Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #21
    Join Date
    Nov 2014
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    Portland, OR
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    10,243
    Added! Anyone else?

  2. #22
    Join Date
    Feb 2014
    Location
    Kitchener, ON
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    6,036
    i run stock sized michelin PSS, as well as 225/45/17 and 245/40/17 michelin pilot sport AS3, both sets with 32F/38R.

    running 215/50/17 michelin x-ice3's with varying tire pressures - trying different values with the new suspension.
    peter

    2004 330i ZHP
    2005 330iT ZHP
    2010 328iT M Sport

  3. #23
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    Nov 2014
    Location
    Portland, OR
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    10,243
    Non-winter tires added.

  4. #24
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    Nov 2014
    Location
    Portland, OR
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    10,243
    Bump for additional members' tire/wheel setups and pressures.

  5. #25
    Join Date
    Feb 2015
    Location
    Utah
    Posts
    419
    Michelin Pilot Sport A/S3

    Front: 225/40/18 - 35psi
    Rear: 255/35/18 - 40psi
    Shawn, 801

  6. #26
    Join Date
    Nov 2014
    Location
    Portland, OR
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    Added!

  7. #27
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    Nov 2014
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    Portland, OR
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    Bump.

  8. #28
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729
    LOLs at "understeer is for gutless commies".

    I'll update once I get my new PSS's and have a few miles to evaluate a couple of different combos.

    I am confused about the table posted above and at Tire Rack, though...

    The table says to decrease understeer (i.e. increase oversteer), the proper combo would be higher front tire pressure and lower rear tire pressure. Why is that? I thought that as you increased tire pressure, you reduced the contact patch (and traction). If you're raising pressure (and decreasing traction) in the front and running less pressure (and more traction) in the rear, that's going to make the car push/understeer, is it not? Where am I going wrong?

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

  9. #29
    Join Date
    Jun 2011
    Location
    Colorado
    Posts
    729
    Hmmm... Lots of good info in this thread on Rennlist...
    http://rennlist.com/forums/racing-an...ndersteer.html

    I think my intuition is right on this. The table above and that posted on Tire Rack and other places are a gross oversimplification because it really depends where you start, and what the tire's optimal pressure is. This guy said it better than I can...

    Originally Posted by RedlineMan
    Craig;

    Think of graphing tire performance; pressure on the bottom (X), and performance up the side (Y). The graph will look roughly like a pyramid. ...

    To say that you always add or always subtract air to get an effect now can be seen to be wrong. ...
    +100000000000. It never ceases to amaze me that people say to increase front pressure for more front grip. Like RM explained, if you're already high, more pressure will make it WORSE. Overinflate your street front tires sometime and you'll understand quickly.

    Great thread. More people need to understand this issue.
    But, then looking at the BMW recommended tire pressures of 32 front/36 rear on the vert are a little counter-intuitive, at least with the narrative that "biasing the car toward mild understeer" is safer for novice drivers. I'm not sure it's the lower front/higher rear that causes that because it isn't just tires that bias the car one way or the other, but also the suspension. If the suspension is tuned to be biased toward understeer, then the tire inflation could be counteracting that. The 36psi on the rear would be making the rear a little less sticky, and the 32psi on the front is making it a little more sticky. Same with the coupe.

    Am I completely out in left field here?

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Rocky Mountain Chapter #504522
    ZHP Replacement: 2012 E93 M3 * Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2016 VW Touareg Exec

  10. #30
    Join Date
    Nov 2014
    Location
    Portland, OR
    Posts
    10,243
    TIRERACK.com - Revolutionizing Tire Buying
    Quote Originally Posted by ecrabb View Post
    LOLs at "understeer is for gutless commies".

    I'll update once I get my new PSS's and have a few miles to evaluate a couple of different combos.

    I am confused about the table posted above and at Tire Rack, though...

    The table says to decrease understeer (i.e. increase oversteer), the proper combo would be higher front tire pressure and lower rear tire pressure. Why is that? I thought that as you increased tire pressure, you reduced the contact patch (and traction). If you're raising pressure (and decreasing traction) in the front and running less pressure (and more traction) in the rear, that's going to make the car push/understeer, is it not? Where am I going wrong?

    SC
    Quote Originally Posted by ecrabb View Post
    Hmmm... Lots of good info in this thread on Rennlist...
    http://rennlist.com/forums/racing-an...ndersteer.html

    I think my intuition is right on this. The table above and that posted on Tire Rack and other places are a gross oversimplification because it really depends where you start, and what the tire's optimal pressure is. This guy said it better than I can...



    But, then looking at the BMW recommended tire pressures of 32 front/36 rear on the vert are a little counter-intuitive, at least with the narrative that "biasing the car toward mild understeer" is safer for novice drivers. I'm not sure it's the lower front/higher rear that causes that because it isn't just tires that bias the car one way or the other, but also the suspension. If the suspension is tuned to be biased toward understeer, then the tire inflation could be counteracting that. The 36psi on the rear would be making the rear a little less sticky, and the 32psi on the front is making it a little more sticky. Same with the coupe.

    Am I completely out in left field here?

    SC
    Whoops, I somehow completely missed your posts when you originally posted them. I look forward to your review of your PSS and your preferred tire pressures.

    As for your oversteer/understeer question, I'll first say I am the opposite of a so-called "expert," but, like any good American, I'll plunge headlong into the discussion anyways. As you say, there's a lot more to handling characteristics than simple tire pressure differences. Engineers definitely build cars today with the average driver in mind and tend to err on the side of understeer characteristics because it's considered safer and easier to handle. My mother's Volvo S40 understeers quite a bit, but I'm sure that's by Volvo's design, despite the tires all being the same size and pressure. My guess for our cars is that the suggested differences in tire pressures are due to BMW wanting to induce understeer and maybe also just a product of different section width tires requiring different tire pressures because of the inherent difference in width. I'm not sure what elements within the E46 chassis promotes understeer. Honestly I don't even notice much understeer in our cars from the factory.

    I don't know, I'm talking in circles.

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