[Archived]

Adjustment for road crown is a caster adjustment. Increasing the caster removes drift to that side. (That adjustment can knock the steering wheel off center by changing toe in.) In some cases the alignment is taken out of specs to eliminate drift or pull depending on the particular vehicle and where it is driven.

I think we are talking more or less about the same thing, but not all vehicles are aligned at Prevost or other superior facility. When the alignment is properly completed the steering wheel should be perfectly straight and the steering gears on center when the wheels are straight. Any further adjustment to the steering wheel position must be done north of the pitman arm, not by the pitman arm.

My comments were generalized and applicable to all vehicles PC members may be concerned with. Most vehicles have only two ways to center a steering wheel: by properly adjusting toe or removing and resetting the steering wheel. In those vehicles the later should never be done.

However, regardless of vehicle if the wheel was always straight before the new tires and new alignment, it should be straight after the new alignment without having to make any adjustments north of the pitman arm to center it. If not, you should be very concerned when that operation is suggested.

[Archived]

I think we agree. If I am interpreting you correctly if the steering box is centered and the steering wheels is centered a proper alignment should end up with the steering wheel still centered.

I think Prevost ignores the steering wheel position relative to the steering box but instead does all their adjustments based on the steering box being centered. Then if needed adjusts the steering wheel as the last action, knowing everything else is correct.

[Tim]

Yes, exactly!

Few alignment shops and technicians have the knowledge and training that Prevost has. Most shops set toe in so the steering wheel is straight regardless of where the gears end up. They don’t know when the steering box is top dead center by any means other than steering wheel position. Additionally, gearbox preload is set on top dead center, so if the wheel is out of position with relation to the shaft, preload would be off.

Even with a perfect alignment the vehicle may pull or drift to one side. (Could be a tire.) The usual fix is to increase caster on that side and in doing so the toe in will change. So will the steering wheel position. This is where the tech may want to reposition the steering wheel rather than going through the trouble of correcting the condition at the tie rods.

Centering a steering wheel by repositioning it on the shaft is not a wise modification and should always be avoided. If the alignment is done correctly there is absolutely no need to do that unless someone did so previously. In that case it’s a correction not a modification.

Here’s a thought: if the vehicle has no existing problem with abnormal tire wear and it drives correctly, don’t mess with the alignment when replacing tires. There’s no need!

[Tim]

I feel my tires. Sounds silly, but visually a tire can look like it is wearing OK, but your hands are very sensitive to even the slightest unusual wear. The left front tire had a barely detectable unusual feel to it compared to the RH side so that was why I had the alignment done. It was on the side where I had replaced the tie rod. I measured as precisely as possible to get the exact same length, but that was likely the cause of the wear.

The price of today’s tires makes an alignment a bargain.