: Severe Tramlining Follow-up—Problem Resolved

01-01-09, 12:15 PM
After researching a problem on this forum yesterday, I realized that a lot of people describe a problem in depth, get input from others, talk about how they’re going to attempt to fix the problem “this weekend”, then don’t post again to let us know if the solution worked (or didn’t). To avoid being one of these people, I wanted to follow-up on a thread I started two years ago on a severe tramlining problem with my 2000 Catera (non-sport). You can find the particulars of the problem in the original thread (http://www.cadillacforums.com/forums/cadillac-catera-cimarron-forum/86944-tramlining-aka-un-happy-wanderer.html).

For those of you unfamiliar with the term, tramlining (sometimes incorrectly referred to as trammeling or tramming) is a tendency of a car to deviate from straight-line travel when encountering longitudinal ruts or irregularities in a road surface. Two examples common on roads I travel each day:

1) A 2-foot wide trench was dug along the length of a 1-mile stretch of road several years ago to replace an underground water pipe. The trench was filled and paved, but compaction of the fill has resulted in the new asphalt being slightly lower (maximum of about 1/2 inch) than the original asphalt. This “rut” is about where the driver’s-side tires fall when I’m in the middle of my lane. The car was impossible to drive in a straight line, as the tires would either pull the car into the rut, or once in the rut, would wander with every irregularity since the trench was not completely flat nor straight. As the tires moved from the center to edge of the rut, they would grab the higher regular road surface, jerking the car out of the rut.

2) Approaches to signaled intersections where heavy trucks sitting on hot summer days have caused alternating ruts and ridges to develop in the asphalt. Driving through these intersections at speed would cause the car to pull and jump from one side of a rut or ridge to the other.
In areas with studded-tire use, ruts that cause tramlining are common from gradual degradation of asphalt or concrete in tire tracks. Note that I’m limiting the term tramlining to these large-scale longitudinal features, not common rain grooves. The “shimmy” experienced by some vehicles on rain-grooved roads is unrelated to the larger-scale tramlining that I’ve described in the examples above.

10,000 miles ago, I finally replaced the original Goodyear Eagle RSAs with Bridgestone Potenza G 009s. The severe tramlining that had plagued this Catera since I can remember disappeared instantly. And I don’t mean it was reduced—it’s GONE. It drives like a new car. I no longer have to fight ruts or other irregularities—it just goes where it’s supposed to, and keeps driving straight. After this experience, including a lot of research on tramlining, I’ve drawn the following conclusions that I hope are helpful to anyone experiencing this problem:

1) It’s the tires!!! Bad alignment, suspension wear, and/or improper inflation may be contributing factors in some cases, but nothing will solve a severe tramlining problem except a different set of tires.

2) Some tires may be less prone to tramlining on a Catera than others. Apparently, severe tramlining is caused by a combination of the suspension geometry of a particular car and the characteristics of a particular model of tire (sidewall stiffness/height, tread width, shoulder profile, etc.). Without spending all day with a tire dealer, changing and test driving various tires, it’s hard to know just what tire will work with the Catera and which won’t.

3) Wide, low-profile tires are more prone to tramlining than narrow, high-profile tires. The 205/65 R15 tires common on the Opel/Vauxhall Omega in Europe seem to be much less prone to tramlining than the 225/55 R16 tires on my Catera or the even wider tires on the Sport version. I considered going to a 205/60 R16 (same circumference as originals), but it’s difficult to find that size tire with a 94 or greater load rating.

4) A rounder “shoulder” profile (where the tread meets the sidewall) may be less prone to tramlining than one that’s squarer. Some posters to other forums indicated that tramlining became worse as the tires wore. Note that the shoulder profile will become squarer as tread is worn off. The Bridgestones that I bought have a very round profile to begin with—much rounder than the new Yokohama YK520s on my other car.

I hope this information is useful to anyone who is experiencing a tramlining problem.

01-02-09, 01:50 AM
Yes this rule of thumb can be applied to any car, the wider/summer/performance tires will tramline more than skinnier/taller/all-season tires.
When I drive my summer weekend car, with its 200 treadwear max performance summer tires, I have to have the steering wheel turned at about 45 degrees from straight when pulling up to a heavily rutted intersection due to the severe tramlining effect.

01-02-09, 10:58 AM
Thanks for the feedback. Too many of us forget to provide a resolution to the problem. Glad it had a happy ending for you.