My father has a 1996 Chevy S-10 Blazer that is his daily driver and weekend wheeler. He has been wheeling it in stock form for almost two years but would like a small lift for bigger tires. He currently has 235/75-R15 tires but would like to clear 31s. We can't afford a lift kit. From what I've read on various online forums, I should be able to crank the torsion bars in the front up to the max and clear the tires in the front, but I would like to make him some custom rear leaf spring shackles for the rear. What I don't know is how long I should make them. If I make them 1 1/2 inches longer than the stock shackles will that be enough, or will I have to make them longer? Any advice would be very appreciated.
Simply cranking up the torsion bars is a recipe for trouble. While it might be technically possible to gain a couple inches of lift to clear larger tires, cranking up the bars will make it difficult if not impossible to align the truck, and the suspension will have little (if any) extension travel (sometimes called downtravel). This places a lot of extra stress on the upper ball joints (which are already kind of weak), not to mention results in a harsh ride. It wouldn’t make sense to invest in a new set of tires only to burn them up due to poor alignment.
If the truck was an off-road-only beater and reliability wasn't all that important, we'd say go for it. But since he uses it as a daily driver, you should really consider investing in a proper lift kit. Several 2- to 2 1/2-inch lift kits out there from companies like Superlift (superlift.com) and Rough Country (roughcountry.com) include new control arms to address alignment and extension travel issues, and most of them won't break the bank. These kits also include add-a-leaves and shackles for the rear, eliminating the guesswork on rear shackle length.
If those kits are outside your budget, you can pick up the front a little (maybe an inch) by adjusting the bars slightly and putting an add-a-leaf out back or longer shackles. If you choose to go with shackles, how long to make them really depends on where you end up with the front. Don't get greedy on front ride height. You need to make sure there's an adequate amount of extension travel available and that the Blazer can be aligned. Set the front and then take some measurements for what you need in the rear. Be sure you use 3/16- or 1/4-inch plate to fabricate the shackles and that you have adequate welding and fabrication skills to build them.
Before we messed with the suspension, however, we would look at trimming the body. The jump from 235/75-R15s to 31s isn't that big. We'd be willing to bet some generous trimming would make them clear without issue. Best of all, the total cost of body modifications is a few sawblades.