Verviticas

hey all

same as many of us here, i have 16.8 wheels. Front 0mm and rears at 16mm. Im buying a new set of wheels (roh snypers go figure) and only see 0mm offset. I really want to preserve the suspension geometry so is it importaint to maintain the 16rear 0 front ratio for optimal handleing? or is the rear offset just on there for another reason. (clearence for example). I did notice significant oversteer with 15.7 camaro wheels. Is this related to the offset change?

thanks all

Verviticas

Not a single person has an opinion?

vsixtoy

Sorry, I never saw this when first posted.

There will be no effect with the rears spaced outward. Matter of fact I have actually added a 1/4" wheel spacer on the rear of mine with 16x8" Irocs trying to push out the rear track width just slightly more to widen the stance. and could actually use anthor 1/2" but thats not safe with wheel spacers.

The fronts want to remain as close to stock track width to retain the proper scrub pattern. The factory geometry on the steering system is setup for proper Akerman angles under normal turning conditions at speed. The wider the track in the front, the more toe out from stock setting is needed.

I'll give an example of Akerman and slip angles. When you turn very tight a u-turn (fully locked), the tires willfight eachother and feel like they are alternately skipping back and forth for grip. They are under different turn radius' in this tight turn because the Akerman angles havegone out of wack with the radical turn of the geometry. AKerman angles are set up so the wheels will take the smae radius to the left or right of center FROM center to aprox 20* while maintaining equal slip angles. When you autoX (at slower speeds than freeway driving) you are taking very tight turns at "fast" low speeds (fast for that tight of a turn) it is very common for an autoX car to be turning the wheels at 35* or more. At this point you go into more of the u-turn senerio and one or the other tires will slip first because they are no longer tracking at the same radius (Hence the term Akerman angles). Want is done to correct this on a lower speed AutoX car is to run the toe out to about +1/8" rather than the stock -3/32" in. Turning into the corner the car will be more responsive at first to want to steer (Harder to go straight like this) and then sitting into and through the corner at say a 35* turn angle, the inner wheel will turn more than stock radius (Tighter radius) turn rematch the outer radius wheel. This agains proper Akerman angle in tight corners and equals the inner and outer slip angles for maximun traction through slower tighter corners.

Rears have no real effect on this. The benefits outweight the negitives when pushing the rears out theaprox 3/4" (or 16mm) that the new rims will do.

90firebird

wow, good stuff Dean. a friend and I had a conversation about that, whether or not front wheels on the rear would affect handling at all.. and that pretty much answers it.

BLOWN85/TA

iTrader: (2)

vsixtoy

Ok if the rear offset 16mm has no effect how will +10mm at the wheel hub affect its handling properties?

vsixtoy

I am not fully understanding your question, Are you asking about the fronts when you say "hubs"?

BLOWN85/TA

iTrader: (2)

Yes it's the thickness added by the rotor hat on one of the conversions. With no other changes just the extra 10mm between the hub and wheel.

DuronClocker

iTrader: (1)

Whoa interesting...which conversion? If this is the LS1/C5 conversion I'm very interested. What is stock BS on the 4th gen rims? That'd be nice if I didn't have to run spacers when I buy 4th gen rims if I upgrade the front brakes.

I like the look of my car with the rear tires kicked out because of my stock 3rd gen wheels on my LS1 rear. It looks pretty mean. It also seemed a bit harder to lose the rear in a turn at first, but I'm getting better Still crazy driving in the rain...can't wait til it starts snowing/sleeting.

vsixtoy

This is really starting to be taken out of context. The first senerio that Verv asked about had nothing to do with offset, it had everything to do with him just putting better gripping rear tires onto the car. 15"x7 rims and tires are not performance on a third gen, you are utilizing a taller flexable 60series skinny tread tire that has very little cornering traction. going to 16x8's gets into a different realm of tires that even in the cheaper forms do outperform the best tires on 15x7rims, thus holding the rear in place better expecially when exit throttle is applied out of a corner. Narrower tires in the rear will always increase oversteer.

His offset will not matter at the level of suspension he has combined with tire traction. More traction would just cause greater tire roll and he'd be right back to square one.

I simply gave imput as to what he intends to do, not for what he did already. He was asking about new snyper offset and whanted to utilize the correct purchase to begin with so if/when he enters the point that this starts to matter, then he's set.

Here goes a novel (guess I asked for this one)-

The benefit of widening the track width of a car will "LATERALLY" poorman lower the center of gravilty of the car of the unsprung weight of the car. Its basically a simple height vs. width ratio that comes into play. With the roll center reaining the same, a wider track width will cause the inside tires to remain weighted more than a car wth a narrower track width. Heres the catch: by widening the track width on a solid axle car, you are increasing the unsprung weight AND the increasing wheel leverage on the rear roll center for the suspension to travel uqickly up and down. That increased leverage in essence is the same as increasing unsprung weight. It now takes more force and time for the outer wheels to travel back down after hitting a bump- thus unsettling the car more.

On the front (Blown & Duron) the same principle applies. The pivot point of the A-arm is now a further distance outward to the outside edge of the tire. That distance increases unsprung weight which is bad for handling, however, the greater track width is good (assuming it doesn't push the car wide enough to now induce a turn through a chicane where a thinner track car could simply drive straight through- I had this problem with my Vette in autoX, its 7" wider than my Camaro.) Now to get back to what I first posted about the Ackerman Angles in my first post, A byproduct of widening the front track will cuase different slip angles in the truning ration of the 3rdgen steering geometry. SO they may have better traction with a wder track going straight, but turn the sterering wheel so the wheel are pointed to steer the car at about a 30* angle and the slip angles on the wheels are no longer equal (The fatter the tire and lower the profile, the more previlant this problem will show) thus casing a loss of traction on one front wheel sooner than the other. The track width oif these cars for optimum low and high speed combined handleing is engineered from the factory with the use of the perfpramnce 16x8/245-50-16 tire and whell package. This package has the proper front scrub radius (measured from the center of the tire tread).

Now contact patches or different than scrub radius' based on traction and suspension. The same tire on one car will not have the same contact patch area on the tread through a corner as the same tire on another basically identical car but with a different suspension stiffness and setup (Including track width, roll centers, amount of roll weight, tire holding force, so many many factors)

You can have a car setup for best handling for one tire brand/size, then by simply installing a better or worse gripping tire you have to imediately reset the suspension for the greater increase of traction causing more suspension bind, roll, weight transfer etc. And it needs to be aligned for the speed you intend to drive based on setback of road forces on the tires and suspension points.

I know I just lost most of you, sorry, but this gets very technical at the top level. One little change can affect all others and usually does. Unless you have everything top notch and are competing in time trials for that 1/10 of a second, its not critical for most of you to even worry about. My own Camaro is 99% unimportant but I just do it because I know how and why things work.

Verviticas

Thanks vsixtoy