Thor Forums

[Chance]

Originally Posted by dstankov

I believe they are checking or adjusting the Thrust Angle to ensure the rear axle is properly aligned to the front axle/suspension. Improper thrust angle will result in a vehicle pulling sideways. Ever see a car going straight down the road at an angle where, when the have the wheel pointed straight, you can see all four tires?

Verification of the Thrust Angle is especially important on motorhomes that have had a chassis stretch. 1/8 inch of additional length of frame metal on one side would throw out the thrust angle significantly. One would think that MORyde or whoever does the frame extensions would be required to checking the thrust angle prior to shipment.

A MORyde video I've seen claims they align the chassis before welding it back together. I would expect no less. There is no way a shop like that will get things off by anything close to 1/8-inch. I actually worked in a much smaller shop while in high school where truck frames were stretched. It isn't that hard. And I think MORyde uses some kind of jig based on what I saw on video that should result in straight frames.

Occasionally I've seen a semi trailer dog tracking when the trailer axle(s) were installed in wrong holes of frame, but there we are talking about being inches off alignment across a distance of just 3-feet or so.

Anyway, I'm still not sure what they adjust on a live axle with leaf springs that is not intended to be adjustable. This link covers it well:

Tire Tech Information - Alignment

Originally Posted by from link

Front-End, Thrust Angle and Four-Wheel Alignment

The different types of alignments offered today are front-end, thrust angle, and four-wheel. During a front-end alignment, only the front axle's angles are measured and adjusted. Front-end alignments are fine for some vehicles featuring a solid rear axle, but confirming that the front tires are positioned directly in front of the rear tires is also important.

On a solid rear axle vehicle, this requires a thrust angle alignment that allows the technician to confirm that all four wheels are "square" with each other. Thrust angle alignments also identify vehicles that would "dog track" going down the road with the rear end offset from the front. If the thrust angle isn't zero on many solid rear axle vehicles, a trip to a frame straightening shop is required to return the rear axle to its original location.