Tire wear - pirelli p zeros

Discussion in 'Brakes, Wheels and Tires' started by Wotfun, Nov 25, 2018.

  1. Wotfun

    Wotfun TMO Advanced

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    I’m looking for thoughts on tire wear. I’m running oem pirelli p zeros. Starting with 100% new tires, I put about 2k miles on the tires, including 2 track events. Pictures below are rear tires after approximately eight 20 minute sessions at North Carolina Center for Automotive Research (NCCAR) and eight 30 minute sessions at Carolina Motorsports Park (CMP). I was told both tracks are hard on tires.

    Passenger side tire:
    C3A8C4DA-E3F6-4B4E-86D8-86E5B2EB673B.jpeg

    Drivers side tire:
    E2BA6D28-41A2-421F-B298-6A09CF031891.jpeg

    The tires wore differently. It’s hard to see unless you expand the pictures.

    Passenger side looks “normal” for hard track use, I think. But, still not down to the wear bars. More or less even wear across tread.

    Drivers side...the middle of the tread is worn to the wear bars. But, the outer tread isn’t. Normally, I’d think it’s due to running air pressure too high.

    However, I intentionally ran 30 psi cold, which is 2 lower than Ford specifies. Hot, on track, the car showed 34 psi in both rear tires. (I ran the pressure low because my original tires both wore out in the middle, even though I kept the cold pressure at 32 psi cold. My tire shop said the only explanation was that I ran pressure too high, which was obviously wrong.)

    My son suggested that another possibility is the oem wheels - 9.5” wide - might be too narrow, which would squeeze the 275 width tire and cause the middle to wear. But, that should affect both rear tires the same and both tires wore differently.

    I’m concerned about two things:
    1. Hate the thought of having to buy new tires every couple of track events. (I realize the first thing to help is get a square setup so I can rotate tires.)
    2. Uneven wear that I don’t understand.

    Thoughts?

    Thanks,
    Shea
     
  2. JeffV8

    JeffV8 TMO Race

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    My rear PZeroes lasted 2000 miles I won’t getthem again.
    Michelin tires next
     
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  3. TMSBOSS

    TMSBOSS TMO Addict

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    The P Zero tires on our cars are not a “Great” track tire.
    I would consider going to a square rotatable set up for track days. I have run both Nitto 05’s and 01’s on track. The 05’s make a better all around street tire. The 01’s are the better track tire but are not a good choice if you may drive in the rain.
    I would buy a lighter, almost every wheel is lighter, set of square track wheel and keep the P Zeros for car shows.
     
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  4. Wotfun

    Wotfun TMO Advanced

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    Understand and agree. I’ve been thinking about getting the apex ec7s for months - lighter, rotatable, and cheaper 18” tires. I’ve just delayed pulling the trigger so I could spend the money on track time.

    But, I’ve done 4 HPDEs with the mustang now and I’m pretty comfortable with the car. Maybe it’s time to just bite the bullet and invest in wheels.

    If I stay with my current wheels and the pirellis, it looks like I’m quickly approaching the point of needing new tires for each track event. With the cost of the tires, including mounting and balancing, the inconvenience, and the performance limitations, my current setup is making less and less sense.

    I’d prefer to run a tire that will be acceptable for both street and track. Would the nitto 05s work for that and how do they hold up to track use?
     
    Last edited: Nov 26, 2018
  5. VoodooBoss

    VoodooBoss Rick Moderator

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    You probably know this but depending on if your track is clockwise or counterclockwise you'll have different wear on the "inside or outside" tire. Also if the middle of the tire is wearing that usually means the tire pressure is too high and that can also be dependent on the inside or outside tire relative to the track. It looks like you're keeping a close eye on the pressures though. You should be able to run those tires a couple of more sessions. They probably won't fall off until they are corded. When you buy new tires look at other options including the Michelin PS4S if you drive the car in the rain.
     
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  6. Wotfun

    Wotfun TMO Advanced

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    Thanks. You probably answered my question about the uneven wear. I have read other posts talking about tire wear related to going clockwise or counterclockwise. But, I wasn’t aware previously. I never experienced this sort of wear on my bimmer. But, that was a very different car.

    The mustang is my “daily driver” and I can’t justify two extra sets of wheels and tires yet - one for wet and one for dry. If it weren’t for the cost, I’d already have the PS4S Michelins. I used the Pilot Supersports on my BMW and loved them. From what I’ve read, the PS4S is even better. I just hate to spend that much on tires and wear them out in a two or three weekends. Still, the Michelin’s are probably the best option for me.

    Thanks to everyone who replied. I appreciate it!

    Shea.
     
  7. VoodooBoss

    VoodooBoss Rick Moderator

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    The 4S should be faster and wear better, maybe much better.
     
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  8. Wotfun

    Wotfun TMO Advanced

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    Sounds good - thanks Rick!
     
  9. AustinGT350

    AustinGT350 TMO Intermediate

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    My Pirellis on my GT did the exact same thing.
     
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  10. Wotfun

    Wotfun TMO Advanced

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    What tires are you running now and how do you like them?
     
  11. AustinGT350

    AustinGT350 TMO Intermediate

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    I sold that car, but I had a set of Indy 500s on 18x10 EC 7s that was a pretty decent setup.

    I didn't mind those tires, they were different. The Pirelli's start out slick, have a very short window of grip and then overheat rather quickly. The Indy 500s had quite a bit more grip when cold, never got quite as sticky as the Pirelli's at their best, but didn't fall off anywhere near as quickly. They also seemed to wear like iron.

    Currently on my GT350 I have MPSS, which is a great street tire. They overheat but they don't murder themselves like the Pirelli's seemed to do. I'll most likely end up with a set of RS4s though, my wife has them on her Fiesta ST and that tire is an absolute peach.
     
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  12. Eric62

    Eric62 TMO Intermediate

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    I've used 200 tread wear Nitto NT05's, Hankook S3's and S4's on my GT. The Nitto's are awful in the rain and they don't like cool weather so much. 200 TW tires will be like that. The Hankook's are better road tires, good in the wet and good on the track. I'll get a year of driving and 6 track days on the Kooks with no problems. They last longer than brake pads! But I get very even wear front to back. Correct camber and pressures help that a lot.

    Since most road courses in the US run clockwise, there are always 4 more rights than lefts and the tires will show that. Most 200 TW tires are directional so can't be swapped side to side without remounting. A square setup will allow you to even out front and rear wear, though. You will need to re-tune your setup a bit with a square tire set.
     
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  13. Wotfun

    Wotfun TMO Advanced

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    My suspension and alignment are currently 100% stock. However, a tire/wheel fitment site I found says going to an 18” diameter will lower rise height by 12.7 mm. I’m guessing that’ll add a little negative camber.

    Thinking about 18x10et43 wheels and 275 width tires front and rear, with 300 tread wear. Can you be more specific about the need to retune my setup? What needs to change and to what degree?
     
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  14. Eric62

    Eric62 TMO Intermediate

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    Shorter tires won't affect your alignment setting at all. It just lowers the overall ride height 12.7mm. Shorter springs will affect alignment, shorter tires won't.

    If the car was tuned with wider tires in the rear, that wider tire generally creates more traction than the front. If you make them the same, the car will tend to understeer less and oversteer more. If you are currently well balanced with the narrow front/wider rear, changing to square will tend to make the car looser. If the car currently understeers a bit more than you'd like, square tire widths should help. If the car is now too loose, lower tire pressure at the rear 1-2 psi and up the fronts 1-2 psi. A half degree more negative camber at the rear will help, too.

    How do you know where your car is now? How much pressure do you gain at the front compared to the rear from cold pressures to hot? If the front gains 6 psi and the rears 4 psi, the car understeers. If the rears gain 6 and the fronts 4 psi, it oversteers. Not everybody can feel this in the steering wheel or the seat of your pants, but the pressure rises in proportion to the temperature of the tire. If you don't have a tire pyrometer to measure it, the pressure gain is a pretty good indicator.

    I am running 275/40-18's on 18x10 ET45 wheels on an S197. I run the 40's because 35's or 30's are super short and they look funny! The 40's also give a better ride than 35's. 250 to 300 treadwear should give you a pretty robust tire.
     
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  15. Wotfun

    Wotfun TMO Advanced

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    Thanks, that’s very helpful! I’ll try to give a more complete description of my P Zero experience.

    Front tires...original set wore a lot more on the edges than the middle. They saw about 9k miles, including 3 track weekends. I kept cold pressure at 32 psi, per Ford. During my last track weekend with those front tires, I started with 36 psi cold to make use of the unworn tread in the middle. Doing that worked. The entire tread surface wound up wearing out. But, the car drove like the front tires were over inflated. On a fast straight, the front end felt twitchy - not planted.

    To avoid repeating the same wear problem, I stayed with the same strategy for my new front tires - still P Zeros. So, 36 psi cold.

    On track, psi definitely rose more in front - 6-8 psi front vs 4-5 rear. So, under steering.

    I’ve only had the car since July 2017 and only used P Zero tires. Based on my experience with them, I don’t think I ever had the grip I should’ve had. My impression is that the front was generally looser than the rear. Ie., more under steer than over steer. I just got used to it and learned to drive the car that way.

    I suspect my experience will be very different with better tires. As you described, with no changes other than going from staggered to square and getting better tires, I expect the rear end to be a bit looser relative to the front.

    If I understand correctly, there are several things I might do to reduce over steer:
    - lower psi in rear;
    - smaller / less stiff anti roll bar in rear;
    - add negative camber in rear;
    - higher psi in front;
    - stiffer / bigger anti roll bar in front;
    - reduce negative camber in front.
    Or a combination of changes front and rear. Ie., lower pressure in rear AND raise pressure in front. I don’t think I’ll really know until I get the new setup and try it on the track.

    Do I have all that right?


    Re tires to replace Pirellis, I would prefer 275/40 18 over 275/35 18. I think I can still get that in a Michelin PSS, but not a Michelin PS4S.

    Would you suggest making the 40 aspect ratio my priority and pick tires based on that?
     
  16. Eric62

    Eric62 TMO Intermediate

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    You don't have a ton of oversteer, as I'd expect from a relatively stock car with stock alignment.

    And yes that list is right. You could add softer rear springs as well. For a strut suspension, adding stiffer front springs doesn't always add understeer because of camber gain.

    I doubt going square will get you all the way to oversteer so tire pressures will likely be enough. The wear you see on the fronts is pretty typical of not having enough negative camber. Raising the front pressures over the optimum just makes the understeer worse and, as you found, makes the front squirrely. That is a good example of starting pressures too high and then heating the tires past the point of optimum traction. I've talked to guys that had understeer when first out and oversteer at the end of session - too much tire pressure in the rear and too little in the front. Or the opposite, loose out and balanced at the end - too much front pressure or too little rear

    You can help the front wear by adding a 1/2 degree more camber at the front but you'll need to add that to the rear, too, to balance it out. The bonus is more overall grip with more even wear.

    Whether you choose 40's or 35's depends on what you can buy and how you want the car to look and handle. The 35's will be sharper at turn-in, ride harder and look small in the wheel openings. Both will get the job done. I'd consider 285 or 295's as well. Might help your selection. They will fit the front of my S197 with an ET45 wheel and 10mm spacer. Since Ford sells an S550 with a 305 front, you should be good for fit but not sure about whether an ET43 wheel will allow that to fit. Other S550 owners need to weigh in.
     
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  17. Wotfun

    Wotfun TMO Advanced

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    @Eric62, thank you!

    All, I just came across a YouTube video talking about electronic nannies on mustangs. The video is titled, “The science behind why mustangs crash!” Here’s a link if you’re interested:


    Key takeaways from the video:
    1. Ford designed nannies so we cannot 100% defeat them. Ie, even if you turn them off per Ford’s instructions, the computer can (and will) turn them back on in certain circumstances.
    2. The nannies can do more harm than good, especially if mustangs are modified so they have more grip than the computer expects.

    How this relates to my tire questions:
    I’ve gotten to the point that I’m able to drive my car around a track close to the limits of it’s current set up. So far, I’ve kept the nannies ON and haven’t felt like they hurt my driving experience or created any risks.

    The video seems to say that adding wider and/or stickier tires and/or adding track brake pads can yield very negative results if the nannies kick in unexpectedly.

    Ie, the computer thinks it’s applying braking to a wheel equipped with a Pirelli P Zero 255 width tire and street brake pads. But, the car actually has Michelin PS2 285 width tires and track pads. So, the computer applies more brake than is needed and that throws the car off balance.

    I’m already using track pads and haven’t noticed any negative effects. But, now I’m considering adding wider (and, possibly grippier) tires. Also, adding a bit of negative camber, (per Eric’s advice). This will increase grip beyond factory specs. It seems like the ideal scenario would be to have the nannies tuned to align with the extra braking and grip.

    Questions:
    1. Does adding grip and braking capacity increase risk of the car being thrown off balance IF the nannies kick in?
    2. Does the computer need to be tuned to essentially tell it the car has more grip and braking capacity? (If so, how / where can I get that done?)

    As always, I appreciate you sharing your experience and insights.
     
  18. JeffV8

    JeffV8 TMO Race

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    0DBAA2A1-B023-400A-8F3D-9D514B37C6D5.jpeg 372BBD47-D2B9-46B5-A2D3-A000D4C26313.jpeg I have Apex EC 7 ET52 with 305 on all 4 corners. I have 1” spacers on front. I did rub the left front because I hadn’t put my MM camber plates on until to late. Plus I have eibach sportline springs. With stock or fords lower springs it wouldn’t have hit the fender.
     
  19. SavetheManuals

    SavetheManuals TMO Intermediate

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    I wouldn't worry about the nannies too much, at least with respect to stickier tires.
    ABS is calculated by wheel spin so that will effectively take the stickier tires into account. S197s eventually need the Boss 302R ABS module when they move to wide slicks but I'm not sure about S550s. I haven't had any issues on 275 NT01s.
    Stability control shouldn't upset the car unless you are doing something dumb like full throttle while turning and then over-correcting, which is how most Mustang videos happen.
    I would recommend using Sport mode on the track until you are very comfortable with car/throttle control and feel it actively slowing you down (assuming you are still in control and it is not just doing it's job).
    I'm pretty much always at the limit of the car/tires on the track but I still mostly use sport mode and rarely feel it interfere as long as I'm reasonable with my throttle inputs.

    Back to tire recommendations for you, I would also look into the Bridgestone Potenza S007A, basically the replacement for the RE11. Myself and a few others have just gotten these tires and so far they have been great, especially since they cost a lot less than the PS4S and should do better at the track. Hankook RS4s sound like a good option for you too, but the sizes are limited right now. Depends on your track/street priorities.
    275/40s on 18x10s are a great fit.
    Here's my initial review on the S007As:
    https://trackmustangsonline.com/threads/bridgestone-potenza-s007a.14234/#post-210591
     
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  20. AustinGT350

    AustinGT350 TMO Intermediate

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    Squared 275s are a fantastic fit for a stock S550. It made my car significantly more neutral but it still had a tendency to understeer so I frequently ran 2 psi higher out back.
     
    Last edited: Nov 27, 2018
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