Quote:
Originally Posted by Roffle Waffle
I'm running 265/35/18s on 18x9 up front, -28 offset, -2.5* camber. No issues. Steering feels great. Understeer vastly improved over stock
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Give this article a quick read...
http://www.hrsprings.com/technical/scrub_radius
And use this picture as a referece:
Ideally our type of MacPherson Strut design would perform best with a small to moderate amount of NEGATIVE scrub angle. By adding significant amount of offset and pushing the wheel away from the hub, the end result may be a net ZERO or even positive scrub angle which would result in poor steering response and poor tire contact patch upon cornering.
One of the ways to address this is to increase the steering angle inclination by adding camber on the king-pin side, which on the MZ4 is possible via the addition of camber bolts. However, if the camber is only adjustable via the top mount, adding camber isn't going to increase SAI and therefore additional offset can and most likely WILL result in poor handling characteristics.
If you're using camber bolts, you lucked out in that the addition of the bolt and the addition of offset "offset" (no pun intended) each other. However, if you had kept a smaller offset it can potentially increase the negative scrub radius and result in BETTER steering feel than what you currently feel, and potentially a much better handling car.
FOR EXAMPLE. I run both 245/45/18 on both my street tire (Falken RT-615K) and my R-Comp (Nitto NT-01) on two different tires, the street tire sits on 18"x8.5" replica with 38mm offset, while the r-comp rides on 18"x8" OEM wheel with 42mm offset. The two tires aren't actually THAT far apart, the RT-615K is technically an R-comp as well, but the way both tires behave is night and day. The OEM wheel retain factory scrub radius (actually increases from the factory negative scrub because I have camber bolts installed still) and the handling and steering response is phenomenal. The aftermarket rims, not so much. There's definitely less grip up front despite both being pretty good R-comps, and far less confidence inspiring despite a very minor change in offset.
Now, that's probably not the greatest example because, I still firmly believe the NT-01 is a better tire. However, data does speak for itself. While the tire sizes are identical, the end result is I always end up with higher pressure up front in the Falken RT-615K while the NT-01 would return with identical tire pressure front and rear after a heated session, indication there's more slip going on with the street set-up.
If y'all take nothing away from this post, I hope you take away this point. The way our front suspension works is voodoo magic. Every little change will affect the way it handles and not aways in a way you assume will work. Sometimes throwing a bunch of changes up front will yield positive results, sometimes it won't. I'm just saying, that keep in mind what offset changes alone will do to the suspension and how it works, and adjust OTHER parameters accordingly to maintain optimum performance. DON'T just blindly throw wider tires or wider wheels and insane offset because it looks cool, do some calculation with offset calculators, find out where your scrub radius is, and DO IT RIGHT.