For the last few years, there's been an obvious competition to see who can fit the largest wheel on their truck. This insurgence of oversized wheels has forced the builders to make extreme modifications to the suspension in order to lay these behemoths out and it seems that in many cases there is little regard as to what modifications can be made safely and without destroying the vehicle's usability. I have seen many trucks with the suspension being pushed so far past the design limit or with such radical modifications that the vehicle is almost not drivable. I would say that the majority of the questions that I get these days are either asking how to fix what problems they currently have or how to build a system that doesn't have any issues while still laying out on their colossal wheel of choice. It used to be easy; a two-inch drop spindle would do everything you needed to lay your brand new 17-inch wheels. A few tweaks here and there and you can lay on a tall tire if you wanted, but those days are long gone. What makes things even worse is that the suspension designs on new trucks are geared more towards lifting rather than lowering and there are very few vehicles that have a drop spindle (or most likely a knuckle nowadays) even available for them.
So what can you do? Well, whatever you can to get the damn thing to lay out right!?
The factory suspension is designed to work within a set range and if you wander too far from that range, in some extreme cases (yes John, I did say extreme) the truck can't even be driven unless the suspension is lifted high enough to be back within that original design range. Now, I have seen some fairly ingenious modifications to stock suspension that were quite tolerable for everyday use, but those are few and far between. Several companies have developed A-arms that change the ball joint angle to allow the suspension to go lower than the manufacturers design limit. This fix can work well on many trucks for wheels up to a certain height, but at some point the geometry will go so far south that you're back to square one. Once the A-arm moves past 45 degrees, it begins to narrow the track width more than it lowers the vehicle. What this means is that for every inch that you force the suspension to go lower, the track width gets two inches (or more) narrower and the narrower the suspension gets, the worse the geometry gets. All of these issues that I am describing aren't even taking rack and pinion travel limits into consideration. So with all of this being said, what is the best cure for the big wheel blues? Honestly, the absolute best cure would be to throw everything away and start from scratch, build a new a suspension that is designed to lay down as far as you need while lifting high enough to be drivable, but time, money and knowledge will always make that option difficult to accomplish for most builders. The best answer to almost every stock-type suspension that I have been able to come up with is custom knuckles. A knuckle can be designed to keep the suspension within it's original design limit without throwing the alignment too far out and make full use of the ball joint angle allowing as much travel as possible, but custom knuckles can be fairly difficult to design and build as well.
Now I am fully aware how much like a snake-oil-salesman I sound right now, with me being the only shop that I know of building custom knuckles for many vehicle types, but the fact that they work so well to cure what ales ya' is the reason that I build knuckles instead of A-arms in the first place. So forgive me, but it had to be said. Control arms work well for most minitruck applications 20s and below, but the knuckle is a necessary evil for those big, fullsize trucks stuffing 26s!