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      10-16-2013, 12:20 PM   #23
W///
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Quote:
Originally Posted by dparm View Post
Do you really think BMW hasn't done a shitload of testing to find the perfect pressures? Run the factory spec. The butt dyno is not reliable.
Read the damn thread. If you want comfort, run factory spec. If you want a little more grip add more.

Look at my wheel+tire combo. Hardly factory spec, so that sticker is worthless to me.
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      10-16-2013, 02:36 PM   #24
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Quote:
Originally Posted by W/// View Post
Read the damn thread. If you want comfort, run factory spec. If you want a little more grip add more.

Look at my wheel+tire combo. Hardly factory spec, so that sticker is worthless to me.

My mistake, didn't see your signature.
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      10-16-2013, 08:01 PM   #25
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Quote:
Originally Posted by gatorfast View Post
You have excessive wear in the center because your tires are over inflated! Unless they changed the manual/doorjam in 2012, your pressure should be somewhere in the neighborhood of 35psi all around.
Door jam/manual calls for 44 on the rear tires, so no, they were not over inflated.
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      10-17-2013, 07:05 AM   #26
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Quote:
Originally Posted by KawBoy View Post
Door jam/manual calls for 44 on the rear tires, so no, they were not over inflated.
My door jam says 35psi all around. Yours says 44?!? Thats a huge difference. Are you sure?

I think maybe you are reading it wrong. The manual states 44 rear pressure but only if you have 4 passengers + luggage and are going over 100mph.
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      10-17-2013, 09:20 AM   #27
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Quote:
Originally Posted by W/// View Post
Read the damn thread. If you want comfort, run factory spec. If you want a little more grip add more.

Look at my wheel+tire combo. Hardly factory spec, so that sticker is worthless to me.
Hmm, from what I understand based on reading and my own and others' track experiences, typically you increase grip by REDUCING tire pressure. Obviously that's only true to a point, but that increases your contact patch. Pros for example will typically drop front tire pressure and/or increase rear tire pressure if they want more oversteer because that creates a more front-biased grip setup. However, some have found that increasing tire pressure can make the car FEEL better at turn-in, which I suspect is because there's less rubber in contact with the road that needs to be turned (and at high cornering load there's less chance the tire will roll over onto its sidewall), but your absolute grip wouldn't be as high.

Check out this thread, especially the third post: http://www.f1technical.net/forum/vie...php?f=4&t=6037

This page out of a great book is also informative: http://books.google.com/books?id=cr4...20grip&f=false
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Last edited by jphughan; 10-17-2013 at 09:27 AM.
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      10-17-2013, 09:26 AM   #28
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Quote:
Originally Posted by jphughan View Post
Hmm, from what I understand based on reading and my own and others' track experiences, typically you increase grip by REDUCING tire pressure. Obviously that's only true to a point, but that increases your contact patch. Pros for example will typically drop front tire pressure and/or increase rear tire pressure if they want more oversteer because that creates a more front-biased grip setup. However, some have found that increasing tire pressure can make the car FEEL better at turn-in, which I suspect is because there's less rubber in contact with the road that needs to be turned (and at high cornering load there's less chance the tire will roll over onto its sidewall), but your absolute grip wouldn't be as high.

Check out this thread, especially the third post: http://www.f1technical.net/forum/vie...php?f=4&t=6037
You are absolutely correct actually. More pressure means stiffer sidewalls, and on my old E46 with Hankook V12's, it was a must.

Having said that, I never deviate that far from mfg specs though, never by 5+ psi. Just my personal preference. Right now on these HRE's, I'm running -1 or 2 actually.
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      10-21-2013, 01:08 PM   #29
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UPDATE: I contacted BMWNA about this in the hopes of getting an explanation behind the update tire pressure recommendations. I spoke with Cameron from BMWNA Customer Relations, who informed me that after checking with a tech expert on the M3, the only explanation he could get as to why the pressure might have changed is because around the time the Competition Package was introduced, there was a miscommunication about correct tire pressures and that therefore it's advised to stick to the original recommendations.

Thinking about that after I got off the phone I'm not entirely satisfied with that request. First, recommendations changed for all 3 tire types, not just the 19s, but I thought that might just have been to account for differences in ZCP suspension even if owners fitted 18s or snow tires. But the edition of the Supplement that has the new recommendations appears to have come out in mid-2011, whereas ZCP became available for MY2011.5, production for which started in mid-2010.

In any case, I for one will be sticking to the original pressures.
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      10-21-2013, 04:45 PM   #30
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Quote:
Originally Posted by gatorfast View Post
My door jam says 35psi all around. Yours says 44?!? Thats a huge difference. Are you sure?

I think maybe you are reading it wrong. The manual states 44 rear pressure but only if you have 4 passengers + luggage and are going over 100mph.
You are correct; it says "Use inflation pressure specific above up to 100 mph only!" Manual calls 44/46 for above 100 mph + 4 passengers.

I drive like 50% above 100mph and 50% below. Tires may have been overinflated like you said for this application. I set the new PS2 at 36/38 and will be checking them often.

Thank you.
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