Thought I'd recently seen this elsewhere -
The Ultimate Handling Guide Part V: The One Unforgivable Sin, Overlowering Your Car
Originally Posted by MikeK
A Sentra SE-R is a typical example of a car that should not be lowered more than an inch. It can be lowered more than that but its suspension design isn't happy about it. This situation is common on many cars and not just indicative of the SE-R’s design, we have just thoroughly studied this car's geometry because we race one.
The first problem with lowering the SE-R (and most McPherson strut equipped cars) is that it only has about 2” of jounce travel at stock ride height in the front suspension. Let's say you lower the car the typical 1.5”, you are left with only about .5” before you hit the bump stops. Your typical aftermarket lowering springs only up the spring rate a paltry 20% or so, not enough to keep the car off the bumpstops with only 0.50” of travel.
Not only does this ride poorly, bottoming out frequently and all the time if carrying passengers, but in a corner, when the car leans over, the suspension will quickly settle on the bump stop causing the spring rate to rapidly ramp up approaching infinity quickly as the bump stop smushes down. This causes huge amounts of weight transfer and a build up of slip angle in the outside front tire suddenly resulting in relentless understeer. When the car initially hits the bumpstop, the perceived increase in stiffness makes the car feel responsive, sort of like a go kart but this snappyness in steering response turns into inescapable understeer in a few milliseconds after turn in is initiated.
Mike nailed that one, as usual. Virtually all my front suspension changes are aimed squarely at avoiding these issues. Dave C did a nice writeup when he first went to CO's on the car back in July 2000:
SCC July 2000 Suspension Magic
Not to say we don't have some options today that he didn't have and may have used at the time, but based on the car's handling today he hit most of the issues dead-on. Since that article the CO's went to Progress, w/350F/250R, I found that a little soft for my use, bumped up to new Progress CO's set up with the right damping for 450/350 springs. Also the rear sway is 3-hole adj Progress, not ST. I've added more chassis reinforcements, dialed in a zero toe rear + minimal toe front performance alignment*, but that's about it.
* Note I do NOT recommend this alignment for general street use unless you are really comfortable with how the B13 reacts at or slightly over its limits, it removes most of the safety margin for avoiding snap oversteer - but the gain in control is worth it for braking-induced oversteer. It will make the car fairly sensitive to road imperfections, easier to spin in the wet, and definitely is a "two-hand" driven car
The Ultimate Handling Guide Part V: The One Unforgivable Sin, Overlowering Your Car
Originally Posted by MikeKA Sentra SE-R is a typical example of a car that should not be lowered more than an inch. It can be lowered more than that but its suspension design isn't happy about it. This situation is common on many cars and not just indicative of the SE-R’s design, we have just thoroughly studied this car's geometry because we race one.
The first problem with lowering the SE-R (and most McPherson strut equipped cars) is that it only has about 2” of jounce travel at stock ride height in the front suspension. Let's say you lower the car the typical 1.5”, you are left with only about .5” before you hit the bump stops. Your typical aftermarket lowering springs only up the spring rate a paltry 20% or so, not enough to keep the car off the bumpstops with only 0.50” of travel.
Not only does this ride poorly, bottoming out frequently and all the time if carrying passengers, but in a corner, when the car leans over, the suspension will quickly settle on the bump stop causing the spring rate to rapidly ramp up approaching infinity quickly as the bump stop smushes down. This causes huge amounts of weight transfer and a build up of slip angle in the outside front tire suddenly resulting in relentless understeer. When the car initially hits the bumpstop, the perceived increase in stiffness makes the car feel responsive, sort of like a go kart but this snappyness in steering response turns into inescapable understeer in a few milliseconds after turn in is initiated.
Mike nailed that one, as usual. Virtually all my front suspension changes are aimed squarely at avoiding these issues. Dave C did a nice writeup when he first went to CO's on the car back in July 2000:
SCC July 2000 Suspension Magic
Not to say we don't have some options today that he didn't have and may have used at the time, but based on the car's handling today he hit most of the issues dead-on. Since that article the CO's went to Progress, w/350F/250R, I found that a little soft for my use, bumped up to new Progress CO's set up with the right damping for 450/350 springs. Also the rear sway is 3-hole adj Progress, not ST. I've added more chassis reinforcements, dialed in a zero toe rear + minimal toe front performance alignment*, but that's about it.
* Note I do NOT recommend this alignment for general street use unless you are really comfortable with how the B13 reacts at or slightly over its limits, it removes most of the safety margin for avoiding snap oversteer - but the gain in control is worth it for braking-induced oversteer. It will make the car fairly sensitive to road imperfections, easier to spin in the wet, and definitely is a "two-hand" driven car
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