Quote:
Originally Posted by Snertz
JJ made no claims that this was best thing for handling, I don't understand why all the "purist" feel the need to come into every thread that mentions mods and preach how the good stock is. We're well aware of that, but don't forget that this is also a STREET car, and compromises have already been made from the factory.
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Don't mistake me for a purist. I'm all for modifications that improve functionality. If he'd lowered the car properly with matched valving shocks, etc he could have improved the handling (on some roads/ tracks). Instead he hurt it... He's not planning to drive it the way it was intended, so he thinks that's ok, but obviously I'm not a fan.
Quote:
Originally Posted by Snertz
Not saying you're wrong but care to substantiate that claim? Driving exp? proven data?
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For you to even ask this I need to assume this a totally honest question, so sure- I'll see if I can explain:
1. He added about 3 lbs of unsprung, rotating weight with those spacers. It's not much, but unsprung, rotating weight is the worst kind- by definition it hurts ride, grip and acceleration.
2. He moved the front wheels outboard by 12mm, increasing scrub radius by that much. For those that don't know what scrub radius does, it defines steering feedback and feel. When a magazine article complains that an audi has dead steering feel while the BMW's is full of feedback, that's largely the effect of scrub radius. I don't have the 1M's numbers, but it is generally under 10mm, to which you're adding 12mm with those spacers. A small amount of scrub is needed for steering feedback and feel; a large amount is recognized to hurt performance.
3. Springs and shocks are a carefully matched pair from the factory. The wheel plus spring combo will bounce/ resonate as a certain frequency depending on the spring rate, wheel rate and suspension geometry. The shock's job is to damp this bouncing, as bouncing reduces grip, so the shock is designed with a certain amount of damping (% of critical damping) to rapidly control the bouncing. By changing the springs for stiffer ones but not changing the shock valving he reduced the % of critical damping- this means it takes longer for the shock to control the wheel balancing, and this in turn reduces grip.
4. Shock length/ bump stops- you want to avoid hitting the shock bump stops, as doing so upsets the car. By reducing the ride height significantly but not increasing the spring rate in proportion or changing the bump stop location he's going to be smacking them regularly, perhaps damaging the shocks in the process. This is worse on the street than the track generally as the street tends to be bumpier.
5. Rubbing. Not the end of the world, never desirable...
If one wanted to do similar modifications but
improve handling (or at least speed around a course, as "handling" is subjective) one would:
a) Use wider, lighter wheels with the correct offset so that spacers are not required and the scrub radius isn't changed significantly. This would fill out the fenders and not changed the scrub radius.
b) Use significantly stiffer springs when lowering the car that amount to avoid hitting the bump stops.
c) Use a different shock or a re-valved shock that is matched to the springs.
d) Re-align the car.
With the above you'd have a package that improves handling and where form would follow function. In that case I wouldn't have mentioned posing...
BTW, I don't hate. I laugh. And cry a little...