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Compression Ratio - Ask Anything

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For the sake of tuning (and because this topic is so much fun!), let's take this a little bit further. The rate at which weight transfer occurs in a corner is directly affected by the shock absorber. If we use an adjustable shock absorber, we can change the rate at which the shock (and therefore the suspension) compresses. If we stiffen the shock valving to reduce the rate at which the shock compresses, we can use the handling feedback to tell us what the car wants to improve the handling. Several companies offer adjustable shocks that can be used to help tune the car for superior handling. I spoke with Eric Norrdin from Global West Suspension, and his recommendation was to go with a double-adjustable rather than a single-adjustable shock. Norrdin says that single-adjustable shocks such as those from QA1 or Koni are rebound adjustable, but because of valve design, any increase in valving to the rebound also affects the rate of compression. The ideal way to fine-tune your suspension is to make one change at a time. This is why double-adjustable shocks are superior to singles--you can make separate adjustments to the compression, for example, without that change affecting the rebound adjustment. This makes tuning much easier and quicker. Of course, there's no free lunch in the performance world, and double-adjustable shocks are not cheap. The QA1 double-adjustable Stocker Stars for the front of your S-10 are part number TD505 and will run $227.95 each, while the rear shocks are TD901 and will cost $229.95 each (Summit Racing). That's over $900 for a set of four, but these shocks are rebuildable, which means they can potentially last a lifetime.

For a tuning procedure, let's say you install a smaller rear sway bar, remove two leaves from the rear suspension, and add double-adjustable shocks on all four corners. Let's take your truck to an autocross course. After several baseline runs, we increase the compression stiffness in the front shocks. If the truck responds with improved corner-entry handling, the spring rate in the front is probably too soft, as we're using the shock valving to crutch the front spring rate. We can increase the front spring rate, which will reduce body lean, and then reduce the shock-absorber compression valving to control the rate of weight transfer. Generally, the most efficient process is to improve the front suspension so corner entry is acceptable and then tune the rear suspension to help with corner exit. Most likely with your S-10, there is so little weight on the rear axle (compounded by a stiff rear spring rate) that any amount of added stiffness (such as the sway bar) will make the rear end of the truck step out on corner exit--which is classic oversteer. While this procedure is described for an S-10, it will work with any rear-wheel-drive vehicle.

This is a great question, as we're working on an S-10 of our own that we intend to put on an autocross course as soon as we get that small-block and five-speed bolted in place. The front suspension on the S-10 is very similar to a G-body ('88 Monte Carlo, for example). Global West offers upper and lower tubular control arms, front coil springs, and QA1 shocks for S-10 pickups, which, when combined with a taller spindle and bigger disc brakes, dramatically improve the truck's handling. The taller spindle is available with the 12-inch rotor disc brake conversion kit (DB-2312, $1,065.90). The taller arms produce a negative-roll camber package that really plants the front tires in a corner, which produces a remarkable improvement over the stock front suspension. Addco sells a 11?8-inch front sway bar for the S-10 (PN 739, $224.95; Summit Racing) that will also help. All this costs money, but the beauty is that you can upgrade the system one part at a time as your budget allows.

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1 comments
alkycarssincethe70s
alkycarssincethe70s

Another SUPERB Car Craft article that successfully makes me understand a subject by teaching DIFFERENT aspects of an issue from a DIFFERENT approach. I've read hundreds of articles and textbooks on compression ratio. Yours is better. Thank you.

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