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      04-25-2011, 06:06 PM   #38
The HACK
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Drives: 2006 MZ4C, 2021 Tesla Model 3
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In an effort to re-affirm my side of the discussion, I found this VERY informative post about the relationship between steering angle inclination vs. scrub radius on a MacPherson Strut. The diagram is very helpful in visualizing how increased or decreased OFFSET from factory can affect a car's handling characteristics.

http://forums.rennlist.com/rennforum...768-post6.html

If none of what is discussed here make any sense, don't worry. THIS is the most important part of the discussion:

Quote:
Originally Posted by Bill Verburg
As with anything else, a little of a good thing is great, but lot of a good thing is not necessarily better. When you have excessive scrub, whether it be positive or negative, steering effort increases and road 'feel' increases, as the steering is more susceptible to road shock.
I don't know if our Z4 comes with positive or negative scrub radius, but it comes with MacPherson front strut which commonly have a negative scrub radius. Therefore increasing the offset may result in a ZERO scrub radius situation if you do not know what your actual steering angle inclination is (therefore do not know the actual scrub radius) and may actually be counter-productive to car's actual performance in a turn. And increasing REAR track without increasing front track would end up increasing the tendency to understeer in a car that already has plenty tendency to understeer.

I don't know. Maybe those guys you referenced, crfine88, F360C, GothM, Colatkitty, and Shereef_Osman knows a lot more about chassis dynamics than I do. I'm merely going by what I know and what those that have taught me what I know knows. I'm by no means an expert on this topic, I just pretend to be one.

Do keep in mind, that the steering angle inclination discussion is SECONDARY to the amount of grip you can add by going with a wider tire...The amount of grip you can add up front with MOAR tire is going to easily offset the drawbacks of altering the scrub radius. And you can always INCREASE CAMBER to bring that scrub radius back in line. Or you can do a combination of everything, increase tire width, increase offset, increase camber to retain scrub radius. But to blindly add offset without knowing what your scrub radius based on current tire size, IMO, is counterproductive.

EDIT: Nevermind, it appears you are well aware of scrub radius and SAI and its effect on steering feel.
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Last edited by The HACK; 04-25-2011 at 06:19 PM..
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