Dynamic camber logging bug solved. Observations.

Discussion in 'General Discussion' started by Lgel, Dec 21, 2016.

  1. Lgel

    Lgel Registered

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    I personally ran ISI and URD cars with much lower camber values than default (front -1, rear 0.8), in order to obtain a better spread of temps across tire.

    I ran the URD AM at Sebring and I have seen that the low static camber values in garage translate in much higher values under cornering loads (from -2 to peaks of -4 in front).

    Why, when using those low static values I was obtaining a better theoretical use of the tire is not so strange anymore for me.

    Whether those camber values should vary in such proportions under load is another question.

    Cheers and happy new year.
     
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  2. Lgel

    Lgel Registered

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    What did I find strange?

    The huge difference between default values of camber in most default setups and those, that based on distribution of tire temps I was using (I, may be wrongly, suppose that the outside of the thread of the loaded tire in a car, is subjected to more effort than the inside, due to weight transfer, and roll, hence the need of camber to maintain thread parallel to the ground).

    In my understanding of how a tire works, camber is used to better use the thread when cornering, one indicator of lack of camber being abnormal degradation of the outer part of the tire when cornering.

    In fact an unloaded tire should have positive camber to have more traction.

    Camber is a balance between cornering, braking and traction requirements, in touring cars, default camber is too low for strong cornering loads, but higher camber would eat tires very fast when driving in normal conditions (low cornering loads and lot of straight driving).

    In F1 excessive camber has been used to maintain tires hotter in straights and help them rise quickly when braking and cornering.

    With the default values of camber on many cars in RF2, I saw temps of loaded tire (outer, center, inner) raise in paralell when cornering (inside of thread still hotter than outside).

    With lower camber values, I saw outer temps of loaded tires rise quicker than inner, resulting in a better spread of heat across tire (should mean better traction and less wear).

    Had many private discussions with other sim drivers that didn't share my views (they may be right, but where never able to sustain their views with facts, only with feelings).

    The fact that a suspension geometry is designed to increase the camber of the loaded tire, seems very efficient (avoids using excessive camber when braking and accelerating).

    Feel free to correct me.

    Cheers.
     
  3. Lgel

    Lgel Registered

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    Please read again my first post.

    I was surprised to see that much lower camber values than default worked better for tire temps (tested with ISI C6R GT2 and URD cars which have proven physics in my view).

    When I had access to dynamic camber values I understood why those low values worked, being able to read dynamic camber is a great help for tuning purposes.

    So the question that remains - what I find odd - is why put excessive camber values in practically all default setups, that result, in my view, in a strange thermal behaviour of tires ?

    On many cars those low cambers values help improve thermal behaviour but are not enough, on the contrary with the URD C7R I found near perfect tire temp behaviour (in my view, that could be wrong).

    Please could you try if you have a moment what I describe - same setup, differing only by default camber values or (1.0 front, 0.8 rear) - and confirm or discard my findings based on Motec readings with ISI C6R GT2 or URD C7R? .

    By the fact, I suppose that a joint too stiff between thread and wall of the tire would also contribute to those strange temps distribution across thread with default camber values.

    Cheers and happy new year to all.
     
  4. 64r

    64r Registered

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    In the sim racing world a lot of people seem to set their camber values based on tire temperature spread. In theory this is a good idea, in the real world though if setting the camber based on temperature, the target temperature spread changes based on the car position on the circuit, eg straight, corner entry/exit etc.

    For example, in the F1 world Pirelli set a min/max camber range, this is based on the temperature of the inner edge tire temperature at the end of the main straight to prevent everyone running large amounts of negative camber (which causes massive loading and excessive temperature on the inner side wall). While the F1 teams all have thermal cameras and a range of TPMS equipment, the main application of these is tyre modelling, not specifically to set the camber to achieve an even temperature spread.

    In the FWD racing world, rear camber is often set to help loose rear grip, for example the current BTCC racing cars run about 6/7 degrees negative camber, and the current spec Clio Cup cars run about 8! degrees negative camber. The reason for these large amounts is because FWD cars generally have far too much rear grip, by running large rear cambers (and large pressures 1.4 bar front, 3.6 bar rear) the idea is that the rear tyres are only touching the ground on the inner 30mm or so of tyre, and thus reducing the contact patch (and grip) at the rear of the car. When taking thermal measurements across the rear tyre, the spread can be as large as 60/70 degrees. For the front tyres, the camber is usually set to obtain the best traction on corner exit.

    So while looking at the tyre temperature spread can be helpful, you may want to start focussing on key acceleration areas of the driven tyres to get an understanding on the influence of camber, rather then trying to achieve a nice tyre spread around the circuit.

    upload_2016-12-24_12-42-4.png
     
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  5. Lgel

    Lgel Registered

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    I should have indicated that I only focus in obtaining temp spread across tire under cornering.

    Not being able to evenly heat tire while cornering with default camber setup could indicate that you are using a trick similar to the one you describe on FWD BTCC cars to reduce the contact patch which isn't the goal you are looking for...

    Do you suggest that the default setup of the ISI C6R is using the BTCC trick to reduce the front contact patch and increase understeer to avoid loosing easily rear end?

    Cheers.
     
    Last edited: Dec 24, 2016
  6. 64r

    64r Registered

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    It's been a few years since I had to setup a RWD touring/saloon car, I'm not suggesting that the ISI C6R has been setup to increase understeer, although it is possible that is the case. A bit of time spent with some data analysis tools (MoTeC etc) would help identify if this was the case.

    If I had to setup a real world C6R today without knowing anything about the car and I knew I was working with a professional driver, the rough order I would do things are:
    • Speak to the tyre support engineer and get a rough idea of ideal cold/hot pressures and set the baseline pressure to whatever the recommended value is
    • Set the car up with front => 2mm toe out, 3 degrees neg camber, middle ride height and middle spring choice with middle settings for the dampers, rear => 1mm toe in, 2 degrees neg camber, middle spring and damper clicks
    • Get the driver to do multiple runs of 5 laps (in/out 3x timed laps) recording start/end temp and pressures and recording every change and driver feedback between each run.
    • For each run I would only change 1 thing, eg front ride height
    • For each change I would make a large step change to get a quick feel for the change, eg +10mm front ride height change, or +5 clicks low speed bump on the damper etc.
    • Every 4 runs or so revert back to the first baseline settings for comparison
    • By the end of the day most of the basic settings would have been tested (eg front/rear height up/down, tow in/out, camber +/I etc) and a basic feel of the setup direction would be achieved.
    Of course this is a massive over simplification but is generally how any new racing car is setup. It's quite often normal for 2 or 3 times a year to repeat this basic setup iteration, it's kind of like a blind test to confirm that any setup direction is still valid. One of the key and critical components is the driver, it's important to have a driver that can drive the car consistently and provide good feedback, a lot of drivers tend to adapt and drive to a setup, which is not what testing is about.

    Sorry, I have drifted way off topic here, I guess what I am saying is that I suggest you spend some time testing what works for you, the default ISI values are probably derived from some team supplied baseline configuration, and of course your ideal setup will evolve and change as you understand the car further and of course with different track layouts, surface types, air temperatures, grip level etc. If it was as easy as getting a single setup and using that I would have a lot less grey hair :).
     
    Last edited: Dec 24, 2016
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  7. Lgel

    Lgel Registered

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  8. Slamfunk3

    Slamfunk3 Registered

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    The reason I see for using more negative camber is to help the tires last over a full stint. Yes less negative camber will give you more grip and better temp spread over a short stont, like qualifying for example. But over a course of a long stint all the little mistakes as well as tire wear itself makes the outside of the tire more susceptible to abuse. By having a safety margin built into your setup you sacrifice ultimate pace for longevity. I think this is one of the main reasons the rF2 tire model excels over any other.
    TK
     
  9. Lgel

    Lgel Registered

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    Do you have facts to sustain your claim? Motec comparisons of long runs with different camber settings?

    How, if as you say "the rF2 tire model excels over any other" having constantly less rubber in contact with the road (which translates in high temps of inner and center part of tire, outer part remaining cooler) help preserve your tires?

    Do you agree on the fact that less rubber in contact with the road should mean less traction, braking force, lateral grip?

    So, how can having less rubbber in contact with the track ( outer part of loaded tire not doing it's fair part of the job) help you in avoiding "all the little mistakes"?

    Sorry I don't buy your explanation.

    Cheers.
     
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  10. TJones

    TJones Registered

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    I can't escape the feeling that the temperature meassure points (inner/outer) are to close to the sidewall, close ore even in the radius, which is part of the tread btw.
    This would at least explain this tendence of overflated tyre readings, and very low outer temperature.

    Another point we should took care about, is the temperature readings shown in the garage are surface temps (AFAIK) and therefor fluctuating a lot
    . Outer meassure point on the fronts are usually cooling down a lot on the straight for example. Just a few tenth of a milimeter under the surface the temps are higher and far more steady. Touch probe's, often used in RL motorsport other than IR-sensors should give more steady results, because you push the probe a few tenth into the tread (without damaging the tread of course).

    @Lgel: You may also take a look here: http://www.trackhq.com/forums/tires/
     
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  11. 64r

    64r Registered

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  12. Boldaussie

    Boldaussie Registered

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    One way to work that out would be to compare those suspensions against your Apex cars and see where the differences lie perhaps?

    Merry Christmas
     
  13. Lazza

    Lazza Registered

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    It could be aimed at making the default setup more stable, sure.

    You referred to lower camber leading to the outside of the tyre heating up more during cornering, which made the temperatures (during cornering at least) more balanced. If the outside of the tyre is heating more quickly than the inside, it would suggest the tyre (not wheel) effectively has positive camber at that time. Camber thrust would be pushing you off the corner rather than keeping you on it. Performance wise it would perhaps be better for the load to at least be more even, even if that means the inside is running hotter on average?
     
  14. Boldaussie

    Boldaussie Registered

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    The usual idea of more negative camber is to sacrifice a small amount of braking grip/traction loss, for a larger contact patch when cornering and therefore lower lap time.
    This is from cornering grip gain overall from cornering forces causing roll and suspension droop due to loading which is why negative camber is required in the first place. How much is sacrificed and gained is entirely car/track dependent.
    Over longer distances the core tyre temp rises and not having enough negative camber definitely leads to unwanted tyre overheating.

    In the real world too much negative camber causes tyre blistering and ultimately tyre failure. It can be used as much as it is now due to the newer tyre model which has far more sidewall flex eg radial type tyre, which allows more rubber on the ground even with seemingly excessive negative camber. I have yet to test for myself camber gain loss on track under varying conditions. It will be interesting. I'll now know for sure then if my suspensions are actually working as I have intended them to and appear to via tyre temps alone up till now.
     
  15. Lgel

    Lgel Registered

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    With lower camber settings I used, it was only during cornering that the outside of the tire was heating more quickly than the inside (leading to a better balance of temps on corner exit), and only for the loaded tire. The inside of the tire is still running hotter on average on the whole lap.

    By the fact it is quite normal that the inside of the unloaded tire to be hotter than the rest of the tire, as camber should be positive for this wheel (lowering camber reduces this fact).

    And I tend to prefer objective data to driver feelings, that is why I am a great fan of your plugin.

    @Paul Loatman
    I agree with you whan you say "I make sure the front vs rear temps are balanced".
    Lateral distribution of temps while cornering is a refining I do after finding a good balance for the car, by checking Motec data concentrating on the reading of the most important curves of the track performance wise (in some cases avoiding killing tires too quickly on certain murderous curves).

    @Boldaussie
    The basic idea of camber is to maintain the thread parallel to the road under cornering forces induced by weight transfer and body roll.
    Camber is a balance between contradicting requirements, too much camber is as bad as too little camber - by the fact you are interested in dynamic camber - (now reported to Motec reason of my original post), which is consequence of static camber, ride height, roll, suspension geometry and stiffness, etc.) not the static camber you read in the garage.

    It as simple as this, with too much camber you run more on the inside of the tire, to little camber you run more on the outside of the tire while cornering. In straight line unless very special considerations (in F1 to avoid tire cooling too much) no camber would be optimum for traction and braking.

    The least camber you have on the unloaded tire the better, but the unloaded tire is less important than the loaded tire for overall grip while cornering.

    As 64R stated, excessive camber is used in FWD cars on the rear end, to reduce contact patch of tire, reducing rear end grip and disminishing understeer of the FWD car.

    If you distribute cornering loads more evenly across thread, you avoid local overheating of tires, and should reduce tire wear.

    Cheers and happy new year.
     
  16. Boldaussie

    Boldaussie Registered

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    As an aside. Most mods are running antiackerman ( track dependent if beneficial also ) which alone should reduce the inside edge temp/wear on the unloaded inside tyre and in association with steering axis inclination and caster, in theory giving more positive camber to the unloaded tyre reducing inside edge tyre temps. I have yet to see this effect of caster correctly emulated/simulated in sim and is another reason why I am interested in results from future testing now that camber is read via plugin.

    My interest is all things suspension as it is my area of interest in work and in play. Any extra tools are beneficial and welcome.
     
  17. T1specialist

    T1specialist Registered

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    I'd also imagine the car can run lower in btcc if you add camber. It allows you to use wider track width and lower ride height (because the tires can fit inside the fenders and have some suspension travel as well). Spec series like btcc are not good example of camber (or any physical aspect of suspension design) because the cars are so limited by rules that to get the last hundreths out of the car performance one needs to do things that some of the stuff they do is just completely nuts until you work out why they did it.
     
  18. Lgel

    Lgel Registered

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    I just tried the last version of GPfan M6 GT3, after a quick tuning (playing also with tire pressure) I found a very good behaviour of tires with 2.0 camber in front and 1,8 rear.

    The car is a pleasure to drive, I can't believe that this an error from the modder.

    Particularly interesting is following the evolution of dynamic camber in the same turn of loaded and unloaded tire.

    Cheers.
     
  19. TJones

    TJones Registered

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    I suggest you also try the new Nissan GT500, to me it looks like the carcass is more flexible compared to former GT cars.
    For example after a fast right hand corner you now have higher outer temperature on the front left tyre, and this with -3.5° camber. Dont think this was already the case with older cars like the Cr6.
    Overall temperatures are also higher in generall. A good step in the right direction IMO.

    Agree the M6 GT3 is a pleasure to drive. :)*

    Edit: I mixed things up a bit, the sentence above is related to the GTLM version. Just drove the GT and this car looks very much out of balance to me. I had to make several changes to get rid of oversteering , lap times are still off though.:confused:
     
    Last edited: Dec 25, 2016
  20. Slamfunk3

    Slamfunk3 Registered

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    I think you're making this exercise way to rigid for yourself. I clearly stated that I believe in sacrificing ultimate pace for longevity. So yes i agree that having less rubber in contact with the road means having less traction. But the point is over a full stint (around an hour or so for most GT cars) nothing remains as it was on lap 1. You say you tune for even temp spread across during cornering. But if we take Suzuka as an example then which turn do you use? They're all different corners and most importantly they're all different sequences of corners. If you set up for a perfect temp spread in turn 1 then by the time you get to the last right hander of the esses your LF tire will be overheated. That's my point about a safety margin. Not to mention that if you tune for quicker heating of the outside of the tire on laps 1-5 then by lap 30, with less tread rubber to dissapate that heat, you're gonna overheat the outer edge. At that point tire dropoff just gets worse and worse.

    Unfortunately i do not have any motec data to back this up directly. And even if i did the variations of tracks, driving styles and the 3 different types of tire temp readouts it would still be hard to make a 100% argument proof conclusion. I'm sorry you dont see value in driver feedback but as we all have differing driving styles that's what we have to rely on. Telemetry is not the end all be all. During a major rule change season, as next year is for F1, even they are putting huge stock in having an experienced driver at each team to help them adapt by having reliable feedback.

    And just to finish up, the reason i said i enjoy the new tire model is that it gets rid of a "perfect setup". As in real life there is no such thing. Even Nascar teams can't setup a car to run perfect for a lap. And that's only 4 turns in most cases (really just 2). I think the real issue is you're convinced there's a problem because things don't react in a static manner like you would like them to. Meanwhile everyone is telling you there is nothing static about how a tire works.
    TK
     

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