Tramlining; weird issue.

Need help with this one; 2021 ST w/ 35k miles. Over the past six months I've had an issue I could only describe as "tramlining" where the car would swerve some when going over uneven road surfaces. I posted about it in some FB groups and the usual input was given with regard to tires and suspension.

Last week I was at the dealer for a free oil change and they rotated the tires. After picking the car up, the tramlining was unbelievably bad; the car feels completely unsafe. It feels like a fish swimming down the road.

I had new tires on order and an appointment with my speedshop today so I didn't drive the car over the weekend and just waited for them to look at it. They balanced and mounted the tires today, and went over the entire suspension system and found no issues. Car still behaving the same.

I'm taking it back to the dealer now but wanted to get some feedback here in case anyone else has experienced an issue like this.

The vehicle has Steeda springs and rear sway; nothing else. I've owned a lot of cars and have experienced tramlining before. This feels unlike anything I've ever encountered. Undriveable.

If you are still on the factory wheels with the same size tires, get the alignment checked. Sounds like the rear toe is out. They will be able to look at the steering/suspension parts at that time too. That is not normal on factory wheels and tires.

I have experienced similar issues with other vehicles that ultimately were attributed to alignment issues (Toe), warn control arm bushings, and weight distribution due to an issue with suspension setup.

Brand-new Michelins and alignment at a speed shop today. They went over the entire suspension too...no issues found. This is a weird one.

The only thing wierd about this is that it got worse with the tire change. That doesn't make sense to me. Have your alignment checked and have them pay attention to the rear toe setting as well as the thrust angle. Too much toe-in for the rear can make a vehicle feel like it's being pushed and if the thrust angle is off it will also feel bad.

Looks like some posts got in before me. Can you show us a copy of the alignment printout? One last thing, does it have stock wheels and tire size?

It got worse with the tire rotation last week. Was same after new tires installed today. Dealer also replaced driver-rear axle last week.

Yes, stock wheels and replaced the oem pirellis with same size Michelin Pilot Sports today.

This is kinda crazy because both worn tires and new tires can cause what you are describing. This can be related to how the tires follow the grooves worn in asphalt by normal wear and tear on the roads. I can't imagine the Michelin tire being a cause here but I've been wrong before.

Most of those alignment numbers look good to these eyes. I'd probably want a little more positive camber all the way around if it were mine but you are in spec and in your situation that could exacerbate what you are feeling. Not only that there is only a limited amount of available camber adjustment on these vehicles.

Have there been any modifications or damage (hard speed bump or divot) to the front end? I don't have any idea what the actual spec is for the Steering Axis Inclination (basically a fixed angle). Included Angle (IA = SAI + or - Camber Angle). Alignment equipment doesn't usually show these values because the SAI isn't adjustable per se. That value is related to front-end parts (steering knuckle, for instance) and frame or body position. These shouldn't ever need to be changed unless something is bent or broken. Body shops typically have those numbers.

Those two measurements seem to be a long way apart. Old school (that's where I'm from) Techs were taught that these numbers shouldn't be more than 1.5 degrees apart, side to side or you would feel it. This changed a bit on dedicated front-wheel drive vehicles.

I think the first thing I'd look at doing, given those numbers is to find out what Ford says the SAI number should be and what tolerance between two sides is acceptable.

I agree with you, those numbers do seem a little far apart. And in most cases they are not adjustable. Collision repair technicians us them as diagnostic angles to detect damage.

Did they check your wheel bearings and or steering gear? In theory new tires would grip better and follow the ruts in the road more aggressively with loose steering gear and or front wheel bearings.

[QUOTE="GearHead_1, post: 86628, member:

Have there been any modifications or damage (hard speed bump or divot) to the front end? I don't have any idea what the actual spec is for the Steering Axis Inclination (basically a fixed angle). Included Angle (IA = SAI + or - Camber Angle). Alignment equipment doesn't usually show these values because the SAI isn't adjustable per se. That value is related to front-end parts (steering knuckle, for instance) and frame or body position. These shouldn't ever need to be changed unless something is bent or broken. Body shops typically have those numbers.
[/QUOTE]
Nothing.

The speedshop did not. The car is now at the dealer with 60 miles of bumper-to-bumper left so I'm not picking it up until they resolve the issue.

I have had the same problem since installing lowering springs. Which has been over a year now. I’ve added so much crap to my car to get it fixed and still nothing. It’s kinda nice someone else has the same problem. I’ve replaced tires, adjustable end links, adjustable tie arms. And even new tie rods up front. Still nothing. Have gotten an alignment 4 times now. It blows my mind. Everything else suspension wise is in working order.
Although one person commented about bad wheel bearings and I do have wheel spacers installed. I wonder if that has prematurely made them fail.

Also for full transparency I experienced something like this feeling before the spring install with everything stock. I just chocked it up to the stock tires sucking like so many had said. And it felt like it hydroplaned all the time. Now with where I sit with all the modifications it’s worse. Much worse. And still much worse when it rains. Which sucks. And it’s not like I have modified it to much. I have similar set ups that are very popular in the group.

Dealer just called, said the rear-driver axle they installed last week was misaligned. Claims it's fixed and the did a new alignment this morning. Recall this issue started months ago and progressively got worse over time, then got far worse after their axle service last week. Make sense? Picking car up in an hour.

I should add, I'm well outside of my automotive knowledge here...are there other issues that could've caused the initial axle failure or their initial misalignment? With nearly $2k of new tires on the car, and only 60 miles of bumper-to-bumper left, I want to know what to ask about when I go in to get it.

Just have an open conversation with the shop manager explaining that pulling issue is a concern, and that you want to make sure that they have looked at all of the suspension/driveline components and document that on the repair ticket. That way you have something to fall back on if the problem persist and a better chance to get Ford to cover any other failed components that may be found soon after your warrant runs out.

I’m no mechanic but that doesn’t seem right to me. How did they come to toast assessment. Was it just something that was easy to guess at because it was the last thing they touched. I’m curious though if it did fix it. I’m on the verge of trading this thing in. I’ve drove the piss out of it to try and break something or at least wreck it.