[Qfrank]

I had a corner balance and alignment done a few months ago, with great results. It was done with 17x7.5 fr, and 17x9 rear, ET 52 and 47 respectfully. I recently have been swapping to 17x9 ET55 turbo twists for autocrossing. Is this detrimental for handling?



Seems i have more oversteer, with the addition of width of tire, and rim up front.



Thoughts?



Thanks.

FQ

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[flash]

it's probably not your imagination. you have a narrower stance, which will lead to more oversteer. also, the more outside the offset, the more negative camber will have an effect.

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[MB968]

Weather conditions can have such an impact on how the car performs. Make sure you are comparing before and after for similar track conditions. With the setup I have on my PGT it is very neutral when the weather is above 60 degrees. Depending on my steering wheel inputs, etc. I can keep it very neutral, or make it oversteer at will. But, if the temps are 50-60 degree it has a strong tendency for oversteer. I've spun it a few too many times always on cold days, never on warm days.



Also, the additional width up front should allow the front to bite better, allowing you to push it harder. Since the rear is the same as before, and if you are unknowingly pushing it harder, you'd notice an increase in oversteer.



Have you tried adjusting tire pressures to make it more neutral.



Do you have an adjustable rear bar that you could adjust.

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[Qfrank]

I have a norrower stance with ET55? And 17x9 all around?



I think the car looks better with the street set up, with staggered wheels.

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[Qfrank]

No swaybars yet.....



Temps are warm here, pretty constant.



As i push harder under braking in a turn, seems like the rear end swings around much easier than before, where it was more prone to understeer. This must be grippier rubber on wider tires up front.



Alignment is probably not cause, more weight transfer.

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[flash]

the higher the ET number, the more inward the wheel goes. while you gained front track, you lost rear. that would make the rear swing (oversteer). the front biting better further exacerbates that.



as much as i hate them, i'd stick 7mm (or 8mm if you can find them) spacers on the rear.

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[MB968]

The rear spacers wouldn't hurt and could help, try them if you can.



You should try decreasing the front tire pressure a bit, maybe 5 psi, and increasing the rears by the same amount. What tire pressures are you using currently? If there is room to make the changes, you could even go more than 5 psi (10 psi) on a test run just to see if you could get it to switch back to understeer. Then reduce it to where it came back into balance.



Also, if you have adjustable struts up front, you should make then a little harder.



If the oversteer isn't too bad, I think you should be able to bring it back close to neutral with the above suggestions.



Let us know how it goes.

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[flash]

before doing any guess work and changing tire pressures, chalk the tires and check wear patterns, and measure tire temps. that will tell you what's going on there, and if the problem is tire pressure and you need to make changes.



i would not go trying to create understeer in an attempt to correct oversteer. that is a common mistake many people make. having one does not mean you try to create the other to mitigate it. all that does is create both, and you end up with a twitchy car that feels like it's on marbles. each end of the car works independently of the other. work one end of the car at a time. if the rear is oversteering, don't give up the traction you have up front because the rear is kicking out. make the rear stop kicking out.

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[MB968]

I stand by my suggestions.

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[Qfrank]

I run 34 all around.



Maybe more up front by 3 psi is in order. I will test and report back.

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[flash]

that's ok. it is the most common thing i see happen, as most people don't want to spend the time and resource to actually correct the problem. it's kind of like taking an aspirin for a headache when the cause of the headache is somebody smacking you with a hammer. better to get rid of the hammer.



on the track i regularly see guys monkeying with tire pressures to solve suspension flaws, and it always results in them being slower because it reduces the overall grip of the car.



tire pressures are the absolute last thing you adjust on a car to correct handling problems, after you have sorted out the hardware.

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[MB968]

[quote name='Qfrank' timestamp='1334716105' post='125422']

I run 34 all around.



Maybe more up front by 3 psi is in order. I will test and report back.

[/quote]



I think you meant DECREASE the front. But, with the pressures that low I think I'd first start with increasing the rears. They arean't anywhere near their max pressure. No reason to give up any grip on the front by decreasing the front when you have a lot of room to play on the rears. And, I wouldn't do anything less than 5 psi; I doubt you'd be able to tell the difference with anything less.



I assume you know about chalking the tires as Flash mentioned. You should definitely do that to see how much rollover you are getting (i.e. how far down the sidewalls if at all the tires are contacting the pavement).



To get good controlable rotation on my PGT I typically ran 42frt/37rear, with the struts set to 2frt/4rear (5 is firmest/most damping). And to Flash's point, to get the PGT to a neutral state from a strongly biased understeer car, it also took a lot of other suspension mods. You could always go back to the standard rim/tire sizes. But if you are planning to play the cards you already have, try out the suggestions and let us know how it goes. I'd like to know how the 968 responds.

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[Qfrank]

The tweaking never ends.



My main concern was the alignment i had done, withndifferent offset wheels, and norrower wheelmup front. Considering the ET difference, and the narrower stance, granted a few millimeters, was wondering ifnit could have an impact on alignment. Since we speakmof how important a good alignment is.

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[tamathumper]

Using an iPad this morning?

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[Qfrank]

Yup

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[flash]

every car has understeer or oversteer. it is just a question of which end goes first. in stock form, the front end goes first. widen the front tires a lot, and the rear goes first.



the alignment can have an effect, especially in the rear. the negative camber is magnified when you push a rim outside. this can provide more grip if you don't go too far.



what you have done is the opposite, which is to push the rim inward, reducing the amount of effective negative camber. this can lean to oversteer.



the fact that you have increased tire up front, only means that the front is no longer understeering. it does not mean the rear is oversteering. but due to the increased grip, that means that then the rear is the failure point. when you get the rear to stop sliding, your car will be faster through the corners than before, because you will have increased grip on both ends.



my point is that under no circumstances do you ever want to decrease the grip on one end. by messing with the front tires, you are likely only to make that end suck as much as the rear. the thing to do is to stop the rear from swinging.



since your alignment was done with the other offset, i would add the spacers, bringing you back to those specifications.



these cars handle best when the rear is softer than the front. if your wear pattern is good, increasing rear tire pressure is only going to make the car jounce in the rear.



put the spacers on it so your alignment comes back into its orientation. then chalk your tires and see if they are too soft or too hard. then adjust those pressures until you have as even a wear pattern as possible and as little rollover as possible.

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[danderson]

I just bought a set of Turbo twists from a 993. They are 17x7.5 et 52 and 17x9 et 47. They seem to be more inward than my stock 16 inch wheels. The previous owner of the wheels said they were set inward on his 951. He thought he would need a 28mm spacer in the rear and a 20mm spacer in the front. I have seen twists on 944's but I have no idea if spacers were used. I have yet to fit them to the car for lack of time. I got them yesterday. Maybe I am asking too soon. If I needed to use spacers, it would seem to me that I wuld need longer lug studs. Would that mean pulling the rear bearings to get new studs in? 

Thanks for any suggestions.

Dwight Anderson

94 coupe

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[danderson]

FQ,

   I should not have skimmed so quickly. I see you have the same wheels I have. Have you had any issues with rubbing during full lock turning? DO the wheels sit alright within the wheel wells?  Thank you.

Dwight Anderson

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