I think they have it backwards as well.

 

Originally posted by umdbandit@Apr 4 2005, 07:42 PM
I was looking at the handling adjustment tips on BavAuto, and it says to increase oversteer, lower the pressure in the rear tires and increase pressure in the front.

My thinking is that this would do the opposite because there will be more grip on the rear tires (bigger contact patch) and less grip on the front. So what gives? :dunno

Thanks...i'm here to learn!

[snapback]325721[/snapback]​

Hahaha, nice catch man, I agree they got it mixed up like I get theories mixed up in physics :lmao2

 

no, actually they are correct, oversteer is when the front end is gripping(to some extent) and the back end is very lose so it swings around... they do not have it backwards

 

When you take a turn too fast and the front end hits the guardrail first, thats Understeer. When the back end hits first, thats Oversteer...

If deflating your tires increases traction, then why do so many autocross drivers overinflate their tires to 40 PSI, 45 PSI or more?

Hmmm...

:confused

 

Originally posted by docrobot@Apr 4 2005, 11:43 PM
When you take a turn too fast and the front end hits the guardrail first, thats Understeer. When the back end hits first, thats Oversteer...

If deflating your tires increases traction, then why do so many autocross drivers overinflate their tires to 40 PSI, 45 PSI or more?

Hmmm...

:confused

[snapback]325808[/snapback]​

I've heard that they do that to keep the tires from rolling over on the sidewall and damaging their rims.

 

Originally posted by xsperf@Apr 4 2005, 09:43 PM
no, actually they are correct, oversteer is when the front end is gripping(to some extent) and the back end is very lose so it swings around... they do not have it backwards

[snapback]325777[/snapback]​

Right, but if the back tires have less pressure, they will be gripping more than the front ones. I also believe they have it wrong.

 

It's not just BavAuto actually. I have seen it on other sites as well. I just did a search on google and found a few more. I guess i'll just have to run an experiment one of these weekends to see if it is true.

Go Terps

 

They have it right.

Properly inflated tires grip better than underinflated in a corner. The sidewall roll is what you don't want for traction.

It seems counterintuitive if you've never had a RWD car with a leaky back tire.

 

Originally posted by umdbandit@Apr 5 2005, 05:42 AM
I was looking at the handling adjustment tips on BavAuto, and it says to increase oversteer, lower the pressure in the rear tires and increase pressure in the front.

My thinking is that this would do the opposite because there will be more grip on the rear tires (bigger contact patch) and less grip on the front.  So what gives? :dunno

Thanks...i'm here to learn!

[snapback]325721[/snapback]​

They are 100 % correct. If you want to go a step further than tire pressure, to increase oversteer;

you'll have to also mount a wider tire up front, norrower in the rear

more negative camber up front, more positive camber in the rear

softer springs front, stiffer in the rear

softer front stabilizer, stiffer rear.

Of course you don't need all this if it's minimal. These suggestions are for racing and also dependant on track conditions and your tires.

You get all this tuned to the car and you get a BMW with the characteristics of a Porsche 911.

The best way is to experiment. In small increments. 2 psi will make a world of a difference in the way a car handles especially in the corners. I know my race track is the German Autobahn.

 

i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor. I don't know how this applies to understeer or oversteer but thought i might contribute.

 

Originally posted by spieluhr@Apr 5 2005, 05:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor. I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I too thought it was the other way! Damn s what is a good tire pressur? Right now I have 36 in the rears and 40 in the fronts. BTW I have staggered tires 235 front 255 rear what should I use for best handling?

 

lol, there's a mod over on bimmerforums called silverstreak. Thought that was you. Anyway, sorry for the interruption. Back on topic.

 

Originally posted by spieluhr@Apr 5 2005, 07:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor. I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I was waiting for someone to bring this up.

Drag racing, and going straight traction (or hook, as people call it) is different than sticking in a corner.

I run 32 psi in all four tires when I run my Mustang on the street, and would autocross at about 35. When I run it at the 1/4, I run 40 up front and 20 in the back.

When you are going straigt, the car will squat and give more surface area, so a little less pressure is good. When you corner, the lateral acceleration would cause the tire to roll onto the sidewall and slide at the same pressure. That's bad.

That is also why people don't run drag radials in an autocross. The sidewalls are too flexible.

 

whatever guys, the main point is that bav auto is not stupid enough to make a mistake on their website.. if they had the tip up there, they would make sure its correct before putting it up

 

Hey, hey, hey. This is just a healthy discussion. If we didn't have this what else would we have?

 

Originally posted by Silverstreak+Apr 6 2005, 03:46 AM--><div class='quotetop'>QUOTE(Silverstreak @ Apr 6 2005, 03:46 AM)</div><div class='quotemain'><!--QuoteBegin-spieluhr@Apr 5 2005, 05:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor.  I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I too thought it was the other way! Damn s what is a good tire pressur? Right now I have 36 in the rears and 40 in the fronts. BTW I have staggered tires 235 front 255 rear what should I use for best handling?

[snapback]326322[/snapback]​

[/b][/quote]
Your setup is good and a rear driven car should have a controllable oversteer. It's a lot easier to control than understeer especially when you're trying to accelerate around a corner.

Does your car's ass-end tend to want to slide in a corner at those pressures or does the car feel like wanting to push the front into the siderail?

 

Originally posted by The Deuce+Apr 5 2005, 09:32 PM--><div class='quotetop'>QUOTE(The Deuce @ Apr 5 2005, 09:32 PM)</div><div class='quotemain'><!--QuoteBegin-spieluhr@Apr 5 2005, 07:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor.  I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I was waiting for someone to bring this up.

Drag racing, and going straight traction (or hook, as people call it) is different than sticking in a corner.

I run 32 psi in all four tires when I run my Mustang on the street, and would autocross at about 35. When I run it at the 1/4, I run 40 up front and 20 in the back.

When you are going straigt, the car will squat and give more surface area, so a little less pressure is good. When you corner, the lateral acceleration would cause the tire to roll onto the sidewall and slide at the same pressure. That's bad.
That is also why people don't run drag radials in an autocross. The sidewalls are too flexible.

[snapback]326366[/snapback]​

[/b][/quote]


Thanks Duece, you da man! :wave

 

Originally posted by spieluhr+Apr 6 2005, 01:31 AM--><div class='quotetop'>QUOTE(spieluhr @ Apr 6 2005, 01:31 AM)</div><div class='quotemain'>

Originally posted by The Deuce@Apr 5 2005, 09:32 PM
<!--QuoteBegin-spieluhr

@Apr 5 2005, 07:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor.  I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I was waiting for someone to bring this up.

Drag racing, and going straight traction (or hook, as people call it) is different than sticking in a corner.

I run 32 psi in all four tires when I run my Mustang on the street, and would autocross at about 35. When I run it at the 1/4, I run 40 up front and 20 in the back.

When you are going straigt, the car will squat and give more surface area, so a little less pressure is good. When you corner, the lateral acceleration would cause the tire to roll onto the sidewall and slide at the same pressure. That's bad.
That is also why people don't run drag radials in an autocross. The sidewalls are too flexible.

[snapback]326366[/snapback]​

Thanks Duece, you da man! :wave

[snapback]326456[/snapback]​

[/b][/quote]

Hah, I was waiting for this so I could shove in a story. A friend of mine with his beat up mid 80's chevy always lowered his psi on his rear tires just so he could burn out. It was ultimately his downfall when his car lost control going around a normal bend and kaput it went...

 

Originally posted by Cassandra+Apr 5 2005, 10:31 AM--><div class='quotetop'>QUOTE(Cassandra @ Apr 5 2005, 10:31 AM)</div><div class='quotemain'><!--QuoteBegin-umdbandit@Apr 5 2005, 05:42 AM
I was looking at the handling adjustment tips on BavAuto, and it says to increase oversteer, lower the pressure in the rear tires and increase pressure in the front.

My thinking is that this would do the opposite because there will be more grip on the rear tires (bigger contact patch) and less grip on the front.  So what gives? :dunno

Thanks...i'm here to learn!

[snapback]325721[/snapback]​

They are 100 % correct. If you want to go a step further than tire pressure, to increase oversteer;

you'll have to also mount a wider tire up front, norrower in the rear

more negative camber up front, more positive camber in the rear

softer springs front, stiffer in the rear

softer front stabilizer, stiffer rear.

Of course you don't need all this if it's minimal. These suggestions are for racing and also dependant on track conditions and your tires.

You get all this tuned to the car and you get a BMW with the characteristics of a Porsche 911.

The best way is to experiment. In small increments. 2 psi will make a world of a difference in the way a car handles especially in the corners. I know my race track is the German Autobahn.

[snapback]326045[/snapback]​

[/b][/quote]


:thumbs :thumbs :thumbs
For awesome info! :wink

 

Originally posted by Cassandra+Apr 5 2005, 11:20 PM--><div class='quotetop'>QUOTE(Cassandra @ Apr 5 2005, 11:20 PM)</div><div class='quotemain'>

Originally posted by Silverstreak@Apr 6 2005, 03:46 AM
<!--QuoteBegin-spieluhr

@Apr 5 2005, 05:35 PM
i may be wrong but in terms of traction I think that pro drag cars release pressure on their slicks a little so that their is more surface area on their tires for the traction of the big motor. I don't know how this applies to understeer or oversteer but thought i might contribute.

[snapback]326225[/snapback]​

I too thought it was the other way! Damn s what is a good tire pressur? Right now I have 36 in the rears and 40 in the fronts. BTW I have staggered tires 235 front 255 rear what should I use for best handling?

[snapback]326322[/snapback]​

Your setup is good and a rear driven car should have a controllable oversteer. It's a lot easier to control than understeer especially when you're trying to accelerate around a corner.

Does your car's ass-end tend to want to slide in a corner at those pressures or does the car feel like wanting to push the front into the siderail?

[snapback]326447[/snapback]​

[/b][/quote]

Yea It definitely oversteers when I get on it in a turn! Even with the staggered setup, but I kinda like it that way. I guess if I wanted a more neutral setup I should increase the rears a bit?