More tire stuff..try to look excited!!!

Discussion in 'Rob's Garage' started by blacksheep-1, May 20, 2017.

  1. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    OK, here goes....I wrote this for an FB page, but it's hard to research stuff their. Plus I was banned from a page for (I guess) speaking heretically about one of their heros. In any case, here's the article.

    Hot target 28.5 to 29 psi
    172 194 205 219 123 164
    psi 29.1 28.9

    29.1 28.8
    185 213 196 176 192 168

    Ok, as I was trying to point out someplace else, this is a good example of predictive tire pressures. 28.5 was the max low, 29 the max high, after 20 laps on a road course. Over 30, the tire gives up. These pressures are spot on.
    Why is this important to the casual track guy?
    Because, especially in a bank type of situation, or even a track like Laguna Seca, you can have a catastrophic failure.
    Since I know many of you, and would like to keep knowing you for awhile longer, I thought I'd write this article.
    Basically, this is called pressure mapping, and we've discussed it before on TMO. Get a notebook ( a very large one) and write down the track, date, time, track temp and air temp, then the start psi.
    Run the car for x amount of laps, check the psi and raise or lower it to meet your hot target goal.
    Do this for every session and write it down.
    At the end of the day you will have a " map" showing the temp of air and track, it's effect on hot pressure and a predictable ( rate of rise) for that track.
    Congrats, you have created your first " map".
    Now do that each day, when you go to the next track you have a ballpark place to start your pressures, although the rate of rise will be different for every corner of the car, and every track.
    You will also have to figure a "factor" between ambient and track temp, and that changes with every brand of tire.
    If there's one thing I can stress is that cold pressures (as long as the tire is inflated enough to stay on the wheel) is meaningless, it's the hot PSI that counts.

    With regards to cold start pressures.. you let the hots establish the colds. As an example you put x amount of air in the tire at 8AM at Road Atlanta with 70 ambient 80 track and you add or subtract pressure to get your target max. The next day....if everything is the same . The cold pressures are already established, just write them down for future reference. This will also give you a rate of rise...which is pretty much a constant at a particular track

    So now you have a " map" of a particular day evolving from morning to evening, track temp, ambient and number of laps over several days. This should give you a fairly constant " rate of rise" for that track and that setup.
    So let's say, on the last day a cold front comes through and the temps drop 20 degrees, the start pressures are no longer valid....or are they?
    Go back to your rate of rise numbers, they will give you your hot PSI based on a specific psi. Just run those numbers backwards to get your starting psi for the new day.
    Now those numbers will not be perfect, but after several weekends you can plot a graph based on the temp (s) and come up with your factor to predict psi / temp.
    So, as an example..you know from several days that the RF will rise 10 psi over the course of 10 laps. So, it would be reasonable to assume it would be about the same from whatever psi you put in the tire RIGHT NOW, after the cold front came through.
    Example 2. Over a period of 5 track days, taking careful records of ambient/ track temps you notice that the tire pressure is affected.( Let's say...they're all different) .8psi/10 degrees. So, if the temp dropped 20 degrees overnight and the tires were left alone overnight, you would expect those tires to be about 1.6 psi lower than if the temp stayed the same. (as the day before)
    So.....you would add 1.6 psi to the RF tire, and hopefully, if you did it right, those numbers would be backed up by the rate of rise numbers.
    Simple...right?
    So to recap...if you get lost due to a temp change, you have 2 ways to recoup, that should back each other up.
    1. The predictable rate of rise numbers that will tell you how many psi the tire will gain over time
    2. The psi/ temp " factor" in this case .8 x 20 degrees equals 1.6 that needs to be added.
    Take the temp derived psi number,add the rate/ rise number and you should get really close to the predicted hot PSI.
    I'm warning you..there will be more..lol
     
  2. VoodooBoss

    VoodooBoss Rick Moderator

    Messages:
    17,302
    Likes Received:
    404
    Joined:
    Nov 30, 2010
    Location:
    90 Miles East of Sonoma Raceway
    LOL how do you get banned from a FB page?

    Great article and we all appreciate your efforts to keep us safe!
     
  3. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    I had some "yo" that has contact with that particular FB page try to hijack my thread, too much drama, but in retrospect TMO should be getting an influx of subscribers.
    Funny thing is, a bunch of guys I didn't even know called them out on it..lol
     
    OPMustang Tim and VoodooBoss like this.
  4. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

    Messages:
    7,030
    Likes Received:
    299
    Joined:
    Dec 6, 2010
    Location:
    Arizona, USA
    Very odd circumstance. Came back from a busy week at work to this instance and had to figure out WTF happened.

    Anyways excellent info and this is of course always welcome here on TMO!
     
  5. captdistraction

    captdistraction Not necessarily the Stig

    Messages:
    955
    Likes Received:
    148
    Joined:
    May 16, 2012
    Location:
    Phoenix, Az
    This was the kind of tech that wasn't welcome there (in unsaid group). Glad to see it here, definitely altering some of my data sheets to take better advantage of this info.


    Sent from my iPhone using Tapatalk Pro
     
  6. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
  7. OPMustang Tim

    OPMustang Tim TMO Advanced

    Messages:
    144
    Likes Received:
    67
    Joined:
    Jul 9, 2016
    Location:
    Sunny Florida where it does not snow.
    It's too bad you still don't know what you are talking about. Tire pressures are all over the place, you should be using thermal imaging in real time because you are losing seconds a lap because wins don't matter o_O
     
  8. captdistraction

    captdistraction Not necessarily the Stig

    Messages:
    955
    Likes Received:
    148
    Joined:
    May 16, 2012
    Location:
    Phoenix, Az
    did someone say thermal imaging in real time?

    [​IMG]

    Just open your wallets and the data will come, lol.
     
  9. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    The Porsche has telemetry, and you can "see" the car all around the track, (both temps and pressures) when the tires spin, when there's a long corner, problem is what do you use as a baseline, the temps are all over the planet? in the end, it comes down to pit lane pressures because they are a constant. gathered at a particular point and time.
    You could "snapshot" the telemetry but that only gives you one millisecond of data, what about the rest of the track?
     
  10. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

    Messages:
    7,030
    Likes Received:
    299
    Joined:
    Dec 6, 2010
    Location:
    Arizona, USA
    I was thinking a while back about the real-time imaging stuff, it could be useful to help trigger a couple idiot lights to indicate a certain tire has exceeded its temperature limits while driving on track (indicating need to back off a little)...but at the same time that should be clear to the driver by the behavior of the car. Probably more effort than it's worth.
     
  11. captdistraction

    captdistraction Not necessarily the Stig

    Messages:
    955
    Likes Received:
    148
    Joined:
    May 16, 2012
    Location:
    Phoenix, Az
    also, these types of sensors and the can loop needed are in the 4 digit cost territory. Not something for the "average" racer budget. Maybe Cali club racer budget, but not enough value for me.
     
    ArizonaBOSS likes this.
  12. TMSBOSS

    TMSBOSS TMO Addict

    Messages:
    2,769
    Likes Received:
    161
    Joined:
    Aug 23, 2011
    Location:
    Illinois
    If you can't adjust in Real Time, is there much return on investment?
     
    ArizonaBOSS likes this.
  13. Gab

    Gab Bullitthead

    Messages:
    20
    Likes Received:
    2
    Joined:
    Feb 8, 2017
    Location:
    Greenwood, IN
    I think so. If you plot temps over the course, you can see where on the course tires are over/under target temps/pressures and make adjustments - if not in tire pressures, then in steering/throttle inputs.
     
  14. TMSBOSS

    TMSBOSS TMO Addict

    Messages:
    2,769
    Likes Received:
    161
    Joined:
    Aug 23, 2011
    Location:
    Illinois
    I don't mean to start an arguement but, just a guess. Warmer in braking and turns and cooler down the straights.

    Could be an addition to instrumentation but as mentioned earlier, a bit expensive for the average track rat.

    Receiving feedback while driving? Not the best idea.

    Still, a neat idea. Just not in my budget.
     
  15. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    The telemetry in the Porsche is stored, so we can combine that with steering angle, Gs, acceleration, braking and all the other misc crap that a modern race car can tell you. Even if the tire hits max temp, only for a moment, you live with it if the car is acceptable every place else on the track. the Porsche, and I'm sure the mustangs as well, hit max temps at several different points on the track..say the outer edge of the tire, on a banked track, but if it's not excessive you don't worry about it, and that can only be measured with F1 technology for now.
    The Porsche stuff just tells the air temp inside the tire, not at the tread level. and there is constant debate over which is more important, tread or air temp. IMO the air temp provides more of a constant, although, I'm sure you don't want any massive temp spikes on the tread either. In any case, we go by across the tread temperature measurements and hot psi as measured on pit lane, then just keep and eye on the telemetry during the session to make sure nothing weird pops up.
     
    VoodooBoss likes this.
  16. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    Yeah, then run a daylight practice session and a race that goes into the night and you can really see how insane that gets...massive pressure changes..talk about fudging the numbers just because you have to ..lol
     
  17. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013
    if it weren't for the /.';/&$% slip angles..
     
  18. cobradave

    cobradave TMO Intermediate

    Messages:
    10
    Likes Received:
    1
    Joined:
    Jul 15, 2016
    Location:
    Arlington, WA
  19. cobradave

    cobradave TMO Intermediate

    Messages:
    10
    Likes Received:
    1
    Joined:
    Jul 15, 2016
    Location:
    Arlington, WA
    Please out 3rd 6s I am ata day ts'az deface deface 4ra

    Sent from my SM-G930P using Tapatalk
     
  20. blacksheep-1

    blacksheep-1 TMO Addict

    Messages:
    1,220
    Likes Received:
    83
    Joined:
    Mar 12, 2013

Share This Page