Tire PSI - Page 4


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Thread: Tire PSI

  1. #31
    Senior Member kiryu's Avatar
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    Re: Tire PSI

    Quote Originally Posted by Scott-AhlmanPerformanceLLC View Post
    I just verified with the Audi dealership (and was fairly certain) that mine is a standard V10 - not a plus. Engine code BUJ. My sticker and owner's manual say 45/41. The sticker is mandated to be "right" by NHTSA. I am not sure on the owners manual and don't understand the contradictions you guys are noting...especially if the manual came with the car. Its not that I don't believe the contraction you guys are seeing it is just that the tire pressures are a big deal and seems like a big "miss". The door jamb numbers should supercede all.

    The event that is hardest on the tire and builds the most heat is speed. By far. 150 mph plus for any length of time and you are building serious heat in the tire. Depending on the oval our infrared tire temps go down in the corners...

    So my judgment is that Audi found over time for the more "normal" R8's and usage that they could get away with lower pressures and bias toward ride in more recent years. And left the pressures at the high for the Plus and GT models as they were more likely to see high speed. Not fact, but my best judgment.

    I will run the lower pressures this weekend to get a feel for the difference now that I have the PS4S's on the car.
    Do share what you find out after dropping the pressures. Many of us are running PS4S as well so your feedback will be very helpful

    Thinking back, my terrible understeer happened for the initial 3 years of my ownership on the old shocks. I recently had the shocks replaced so perhaps that could be why it was understeering. I will try 45/41 again to see if it's actually better. I personally felt the lower pressures makes the car feel more planted, especially downhill with the weight of the car. But then again canyon driving is very different from tracks, there's hardly any straight that allow you to get to above 125mph (except perhaps Ojai hwy 33, with everyone doing 150 and above), so maybe the high pressures are more appropriate for track speeds. I will give 45/41 a try and then 39/36 to match the facelift cars.

    One thing which I find rather odd, which perhaps have nothing to do with the topic, was that when i was doing 45/41, i almost have to re-inflat the tires everytime after 1-2 weeks. It seems to lose air if u do 45/41. When I adjusted them to 36/37, I almost dont have to inflat for a year as the pressure's always constant. Always wondered why this is the case
    R8 V10 (k&n, Kline, VF ECU&TCU)
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  3. #32

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    Re: Tire PSI

    Quote Originally Posted by NZV10 View Post
    My car is a late 2010 V10. The sticker has two different pressures, depending on speed ratings. For below 270 km/h the settings are 39/36 (which is what I set mine at as I have no intention of exceeding that speed)! The 45/41 is for speeds above 270 km/h. The geek in me of course smiled at the fact that technically, there appears to be no guidance for correct pressure if at exactly 270 km/h...

    Attachment 236568
    Yep we did this in the '05 FGT...except we said 150 mph...this is 167mph. (forgive me for the english unit...even us automotive guys in the US use metric...but hard to get away from MPH, lbs, psi, etc since I don't have a good feel for many metrics.

    They must have decided to stick with the one higher pressure to cover all speeds in the US (our litigious country), but recently with a lot more experience and I am sure testing was able to show lower was OK even at high speed.
    2012 Audi R8 | V10 | Manual | AWE Exhaust | Carbon Blades | Carbon Engine Bay | Tuscan Brown Interior 2009 Buell 1125R | Barker Exhaust and ECM Tune | Michelin Pilot Road3's

    Ahlman Performance LLC | Audi R8 Ohlins Coil-Overs | Chassis Development

  4. #33

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    Re: Tire PSI

    Quote Originally Posted by kiryu View Post
    Do share what you find out after dropping the pressures. Many of us are running PS4S as well so your feedback will be very helpful

    Thinking back, my terrible understeer happened for the initial 3 years of my ownership on the old shocks. I recently had the shocks replaced so perhaps that could be why it was understeering. I will try 45/41 again to see if it's actually better. I personally felt the lower pressures makes the car feel more planted, especially downhill with the weight of the car. But then again canyon driving is very different from tracks, there's hardly any straight that allow you to get to above 125mph (except perhaps Ojai hwy 33, with everyone doing 150 and above), so maybe the high pressures are more appropriate for track speeds. I will give 45/41 a try and then 39/36 to match the facelift cars.

    One thing which I find rather odd, which perhaps have nothing to do with the topic, was that when i was doing 45/41, i almost have to re-inflat the tires everytime after 1-2 weeks. It seems to lose air if u do 45/41. When I adjusted them to 36/37, I almost dont have to inflat for a year as the pressure's always constant. Always wondered why this is the case
    Definitely quite possible with the shocks going bad. They have a huge affect on grip.

    Honestly I would tend to run lower for the track due to pressure build.

    I will be making a good ride/handling run on Monday, will use the 39/36 psi pressures and report back, but based on all of your guys experience the lower pressure of 39/36 is probably best in most scenarios. Good call to try both. Lower will surely will be better for ride and rough road grip. I am interested to see to what happens to my steering feel and response as well smooth road grip.

    I am guessing the pressure leak down is related to the valve core/TPMS seal at these high pressures, but I am not positive.
    2012 Audi R8 | V10 | Manual | AWE Exhaust | Carbon Blades | Carbon Engine Bay | Tuscan Brown Interior 2009 Buell 1125R | Barker Exhaust and ECM Tune | Michelin Pilot Road3's

    Ahlman Performance LLC | Audi R8 Ohlins Coil-Overs | Chassis Development

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  6. #34
    Senior Member Trev450's Avatar
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    Re: Tire PSI

    OK - 2010 V10 and my sticker says: 39F 36R. I personally found this too harsh and with decent heat in my PS4S they tended to grain on the outer edges when pushed. I now run 36F 34R and find this more to my liking and kinder on the tyres.
    10 V10 Coupe, Ibis, 6MT, Capristo, Carbon Blades, OZ Ultraleggera HLT's, Maxton Splitter.
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  7. #35
    Senior Member GT#298's Avatar
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    Re: Tire PSI

    Are all of you on stock sizes? If you've gone up a size, or increased the width and/or lowered the aspect ratio, the factory specs are nothing more than a starting point. Who here has changed between 19" & 20", 295/305 --> 325-345, 30 --> 25, etc? If you have a non-stock size, what have you found to be optimum? When you go to a lower/wider profile, do you think the pressures should be more or less than the factory sticker? I welcome all thoughts.

    I'm running 20"s (rather than 19"s), 255/30 front, and 345/25 rear. I started with what the stock sticker says, 45/41, and then brought it down to 42/40. I am going to try bringing it down a little more, to 40/38. I don't want to go too low because these tires are so short and wheels are expensive. I'd like to see some other pressures for after-market sizes.

    BTW. . .The rear tires aren't necessarily lower in pressure when they're warm. There is a higher volume of air in the rear tires, which expands more when the warm up.
    Last edited by GT#298; 06-16-2019 at 11:29 AM.

  8. #36
    Senior Member classba's Avatar
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    Re: Tire PSI

    I run my regular 235/305 36 psi all round and on the Trofeo-R's I run them 32F/34R psi. All are for COLD.

  9. #37

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    Re: Tire PSI

    Hey All,

    I ran the lower pressures of 39/36 psi and completed our full ride and handling evaluation that I can't seem to attach here. This was with the PS4S's and both mag ride modes.
    Tradeoffs as you might expect. Not an easy choice for me with the following highlights.

    Ride - I agree as all of you have reported and to be expected that the ride is a lot better at the lower pressures - in normal mode (primary ride - big rises and dips), secondary ride - impacts and choppiness. However, sport mode is even worse for me at these pressures with the suspension feeling locked up and bouncing on the tire even more. The accelerations in sport mode are very undesirable for me. Actually messes my vision up.

    Steering - in general the R8 lost its steering precision and linearity a lot at the lower pressures with PS4S's. More than I would have expected. I turn in and have huge lag and then big response. Very non-linear for me. This is where Sport Mode is needed and certainly helps a lot compared to normal mode so I now better understand your guys feedback on sport mode for spirited driving...with lower pressures. My center feel was also not as good at lower pressures. The positive steering change that makes sense with lower pressure and this big reduction in steering response is wheel fight. Wheel fight (steering wheel kicking back and forth on the bumps) was considerably better. More than I would have expected. At the recommended high pressures of 45/41 the wheel fight is really undesirable.

    Handling - Yes, I noticed more grip, especially power down, which was good. But I had a harder time predicting and keeping the R8 on the edge of that limit. Further I had to make small corrections through the corner whereas before with the 45/41 pressures I could easily carve one smooth arc. Especially fast sweepers at 60 - 90 mph.

    NVH - Better at lower pressures for vibrations in general and road noise as you would expect.

    Of note, I am on the road (a 29 mile loop through the hills), but pushing the car hard enough through a lot of great corners to raise the front pressures 5 psi and the rear 6.5 psi. Corner exit for me with this Quattro is exceptional in such a high horsepower car. I thought the AWD would just be an advantage in the wet, but I am impressed in the dry and it moves weight forward and down so it is a win win for me.

    So I am quite torn right now on pressures with many contradictions for the road. Higher speed ~70 mph and above on pretty smooth roads I will run the higher pressure. Grocery runs and crappy roads I will run the lower pressures. But I don't feel this pressure adjustment should be necessary. I look forward to getting our Ohlins suspension on the car in two weeks and solve some of these contradictions as the Mag ride in the R8 just doesn't feel right to me in either mode (no leaks). It feels artificial to me. Too soft one second and too harsh the next.

    I should also note this is with 245/35R19's and 305/30R19's. The 245's are better than 235's for front grip but at the same time a hit for steering precision and linearity on the OEM wheel sizes. Next set I may go back!


    ...now to figure out how to post a pdf...


    Scott
    2012 Audi R8 | V10 | Manual | AWE Exhaust | Carbon Blades | Carbon Engine Bay | Tuscan Brown Interior 2009 Buell 1125R | Barker Exhaust and ECM Tune | Michelin Pilot Road3's

    Ahlman Performance LLC | Audi R8 Ohlins Coil-Overs | Chassis Development

  10. #38
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    My 2010 5.2 has 295 rear, 305 was an option. Not sure the effect of bigger DIA rear due to center dif. Maybe increases rearward torque bias and INCREASES understeer at turn in before power on?
    My door jamb sticker is 39f/36r. I run 38/37 to soften front a little. On track, I drop front to same as rear and goes up to Mid 40’s with heat build up. My limited experience (I have a dedicated track Lotus) would suggest 44+/- max on track HOT, more to protect shoulder wear, less to maximize grip.
    I bought Michelin Pilot SS 2 years ago and had wheel alignment done where my friendly dealer did it to GT (I think) spec which has more negative camber and I think less toe in at rear. Understeer all gone on street and track and rear actually steps out slightly at initial turn in when driving fast, but stabilizes immediately. Incredible initial turn in. A little looser than is my preference but VERY fast through corners especially off camber and low speed (Mid Ohio?!).
    Michelin PSS MUCH better than P Zero (grip, comfort, noise, wear) and great choice if you drive big miles or many track days.

  11. #39
    Senior Member GT#298's Avatar
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    Re: Tire PSI

    Quote Originally Posted by FaR8 View Post
    My 2010 5.2 has 295 rear, 305 was an option. Not sure the effect of bigger DIA rear due to center dif. Maybe increases rearward torque bias and INCREASES understeer at turn in before power on?
    My door jamb sticker is 39f/36r. I run 38/37 to soften front a little. On track, I drop front to same as rear and goes up to Mid 40’s with heat build up. My limited experience (I have a dedicated track Lotus) would suggest 44+/- max on track HOT, more to protect shoulder wear, less to maximize grip.
    I bought Michelin Pilot SS 2 years ago and had wheel alignment done where my friendly dealer did it to GT (I think) spec which has more negative camber and I think less toe in at rear. Understeer all gone on street and track and rear actually steps out slightly at initial turn in when driving fast, but stabilizes immediately. Incredible initial turn in. A little looser than is my preference but VERY fast through corners especially off camber and low speed (Mid Ohio?!).
    Michelin PSS MUCH better than P Zero (grip, comfort, noise, wear) and great choice if you drive big miles or many track days.
    Ah man, PSS are so last year. We've moved on to PS4S. Get with the program.

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