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E85 / E86 Z4 (2003-2008)
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  #26  
Old 04-22-2019, 10:13 PM
Rotorblade Rotorblade is offline
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I suppose ps4s is the plural for ps4. They seem to provide good grip and I've also noticed they do very well on wet roads. The road noise is also low. Anyway I haven't use any other tires on this car so I can't make a comparison.
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  #27  
Old 05-08-2019, 01:47 PM
Rotorblade Rotorblade is offline
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I went today on a small track with the 225F 255R PS4, temperature 12C, pressure 2.1 Bar Fr, 2.6 bar Re and they didn't feel as grippy as the 255F 265R ones, possibly because of the track temperature or the tire pressure!?
I also have a system, not sure exactly how it is used, but when a certain lateral acceleration is achieved there is a weight that slides on a bar and you can hear it rattle. This time it would do anything... it could be stuck also
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  #28  
Old 05-10-2019, 06:23 PM
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dc_wright dc_wright is offline
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Mein Auto: '06 Z4 3.0si, '11 128CiC
Everything else being equal, the narrower tires will have less grip as their contact patch is smaller. No surprise they felt like less grip.
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  #29  
Old 05-12-2019, 07:51 PM
Andyz4 Andyz4 is offline
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Actually the size of the contact patch remains the same with wider tires, it just shifts it laterally.
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Old 05-13-2019, 01:09 PM
Rotorblade Rotorblade is offline
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Quote:
Originally Posted by Andyz4 View Post
Actually the size of the contact patch remains the same with wider tires, it just shifts it laterally.
I've watched a test on different tire sizes on a 3series and it showed that for a wider size tire the pattern becomes wider but narrower (because the tire doesn't deform under the weight of the car that much I suppose) so the area doesn't increase that much. Anyway the wider tires had slightly more grip and with wider front tires there was less understeering.
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Old 05-13-2019, 07:34 PM
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dc_wright dc_wright is offline
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Quote:
Originally Posted by Rotorblade View Post
I've watched a test on different tire sizes on a 3series and it showed that for a wider size tire the pattern becomes wider but narrower (because the tire doesn't deform under the weight of the car that much I suppose) so the area doesn't increase that much. Anyway the wider tires had slightly more grip and with wider front tires there was less understeering.
The static contact patch doesn't change much with wider tires, but the dynamic contact patch changes dramatically. As you laterally load the tire and the tread starts to roll under the load the wider tire has more tread to roll through before grip drops off.
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  #32  
Old 05-13-2019, 08:52 PM
Andyz4 Andyz4 is offline
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Yes wider tires will increase the lateral patch/lateral grip but at the expense of the longtitudinal (fore/aft) patch used for acceleration and braking. No free lunch here.
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