Staggered versus Square Tires Setup on S550 with Performance Package

[1958cyclist]

I recently purchased a set of ForgeStar wheels from Vorshlag so I can run 305/19/30's at at all four corners with Bridgestone RE71R tires. My understanding is that this new square set up will reduce under-steer. My question is to what degree? I'm just getting back into HPDRE Track Events after having been away from autocrossing for many, many years. Has anyone experienced whether such a set up will just reduce under-steer close to their adhesion limit versus sending the car car into over-steer? Terry Fair owner of Vorshlag said that he likes the Bridgestones because they telegraph well in advance when their getting close to their limit. The rest of the suspension is stock, except that I'll be having Vorshlag's Camber plates installed so the front tires will clear the fender lips. Thanks much!

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[BmacIL]

The tires alone will reduce understeer compared to many street tires, but the square setup is the way to go for handling balance. As much front tire as you can fit under there (and an equal rear) is the ticket. You need a suspension that will complement those tires, though. With that much grip, the lack of control via the dampers and excessive body motion from the soft springs will be exposed quickly. Camber plates are strongly recommended immediately for track use. You don't want to fry your new $1500 tires for lack of camber.

 

[Grintch]

It will reduce understeer, but with the stock suspension you don't have to worry about it being loose.

Camber plates are a must to keep from wearing out the outside of the tire. I would add stiffer anti roll bars as well.

Though sticking with the stock springs is probably not a bad idea if keeping the Magride shocks. We talking PP1, PP1 with Magride, or PP2?

 

[2morrow]

I just did the hub conversion to run a full square set up for next season. Super easy to do BTW.

I wanted to limit understeer as well on track so that was my motivation for going 305 square. My initial test drive (non-track environment) has yielded a much grippy-er front end.

Almost every time I had an oversteer situation it was driver error. I think that both situations can be resolved by driving style and situational awareness but the 305's in front will
greatly help with understeer (compared to the 285's I previously ran). Tires are RE-71R.

Side question and not to thread-jack but what is everyones preferred camber adjustment? I was running a -2.75° last season.

 

[BmacIL]

I just did the hub conversion to run a full square set up for next season. Super easy to do BTW.

I wanted to limit understeer as well on track so that was my motivation for going 305 square. My initial test drive (non-track environment) has yielded a much grippy-er front end.

Almost every time I had an oversteer situation it was driver error. I think that both situations can be resolved by driving style and situational awareness but the 305's in front will
greatly help with understeer (compared to the 285's I previously ran). Tires are RE-71R.

Side question and not to thread-jack but what is everyones preferred camber adjustment? I was running a -2.75° last season.

Depends on the rest of your setup. I'd target -3.0 or more for regular track use.

 

[Zelek]

305 squared? Damn that's a lot of tire. I'm running 285's.

 

[Grintch]

I just did the hub conversion to run a full square set up for next season. Super easy to do BTW.

I wanted to limit understeer as well on track so that was my motivation for going 305 square. My initial test drive (non-track environment) has yielded a much grippy-er front end.

Almost every time I had an oversteer situation it was driver error. I think that both situations can be resolved by driving style and situational awareness but the 305's in front will
greatly help with understeer (compared to the 285's I previously ran). Tires are RE-71R.

Side question and not to thread-jack but what is everyones preferred camber adjustment? I was running a -2.75° last season.

What hub conversion?

I am at - 2.6 or 2.7, and still wearing the outer edge more. So am considering grinding a relief in the center hole so I can dial in more (currently maxed out with the Steeda plates on the stock hole).

 

[2morrow]

What hub conversion?

I am at - 2.6 or 2.7, and still wearing the outer edge more. So am considering grinding a relief in the center hole so I can dial in more (currently maxed out with the Steeda plates on the stock hole).

I put these on yesterday as well as a 25mm spacer to accommodate a 19x11 +52 offset wheel. Now I can swap wheels front to rear.

I ran a -2.7° last season and I was still cooking the outer edges too. I drilled out my shock towers to gain a little more. Thinking about doing 3° this season.

If you want to see how I did it. I've done several car in my area. I have to upgrade my bracket now though.

 

[NightmareMoon]

Yeah I’m also wearing the outside edge with *only* 2.7 deg of camber, so the tires get flipped once on the wheels mid-way through their life and so far they shoulders are lasting long enough. Clearly the car wants a bit more camber for track/autox.

square tires go a long way to reducing oversteer in the factory setup, but you still may want to tweak with swaybars and shock settings to dial it in to your tastes. When squared up, the nearly stock PP is a little floppy and slightly understeery with stock swaybars, springs, and shocks, but its a lot closer to neutral. Probably neutral (within the range of driver preference).

Alignment matters too. Front toe for example has different opposing effects on turn in and mid corner steady state understeer. Toe out helps turn in (less understeer), but increases steady state mid corner understeer.

if you really want to tune oversteer/understeer, a set of adjustable swaybars are your friend.

 

[1958cyclist]

It will reduce understeer, but with the stock suspension you don't have to worry about it being loose.

Camber plates are a must to keep from wearing out the outside of the tire. I would add stiffer anti roll bars as well.

Though sticking with the stock springs is probably not a bad idea if keeping the Magride shocks. We talking PP1, PP1 with Magride, or PP2?

The 2017 Performance Package was bit early to offer the Magnaride option, so just the upgraded struts and shocks, stiffer springs and larger sway bars than the stock platform.

 

[1958cyclist]

The 2017 Performance Package was bit early to offer the Magnaride option, so just the upgraded struts and shocks, stiffer springs and larger sway bars than the stock platform.

Non-Magna ride PP1. Vorshlag offered a proprietary front and rear offest which keeps the wheels/tires flush with the sheetmetal. They do recommend their camber plates which I have purchased with a suggested 2 degree negative in the front for occassional track days and mostly street driving. They do however offer a relatively inexpensive jig for opening up the strut towers if one prefers even more negative camber. The car comes with 255/40/19 in the front and 275/40/19 in the back stock. The only downside with the ForgeStar F-14 wheels is that you can't swap front to rear with removing the tires.

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