Player0

So DE season is rapidly approaching and I'd like to reduce an issue I was having at the track last year: I can't apply power to the road going up hills. I don't have a LSD in this car. I run 16x7 and 16x8 fuchs with the stock tire widths. These are Bridgestone RE-11.

This happens when the car is settled in and squatted trying to apply the power. I can only apply about 70% throttle without releasing the back end. I'm getting tire spin in the wheel applying the power.

Someone suggested to me that they run wider fuchs on the 86 944. I've done some searching and it looks like the 16x8 will bolt right to the front. I have a 5mm spacer there and extended lugs anyway due to the S4 calipers needing a bit of clearance. This is an early offset car and I think the 16x7 and 16x8 are both 23mm offsets. I have 2.5 coils front and rear.

I do not want to modify the fenders or adjust camber if I can avoid it.

Questions:

What offsets are available in the 16x9 fuchs that would work with an 86 turbo?

I hear 255/40 is the best size for the rear but is possibly hard to find. Is 245 better for fitment anyway? And I assume 265 is right out?

Will the 5mm spacer ruin the fitment of 16x8 on the front? Granted, this is easy to find out... but it's cold outside

I already have good 225 tires on 16x8 fuchs so I'm inclined to leave that in the front. But later on, would it be possible to use 245s? I hear this is a common upgrade for rear 16x8s but not sure if they'd fit in the front, even with the 2.5 coils.

Player0

I guess a better question is... if I can only run 245s on the 16x9s, and the 245s will fit on the 16x8s, is there any reason to spend all that money on the extra rims and added weight? The sidewalls would be less bulged and probably tighter in the turns. Would there be additional wear?

Van

You're getting the inside wheel to spin, or the outside wheel? Does it happen more often on left or right hand turns?

In addition to using better tires, your corner balance may be off - which would put different amounts of weight on the rear tires - making one more likely to spin due to a lack of grip. Also, with an open diff, you may find it beneficial to run without a rear sway bar.

Paulyy

Toyo R888 or Dunlop direzza ZII

V2Rocket

can you explain, for the uneducated?

Player0

The more serious issue seems to be right handed turns up the hills. I have an adjustable rear sway bar and I was considering softening it a bit. The car is pretty much set up for as much balance as possible right now in over/under steer. I had it corner balanced last summer (which made a world of difference to the handling).

But I can try adjusting/removing the sway bar to see if that helps. But the car does feel pretty settled when this happens. It's not immediately after shifting the cars weight. All the weight should be on that rear left tire which is slipping. I don't know where that right tire is, flat or pivoted, but I'm assuming it'd be giving roughly 0% anyway.

Wouldn't having it flatter on the ground be more beneficial in case it does want to contribute power? Or is the thought here that allowing it to lift a little puts more weight on the left tire which is actually trying to stick to the ground?

R888s would be nice but I can't run R compounds at events, which I think that is right?

f1rocks

Or spend the money on a good LSD transmission. Put the 225's on the front 7" wheels (we race those week after week) and 245's on the rear. Consider dropping the rear spring rate a little as well or as Van said run without the rear sway for a session and see what it does.

I would not suggest the 888's based on two miserable years of racing with them.

f1rocks

No flatter is not necessarily going to allow power transfer on a car with "hard" tires. Tight right handers are going to suck on an open diff car no matter what you do. If you are already experiencing that....you'll just get frustrated picking the inside tire up and listening the motor wind up.

I've not seen an event that tells you what tire compound to run....who do you do events with?

konakat

Here is a reference on a good majority of OEM Porsche wheels ever offered. I imagine the bigger Fuchs would fit without much effort. http://www.944racing.de/wheelweights.php

Butters944

Why don't you run 255s all around on 16x8/9 Fuchs?

Van

People think that a sway bar can "keep the car flat" - but that's not exactly what it does... What it really does is link both sides of the suspension.

Picture this: your car is on a lift, or on jack stands, supported by the body. If you jack up one suspension arm, the sway bar will start to twist, and eventually, it will twist to the point that it's reached equilibrium working against the spring of the other side's suspension (either torsion bar or coil over). At this point, if you keep jacking, the other side will also move up. A larger sway bar will reach this equilibrium point earlier, so the other-side suspension will start to move up sooner.

Now, when you're in a corner, the body roll of the car pushes down (compresses) the outside suspension and extends the inside suspension. With a stiff sway bar, as the outside suspension compresses, it wants to transfer that force to also compress the inside suspension. This actually starts to move the inside wheel upward. Have you ever seen a picture where the inside wheel of a race car is lifted in the air, even though that wheel isn't at "full droop"? That's because the sway bar is holding it up!

So, now, if you disconnect that rear sway bar (in the case of an open diff that's spinning the inside wheel), there is one less force trying to pick that wheel off the pavement, and thus that wheel will have a little more weight on it. This is called "softening" the suspension, and it will give that end of the car more grip. This added amount of grip *may* be enough to keep that inside wheel from spinning.

When we talk about car balance and grip, the simple rule exists: for whichever end of the car you want more grip, you either have to soften that end or stiffen the other end.

Skinnier sway bars are softer than fatter ones. Lighter springs are softer than heavy ones. More compliant shocks are softer than firmer ones.

By changing these parameters, we can fine-tune the balance of the car.

Here's a caveat: lots of people ask, "what's the best combination for a neutral handling car?" - but cars (especially on the track) are very dynamic things, and one of the reasons is weight transfer. There is no one setting that give "balance" at all weight transfers. You can reduce understeer at corner turn-in (where there's extra weight on the front end), but then that can upset the balance of the car causing great oversteer when you're powering out of the corner to track-out.

You have to find what works well for your driving style and what works well for the track's layout/conditions.

Van

p.s. to illustrate my point about sway bars... and because I love sharing this picture, look how the sway bar is holding up the right front wheel:

ZR8ED

Good summary. To put it even shorter, setup the "major" suspension components (strut/spring/shock) first. THEN use the swaybars/Antiroll bars for fine tuning.

Good luck!

StoogeMoe

You can adjust your driving style too for that problematic corner by taking a later apex. Then you can straighten the car out quicker and get the power down.

Softening the rear bars will help, but may cause your car to understeer in other corners. That may make your car faster out of that one corner, but slower for the whole lap. You'll have to find the best compromise until you get an LSD.

Van

To go a step further: sway bars also have the majority of their effect mid-corner, where the weight transfer is somewhat steady-state.