire will increase.
 

Greg

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I don't care if they run 15" or 18" tires. I just want to see some more tire wear and short pitting becoming more of an option. I think that is the best way to create more passing and (imo) it definitely makes the various race strategies more interesting.
 

Greg

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I wonder what the rate gain will be at the same air pressure? Of course I'm assuming gain in the rate instead of losing considering the sidewall will be a couple inches shorter
I wonder if there will be more issues with breaking the tire bead. I also wonder if the wheel and tire becomes less tolerant to contact due to a shorter sidewall.
 

Greg

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The circumference of the new tire will be the same as the old ones - give or take an eighth of an inch.

The difference is in the aspect ratio and because of that, the spring rate.
I assuming the 18" wheel and tire assembly will weigh less than a 15" assembly? If true wouldn't it essentially represent a small HP gain, and less wear and tare on the drive train, suspension, and brakes?.
 

aunty dive

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I assuming the 18" wheel and tire assembly will weigh less than a 15" assembly? If true wouldn't it essentially represent a small HP gain, and less wear and tare on the drive train, suspension, and brakes?.
If the wheels are steel, I’d say the 18” combination would weigh a little more.
 

Charlie Spencer

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I wonder if there will be more issues with breaking the tire bead. I also wonder if the wheel and tire becomes less tolerant to contact due to a shorter sidewall.
If the wheels are steel, I’d say the 18” combination would weigh a little more.
And I wonder if a larger wheel with more mass will heat slower during braking, reducing the chances of the bead melting.
 

Formerjackman

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And I wonder if a larger wheel with more mass will heat slower during braking, reducing the chances of the bead melting.
Assuming NASCAR doesn't allow the teams to just fill up the new found space with ever larger brake packages, the larger wheel theoretically would move the bead further away from the heat sources.
If the wheels are steel, I’d say the 18” combination would weigh a little more.
Maybe I'm all wet, but I'm assuming the new wheel WON'T be steel, which I fully support, especially if they go to the single nut system, which I could not be more opposed to by the way.
I wonder if there will be more issues with breaking the tire bead. I also wonder if the wheel and tire becomes less tolerant to contact due to a shorter sidewall.
My guess would be fewer sidewall cuts from body contact (the new body may take some of that away anyway) but I would expect wheel more damage, although it doesn't seem to be a big issue in other forms of racing. Theoretically, the short sidewall would not like curb and rumble strips as well, but once again, it doesn't seem to effect other cars that much.
I wonder what the rate gain will be at the same air pressure? Of course I'm assuming gain in the rate instead of losing considering the sidewall will be a couple inches shorter
I think that is going to be a HUGE deal, maybe as big as the changes to the car itself as far as chassis setups. One would have to think that teams that have in house knowledge of Indy cars and sports cars like Penske and Ganassi could have a big advantage, at least early on. I wonder if some of the other teams won't have to leverage some outside resources (Chevy teams could work with Pratt and Miller for instance) to get up to speed quicker.
 

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I'm not very optimistic it will make much of a difference. Rocks are rocks. I expect to see even longer runs for the tires and tires being less of a factor going by Goodyear's history of doing so while telling everybody the tires will have fall off.
 

Formerjackman

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I'm not very optimistic it will make much of a difference. Rocks are rocks. I expect to see even longer runs for the tires and tires being less of a factor going by Goodyear's history of doing so while telling everybody the tires will have fall off.
I think because of the sidewall difference, I think it's going to be back to square one on setups. I have no clue whether this will be a good thing or a bad thing, just that I expect it to be a LOT different.
 

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I'm not very optimistic it will make much of a difference. Rocks are rocks. I expect to see even longer runs for the tires and tires being less of a factor going by Goodyear's history of doing so while telling everybody the tires will have fall off.
Less of a factor than this year? May God have mercy on our soul.
 

StandOnIt

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I think because of the sidewall difference, I think it's going to be back to square one on setups. I have no clue whether this will be a good thing or a bad thing, just that I expect it to be a LOT different.
yeah for sure. I'm no tire expert but less sidewall means less flex. The prototype was running a wider tire also on the rear. Couple that with hard compounds Goodyeer characteristically uses, I can't see tire fall off being greater than it is now but less. Traction should be better
 

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Assuming NASCAR doesn't allow the teams to just fill up the new found space with ever larger brake packages, the larger wheel theoretically would move the bead further away from the heat sources.

.
How so? The caliper will remain consistent
 

Spotter22

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I wonder if there will be more issues with breaking the tire bead. I also wonder if the wheel and tire becomes less tolerant to contact due to a shorter sidewall.
I think more tolerant, less target if you will.. you are more then likely to contact the wheel instead of the tire considering a 2 inch loss in sidewall
 

Charlie Spencer

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If NASCAR allows the teams to run a larger rotor to take advantage of the larger wheel, the caliper will end up just as close to the wheel as it is now.
Okay, there's one of the 'IF's I was looking for. I mostly wondered if a bigger wheel would have more mass to spread the heat across and more surface area available to cool, taking longer to heat up to melting temp. But then I'd also have to factor in whether they change the material, and whether the new one would heat faster or slower.

So many questions on this one. I agree spinning it off from the main 2021 discussion was a good idea.
 

Spotter22

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If NASCAR allows the teams to run a larger rotor to take advantage of the larger wheel, the caliper will end up just as close to the wheel as it is now.
Thats what I said, the caliper will remain consistent and I havent heard anything about larger rotors
 

Formerjackman

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Thats what I said, the caliper will remain consistent and I havent heard anything about larger rotors
I haven't heard anything either, but if left with the option, the teams will likely make use of that space, and if the rotor gets bigger, the caliper will too.
 

Spotter22

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for better more precise braking. Unless Nascar has a rule, knowing teams, they will have a different brake for every track and a different spindle for the front end.
You're gonna add weight for better braking? The calipers and rotors and brake pads they have now could stop an airplane.
 

Formerjackman

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You're gonna add weight for better braking? The calipers and rotors and brake pads they have now could stop an airplane.
Well, just for perspective, the Corvette C7R race car uses 14.8" rotors up front and 14.0" rotors out back (steel by rule) along with the HUGE calipers and pads that go with them, and those cars weight a LOT less than a Cup car and have more downforce, meaning they should be a LOT easier to get stopped, but yet they are willing to sacrifice unsprung weight for braking capability. I would imagine at tracks like Martinsville, Hew Hampshire, Phoenix and Sonoma, many Cup teams would too.
 

StandOnIt

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You're gonna add weight for better braking? The calipers and rotors and brake pads they have now could stop an airplane.
not sure about weight, they have carbon fiber or ceramic brakes these days on street cars. You can buy them from your local AutoZone
 

Spotter22

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not sure about weight, they have carbon fiber or ceramic brakes these days on street cars. You can buy them from your local AutoZone
Im sure the cost of a carbon fiber braking system wont excite the owners, I'm all for carbon fiber wheels to offset the unsprung weight
 

Spotter22

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Well, just for perspective, the Corvette C7R race car uses 14.8" rotors up front and 14.0" rotors out back (steel by rule) along with the HUGE calipers and pads that go with them, and those cars weight a LOT less than a Cup car and have more downforce, meaning they should be a LOT easier to get stopped, but yet they are willing to sacrifice unsprung weight for braking capability. I would imagine at tracks like Martinsville, Hew Hampshire, Phoenix and Sonoma, many Cup teams would too.
I have no idea what the rule book says in that class. You say steel rotors are required so are the the rotor size and caliper type also?
 
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