SPD Tuning Service
Page down for detailed information. Suggestions, comments and questions are always welcome.
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SPD Tuning Service Page down for detailed information. Suggestions, comments and questions are always welcome.
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Alignment recommendations for autocross. Front: ~ 3/4 degree negative camber, 1/16+ inch toe-out. Rear: leave stock, see below. This setting is a "go fast" where you open of the adjuster slot in the strut a tad with a die grinder and re-align the front end. I will elaborate so you will understand the effects. The steering is a bit lively on the street ant the brakes may seem a bit darty as well. Hey, no free lunch. The settings are approximate and will vary some with tires and pressures. The recommendations (~ 3/4 degree negative, 1/16-3/32 inch toe-out) are given to put more grip into the front tires relative to the back when in a curve under power. As you know the 50/50 torque split is sub-optimal for dry tarmac and the car reaches terminal understeer easily with the power on. IF driven very smoothly it will perform quite well. The intention of the negative camber in the nose is to make the steering very powerful, so that you are able to rotate easily, inducing the very minimum of steering input. This reduces the slip angles of the front tires and lets you put down more power earlier. This setup needs a front tire pressure set for the best grip. This is very easy to feel in your hands. If too high the front will want to "skate" i.e it turns in fine, but the limited bite causes understeer to develop with noticeably high slip angles felt in your hands. If too low, the steering will be "mush" from the start of turn-in. It will vary from tire to tire. Start high, ~37 lbs and work down. I found 205/45-17 PZeros to like 35 pounds, cold. You then use a variance of rear pressure to control events. By using a roughly -2 lbs less pressure from the optimal front setting (This is a function of weight distribution, BTW) you should achieve the best high speed bite. However, the car may not want to turn in the really twisty <70 kph sections. For this problem, you run up the back pressure 2 to 4 pounds. But watch your high speed trail braking and turn in. Make changes one at a time and in 1 lb increments until you have a feel for what is what. If you "lose the Rabbit" set things back and start over. Keep notes. Suffice it to say that as you run up your rear pressures the car becomes ever more sensitive to throttle placement at turn-in. With the back pressures up, if the car starts to rotate into a threatened spin, counter steer alone is not going to bail all the water out of the boat. You must force yourself to get into at least neutral throttle if not a slight acceleration mode to get weight off the nose and into those over inflated rear tires. The car will then hook up, as they say in NASCAR, and (should) head off in the general direction it is pointed at the time. As J.M.Fangio said in response to why he was faster than others: "More throttle, Less Brake!" You'll look like McRae in no time. If the car begins to feel spooky - where you can't feel the back from the front breaking away- you need to bring the back pressure down. Note that the '97+ cars have gone from an 18mm to a 20mm rear bar. Those desiring more "confidence" in their steering could change to the smaller bar for a bit more residual understeer, all else being equal. My comments have been taking you in the other direction! You want to keep an eye on the rear camber settings, as these will "change". i.e. tend to go negative if you are crashing the suspension or tapping curbs from time to time. You need to keep the rear camber under -1/4 or the rear tires get so much bite that nothing done up front will have effect. You could run higher front negative camber and add some into the back, but on a road car excessive negative camber will cause poor inside edge tire wear. As it is, be sure to rotate your tires front to back every 4000mi or so. |
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