Recommended tire pressure for auto-x w/Kumho Victor Racer 17x225? Oh, Please Oh,Please Oh. Anybody?
03-20-2001, 04:46 PM
#2
what car? On my A4, I use 42 front, 39-40 rear, but that was after installing a 19mm swaybar...
previous to that, I set the rears higher than the front by 2psi just to make them less efficient, loose grip and reduce my understeer.
Note that these are warm pressures, or I would drive to the AutoX with the Kuhmo's on (as long as about 50 miles away), and measure them there.
Note that these are warm pressures, or I would drive to the AutoX with the Kuhmo's on (as long as about 50 miles away), and measure them there.
03-20-2001, 05:36 PM
#5
Depends on the optimum pressure setting for that car. If you are understeering and you check your
front sidewalls to be completely trashed as you are rolling them in on heavy cornering, then you will need to add pressure to the front to keep the footprint flatter to the ground. Hence, more pressure in front provides more front traction and induces oversteer, and so forth and so on. When I wanted oversteer, I run the rears higher than the fronts, and you can clearly see that only the inside thread (slighlty over inflated) gets used.
03-20-2001, 06:48 PM
#6
Member
Join Date: Mar 2000
Posts: 10,197
Likes: 0
Received 0 Likes
on
0 Posts
Agreed...higher REAR pressure produces OVERSTEER...
This is essentially the same as putting in stiffer springs and a thicker rear swaybar. The rear stiffens up and will kick out alot more easily.
03-20-2001, 07:09 PM
#7
Rest In Peace
Join Date: Mar 2000
Location: Chicago
Posts: 37,562
Likes: 0
Received 0 Likes
on
0 Posts
It depends. Less OR more can produce oversteer. The key is........
that reducing the grip of the rear tires invokes oversteer. So if you're already pumped up high, and then you INCREASE pressure, you're increasing oversteer. If you're running low pressures and then you REDUCE the pressure even more, you're also increasing oversteer because in both circumstances you're reducing the overall grip of the tires by taking them outside their optimal grip range.
Make sense?
Make sense?
Trending Topics
03-20-2001, 07:11 PM
#8
Rest In Peace
Join Date: Mar 2000
Location: Chicago
Posts: 37,562
Likes: 0
Received 0 Likes
on
0 Posts
But, along the same lines, if you wanted to run low pressures, you'd REDUCE the rear pressures......
to get oversteer. Then you'd have less wear in the middle and more on the outer part of the tread.
See my post above.
See my post above.
03-21-2001, 05:11 AM
#10
AudiWorld Member
Join Date: Mar 2000
Posts: 110
Likes: 0
Received 0 Likes
on
0 Posts
It all depends on where you're starting from...
First of all you have to have reasonable pressures so the tires are neither so soft that they are deflecting so much that only the outer two ribs are in contact or they are so hard that the tread is crowned again limiting contact area.
Once you are within this range increasing pressure increases overall tire stiffness and reduces slip angle. So, increasing rear pressure would reduce rear slip angle = LESS oversteer.
If you are getting MORE oversteer by increasing rear pressure then your overall tire pressures are set too high. Diddling tire pressure is a relatively small effect and will not correct for a fundamentally unbalanced car.
Once you are within this range increasing pressure increases overall tire stiffness and reduces slip angle. So, increasing rear pressure would reduce rear slip angle = LESS oversteer.
If you are getting MORE oversteer by increasing rear pressure then your overall tire pressures are set too high. Diddling tire pressure is a relatively small effect and will not correct for a fundamentally unbalanced car.