Ladder bars.

Why not a four link?

I am a big fan of ladder bars. For the majority of racers out there a ladder bar will do everything they require. But a four link is better, I hear this all the time, and yes in some perspectives a four link is a much better drag racing rear suspension setup. The biggest advantage to a four link is it’s adjust-ability.  This can be a great advantage. . .  if you know how to adjust it. When I look around the track, I see very few people adjusting their four links. Generally what I see are four links that have been setup, either by someone who knows how to tune them, or after a certain amount of aggravation, or “that’s how I bought the car, and I am not going to touch it ’cause it is working just fine the way it is”., and because the car is going straight, and running consistent, the owner leaves it alone.

The problem with a four link is that very few people have spent the time to work out how to make adjustments. I am not going to get into how to adjust a four link here, but I will tell you that the procedure starts when the car is being built. The chassis builder should have given you a chart of instant centres. If you don’t have one, you need to get one. You can generate one yourself. There are computer programs you can buy that make it easier, or you can do it the old fashioned way on the floor. I have done both. I now have a computer program I find reasonably easy to use although it does not allow for as many holes as we are using in newer four link setups, so I have to run the program twice. Once you have your instant centre chart, you then need some sort of preload reference. How much weight, does a quarter turn on the bar add, or subtract, form each corner. Of course this will change with a change in instant centre, so if you change bar locations, you then need to know the preload adjustments for that location. The point I am trying to make here is that although a four link is a great rear suspension setup, the adjustment procedure is too involved many drag racers. They generally get it working, then never adjust it.

If that is going to be the case, why not use a ladder bar then? A ladder bar generally has three choices for instant centre, and you can see them all on the car, you don’t need a chart. Preload can be set with a ruler if you want, although I do prefer to weigh the car so I have a reference point for preload adjustments. Often, unless it is a very high horsepower car, little or no preload is required with a ladder bar.

Ladder bars do take up a little more space forward in the chassis, if you are building a car with a lot of rearward driver position it can be a challenge to get a long enough bar in the car.

One of the cars I am currently building is a ladder bar setup. It is a very short wheelbase at 100.5 inches, so getting bars in there can be done. This one is interesting in that the owner wanted to use his rear axle housing which was already setup for a four link. It has a range of holes on the axle housing that could be used, and they are not in the usual location for a ladder bar. I had to get creative. One problem the typical ladder bar has is because of the angle of the two bars, as soon as you adjust the rear of the bar for pinion angle, the hole spacing changes, causing a side load on the rod ends, this is not good at all. It can also cause a certain amount of stress and cursing when trying to install the bars after making an adjustment.

For this car, I wanted to take advantage of the range of holes in the housing. I accomplished this by putting a pivot in the top tube, allowing the hole spacing at the rear to be adjustable. This solves two problems, first there is now no side loading on the rear rod ends after adjustment, and second, because I made the top bar adjustable, pinion angle can be changed very easily. Now that I have built these bars, I wouldn’t build them any other way. They are a little more expensive, but worth it. They offer a large range of adjust-ability, without the confusion of a four link. They are very strong, with large diameter thick wall 4130 tubing. And they can be built to suit any set of brackets you may already have.

Questions? Ask away, at the contacts page

Since I published this post a few days ago, it is interesting to note that people are finding it when searching “how to adjust four links”. I will compose an in depth look at how to adjust a four link suspension for future post. It may take a while so check back often. If you have any specific questions concerning your setup, my email is on my contacts page.