Alignment change after changing from drum to disc
Like many of you, I’ve owned a few A body cars with 4 wheel drum brakes. Many of us convert to front discs, many times using the popular 1973-76 A body 11” discs. Throughout the years, I’ve noticed that every time I’ve made this switch, the front end alignment changes a LOT. Going from drum to disc meant the tires went toe OUT by a lot. The opposite happens when you pull discs from a car and put drums back on.
I had suspicions as to why but here is what I saw today.
76 Dart Sport that had discs, the prior owner pulled and sold them. To make the car a roller, I put on a set of drums I had. It toed WAY in as expected.
I took a look at the lower ball joint steering arm on each.
Right side Drum.
The steering arm has a strong offset to the center.
Disc setup:
The steering arm has less of a bend. Less offset.
What this tells me is that if you measure center to center on the outer tie rod ends of a disc, then a drum car, you’ll see that the distance is further apart on a disc car.
Now with discs:
Before, it was toed in heavily and now it is much better.
There are surely some members that already knew this but I thought I’d pop in to mention it for those that didn’t.
Like many of you, I’ve owned a few A body cars with 4 wheel drum brakes. Many of us convert to front discs, many times using the popular 1973-76 A body 11” discs. Throughout the years, I’ve noticed that every time I’ve made this switch, the front end alignment changes a LOT. Going from drum to disc meant the tires went toe OUT by a lot. The opposite happens when you pull discs from a car and put drums back on.
I had suspicions as to why but here is what I saw today.
76 Dart Sport that had discs, the prior owner pulled and sold them. To make the car a roller, I put on a set of drums I had. It toed WAY in as expected.
I took a look at the lower ball joint steering arm on each.
Right side Drum.
The steering arm has a strong offset to the center.
Disc setup:
The steering arm has less of a bend. Less offset.
What this tells me is that if you measure center to center on the outer tie rod ends of a disc, then a drum car, you’ll see that the distance is further apart on a disc car.
Now with discs:
Before, it was toed in heavily and now it is much better.
There are surely some members that already knew this but I thought I’d pop in to mention it for those that didn’t.