I found this Mark Ortiz article from Oct 25, 2005 about that common question of the inside rear tire lifting. It is comforting to see that even guys who write for Race Car Engineering mag also have to think about this tricky question.

http://www.auto-ware.com/ubbth...0#703

For reference, see this recent series of posts where we discussed this same subject with even equations on the last page.

https://honda-tech.com/zero...age=5

 

Wow.

Since I'm such a simple bastard, I try not to analyze this pissin' dog thing.

What I do understand that FWD cars which are winning races and poles lift their inside rears, and usually all the way from turn-in to track out...so I'm ok with it

 

And What does this prove?

Just another regurgitation of narrow minded dogma!

Has Mr Ortiz an intimate acquaintance with Mr Euler?

And what of Reactive Kinematics?

Scott, who's dynamic cornerweights total to a value Greater then their static weights thanks to my acquaintance with Mr Maharishi..."when they're levitating I'm gettin downforce".

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Track rat &raquo;</TD></TR><TR><TD CLASS="quote">Wow.

Since I'm such a simple bastard, I try not to analyze this pissin' dog thing.

</TD></TR></TABLE>

But why do some dogs **** more than other dogs?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">

But why do some dogs **** more than other dogs?</TD></TR></TABLE>

Beer?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">And What does this prove?

Just another regurgitation of narrow minded dogma!

Has Mr Ortiz an intimate acquaintance with Mr Euler?

And what of Reactive Kinematics?

Scott, who's dynamic cornerweights total to a value Greater then their static weights thanks to my acquaintance with Mr Maharishi..."when they're levitating I'm gettin downforce".</TD></TR></TABLE>

True, success at the club level should not be taking as gospel. Wide disparities in driving talent more than make up for little nuances such as three wheelin' it through the corners.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">

But why do some dogs **** more than other dogs?</TD></TR></TABLE>

trick question? I know, because some dogs drink more beer than others.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">

But why do some dogs **** more than other dogs?</TD></TR></TABLE>

Maybe it just seems simple to me, but looks like a combination of things, but mainly front/rear spring and rear swaybar efficiency.

Very soft front spring with efficient rear bar = big pisser....

Stiff front springs with inefficient rear bar = slow understeering next to no pisser..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">But why do some dogs **** more than other dogs?</TD></TR></TABLE>

sometimes when I'm gone for a long time I let my dog out and he pissees for a long time.... it's like that scene from Austin Powers. Evacuation comp ....... evacuation comp ......... evacuation complete.

oh with the car thingy. I look at it like this. If you're inside rear tire is on the ground at all you're either not going fast enough around the corner, and/or the weight on an inside tire that is touching is so minimal that it's not going to make much of a difference in traction. Besides, don't FWD racers do everything in their power to REDUCE rear grip and increase front grip? So if a car has 3 wheels on the ground you better hope that 2 of them are the ones trying to put down power.


EDIT: one time my dog had surgery on his left rear leg ... I noticed that he was slower going around corners when he was walking on 3 legs, so maybe there is something to this?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RR98ITR &raquo;</TD></TR><TR><TD CLASS="quote">
And what of Reactive Kinematics?
</TD></TR></TABLE>

You're kidding, right?

 

Dangit, all that time he spends talking about what's physically happening but nothing about how to improve the handling.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bb6h22a &raquo;</TD></TR><TR><TD CLASS="quote">

You're kidding, right?</TD></TR></TABLE>

Me? Kidding? YOU must be kidding!

Scott, who's gotten so much more serious since drinking the Maharishi's Koolaid..."Enlightenment - Now That's some Good ****!"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Another Drew &raquo;</TD></TR><TR><TD CLASS="quote">Dangit, all that time he spends talking about what's physically happening but nothing about how to improve the handling.</TD></TR></TABLE>

he talks about THAT elsewhere. long and short, don't lift the tire off the ground, but don't leave any load on it either.

nate

 

a car won't 3 leg if it has a small rear bar and lots of droop travel. ^_^

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quisp &raquo;</TD></TR><TR><TD CLASS="quote">a car won't 3 leg if it has a small rear bar and lots of droop travel. ^_^</TD></TR></TABLE>

where ya goin' with that? i missed the joke i think.

nate

 

sorry i was just making a useless point and observation.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">he talks about THAT elsewhere. long and short, don't lift the tire off the ground, but don't leave any load on it either.

nate</TD></TR></TABLE> So whats the difference between that and 1/4" of lift or something small and insignificant.

-Tom

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quisp &raquo;</TD></TR><TR><TD CLASS="quote">a car won't 3 leg if it has a small rear bar and lots of droop travel. ^_^</TD></TR></TABLE>

explain the RTR cars then, huge rear bar small amount of droop, no front bar, and soft front rates.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">
explain the RTR cars then, huge rear bar small amount of droop, no front bar, and soft front rates.</TD></TR></TABLE>

Exactly! Show me a winning FWD car with a puny rear bar.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">

explain the RTR cars then, huge rear bar small amount of droop, no front bar, and soft front rates.</TD></TR></TABLE>

RTR Spring rates: 600 lbs/in front and 1500 lbs/in rear. The big bar in the rear is attached to blade type adjustable end bars that probably contribute most to the flexibility of the overall ARB stiffness. So its hard to say how stiff the rear bar is without taking their exact setup and analyzing it.

 

Also, with Motons, they have high speed rebound adjustment to minimize jacking forces.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by trhoppe &raquo;</TD></TR><TR><TD CLASS="quote"> So whats the difference between that and 1/4" of lift or something small and insignificant.

-Tom</TD></TR></TABLE>

nothing any of us will notice. i'm probably one of the stronger proponents of the no lift theory and even my car will lift the inside rear in some situations. rr98itr has a good counterpoint argument that makes sense too. basically lifting the inside tire at low g loads to improve inside front bite during late corner exit. it would seem that RTR was taking a similar approach, though i question any pro team divulging setup secrets as intimate as spring rates. one has to question why they would divulge something like that but not the bar rate of that custom rear bar setup they used. (and for the guy who says you can just look at the spring, there are autocrossers that paint different numbers on their springs just to screw with their competition)

nate - off for some indoor karting

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">Also, with Motons, they have high speed rebound adjustment to minimize jacking forces. </TD></TR></TABLE>

care to expand on that? jacking is due to suspension geometry that shocks wouldn't have much of an effect on. packing down the suspension over bumps would be low speed rebound dependant. i'm not following what you meant by your statement?

 

I like the paint idea

-Tom
who will have stock sized, red "Eibachs" in T2 next year

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">care to expand on that? jacking is due to suspension geometry that shocks wouldn't have much of an effect on. packing down the suspension over bumps would be low speed rebound dependant. i'm not following what you meant by your statement?</TD></TR></TABLE>

The amplitude of an "event" (wheel movement from a bump) will be dependent upon damping since it will change the time it takes for the movement to occur. Think of it as applying enough resistive force such that the movement takes so long that it never completes (a car is so slow to roll that the car is already on the straight before the suspension has reached normal compression).

Shock tuning is pretty important in ride height tuning for aero cars, and many teams tune ride heights with compression valving, though it is important to prevent front lift (rebound) on an aero car. Compression damping keeps the chassis from bottoming without using rediculous spring rates (even though they still do).

Edit: I suck at typing


Modified by GSpeedR at 6:56 PM 10/26/2005