2003 LLbean OBW- crappy handling

[thatswhatshesaid]

I think the real problem here lies in the fact that the Scandinavian Flick should not be performed on dry pavement in a car with an auto tranny and ABS...especially on public roadways. Leave those maneuvers to the pros in rally cars.

 

[CNY_Dave]

I think the real problem here lies in the fact that the Scandinavian Flick should not be performed on dry pavement in a car with an auto tranny and ABS...especially on public roadways. Leave those maneuvers to the pros in rally cars.

 

 

It wasn't necc. the case today, but being able to do 'the flick' if need be can be a life saver.

 

Did some practice on the way home and I have a much better feel for it.

Pretty sure if there was less body roll there'd be less oversteer.

 

And also, of course, less body roll would cause less weight transfer.

 

Dave

[jamal]

And also, of course, less body roll would cause less weight transfer.

 

Dave

 

Sorry no that is wrong.

 

Given the same cornering force, the total weight transfer is the same regardless of spring rate or swaybar size. Stiffening things up causes the weight to transfer more quickly, and changing swaybars alters the transfer distribution from front to rear.

[keltik]

No VDC.

 

And yeah, had I been a n00b, that would have been a spin into the ditch.

 

Hello ....been there and done that

 

I Just HAD to step in here and say my '97 GT Manual was dam horrible for this - if the back stepped out it was very difficult to catch and resulted in fishtailing.

 

After driving my mates old '97 GT Auto i can confidently say the clutched awd makes a noticeable difference to handling characteristics.

 

IMHO Excess Body roll creates a pendulum effect which can easily cause loss of control in this sort of maneuvre (sp?). Stiffer sptings means any weight shift is immediate and can be easily compensated for.

 

Im also certain my '02 H6 does not have VDC - but the low profile tires with a wider tread, combined with bilstein struts all round, stiffer sway bars and clutched awd make it a VERY controllable car.

[CNY_Dave]

Sorry no that is wrong.

 

Given the same cornering force, the total weight transfer is the same regardless of spring rate or swaybar size. Stiffening things up causes the weight to transfer more quickly, and changing swaybars alters the transfer distribution from front to rear.

 

Sorry, no, that is wrong.

 

When the body rolls Left/Right, the CG moves Left/Right, the further the CG moves the more the weight will transfer. Simple physics. If body roll didn't affact weight transfer, SUVs wouldn't roll over during accident avoidance maneuvers.

 

When the car turns right, and the body rolls left on the suspension, the CG moves left as well. All weight transfer is not because of body roll, but the amount of body roll affects the weight transfer.

 

I'm, not talking about how to limit the roll; but, if you lessen body roll, you limit the weight transfer.

 

Or are you talking just about front/rear transfer?

 

Dave

[thatswhatshesaid]

Weight transfer from left-to-right (or vice versa) will ALWAYS be the same. The gravity and lateral force will be present no matter what suspension set-up you have. The weight of the car and common laws of physics are NOT CHANGING.

 

The point you brought up regarding SUVs is a completely different - the reason SUVs roll over is because they are waaaaay taller and higher off the ground. They also have more weight up high (high center of gravity). Now we're talking about up-and-down center of gravity. Not side-to-side weight transfer. Newton's laws act on SUVs and Subarus exactly the same. No exceptions. The SUVs roll over because (A) the suspension on one side compresses much more than it would on a Subaru and ( because the monstrous amount of lateral (centrifugal) force applied to a vehicle with a much higher center of gravity. The side-to-side weight transfer is no different on a 4,000-lb. Jeep than a 4000-lb. Outback (assuming the front-back weight distribution is the same for the sake of argument). It's the top-to-bottom C.O.G. that meks the Jeep flip.

 

 

The laws of physics that we've known for centuries are always present. They cannot be ignored with swaybars and struts.

 

In short, Sir Isaac Newton isn't a liar. STILL.

[thatswhatshesaid]

We need to clarify...

 

In the future, please specify whether your arguments are regarding side-to-side forces, front-to-back, or top-to-bottom. That will make the argumentative/ranting process much easier.

[bulwnkl]

To the OP: I'm glad you're learning your Subie's handling characteristics.

 

Can we all clarify that roll center and center of gravity are 2 different things and are in 2 different places on road cars (RC is below CG)? Tall vehicles (like SUVs) roll over because the CG is well above the RC.

 

So, CNY_Dave is actually correct that body roll alters weight transfer. However, it does so to a limited extent, often extremely limited.

[jamal]

The calculation for lateral weight transfer is this:

 

centrifugal force x CG height / track width.

 

The lateral movement of the CG due to body roll contributes a negligible amount of transfer.

 

So the maximum corning force is also determined by the track width and CG height. Take a tall SUV and put super stuff swaybars and springs and sticky tires on it. The CG height hasn't changed and the car is just as likely to roll in a sharp corner.

 

I suggest you read the book How to make your car handle by Fred Puhn if you want to learn about this stuff instead of just arguing incorrectly about it on the internet.

[Skip]

I must admit Fred knows his stuff but

centrifugal force is fictitious, he should be using

centripetal force.

 

A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis. The (true) frame acceleration is substituted by a (fictitious) centrifugal force that is exerted on all objects, and directed away from the axis of rotation.

[CNY_Dave]

To the OP: I'm glad you're learning your Subie's handling characteristics.

 

Can we all clarify that roll center and center of gravity are 2 different things and are in 2 different places on road cars (RC is below CG)? Tall vehicles (like SUVs) roll over because the CG is well above the RC.

 

So, CNY_Dave is actually correct that body roll alters weight transfer. However, it does so to a limited extent, often extremely limited.

 

Don't forget we're talking about my piggy LL bean with extra option weight and its a wagon, to boot!

 

A little bit more weight and a slightly higher CG than some of what other folks here are driving. Not a big difference, but its there.

 

 

Dave

[bulwnkl]

CNY_Dave: I always wondered how a turbo XT would have felt compared to my XT-6. Everybody 'knows' that a 4-cyl version of a vehicle handles better than a large V-6 or V-8, but often the difference in weight is almost nothing. I don't know how much difference there is in an Outback, but I wonder whether you're right. I often wished for less push from my XT-6, and blamed it partly on the larger, heavier engine. I blamed the rest on Subaru's drivetrain layout and suspension, of course.

 

I'm sure you meant to quote someone, jamal, but it's not clear whom. Having read most of the book, including the section relevant to this thread (quite good; wish I had bought instead of borrowing), I posted. I agree that putting ultra-stiff springs and sways on a vehicle with a long moment arm (CG vs. RC) will not prevent it rolling over, and my post was to that effect. The sticky tires make it worse, of course. Interestingly, tires do in fact make a significant difference in cornering (and acceleration and braking) ability, even though the equations used in things like Physics 101 and many books would seem to indicate otherwise. Cheers!

[CNY_Dave]

CNY_Dave: I always wondered how a turbo XT would have felt compared to my XT-6. Everybody 'knows' that a 4-cyl version of a vehicle handles better than a large V-6 or V-8, but often the difference in weight is almost nothing. I don't know how much difference there is in an Outback, but I wonder whether you're right. I often wished for less push from my XT-6, and blamed it partly on the larger, heavier engine. I blamed the rest on Subaru's drivetrain layout and suspension, of course.

 

I'm sure you meant to quote someone, jamal, but it's not clear whom. Having read most of the book, including the section relevant to this thread (quite good; wish I had bought instead of borrowing), I posted. I agree that putting ultra-stiff springs and sways on a vehicle with a long moment arm (CG vs. RC) will not prevent it rolling over, and my post was to that effect. The sticky tires make it worse, of course. Interestingly, tires do in fact make a significant difference in cornering (and acceleration and braking) ability, even though the equations used in things like Physics 101 and many books would seem to indicate otherwise. Cheers!

 

 

Tires make a difference? Hogwash!!!

[subaruplatt]

This is kicking around the outback board, and it looks like they are really sensative to tire pressure. 31 psi seems to be the magic number. Go higher then that and everything gets scary.

 

If you feel like reading 10 pages of posts

 

http://www.subaruoutback.org/forums/showthread.php?s=&threadid=11267&perpage=20&highlight=dangerous&pagenumber=1

 

One guy did extensive testing with dead weight in the car and air pressure

and 31psi may resolve it.

 

I did read all 10 pages!

I just drove back from the mother in laws in Burlington.

Had the stock 33/30 on the way there in it but wanted to see what 36.5/33 felt like on the return. Full tank. Ratio of 1.1 front to the back pressure.

Absolutely amazing on the highway!

 

Smooth and in control.

 

Eskimo 3's are good on the highway.

 

The reason I fooled around with the TP is that I noticed with stock pressures the car was too sensitive to occupant weight and especially road grade which shifts the balance of the car and then alters the weight . It would then slightly steer in the direction of those similar influences. (perfect alignment)

Any car can literally slide in the direction of the heaviest wheel on ice.

I increased the tire pressures based on the theory that higher tire pressures would minimize weight shift.

I'm not having handling problems but I do like a more direct feeling when I drive.

 

The biggest problem faced by drivers is the overly curved road bed.

Driving along your always fighting to stay on top of it.

 

One never discussed factor is wheel offset which I believe is altered more often than not when you get snow tires.

 

Another sneaky factor may be load index.

Do tires of the same general specification with different load indexes behave

differently? More pressure or less pressure or the same pressure ?

[jib]

Granted, I have Dunlop Graspic DS2s on there, not fabulous dry-road tires, but maybe the struts are gettin' weak?

 

Dave,

 

If the suspension checks out OK and you are running standard tire pressures in those Graspics, try upping it 5-8 psi all the way around.

 

Snow tires have notoriously soft side walls to work well in snow and the extra pressure helps out a great deal with handling, while affecting the snow performance minimally.

 

Jack

[CNY_Dave]

Dave,

 

If the suspension checks out OK and you are running standard tire pressures in those Graspics, try upping it 5-8 psi all the way around.

 

Snow tires have notoriously soft side walls to work well in snow and the extra pressure helps out a great deal with handling, while affecting the snow performance minimally.

 

Jack

 

They had about 30-31 in 'em last night, was about 42 degrees, 'at speed' on the interstate last night they seemed to be squishy, but then 'settle in' on the tighter curves.

 

Dave