I just swapped out my factory PP wheels for a set of MRR 19x10/11 staggered setup. I was planning on running a square setup originally but someone offered to swap strait up with mr so i took it. I hear people say the car feels more balanced on a square setuo but i am wondering by how much and where. Initial turn in, mid corner feel. And also curious about snap oversteer. I have a gt250 wing and a custom diffuser on back so im not worried about mid speed corners, and would ideally like a alight oversteer bias at low speed and setup the aero to understeer slightly in high speed corners. Just looking for some opinions with personal experience.

Lots of variables here. For track performance a square setup with wide tires will result in the fastest lap times but that’s only if the car is setup properly. The balance is based on tires and suspension. I believe your car came from the factory staggered so you won’t have to do much. When you soften spring rates or sway bars that typically adds grip. Typically when you move to a square setup you either stiffen the front or soften the rear. But you need to drive the car and determine the balance for your driving style. There are other members that know how to setup a car better than me.

Yes I would highly advise driving it first before making any changes. On the S197 with a wing and diffuser on a stock setup you would be on a one way trip to Understeer Town, but on S550 I’m not so sure.

You could still run square with those rims using tires in the 275 to 295 (maybe even 305) range.

If you use staggered tires, then you'd likely need to go a bit stiffer than stock with the rear bar to be balanced under say the 80mph range. I don't know the S550 rates and such for any specific bar suggestions.

With the wing you should be able to dial in the downforce to get the high speed push you want.

I don't think of snap oversteer as being a problem for our nose heavy cars. I think you'd have to make some big setup mistakes to get your car to do it. Driver error could induce it, say on a turn that needs or benefits from being on the gas mid turn to 'load' the rear. (T5 at WSIR comes to mind). Lifting there or mis-shifting before T6 would bring the tail around.

I don't think of turn-in as a time to measure 'balance', more of a 'feel' description. Tight/fast vs. slow or unresponsive.

ArizonaBOSS said:

Yes I would highly advise driving it first before making any changes. On the S197 with a wing and diffuser on a stock setup you would be on a one way trip to Understeer Town, but on S550 I’m not so sure.

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I can say without a doubt that wing and splitter on the s550 sends you right to understeer city. When I got on the car through the canyons i noticed it slightly pushing outside my lines "safer for street use i guess" but the back was nowhere near the limit when the front gave up

Grant, thanks for the input. The car is on eibach springs at the moment but will hopefully be on a set of AFE coilovers in the near future, so i will have the adjustability i need for shocks, as for dialing in the aero I have played with it some and found 5* to be the sweet spot for the rear end, however the front end just cant keep up on tighter corners "going roughly 60-80" hoping the 275 up front will help. Eventually the plan is 18x11.5 forgelines on all 4 corners

I would think that a 295 front and a 305 or 315 rear would be a nice combo.. My buddies S550 with a GT350 rear wing was very neutral with 295/305' Yokohamas and very nice with 295/315 Hoosiers on 19x10 and 19x11 wheels.

My personal opinion without real data on S550 would be to run square, simply for rotation/maximization of tire life aka fully utilizing the dollars you spent on tires. If the car was neutral from the factory with a staggered setup, additional front grip from a square setup will bias it towards oversteer.

ArizonaBOSS said:

My personal opinion without real data on S550 would be to run square, simply for rotation/maximization of tire life aka fully utilizing the dollars you spent on tires.

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I don't think it matters as much for dual-purpose cars. Matters more for those who try to run one geometry/camber/tire pressure setting for both. But if staggered setups are carefully managed, wear and complete use of tires isn't a problem. Management is different for directional and asymmetric treads, but both are do-able. Directional/staggered is easier, IMO. Just takes time to learn and diligence checking wear, profile temps, pressures, etc. Experience doing all that makes it relatively easy.

ArizonaBOSS said:

My personal opinion without real data on S550 would be to run square, simply for rotation/maximization of tire life aka fully utilizing the dollars you spent on tires. If the car was neutral from the factory with a staggered setup, additional front grip from a square setup will bias it towards oversteer.

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That's in line with the way I see it.

Maybe the next thought concerns how well slightly oversteerish suspension tuning combined with a slightly understeerish tire setup is going to compare against a less understeerish tire setup combined with less oversteerish suspension tuning. IOW, how closely would those two philosophies match over the range of driving from, say, hard street through time trialing?


Norm

Guys gotta remember that the S550 has the potential to be running too low camber on both axles...rotating isn't gonna solve *all* setup and geometry issues with an IRS rear.

When I went to bigger wheels and tires (285s on 10" front, 305s on 11" rear) I did this because I wanted to keep the stagger similar to the stock PP, figuring that Ford set the PP suspension up for a 20mm difference front to rear. I found the car was easy to drive quickly on track, had no bad habits and it's final steady cornering state was light understeer. If you drive it too hard into the corner it will push, a lot. This was totally stock suspension.

I've since installed a stickier tire that is 295/305 and runs almost an inch wider at both ends, this setup has less understeer, as expected. It is still on stock springs/shocks but has upgraded bushings throughout, motor mounts/trans mounts and CC plates. I found that the car will oversteer under certain conditions in places it did not before, like one particular mid-corner bump, but it is easily caught, almost self correcting. This was not unexpected given the slight change in front vs rear grip. The changes in the handling are fairly subtle and nothing alarming, when driven relatively sanely into the corner. But that last part is really important, corner entry is key to getting the front end stuck and be set up well for a balanced mid-corner and early on the gas exit.