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I think your control arm is fine. The problem is the new tire (left tire). No matter how small the difference in the treads, it is best to replace both rear tires together. If one tire has more tread than the other, the car will pull to the one with more rubbers.

In physics, I can think of two explanations:

1) Generally car moves when torque of the driveshaft < torque of the friction (Td < Tf). On the other hand if Td > Tf, the car slips. Torque of friction (Tf) is calculated with this formula Tf = (WD or weight distribution of car to each tires) x road friction x (TW or tire width / distance from axel to end of tire).

So you see, when a tire has less tread, it has less TW. This means it has smaller torque friction or smaller Tf.

Comparing your new left tire and old right tire:
Left tire: has larger torque friction or larger Tf.
Right tire: has smaller torque friction or smaller Tf.

2) Also, there is a difference in kinetic friction between new tire and old tires. This kinetic friction happens when the tires are rolling and will affect acceleration.

a = F of the friction / mass
acceleration = 0.5 x m x g x kinetic friction / mass of the car

So during hard acceleration, your car will pull to the left.
 

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I think your control arm is fine. The problem is the new tire (left tire). No matter how small the difference in the treads, it is best to replace both rear tires together. If one tire has more tread than the other, the car will pull to the one with more rubbers.

In physics, I can think of two explanations:

1) Generally car moves when torque of the driveshaft < torque of the friction (Td < Tf). On the other hand if Td > Tf, the car slips. Torque of friction (Tf) is calculated with this formula Tf = (WD or weight distribution of car to each tires) x road friction x (TW or tire width / distance from axel to end of tire).

So you see, when a tire has less tread, it has less TW. This means it has smaller torque friction or smaller Tf.

Comparing your new left tire and old right tire:
Left tire: has larger torque friction or larger Tf.
Right tire: has smaller torque friction or smaller Tf.

2) Also, there is a difference in kinetic friction between new tire and old tires. This kinetic friction happens when the tires are rolling and will affect acceleration.

a = F of the friction / mass
acceleration = 0.5 x m x g x kinetic friction / mass of the car

So during hard acceleration, your car will pull to the left.
Wow, this was such a beautiful explaination. My god. I want to go back to physics so I can follow along with that. So yes, the old tire does have about 3500 miles on it. My stock Pirellis had lasted until 18,000 miles, at which point I had gotten these new PS4S. Honestly, I had gotten my energy out in the first 20k miles and had been driving it like a Honda Accord nowadays. I'm not planning on driving it hard/ launching it anyways.
Your explanation makes sense.
So what we have here is a case of torque steering right? I had just gotten concerned because I had read that torque steering could be caused by a suspension issue (Although my mechanical knoweldge is zilch to none, this is all just google searching).
I do also remember the pressure in the right rear being 2.5barr, while everywhere else it was 2.7barr. I'll go and get this adjusted, but could that play into it?
Another note, the harder I accelerate, the harder it pulls left. And again, when I drive this car like a honda accord, I can't even tell anything is wrong. So in that case, it's even less likely a suspension/ alligment issue right? Because otherwise I would get the pull in other cirsumstances too, like braking, gentle acceleration, and cruising.
 

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Wow, this was such a beautiful explaination. My god. I want to go back to physics so I can follow along with that. So yes, the old tire does have about 3500 miles on it. My stock Pirellis had lasted until 18,000 miles, at which point I had gotten these new PS4S. Honestly, I had gotten my energy out in the first 20k miles and had been driving it like a Honda Accord nowadays. I'm not planning on driving it hard/ launching it anyways.
Your explanation makes sense.
So what we have here is a case of torque steering right? I had just gotten concerned because I had read that torque steering could be caused by a suspension issue (Although my mechanical knoweldge is zilch to none, this is all just google searching).
I do also remember the pressure in the right rear being 2.5barr, while everywhere else it was 2.7barr. I'll go and get this adjusted, but could that play into it?
Another note, the harder I accelerate, the harder it pulls left. And again, when I drive this car like a honda accord, I can't even tell anything is wrong. So in that case, it's even less likely a suspension/ alligment issue right? Because otherwise I would get the pull in other cirsumstances too, like braking, gentle acceleration, and cruising.
Haha glad you like the explanation :D

Yes, torque steer can be caused by suspension error. But I don't think it is the suspension issue because you will have to run the car over a very large curb to break or bend the control arm. Pulling it slowly to a flatbed will not affect it. This part can withstand a very large force.

The kinetic friction and torque friction of 3500 miles tire vs new tire has more factor than 2.5 bar vs 2.7 bar. I don't think this slight difference in air pressure is the cause. You can try putting the same amount of air and see how it goes, but I'm pretty sure it won't make any difference. Also, if you did a lot of spirited driving during the first 3500 miles, the tread difference would become even much bigger.

If you drive the car slowly and can't tell anything is wrong, generally this means the suspension is OK. If there is an error in suspension, you can feel or hear it almost immediately. The sensor would go nuts. For example, when people hurt their left leg (suspension), they will limp even when they walk slowly. On the other hand, people wearing slightly uneven soles on their shoes (uneven tire treads) can walk slowly just fine without noticing much difference. But, when they try to run at high speed, most of them will either slip, trip and fall.

Also, since veering to the left is actually very dangerous at high speed, I recommend having the dealer look into everything again just in case.
 

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If possible, try to swap the wheel form left to right and see if the behaviour changes. Dunno if the tire is directional but afaik the PS4S is not.
 

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2019 Huracan 580-2
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Interesting question and great explanation by @Sakura who is not only our resident chemist but now, apparently, our resident physicist. My friend in addition to your Santa hat you have many others hats as well.(y)

BTW, agree I always change the tires in pairs as well.......now I know why based upon the physics. ;)
 

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100% your tire...I’ve gone thru this every expensive experiment..even 50miles on ur new tire and replacing the other will cause it to pull..it’s very frustrating..you need brand new TWO rears..these cars are Uber sensitive
 

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Just to add one more thing new tires come with a releasing agent to remove them from the mold. Depending on how you drive it could take a few hundred miles to burn that off. Although, I do like the physics explanation.

Edit: just to add something else. On my sportbike I use scotchbrite on new tires to try and remove the releasing agent, otherwise the bike slides around too much. I wouldn't do it on a car because I am not going to fall off a car.
 

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2018 Huracan Spyder 580-2
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Sakura, you have made me a believer! Love that detailed explanation. I would also love to see the OP explain that to the dealer!
 
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I punctured my rear right tire with only 3000 kms. I changed both rears when I replaced as recommended by Lambo dealer - no issue such as yours
 

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So here's what happened. I got a flat tire on my rear driver's side. The tires were PS4S. I called a flat bed and at the time I didn't realize, but in order to pull the huracan onto the flat-bed, the tow truck driver attached the tow strap onto what I believe is the driver's side suspension control arm. He did not use the tow-hook on the front bumper. I just got the car back today from the dealer with only the damaged tire replaced with an identical PS4S. (I opted not to change the other rear tire). The passenger rear tire is unchanged, and I'd guess I have used up 4/32 to 8/32s of the tread. I drove the car home today and noticed that ONLY during modest to hard acceleration, the car pulls to the left. It's not an extreme pull, but it's very much there. It does not pull at all if I drive normally, accelerate normally, brake, etc. This left side is the same side as the new tire, and also the side where the car was pulled up by the tow strap. So let me hear it guys, did the tow truck driver damage my suspension control arm? When I visually examine the control arm, it appears to be okay. Could this be the result of un-even tread on the rear tires? Could the car just be out of alignment? Keep in mind everything was fine before the flat incident.
My dad had a Gallardo he recently traded in for LP610-4...his 560-4 pulled hard to one side... took it to the dealer (where I work) for an alignment, they never did the alignment because he had larger after market forged rims and cup 2's...they kept giving us the run around saying they rack says it already drives straight... long story short bigger rims could have been the issue (which I know is hard to believe), are you running factory spec? also tread life may for some reason be off on one side, I'd recommend getting an alignment and making sure they have the same amount of tread on both sides for starters...
 

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sakura, i though you are just a santa with a violin :cool:
It helps after many years of riding a sleigh with deer power :ROFLMAO:

Interesting question and great explanation by @Sakura who is not only our resident chemist but now, apparently, our resident physicist. My friend in addition to your Santa hat you have many others hats as well.(y) BTW, agree I always change the tires in pairs as well.......now I know why based upon the physics. ;)
Thank you my friend for the compliments :D

Sakura, you have made me a believer! Love that detailed explanation. I would also love to see the OP explain that to the dealer!
I think tire makers would also love this explanation to sell more tires :ROFLMAO:
 

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@Sakura the compliment came easy given its clearly earned and well deserved!
 
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