I’m trying to figure out tuning by taking one variable at a time and playing with it, but I’m having trouble understanding the results I’m getting.
I took an Infiniti Q60 Coupe Concept, which is B-class stock and, I thought, drives decently if not superbly. I put in a set of adjustable parts, which brings it up to A class–so it’s got Race Brakes, full tire upgrades, and so on. It doesn’t handle quite as reliably in this state, but I figured I could try tuning it.
So today I played with the springs. My understanding of springs is this: when a car accelerates, weight is pushed back, and when it brakes, weight is thrown forward. During a turn, weight moves toward the outside of the turn. Spring stiffness controls how much of the weight is “accepted” by a given end of the car (weight transfer during corners being controlled more by anti-roll bars). Stiffening the springs helps keep the car’s weight closer to center. Someone please correct me if I’m wrong on any of this. (I started out by watching Stella Stig’s excellent video on spring tuning.)
The Q60’s defaults for springs are Front 774.9/Rear 732.5. I started pulling the sliders first one way and then another, and this is what I found:
Very soft front: Good grip in and out of turns, but car rolls over on sharp corners. (Oops.)
Very stiff front: Understeers badly, esp. in corners, but very stable.
Very soft rear: Severe understeer, esp. in turns; fairly stable, with some minor fishtailing.
Very stiff rear: Stable on straights, fairly stable into corners, but wanders coming out. Understeer in corners.
I played around with the numbers, and found the following were closest to being tolerable:
723.4/1,100: Balance between stability and steering response is better, but rear wheels lose traction at a moment’s notice (even while making minor corrections along a straightaway).
856.4/910.5: The offsets hover between about .6 and .8 at almost all times–but all four tires lose traction readily, especially in turns.
Since I’m seeing offset numbers I like in this latter setup, it makes me think something else is causing the frequent loss of grip; where do people usually turn after tuning their springs?
I know there are some threads/videos/etc. that give numbers to use as a “base tune,” but I’m interested in understanding why certain changes have the effect they do. I’d appreciate if anyone could shed some light on this subject.
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