Cloud9...68

Thanks - it doesn't look like steel was added, but at the same time, I'm amazed they were able to move that much metal without cracking the paint. Like you, I need an inch of flare at the very most - I'm not rubbing as it is, but it's very tight under there! Definitely not interested in the huge tack-on flares - that's WAY more than I need. I'll see what the shop or shops I visit tomorrow say.

Cloud9...68

Made an appointment with a shop to flare my fenders next Friday 3/29. I'll post before and after pictures.

968to986

Cloud9...68

Just a quick update - I've been chasing down an oversteer problem with my car for a long time, which I think was exacerbated when I switched from the stock staggered wheel set-up to a square set-up (17 x 10.5", 49 mm offset all around), which iincreased my front grip more relative to the rear. I was under the impression that increasing the rear track would move the car toward a more understeering attitude, but further research releaved that this is not necessarily true, at least under steady-state cornerning. So I'm going to hold off on the spacer installation and fender flaring until I correct the oversteer. I'm working with a professional suspension tuner, who takes a very back-to-basics approach, so I'm in the latter stages of measuring and weighing all the key parameters of my suspension, allowing a quantitative approach to sorting out my somewhat unusual set-up. After that's completed, I may revisit widening the rear track, as that might help my car's transient responses, and I'll report back on my fender flaring project at that time.

J1NX3D

Any updates @Cloud?

Red1

315s under stock bodywork. But I always did like the look of the bolt-on flares.

Cloud9...68

No, I never pursued widening my rear track. I should have researched this more before buying the spacers and installing the longer studs. It turns out that widening the rear track actually slightly increases the tendency toward oversteer, which is the exact opposite of what I wanted. Suspension dynamics is a complex subject, and things don't always go in the direction that you would think they should.

MAGK944

If you just fitted wider tires at the rear then it should have promoted more understeer, however it seems like you went wider on the tires and also increased the track, it’s the increase of track that likely moved you to oversteer. If you just went wide without increasing track you’d have achieved the oversteer correction you desired.

Cloud9...68

Actually, it's a little more complicated. I went from the standard 968 staggered setup to a square setup, 17 x 10.5" all around. I went with an offset (49 mm) that allowed me to fit these wheels without having to either add spacers, or flare the fenders. The huge increase in front wheel/tire width relative to the rear is what I believe played a big part in promoting the oversteer I was experiencing. Through my work on troubleshooting the oversteer problem, I measured the front and rear track, and found that the front track was over an inch wider than the front. I jumped to the conclusion that as a result of the inverse relationship between track width and weight transfer, I would benefit from widening the rear track to match the front through the use of spacers. But I made two mistakes - first, I didn't realize that the 968 comes from the factory with a half-inch wider front track than rear. Second, after digging more deeply into the suspension dynamics, I discovered that widening the rear track actually tends to promote oversteer, not understeer. I can't say I understand why completely, but multiple highly reliable sources agreed that this is in fact the case. It isn't a huge effect, but my thought process was still in the wrong direction. So, no rear fender flares for me.

MAGK944

Yes that afaik is correct for torsion bars like I said. But beware if you have coilovers that all else being equal widening the track on coilover suspension has the same effect as softening the springs which would promote understeer. It’s all about leverage and an increase in track would increase the leverage on the spring causing the spring to compress more “softer” for the same force at the wheel

Cloud9...68

That's what I thought as well, but it turns out to be incorrect, as counterintuitive as it seems. The issue seems to be that the "level arm" that causes elastic weight transfer acts on the center of gravity, not at one or the other end of the car. Therefore changing the track doesn't have that much impact on steady state handling, the optimization of which is the first step in any suspension set-up. I'm still puzzled why widening the track predicts slightly more oversteer in the calculator I'm using (from a suspension dynamics outfit in Australia called Racing Car Technology). The effect isn't very big, but it goes in the wrong direction. The owner of Racing Car Technology told me that tweaking the track may ultimately offer some benefit in transisent responses, like at corner entry or when applying power coming out of the turns, so I haven't given up completely on the idea of eventually widening the rear track, but I first want to have a pro driver drive my car when the weather cools off, and when I have new tires, and get their impressions. But to me, the car feels very neutral right now, so I'm reluctant to mess with it after all the work I've recently done.

MAGK944

Interesting, it’s been discussed to death in every performance car forum yet it’s still seems to be a black art even in steady state, and as for dynamically I throw away the calculator and go by seat-of-the-pants, tire temps and intuition.

Cloud9...68

Sounds like good advice!