TTopJohn

Okay, here's what we've (supposedly - see my more recent post with what I really had)got right now -
-.7 camber
+4.5 caster
1/16 toe in

It feels great on the freeway in town, but took a road trip last weekend and some of the LONG straight stretches required a bit too much concentration and slight steering correction. Ever so slight side to side on certain surfaces.

I'd prefer it to track down the highway like a DeVille or a freight train.

Do I need to dial back the camber to say -.5 or -.25?

Different Caster setting?

More toe in?


Note - this could also just be the messed up wear pattern on my near time to be replaced Firehawk SZ50s - the outside edge is worn down pretty bad, and the recent alignmetn with -.7 negative camber is in the process of correcting that by shifting to the inside edge. I think this corrective action on the wear pattern could produce a squirlley feeling from time to time.

ZaneO

I was under the impression that 0 toe would track straighter, but I could be wrong.

technical

Your tires are probably not helping. A little more toe-in would help when going faster down a highway at the expense of "turn in" quickness while going slower.
The camber and caster should be fine. You can bump the caster up to slow down the steering as well without hurting tire wear.

APeteSS

Actually, since I've set up my negative camber (about where your is), I've got the same symptoms. The car really 'plants' well in a turn, but is twitchy when going fast in a straight line. This is due to the car riding of the insides of the tires when going straight and rolling over to the full tread surface in the turns.

Also, when going fast in a straight line, there's less 'plant' on the tires, making the car run even more on the insides of the tires. Not to mention the centrifugal force making the tires taller at speed, and shrinking the contact patch.

TTopJohn

See, that's what I was thinking.

But here's another theory building on that - Caster shouldn't do anything when I'm going in a straight line. But maybe what I'm experienceing is this
1)car encounters something that deviates it from it's intended path, a bump, dip, change in pavement texture, whatever
2)I correct, based on the amount of correction I had been giving it with the old factory alingment specs
3)this ends up being too much correction, because the increased + caster, combined with the increased baseline - camber, mean that for each degree I turn teh wheel, there's a LOT more negative camber than there was with teh factory alignment specs.

All this would seem to exacerbate the problem as APeteSS's post puts it. And so the cure might be to dial back - camber and dial back + caster?

But on the other hand, the + caster seems to provide good self centering and firm steering - kind of an "anti twitchy" feeling - is this the case or am I imagining things?

technical

The less caster you have, the more "unstable" the steering will feel. Think of a motorcyle with a decent rake vs a shopping cart wheel, which one tends to go nuts. As for tires growing at speed...unless you're running slicks at 200mph, I doubt your 245's or 275's low profile tires or whatever you're running are balooning at all. -.7 is not much camber. I ran -2.0 without any instability. You're also running worn tires!!!

TTopJohn

I should have been more clear above, I agreed with his theory about the negative camber being a possible culprit - because between caster and camber, camber is the only one that should have an effect if you are not turning the wheel. I don't think my tires are getting taller at speed.

The worn tires thing - that could be the whole explanation right there?

technical

-.7 camber will not reduce the contact patch dramatically.

Worn tires can cause all kinds of strange results especially wandering. See what happens when you get new ones.

TTopJohn

Yeah, I think that's what I'm going to do. Planning on a set of Goodyear Eagle F1 GS-D3s sometime in August.

jRaskell

iTrader: (1)

GS-D3s These tires ROCK!

Get tires before making any adjustments. Trying to make appropriate adjustments on old worn out unknown treads would be like trying to eyeball align a cabinet frame on a row boat in choppy seas. Maybe not quite THAT severe, but you get the idea.

TTopJohn

I'm revisiting this since my Eagle F1 GS-D3s are on the way to my crib.

From reading up on alignment settings, I've found that increased negative camber can increase tramlining - because the tire is trying to turn, the way a bicycle turns when you lean it to one side.

With that in mind, I think I'm going to go with a new allignment for the new tires, and slightly dial back the negative camber. While I do enjoy the corners, the VAST majority of my mileage is in a straight line. And with the massive positive caster, when I DO get to a corner, I'll have plenty of negative camber as soon as I turn the steering wheel.

Camber -.5 (down from the previous setting of -.7)
Caster +maxed out
Toe In 1/16


Thoughts?

TTopJohn

HEre's what I ended up with

BEFORE:
Camber -.5 -.3
Caster +4.9 +5.0
Toe -.24 -.23 (note - I don't know what the hell + or - toe is, I just know toe in and toe out. The dudes at NTB said - toe is toe out and + toe is toe in. Is this right?)

AFTER:
Camber -.5 -.6
Caster +4.9 +5.0
Toe +.06 +.05 (this is a touch of Toe In, right?)

ANyhow, it's closer matched side to side than it was, and now I've got a printout v. just a verbal confirmation of what the specs are/were. And if it was toed out before and it's toed in a bit now (still confused as to what positive and negative toe is) then that should cure my tramlining. It felt good in the quick interstate blast after the alignment. The road trip to Gulf Shores labor day weekend will be the true test.

You would not believe the way they tried to talk me out of the -.5 negative camber, they wanted dead 0 or positive. I stood my ground, I know better than to listen to them when they want to just "put it in the green" - I've killed the outside edge of a set of tires doing that.

roy

Also remember , depending on your tire size , this twitchy feeling may never go away completely with a perfromance oriented alignment. Especially with roads that have crowns or ruts. But you can ever so silghtly deaden the feeling like you did. Some shops will put in an extra 1/2 degree of +caster on the passenger side to help negate this . Plus upping the (+) toein to 3/32 total.

TTopJohn

Drove out to fort worth last night for Laps for Charity at Texas Motor Speedway. In addition to checking out all the cool cars and driving 3 laps on the track (FUN - touched 95 on the last lap, and the banking is wicked cool) I got to drive about 75 miles of freeway - some in really good shape, some in disrepair.

The verdict is the new settings feel great. While it may not track down the road with one finger on the wheel like Dad's old 78 Coupe DeVille, it doesn't feel twitchy in the least, and only requires minute correction over the worst ruts and roads where the pavement is at two different levels due to construction.

I agree with you Roy, it won't ever feel like a Lincoln Town Car on the interstate. But think I've gotten as close as I can while keeping a 245/50/16 tire on there and maintaining handling precision. Any more toe in I'm afraid would wear the tires too quickly, and any less - camber would wear the outside edge of the tires to quickly, while giving up some cornering ability.

white01ss

iTrader: (37)

I found a link on the internet that said toe in was positive and tow out is negative. Looks like you had a good bit of Toe out before. This would explain why your car was so touchy.

Factory wants toe in of around +0.15 for our cars so people can drive with their knees and eat a burger and fries without running off the road. The wheels are constantly fighting each other which creates a stable tracking at highway speeds.

Toe out has the opposite effect in that the inner wheel is already turned into a corner and a little nudge in either direction causes the car to dive into the corner.

The info I found seems to back what you experienced. I'm shooting for 0 to +0.05 toe on my setup.

rambo benson

I'm really glad to read this. I've had my SS vert aligned so many times now. Bumps or wobbles in a road literally trying pull me in the ditch. I think I must have a lot of toe out.

With New Potenzas and alignments, I thought must be something wrong with the suspension. Worn out bushings or something...but only 30K miles.

Thanks, I'll take this info back to Firestone for free lifetime alignment tune-up.