Track, hot & cold pressures?

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This topic contains 12 replies, has 9 voices, and was last updated by bobcat bobcat 7 months, 1 week ago.

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  • #66769
    Simon Evans
    Simon Evans
    Participant

    United Kingdom

    Posts: 16

    I’ve got an open pit lane day at Silverstone next Monday.  Just wanted to know from anyone who’s tracked the car on the Michelin PSS’s what pressure they found worked best?

    #66772
    mart
    mart
    Participant

    UK - Wales

    Posts: 153

    Well it’s supposed to be 41F 38R

    after about 15 -20 minutes full on, it started to squirm about a lot once the tyres were red hot. I thought they were going to grow warts on them.

    I’ve got nitrous oxide in them, which makes the pressure more stable.  It hadn’t changed when I came in and checked them.

    I reduced them all by 7psi

    34F 31R

    felt a lot better, but found by only doing 15 minutes track time was better for the tyres.

    All the rain groves in the tyres had peaked over, they looked like sicks after I came in. But a quick scrub on a normal road, they were back to normal.

    Ive done 3 full track days and the tyres could probably do another 3 before there bald.

    Its all personal choice on pressures, as to what you feel comfortable with.

    Go out, do 15 minutes, 29 max.

    Then come in and test the pressures.

    You may need to drop them down, because they expand quite a lot.

    Hope this gives you something to go on.

     

    #66773
    mart
    mart
    Participant

    UK - Wales

    Posts: 153

    Sorry meant 20 minutes max.

    Sausage fingers on my phone keypad lol 😂

    #66774
    Simon Evans
    Simon Evans
    Participant

    United Kingdom

    Posts: 16

    Thanks for reply Mart, I’m hoping you mean Nitogen rather Nirous Oxide. One being inert & the other being an octane booster. 😉

    Did you check what the 7 psi off cold gave you after a few laps?

    I didn’t bother altering pressures when I went to Nurburgring as had enough to worry about trying to remember my way round, but by halfway round handling did get a bit iffy.

    Think I’ll start by knocking a few psi off then checking hot pressure after a few laps.  Tyres have done 8k with a few adventures so this should finish them off.

    #66779
    mart
    mart
    Participant

    UK - Wales

    Posts: 153

    Nice one. Hope you enjoy it.

    I did mean nitrogen lol 😂.

    Yep the tyre pressure remained constant,  41 and 38 is definitely too much for track, when I get my car back I might just try 30 all round.  I’m booked in on the 27th at oulton park. Hopefully it will have bedded in by then, but what best place to run an engine in.

     

    I would love to try the Nurburgring in an RS

    done it on a fireblade.

    #66786
    rampant
    rampant
    Participant

    UK - England

    Posts: 399

    If it were me I’d start with 38F/36R, do 1 warm up, 1 fast and 1 cool down lap, come back in and then check pressures. Then adjust from there to ensure they don’t go above the recommended road pressures.

    I’d also aim to do no more than 5 hot laps and 1 cooldown every time out to keep temperatures in check.

    Yours Aye

    Mark H



    // ’17 Nitrous Blue // Forged Alloys // Michelin Super Sports // Painted Calipers // Sync 3 // Lux Pack // Winter Pack // Black Gel Spoiler Badges // Blue Gel Wheel Inserts // GTechniq Liquid Crystal // GTechniq Alloy Armour // sold Jun ’18

    #66877
    Simon Evans
    Simon Evans
    Participant

    United Kingdom

    Posts: 16

    Kept an eye on the pressures after every run, found 36psi (hot) worked pretty well for me.

    Ran for 20 mins at a time, didn’t have any fade or overheating issues either thankfully.

    #66884
    71-bda
    71-bda
    Participant

    UK - England

    Posts: 5548

    30 psi at the front will have you taking the paint off the rims as the front tyres roll off on the bends!!



    No nothing.

    No Mods. No rockers. Just a chunky knob.

    No tackiness.

    Std as Ford intended, but with a space saver wheel and jack and nuts and wheel brace. oh.. and flaps, a man has got to have flaps.

    Innit?

     

    #66891
    hillman998
    hillman998
    Participant

    New Zealand

    Posts: 59

    Don’t start off too low or to high.

    An idea which I have found useful is to go out with the tyres as per the manual do a few laps and come in and measure the pressures, assuming they will have heated up, reduce the pressures down to the starting pressure and go back out and see if it feels better.  This will provide a starting point and let you know if the pressures should go up or down.  At the end of the day if you don’t have a tyre pyrometer, time to do testing and adjustable suspension you are just going to get a best compromise and will need to do the rest by trial and error until you feel comfortable.  I found doing the above gives between 34 and 36 psi when cold varying from front and rear left to right depending on track temp, the circuit direction and number of laps.

    Don’t forget to adjust the pressures for the drive home they will not be even (and they could be low enough to upset the sensors when cold) and rotate the front and rear tyres after each track day.

    The limited camber and the front end weight means that the fronts do get very hot and you need to spread the heat cycles and wear on each tyre if you want them to last more than a few sessions.  Generally speaking I have found that after aggressive driving the front outside edge starts to melt after a few laps irrespective of the tyre pressure used and this has the greatest impact on handling causing under steer as the tyre edge overheats.  The only solution to this is to fit coilovers and add -ve camber, but that is for track cars.

     

    #67608

    Ger Mc Namara
    Participant

    Ireland

    Posts: 4

    If you Google for “Pierre Chaput, Developer for MICHELIN Pilot Super Sport and MICHELIN Pilot Sport Cup 2 tyres for the Ford Focus RS”. You will find some good information, in particular a 24 page .pdf on the PSS and Cup2 tyres, pressures for track days and how to interpret inside, middle and outside temperature differences across the tyre. I’d post the .PDF here, but I don’t see a way to add an attachment (only an image)

    With either tyre, the hot pressures recommended for the RS are 36psi all around and the operating window for the tyres is 72°C-104°C. Make sure you measure temp with a contact probe as the IR probes only read the surface and that will be lower than the actual tyre temp by the time you get a cool down lap in, stop and get measuring temps.

    Note for other cars using PSS and CUP2 hot pressures are in the 32psi to 36psi range. Generally the pressure will be lower the wider the tyre and or the lighter the car.

    I drive to the track with the usual 40/38, then drop to 30psi cold and build up the speed during laps 1 and 2 and then roll off 4 or 5 hot laps depending on how cold the track is. Chances are the pressures will be up to 36psi or higher + each tyre is likely to have different psi’s at this point depending on whether the track is clockwise, anti-clockwise, has more high speed long left handers vs slow short right handers etc.

    In any case get them all to 36psi before there is any significant cooling and repeat the process above. 36psi may sound high, but the RS is heavy compared to a striped out track specific car and the tyres are not super wide. You can try a few psi more or less and see how it goes, bit more on the front, but less on the back and vice versa, all good fun seeing how it changes the handling.

    Looking at the inside, middle and outside tyre temps on each tyre will help indicate if the tyre pressures are good as well as providing some insights into the camber and how suitable the normal settings are for the track you are on.

    Note: The tyres should be fine starting at 30psi. Michelin say to never run below 20psi cold as the tyre will unseat. They talk about starting with cold pressures as low as 25psi.

     

     

    #67756
    kr1s
    kr1s
    Participant

    UK - England

    Posts: 206

    Brilliant advice.

    Thank you.

    #106749
    motelec
    motelec
    Participant

    Mexico

    Posts: 3

    Do you have the pdf of 24 pages ? i cant find this pdf on google. Only a 4 pages pdf with little information.

    thanks.

    #106757
    bobcat
    bobcat
    Participant

    UK - England

    Posts: 5298

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