The man wants MORE caster. How about this idea?

[Dale Davies]

Shouldn't toe be taken at 90* to the kingpin, thus +6(?)* Off horizontal, - up in the fenderwell front, - down on the ground behind the wheel ?

When measuring and setting toe, the measurement is taken horizontal or parallel to the ground, at a height about the center of the spindle or wheel bearing. Caster and camber are already adjusted when you check and adjust toe. The 6°, do not sweat it as it makes no difference to toe. If this concept is too difficult to grasp, take it to an alignment shop.

Historically toe is measured at the contact patch. And that makes sense, because it's a tire wearing angle. And the tires wear at the contact patch don't they?

The other thing is, it is a difference. So as long as you measure at the same place on each side, the camber angle is taken out of it completely (if they're the same side to side).

Realistically, the camber should be very similar from one side to the other. As in within a degree. So, even if there was a slight difference in camber from one side to the other, the effect on the toe would be VERY minor.

My good gosh, your ship sailed about half an hour before you got there. To measure toe the old way, you jack up each front wheel and rotate the tire as you put a chalk mark around the circumference for each wheel about the center of the tread. This gives a true straight center to measure from. When you let the wheels down again you roll the car back and forth a few inches to settle the suspension. The final roll should be forward as you drive. Then toe is measured between the two marks and compared between the from of the tires and the rear, at the center of the hub height.
Modern alignment equipement does this by laser and computer.
The contact patch has nothing to do with toe other than being a source of excess wear if the toe is wrong.
Camber has a slightly different settling spec left to right to compensate for road crown. Caster can be used that way also. This is taken into account in the factory setting specs.

 

[72bluNblu]

I "think" I am agreeing with you but measuring from a "rack" I'm thinking you are talking about computerized equipment. That is how computerized equipment do it. Not to mention set-back. How could we ever take that into consideration. I guess there is some trigonometry involved there. Without taking set-back into consideration, we end up setting toe equal to set-back.

I'm talking about measuring toe directly, because that's how I do it. And it's actually how toe is defined.

A modern alignment rack does the toe measurement from the spindle/hub, because it does all of its measuring from the hub. But you hit it, that's a computerized system and it's programmed with the equations to come up with those numbers.

When measuring and setting toe, the measurement is taken horizontal or parallel to the ground, at a height about the center of the spindle or wheel bearing. Caster and camber are already adjusted when you check and adjust toe. The 6°, do not sweat it as it makes no difference to toe. If this concept is too difficult to grasp, take it to an alignment shop.

My good gosh, your ship sailed about half an hour before you got there. To measure toe the old way, you jack up each front wheel and rotate the tire as you put a chalk mark around the circumference for each wheel about the center of the tread. This gives a true straight center to measure from. When you let the wheels down again you roll the car back and forth a few inches to settle the suspension. The final roll should be forward as you drive. Then toe is measured between the two marks and compared between the from of the tires and the rear, at the center of the hub height.
Modern alignment equipement does this by laser and computer.
The contact patch has nothing to do with toe other than being a source of excess wear if the toe is wrong.
Camber has a slightly different settling spec left to right to compensate for road crown. Caster can be used that way also. This is taken into account in the factory setting specs.

I'm well aware of how to measure toe "the old way", that's how I do it. The better tool doesn't use chalk either, it scribes a line on the tire tread.

Toe is defined as the difference of those measurements between the tires. How the modern alignment equipment does it is a computer short cut, it's easy to program the computer to measure the toe from the hub/spindle, and doing it that way you don't need a tech to set up a different measurement or more equipment. You just do it all from the single attachment point. It's not necessarily the better way to do it, it's just the faster/easier way if you have a computer doing the math and an unskilled tech setting up the equipment.

The contact patch is the only thing that matters. Maximizing the area of the contact patch under all of your different driving conditions is what should be determining what your alignment settings are, maximizing traction and even tire wear. Otherwise you're just looking at a bunch of numbers that don't mean anything.

 

[Bodyperson]

I'm talking about measuring toe directly, because that's how I do it. And it's actually how toe is defined.

A modern alignment rack does the toe measurement from the spindle/hub, because it does all of its measuring from the hub. But you hit it, that's a computerized system and it's programmed with the equations to come up with those numbers.





I'm well aware of how to measure toe "the old way", that's how I do it. The better tool doesn't use chalk either, it scribes a line on the tire tread.

Toe is defined as the difference of those measurements between the tires. How the modern alignment equipment does it is a computer short cut, it's easy to program the computer to measure the toe from the hub/spindle, and doing it that way you don't need a tech to set up a different measurement or more equipment. You just do it all from the single attachment point. It's not necessarily the better way to do it, it's just the faster/easier way if you have a computer doing the math and an unskilled tech setting up the equipment.

The contact patch is the only thing that matters. Maximizing the area of the contact patch under all of your different driving conditions is what should be determining what your alignment settings are, maximizing traction and even tire wear. Otherwise you're just looking at a bunch of numbers that don't mean anything.

With the parallel suspension's inherent design flaws, I have to think bump steer is a bigger problem than the hair splitting geometry we are discussing at this point.

 

[72bluNblu]

With the parallel suspension's inherent design flaws, I have to think bump steer is a bigger problem than the hair splitting geometry we are discussing at this point.

Sure, toe change (bump steer) is more important for controlling the car than how you actually go about measuring the toe. As long as you measure the toe in a way that's consistent and repeatable it's fine. There are pretty well established standards for measuring it fractionally or by degrees, and even online calculators to convert between the two if you need. Really that just comes down to if your tires are going to wear correctly and the car will drive straight.

And it still depends on what you're doing with the car, a street car should pretty much always have toe-in because it's easier to control. Less focus on toe-in for a drag car, you want just enough to offset the play in the steering system so you're running at zero toe down the track because that's the least rolling resistance. For AutoX, and less so for road tracks, some folks will set a little toe out, because it makes changing directions a smidge faster. But on the street it would feel flighty and loose.

I just think it's important to understand what toe is, so you're not confusing how it's measured with what the actual purpose is. And that's totally splitting hairs, absolutely.

Regardless, measuring static toe for an alignment is the same if you've got -1° caster or +10° caster, like I said earlier. That actual caster setting will affect the toe change curve, but so will the ride height and a lot of other things. And whether that caster setting improves or degrades the toe change curve on a given car would depend on the rest of its geometry.

 

[Bodyperson]

Sure, toe change (bump steer) is more important for controlling the car than how you actually go about measuring the toe. As long as you measure the toe in a way that's consistent and repeatable it's fine. There are pretty well established standards for measuring it fractionally or by degrees, and even online calculators to convert between the two if you need. Really that just comes down to if your tires are going to wear correctly and the car will drive straight.

And it still depends on what you're doing with the car, a street car should pretty much always have toe-in because it's easier to control. Less focus on toe-in for a drag car, you want just enough to offset the play in the steering system so you're running at zero toe down the track because that's the least rolling resistance. For AutoX, and less so for road tracks, some folks will set a little toe out, because it makes changing directions a smidge faster. But on the street it would feel flighty and loose.

I just think it's important to understand what toe is, so you're not confusing how it's measured with what the actual purpose is. And that's totally splitting hairs, absolutely.

I like that. I always thought running loose wheel bearings and giving the rotors a shake at the the drag strip starting line might change times if you can stay out of the front brakes. Once again, splitting hairs. A good reason to run drum brakes if a drag racer. Okay, getting way off track.

 

[autoxcuda]

With the parallel suspension's inherent design flaws, I have to think bump steer is a bigger problem than the hair splitting geometry we are discussing at this point.

Inherent from design bump steer geometry is not that big of deal with stock Mopar systems. Especially with street driving. Even spirited street driving.

Now if you have worn or incorrect parts that cause toe change and wondering then you have a problem. Most people call this bump steer. That’s not really bump steer geometry.

If you’re balancing your car in a 4 wheel drift all leaned over… bump steer is more of a factor. Like this….

 

[72bluNblu]

I like that. I always thought running loose wheel bearings and giving the rotors a shake at the the drag strip starting line might change times if you can stay out of the front brakes. Once again, splitting hairs. A good reason to run drum brakes if a drag racer. Okay, getting way off track.

Exactly!

To me it's the little stuff. Like knowing that the forces on the rotating tire are going to pull the slack out of your tie rod ends and steering components. So, that's why you set toe in, and for best results you want the toe on YOUR car to match the amount of slack getting pulled out of those components, to run close to 0 toe on the road. So if you've got brand new tight tie rod ends and steering arms you might want 1/16" toe in, but if you're stuff is a little looser you might want 1/8". And understanding that how the steering feels out on the road could tell you that you need more/less toe in.

Or you could just set it to the spec in the book and not worry about it, even if it's not perfect for your car it won't rip the tread off your tires. But some of those little adjustments can make a car feel a lot different.

Inherent from design bump steer geometry is not that big of deal with stock Mopar systems. Especially with street driving. Even spirited street driving.

Now if you have worn or incorrect parts that cause toe change and wondering then you have a problem. Most people call this bump steer. That’s not really bump steer geometry.

If you’re balancing your car in a 4 wheel drift all leaned over… bump steer is more of a factor.

100%, spot on. Lots of people confuse worn out parts and poor alignment settings for "bump steer". But really the time you're going to notice bump steer is hard into a corner with an uneven surface.

When I made the mistake of running 2" drop spindles on my Challenger that was when I actually noticed things weren't right. Doing some "spirited" driving/cornering on winding mountain roads. Under more standard street conditions it wasn't noticeable. When I was able to plug some geometry numbers into a program it was pretty clear that the 2" drop spindles increase bump steer noticeably compared to lowered the same with the stock spindles, and that was the unsettling feeling I was getting when I was pushing the car a bit harder into the corners.

 

[Bodyperson]

Exactly!

To me it's the little stuff. Like knowing that the forces on the rotating tire are going to pull the slack out of your tie rod ends and steering components. So, that's why you set toe in, and for best results you want the toe on YOUR car to match the amount of slack getting pulled out of those components, to run close to 0 toe on the road. So if you've got brand new tight tie rod ends and steering arms you might want 1/16" toe in, but if you're stuff is a little looser you might want 1/8".

I'm gonna have to think about that one for a bit.

 

[HemiDenny]

When I made the mistake of running 2" drop spindles on my Challenger that was when I actually noticed things weren't right. Doing some "spirited" driving/cornering on winding mountain roads. Under more standard street conditions it wasn't noticeable. When I was able to plug some geometry numbers into a program it was pretty clear that the 2" drop spindles increase bump steer noticeably compared to lowered the same with the stock spindles, and that was the unsettling feeling I was getting when I was pushing the car a bit harder into the corners.

this is interesting, at least to me, when you had the 2" drop spindles installed,..... did you also lower the front 2"?

 

[72bluNblu]

this is interesting, at least to me, when you had the 2" drop spindles installed,..... did you also lower the front 2"?

It was lowered close to 2" but probably not the full 2". I wish I had a better answer, but at the time I was running the drop spindles I was very much still learning about Mopar suspension and I never took a proper "A-B" measurement to compare to the factory ride height, I was just measuring the distances from the ground to the fender and the header flanges because that's really all I was worried about.

As you know if you run 2" drop spindles without the full 2" lowering of the car you're actually making the control arm angles worse than stock, the equivalent of raising the car with stock spindles. So roll center, toe change, camber curves, etc all get worse.

When I did the comparison though it was between my car with the 2" drop spindles and another E-body that was lowered so the A-B value was 0, which results in the better suspension geometry than at the factory ride height. So even if I was lowered a full 2" the car lowered with stock spindles would have had better geometry because of the improved control arm angles. Compared to that car, the roll center on my car was substantially higher, and the toe change through the same travel was worse. The bump steer in the car wasn't obvious under normal conditions, and even pushing the car in the corners I wouldn't say it was terrible. But there was a little instability that was noticeable, especially on rougher roads.

 

[Sublime one]

It was lowered close to 2" but probably not the full 2". I wish I had a better answer, but at the time I was running the drop spindles I was very much still learning about Mopar suspension and I never took a proper "A-B" measurement to compare to the factory ride height, I was just measuring the distances from the ground to the fender and the header flanges because that's really all I was worried about.

As you know if you run 2" drop spindles without the full 2" lowering of the car you're actually making the control arm angles worse than stock, the equivalent of raising the car with stock spindles. So roll center, toe change, camber curves, etc all get worse.

When I did the comparison though it was between my car with the 2" drop spindles and another E-body that was lowered so the A-B value was 0, which results in the better suspension geometry than at the factory ride height. So even if I was lowered a full 2" the car lowered with stock spindles would have had better geometry because of the improved control arm angles. Compared to that car, the roll center on my car was substantially higher, and the toe change through the same travel was worse. The bump steer in the car wasn't obvious under normal conditions, and even pushing the car in the corners I wouldn't say it was terrible. But there was a little instability that was noticeable, especially on rougher roads.

You guys just keep writing, and I will keep learning, even tho on occasion I don’t understand what you guys write given my ignorance of all things front end. The knowledge here never ceases to amaze me.

 

[Inertia]

Good job.
Parasitic loss, in many areas, - that's where I was headed .

 

[Inertia]

I'm curious if some of you folks that change over to big caster -
If you kept track of fuel mileage before the change, then track it after, - cuz everytime you move the steering wheel, caster lifts one side of the car, - that's gonna use more power, even down a straight road, little tweek here/there, puts much bigger drag than it did before, in every turn.
You've heard how the engine slows when you turn the wheel when idling in the driveway.
Also interested if any tried going to 3* then 4* then 5* degrees caster, and when it stopped improving ?
Thnx
Great discussion.

 

[72bluNblu]

I'm curious if some of you folks that change over to big caster -
If you kept track of fuel mileage before the change, then track it after, - cuz everytime you move the steering wheel, that's gonna use more power, even down a straight road, little tweek here/there, puts much bigger drag than it did before in every turn.
Also interested if any tried going to 3 then 4 then 5 degrees caster, and when it stopped improving ?
Thnx
Great discussion.

As I've said before, I've run pretty much everything from +3.5° caster all the way up to +8° caster on my Duster. I do my own alignments, so I've arrived at running +6.5° by running both more and less than that.

When I went above +7° the steering effort began increasing dramatically, but high speed stability didn't seem to improve dramatically with it. When I went below +6° I started noticing some "tracking" coming back into the straight line stability for the steering and dropping lower than about +5.5° didn't seem to continue to make the steering effort noticeably less, but it increased tracking further. So the +6.5° I run now is basically the "sweet spot" for balancing stability and steering effort, at least on my car running 275/35/18's up front. The tracking issue has a lot to do with how wide those tires are, the wider the front tire the more the tendency for them to track the road imperfections. So with a 245 up front you might not want/need +6.5° to get your straight line stability.

As for gas mileage, I'm not sure you're thinking about this correctly. Driving straight ahead caster has no impact on the contact patch, and driving straight ahead is when you're going to have the most tire area on the ground and therefore the highest rolling resistance or what you called drag.

As you add caster to the alignment, the wheels will tip more on edge as you turn (more camber). That's where the added steering effort comes from, tipping the wheels more on edge is basically trying to lift the car. So steering effort increases.

But drag? Nope. Tipping the wheels on edge is actually going to decrease your contact patch. Less tire area on the ground, less rolling resistance. Now, if you've matched the camber gain from your suspension and what you're getting from the caster angle to the body lean angle of the car in a corner, you're going to keep the contact patch on the outside the same. That's the goal, maintaining the tire contact patch on the outside wheel. If you haven't done that and you've got too much (or too little) camber on the wheels you're actually reducing the tire contact patch while you're cornering. So, less tire area on the ground, less rolling resistance.

And sure, too much camber will wear out the tire on one edge because of how the tire is angled. But that's not because you've added rolling resistance, it's because a smaller part of the tire is bearing the weight of the car. Less tire area on the ground means higher pressure on the tire because it's bearing the same amount of weight. But the friction coefficient of the tire doesn't change, so, less area on the ground means less friction.

 

[michiganpat]

my $.02 as an engineer with a fair amount of weld fatigue analysis under my belt, is this: the fatigue life of welds are orders of magnitude lower than the parent material. with 50 year old stamped steel parts I would not trust one that's been cut and rewelded for a street driver that you're planning on putting any significant miles on, especially with roads like we have here in MI. if you feel you have to do it, I'd probably sandwich the welded area and do a combination plug and lap weld to span the newly created gap, and then grind all imperfections in the weld bead out. that's you're best bet to maximize longevity. I'd also be inpecting them at least every fall or spring...

 

[Dale Davies]

With the parallel suspension's inherent design flaws, I have to think bump steer is a bigger problem than the hair splitting geometry we are discussing at this point.

Alignment geometry is making sure the wheels are pointed the right direction to track straight on a level road.
Bump steer is a whole other discussion. It is actually roll steer engineered into the suspension to try to straighten the vehicle as it rolls in a turn. It is less scary for the average driver to go straight off a turn and hit something than to go backwards off the road and whack something they can not see.
For front suspension the rack or tierod height is moved to make the wheels turn a bit as the body rolls.
For rear suspension it depends on the suspension used, whether parrallel leaf springs or some form of multilink. On parrallel leaf springs for example, the front mount is lower than the rear mount on the shakle. As the body rolls this causes the live axle to turn a bit to straighten the vehicle. This can be reduced by moving the front mount point up a bit bit cate must be taken to not move it higher than the rear. This reduces the amount the axle turns. Of course the pinion angle is changed doing this and must then be corrected. Two link like the 60's Chev trucks, 3 and 4 link all require different procedures.

 

[Dale Davies]

As I've said before, I've run pretty much everything from +3.5° caster all the way up to +8° caster on my Duster. I do my own alignments, so I've arrived at running +6.5° by running both more and less than that.

When I went above +7° the steering effort began increasing dramatically, but high speed stability didn't seem to improve dramatically with it. When I went below +6° I started noticing some "tracking" coming back into the straight line stability for the steering and dropping lower than about +5.5° didn't seem to continue to make the steering effort noticeably less, but it increased tracking further. So the +6.5° I run now is basically the "sweet spot" for balancing stability and steering effort, at least on my car running 275/35/18's up front. The tracking issue has a lot to do with how wide those tires are, the wider the front tire the more the tendency for them to track the road imperfections. So with a 245 up front you might not want/need +6.5° to get your straight line stability.

As for gas mileage, I'm not sure you're thinking about this correctly. Driving straight ahead caster has no impact on the contact patch, and driving straight ahead is when you're going to have the most tire area on the ground and therefore the highest rolling resistance or what you called drag.

As you add caster to the alignment, the wheels will tip more on edge as you turn (more camber). That's where the added steering effort comes from, tipping the wheels more on edge is basically trying to lift the car. So steering effort increases.

But drag? Nope. Tipping the wheels on edge is actually going to decrease your contact patch. Less tire area on the ground, less rolling resistance. Now, if you've matched the camber gain from your suspension and what you're getting from the caster angle to the body lean angle of the car in a corner, you're going to keep the contact patch on the inside the same. That's the goal, maintaining the tire contact patch on the inside wheel. If you haven't done that and you've got too much (or too little) camber on the wheels you're actually reducing the tire contact patch while you're cornering. So, less tire area on the ground, less rolling resistance.

And sure, too much camber will wear out the tire on one edge because of how the tire is angled. But that's not because you've added rolling resistance, it's because a smaller part of the tire is bearing the weight of the car. Less tire area on the ground means higher pressure on the tire because it's bearing the same amount of weight. But the friction coefficient of the tire doesn't change, so, less area on the ground means less friction.

Increasing caster increases camber change in a beneficial manner. As the body rolls in a corner, both wheels lean over, the outside wheel wants to add positive camber and the inside wants to have negative camber. On unequal length A arm suspension you want the outside upper control arm to pull the top of the wheel toward the center of the vehicle. In like manner you want the inside wheel upper control arm to push the top of the wheel out. This works to maintain as much contact patch area on each tire as possible. The outside tire gets the weight transfer and is required to do the most to keep traction in the corner.
Increased caster also aids camber gain in a desireable direction.

 

[72bluNblu]

Increasing caster increases camber change in a beneficial manner. As the body rolls in a corner, both wheels lean over, the outside wheel wants to add positive camber and the inside wants to have negative camber. On unequal length A arm suspension you want the outside upper control arm to pull the top of the wheel toward the center of the vehicle. In like manner you want the inside wheel upper control arm to push the top of the wheel out. This works to maintain as much contact patch area on each tire as possible. The outside tire gets the weight transfer and is required to do the most to keep traction in the corner.
Increased caster also aids camber gain in a desireable direction.

Yeah, that's what I said. In a perfect world the combination of your static camber, camber gain from the control arm travel, and camber gain from the caster angle would combine to match the lean angle of the car and keep the outside wheel flat on the ground to maximize traction.

@inertia 's question was about fuel mileage, and the way that the geometry works, if everything is set up perfect in a perfect world, you'd maintain the contact patch you'd have when everything is going straight and level. Realistically, the best you'll do is maintain the contact patch on the outsidee wheel, with the inside wheel patch getting smaller as the weight of the car is shifted. Regardless, you're not going to be increasing the contact patch overall, so, no lost mileage.

 

[72bluNblu]

my $.02 as an engineer with a fair amount of weld fatigue analysis under my belt, is this: the fatigue life of welds are orders of magnitude lower than the parent material. with 50 year old stamped steel parts I would not trust one that's been cut and rewelded for a street driver that you're planning on putting any significant miles on, especially with roads like we have here in MI. if you feel you have to do it, I'd probably sandwich the welded area and do a combination plug and lap weld to span the newly created gap, and then grind all imperfections in the weld bead out. that's you're best bet to maximize longevity. I'd also be inpecting them at least every fall or spring...

I think inertia had the best idea for the stock UCA's if you wanted to use them. Buy or make a ball joint plate to switch the ball joint over to a bolt in style, no more wearing out threaded ball joint mounts.

You could cut the end off the factory UCA, through the flat section. If you did this at an angle, it would add caster. Then butt-well the ball joint mounting plate to the factory UCA. Either section back, or overlap the shoulder on the factory UCA with a piece of flat stock, wrapping it and welding it all the way around the plate if possible to create a shoulder on it as well. You could then gusset the ball joint mounting plate to the UCA across the bottom with a flat plate, or get really fancy and gusset it across the top, shoulder to shoulder, with a section in the middle coming down to tie into the ball joint plate.

All said and done I'd just buy a set of SPC adjustable UCA's. Much less work and double adjustable. Probably not even more expensive if you figured your time at the shop rate for someone that could do this kind of work.

 

[autoxcuda]

I think inertia had the best idea for the stock UCA's if you wanted to use them. Buy or make a ball joint plate to switch the ball joint over to a bolt in style, no more wearing out threaded ball joint mounts.

You could cut the end off the factory UCA, through the flat section. If you did this at an angle, it would add caster. Then butt-well the ball joint mounting plate to the factory UCA. Either section back, or overlap the shoulder on the factory UCA with a piece of flat stock, wrapping it and welding it all the way around the plate if possible to create a shoulder on it as well. You could then gusset the ball joint mounting plate to the UCA across the bottom with a flat plate, or get really fancy and gusset it across the top, shoulder to shoulder, with a section in the middle coming down to tie into the ball joint plate.

View attachment 1716209847

View attachment 1716209848

All said and done I'd just buy a set of SPC adjustable UCA's. Much less work and double adjustable. Probably not even more expensive if you figured your time at the shop rate for someone that could do this kind of work.

Or buy this replacement sleeve for the K727 screw in ball joints. Steel Upper Ball Joint Sleeve, K772 Style

 

[Dale Davies]

Yeah, that's what I said. In a perfect world the combination of your static camber, camber gain from the control arm travel, and camber gain from the caster angle would combine to match the lean angle of the car and keep the inside wheel flat on the ground to maximize traction.

@inertia 's question was about fuel mileage, and the way that the geometry works, if everything is set up perfect in a perfect world, you'd maintain the contact patch you'd have when everything is going straight and level. Realistically, the best you'll do is maintain the contact patch on the inside wheel, with the outside wheel patch getting smaller as the weight of the car is shifted. Regardless, you're not going to be increasing the contact patch overall, so, no lost mileage.

The caster will also help keep the outside wheel.vertical or just a bit more negative camber with the lran to mazimize that contact patch also. It is the outside tire that is most important.
When Trans Am changed to sports cars, allowing Corvettes to run with the 911RSR Porsches, yhe Porsches lifted the inside front wheel. The low front mass allowed them to be fast in corners on three wheels. They used a stiff front antiroll bar to keep as much weight as possible on the inside rear for traction to accelerate out of the corner.