Cameron

I am looking at the high res pics that I received last night of my Sebring DE day. In a couple of the high speed cornering pics, I can clearly see that the inside tire contact patch is reduced by what looks like about 1/4 of the tire width - looks like the inside wheel / tire is lifted 911 style (but to a lesser degree) under hard cornering. You can kind of see it in the low res pics called 'Hold on' and 'Right' at the link below. In the high res pics it is very clear.

http://f1.pg.photos.yahoo.com/ph/nee...nan1/my_photos

I had my warm tire pressures set to 36 psi front and 44 psi rear (I have to check my notes to confirm).

Is this reduction of contact patch normal for a stock weight 928 under high lateral acceleration? Are my tire pressures set to high for a DE, contributing to this effect?

Thanks!

......Cameron
'91 Euro GT

Weissach

Wicked looking 928!

sharkmeister85

Great photos! I like "Rain" the best. Perhaps 'cause it reminds me of the "Wet Coast" out here. I think the photos show what I would expect from a stock 928. The reduced contact patch on the inside tire is normal as weight is transfered to the outside tire. I don't think your tire pressures can be adjusted to have much effect on this.
Glenn

Shane

A way to check next time is to bring along an infrared thermometer and take temp readings across the width of the tire and check your tire pressure at temp, then adjust those pressures up or down to get more tire contact through the corners within the allowance of your suspension.

shaaark89

cameron,
not necessarily abnormal, and definitely more related to suspension than tires. softer springs and less sway bar will tend to make this more apt to occur.\
even big time springs and heavy swaybars can allow it:

mark kibort

how are you wearing the tires out? i dont know the degree of g loading on that turn, but if it is significant, then this is normal.
if not, then you may have too much camber. camber for our cars in race form should be in the 1.5 degree range. if you are 2 in front, that probably is way too much.

GlenL

Stiffer shocks, springs, sway bar or sway bar bushings can help keep that wheel down.

As to the pressures, those are highly dependent on the model of tire.

mark kibort

front is fine, rear is brain dead off! car feel loose (ha ha ha) get that 44 lbs down to within a couple of lbs of the front pressures. I hope we are talking about DOT hoosiers or other DOT tires, otherwise, if you are running real slicks, you are WAY to high .

based on the picture, your not pulling too many Gs. you probably have a little too much camber up front. i would guess 2+ degrees.
I forgot what suspension you are running, but you have no body roll or compression at all.

mk




I had my warm tire pressures set to 36 psi front and 44 psi rear (I have to check my notes to confirm).

Is this reduction of contact patch normal for a stock weight 928 under high lateral acceleration? Are my tire pressures set to high for a DE, contributing to this effect?

Thanks!

......Cameron
'91 Euro GT [/B][/QUOTE]

mark kibort

I was talking about Tilo's old car. from those low rez pics, the car looks normal. i would address the tire pressures in the rear. that will help quite a bit.
mk

Cameron

Thanks for the feedback. I have club sport front springs, stock rear springs. Standard (but pretty new) Boge shocks all around. Tires are Continental ContiSport II's. Re the camber in the front, it should be in spec for a stock alignment and setup. I did not tweek it for DE.

I thought the rear tire pressure was too high as well. Someone at the tech inspection told me that 44psi was a good rear tire pressure for this car. I wasn't sure, being my first PCA DE. He stated this so matter of factly that I went with it. Live and learn.

Thanks for the pics. Damn fun to look at pics.

.....Cameron
'91 Euro GT

mark kibort

Dont ever take the advice of any of the DE folks. (unless they have been qualified) generally, ive heard more BS from that group, than imaginable.
show me a group of DE's running 44psi rear, and Ill show you (and have seen) a bunch of guys off track looping on almost all the hard turns!

sounds like you had fun. great shots.

Now, we need to see more of the x-tilo racer!!

mk

mark kibort

anderson at sears after a poke in the rear. ha ha

Cameron

Is that the result of the Vette incident?

.....Cameron
'91 Euro GT

mark kibort

my car (pre holbert) at sears 2001 Speedvision WC

mark kibort

Yep. Those vets had quite a thing for Mark Andersons car!

mk