Radial Pull


#1

My truck has always pulled to the right. I was told by Dodge it was the way the camber was set so the tiers would track straight at highway speeds, even on the highway I thought it pulled hard to the right. My arm would get tired from pulling the steering wheel to the left on long drives. The OEM front tires developed over time a uneven wear pattern and at 37k miles I decided to get new tires and a front end alignment.

A big name tire sales company in the pacific north west did the alignment and I got 2 new Toyo tires for the front. The rear OEM tires are still in very good condition.

While driving from one town to another on a state highway I noticed it was still pulling a little to the right, not near any where as bad as it was. I called the BNTSC and went in to have them check the alignment. I got the truck back and was told I had Radial Pull. When I asked what that was the question was deflected and I was told the changed the tires left to right and that should fix it. I asked again what Radial Pull was and the tire tech mumbled something about differences in tires and changing them side to side should fix it. I asked about didn’t I get the new tires, spin balance, and mounting I paid for, why or how could the tires be that different to be causing side pull, sounds like the tires have a defect so bad you could not put enough weights to make it track straight? The tire tech said if they still pulled to come back in and they would change out the tires.

My question are tires with Radial Pull defective and are they safe to drive, or did they mess up the alignment? At $260+ per tire I want good tires, not borderline defects.

Any Ideals?

Thanks,
Ray


#2

Yes radial pull does exist. There are minor variations, not defects, in the tires that can cause this. It is usually noticeable on vehicles that are sensitive to leads and pulls. Sometimes swapping tires side to side can fix a small pull that the alignment specs don’t show. If the pull is fixed, hooray, don’t worry any further. It most likely won’t re-occur when you rotate the tires.

And by the way, weights on the tires do no affect the alignment. They are there to remove the vibrations from minor variations in the tire and wheels.


#3

I’m sorry, but based on your description of the symptoms I’m not buying that “radial pull” line. And that old line about the alignment specs being biased to compensate for road crown… I’ve never seen it, and if you ask them to see the alignment specs Ill bet you won’t see it either. That “uneven wear pattern at 37k miles” you mentioned is cold hard evidence that something is amiss. And since it’s still doing it with the new tires, it’s the truck that’s harboring the problem, not the tires.

Can you describe how the wear was uneven at 37K miles?
Is the truck 4x4?
Are you the original owner?

As a minimum, I’m thinking you need a good four wheel alignment and not just a front end alignment. A rear axle that isn’t square to the frame… and yes, I’ve seen this on a brand new vehicle… would cause pulling to one side. That possibility should be investigated.

I disagree that rotating tires will help. Your problem existed before you had these tires.


#4

Thanks for your quick replies.

I’m the original owner. My truck is a 2006 4wd SLT crew cab 4 door Dakota magnum V8. The Dodge dealer gave me the song and dance about the front end being within specifications. The tires are cheap version Goodyear Wranglers supplied to Dodge as OEM. IIRC they only have a 40 or 50k millage warranty.

The wear was on the left side (worse) to right (not as bad). The left most tread was about wore completely away with the tread on the right covering Lincolns head. The rear tires, same age and mileage are in great shape, they have another 20-30k miles left in them.

The front end alignment I got Saturday is the only alignment that’s ever been done. The BNTSC alignment tech reported the following: see attached file for photo copy of paper work

When I took it back in the paper work only says warranty rotation, changed sides on front end…nothing about Radial Pull.

Any additional ideals/thoughts?

Thanks for your help.

Ray


#5

Your toe was WAY off on the left

That is what killed the tires early, in my opinion

The right tire wasn’t quite as worn, because the toe was way off on the left side only

The right side camber was slightly too negative, but it wasn’t as far off as that left toe

Incorrect toe can lead to short tire life


#6

They clearly made some adjustments, and those are I believe what reduced the amount of pulling you’re feeling. Clearly the alignment was screwy from the factory. I consider that to be additional hard evidence that the problem is the vehicle and not the tires and that the dealer was “blowing you off”.

You’ll also notice that there is no variation in the left and right specs. That “aligned that way to compensate for the crown in the road” is clearly bull. I’ve heard that line before, and never seen it in any alignment specs.

I do see a 2 degree difference in the SAI, the Steering Axis Inclination. The SAI is a not-individually-adjustable (result of other adjustments) angle of inclination between true vertical and the angle of the true axis around which your steering knuckle rotates. It IS a definite factor in your vehicle’s returning to straight after turning and in your vehicle’s willingness to roll straight. Included Angle, another secondary angle, is a combination of the SAI and the camber, so ignore that. It’s different because the SAI is different.

And now I’ll solicit input from those much more experienced than I for an opinion on the two degree difference in the SAI between the right and left sides. My feeling is that is your “smoking gun”, but I’d really appreciate hearing from asemaster, capriracer, ok4450, and the other experienced pros here on that opinion.

Thanks a million for posting the printout. That’s a huge help.


#7

I own and have owned Dodge Dakotas since 1986. The Dodge dealer is full of beans. I’ve never owned a Dakota that ever had any handling issues and none have pulled to the right or the left. You need a “quality” front end inspection and alignment. You won’t find that kind of service at any dealership so I suggest you avoid them. Alignments are a specialty service which dealerships simply do not offer.


#8

On another note, it’s safer to have the new tires on the back, not the front. I’m surprised that they did that, as most tire shops have a strict rule about that now.


#9

I can’t read the numbers on your pic but can offer a couple of things:

Steering Axis Inclination, also known as Caster must be equal on both sides or else steering pull will result. From what I can see on the Internet, you have a double “A” frame front suspension. It appears that the upper “A” frame is adjustable with shims to make your caster angles equal. It is possible that Toe on one side or the other could be adjusted to the permissible limit or even outside the limit to mask the unequal caster but that could result in odd tire wear that you might not see for a while after which it is easy for a front end person to duck responsibility by not being accountable for work done long ago.

My overall view is that you need better qualified front end people with equipment that is calibrated correctly.


#10

SAI is not caster. Caster on this printout was brought within specs and within .2 degrees of difference.

Caster is a measurement of the angle in the vehicle’s longitudinal axis between its upper articulated point and its lower articulated point, a measurement of the way the suspension moves vertically. SAI is the axis around which the steering knuckle rotates. The two are related, but very different measurements.

Normally an SAI problem is due to damage. In this case it was probably manufacturing error.


#11

I’ll argue that SAI is the same as caster as viewed from the side of the vehicle when the front wheels are aimed straight ahead which is where the OP is experiencing steering pull.


#12

In the OP’s case, the final angles are
caster: 4.0 degrees and 3.8 degrees
SAI: 13.6 degrees and 15.8 degrees.

Would you like to explain to me how these are the same?

Caster Definition:
Caster can be defined as the forward or rearward tilt of the projected steering axis from true vertical, as viewed from the side. This line is formed by extending a line through the upper and lower steering knuckle pivot points. For vehicles with front control arms, visualize the line extending through the upper and lower ball joints. On strut equipped vehicles, the line extends through the lower ball joint to the center of the upper strut mount. Caster is always viewed from the side of the vehicle.When the upper pivot point is rearward of the lower pivot point, caster is positive. If the upper pivot is forward of the lower pivot point, caster is negative. When the two points are straight up and down from each other, the caster is zero. A maximum side to side variation of ±.5° is recommended on most vehicles. Caster is NOT a normal tire wearing angle and is used as a directional control for stability and steering returnability.

SAI Definition:
The angle between the centerline of the steering axis and vertical line from center contact area of the tire (as viewed from the front). SAI is typically not adjustable, but deviations from specification can indicate vehicle damage. A maximum variation side to side of ± 1.0° may also indicate vehicle damage. This topic is covered in detailed charts later.
Effects of SAI

SAI urges the wheels to a straight ahead position after a turn. By inclining the steering axis inward, it causes the spindle to rise and fall as the wheels are turned in one direction or the other. Because the tire cannot be forced into the ground as the spindle travels in an arc, the tire/wheel assembly raises the suspension and thus causes the tire/wheel assembly to seek the low (center) return point when it is allowed to return. Thus, since it has a tendency to maintain or seek a straight ahead position, less positive caster is needed to maintain directional stability. A vehicle provides stable handling without any of the drawbacks of high positive caster because of SAI.


#13

This is the only ‘radial pull’ I’m familiar with:


#14

That’s the only one that’s valid!
Sweet ride, by the way.


#15

If I have a flat tire, the odds are it will be one of the older tires, why would I want that tire in the front where it will severely affect steering?

I’m a little confused now, should I do anything if the Radial Pull is gone now that the front tires were changed side to side?

I look at the alignment report and it appears there are some actual settings that are at the edge of specified range. Should not the actual settings be in the center of the specified range?

What do I need to do now?

Thanks for your help.

Ray


#16

The theory of putting the better tires on the rear comes from the recognition that the front of the vehicle will typically have more weight, especially with FWD vehicles and with pickup trucks. By virtue of the extra weight, the front has a built in traction advantage. The front/rear imbalance, the lighter rear end, can allow the rear of the vehicle to lose traction first and slide sideways, spinning out the vehicle. Putting the better tires on the rear is to compensate for the difference in traction between the wheels with the lesser weight on them and the wheels with the greater weight, in an attempt to prevent spinout.

The theory has, by the way, been proven with wet-pavement testing. I’ve seen the films.

If you’re happy with the handling now, just enjoy the driving. It was my understanding, perhaps assumption, that you were still feeling some pulling, but if I’m wrong I apologize.


#17

A search on the web will find a lot of articles to explain why two new tires only should go on the rear no matter which are the driven wheels. I also wonder why any responsible tire store would not know this.


#18

There is such a thing as tire pull even with tires that are not a safety issue. The thing that sticks out to me here is what db4690 mentioned; the toe. It was off a lot.

It could be that the toe was incorrect from day one at the factory or it could be that it was caused by rough unloading from a transport truck, pothole, curb strike, etc.

It doesn’t hurt to add a bit more negative camber and positive caster into the right front to account for road crown.


#19

TSM, I stand corrected. It seems that SAI is more related to camber, not caster. When successfully doing front and rear wheel alignments at home with simple tools I have worked only with caster, camber and toe. The other alignment design specifications are not easily adjustable and I have not had to work with a damaged vehicle other than alignment upset during normal vehicle use.


#20

If it’s "Radial Pull, you swap the tires side to side and it should now pull the other way…It’s caused by the belts in a radial tire not being centered exactly.

If you swap the tires side to side and it still pulls to the right, then something else is causing it.

Move the rear tires up to the front and see what happens…