 | |
Re: Tire pressure to help dial out understeer
Audi Audi Automobiles Discussions (alt.autos.audi)
 |
| | Thread Tools | Search this Thread | Display Modes |
#1
 
| |||
| |||
|
Re: Tire pressure to help dial out understeer -
06-25-2003
, 01:08 PM
|
"C.R. Krieger" <warp2_shadow (AT) yahoo (DOT) com> wrote in message I don't know how it is where you are, but the *last* thing I'd ever expect to see one of those morons (known as 'insurance adjusters' here) checking is tire pressures. You rashly assume much more expertise in traffic crash investigation than there really is. While I suppose the tire pressure data from the Lady Di case or Ayrton Senna's last ride might be available, I'd seriously doubt there are even a dozen such cases in the US. -- C.R. Krieger (0.75 G every day - every way) But it might form part of a police accident report in serious cases? |
Usenet with one of the better police experts and I was stunned to find
that he used a *standard* weighted 'drag block' to determine
coefficient of friction on various surfaces. It had a rubber compound
good for about 0.75G. His speed calculations would therefore be
wildly incorrect for something carrying the kind of 'gumballs' I've
run in the past.
You could *probably* find out just about anything you wanted to about
the circumstances of a given crash - if you could afford it.
--
C.R. Krieger
(Been there; didn't crash)
#2
| |||
| |||
|
|
On 20 Jun 2003 10:47:30 -0700, warp2_shadow (AT) yahoo (DOT) com (C.R. Krieger) wrote: Peter Bell <peter (AT) bellfamily (DOT) org.uk> wrote Indeed, that has been my experience on some cars I have owned. However, the effect on handling of altering tyre pressures is a fairly complex issue, and depends on the setup of the rest of the car. No, it really isn't. To reduce the designed-in inherent understeer in virtually all cars, one increases the front tire pressures relative to the rear pressures. IOW, you can either reduce the rear pressures or increase the front pressures, or both. To determine the window of pressures in which to work requires a bit of experience, some educated guesswork, and maybe the standerd autocrosser's trick of a bit of chalk or shoe polish on the shoulders & sidewalls. [This is only to measure rollunder - *do not* run it to the wheel or you'll look like a total idiot. *Drag racers* run the lines to the wheel in order to see wheelspin, not to see how much of the shoulder is being used in turns, as autocrossers do.] Further, this general rule applies to *all* front vs. rear suspension settings (anti-roll bars, springs, shocks, etc.). To reduce understeer, one *stiffens* or *tightens* the front while *loosening* the rear. To increase understeer (reduce oversteer), one does the opposite. It isn't just the physical grip which determines this - the tyre effectively forms part of the suspension setup, affecting effective roll centre height. I think you're trying to make this more complicated than it really is. Under- and oversteer is only indirectly (if at all - I have my doubts) influenced by roll center height and, at best, tire pressures can only affect this on a virtually undetectable level. Tire pressures *do*, however, have a direct, discernible and immediate effect on over- and understeer. Gentlemen, Thanks for all of the lively interaction. I have been trying a 43/38 split since Sunday. I'm onMichelin Pilot Sports, and that seems to be a pretty good setting so far. I'll let everyone know in a month or so after my next outing. Regards, Elroy |
|
« Previous Thread
|
Next Thread »
| Thread Tools | Search this Thread |
| Display Modes | |
Linear Mode
| |
Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.