When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Are you saying Porsche set up the 86 944 turbo to understeer? And European E36 M3's, that incidentally came with much higher outputs than US cars, didn't come with a square setup.
Are you saying Porsche set up the 86 944 turbo to understeer? And European E36 M3's, that incidentally came with much higher outputs than US cars, didn't come with a square setup.
While I don't have direct access to the chassis engineers of each model for an exact answer to your question, I think it is a safe assumption that most OE setups were designed with a mild amount of understeer at the limit for safety, especially as the 1990s went on and the potential for litigation was on the rise (especially in the US). It makes sense that the higher-output Euro E36 M3 had a staggered tire setup, it was standard practice in period for Germans to do so with the highest output models, this was before traction/stability control algorithms could easily be tweaked between different versions of the same chassis.
As stated in my previous post, a square wheel and tire configuration is not the be all, end all in chassis setup, but is an easy way to tip the balance, which is why so many track enthusiasts with front engine/RWD cars go to it, and conversely, why so many OEs still use staggered setups even in the era of sophisticated stability control systems and driver aids.
Another good reason for a square setup is wheels/tires can easily be rotated/flipped to maximize their lifespan, assuming that wheel offsets are same front to rear.
Seems to be some different opinions on that thread, is going wide on the front a short cut, instead of a better front suspension setup? I had an Audi A4 quattro with a square setup, that was easy to control in 4 wheel slides, in the wet, but the front pushed in the dry. I now have a SEAT Cupra R AWD that came from the factory with 2 degrees negative camber all round, and a square setup. And it doesn't understeer anything like as much.
I think you've asked and answered some of your own questions. Yes, with some sort of sophisiticated multi link suspension you might find a different result. With the Mac Strut front suspension I can concur that the square setup works very well. Of course most road cars are setup with understeer as the default. When I started going quicker in my original slate grey metallic '89 I found the square setup was a must. Along with some better quality suspension components. But the tendency to push-understeer in slow to medium speed corners was something that we tuned out of the car. The Enkei 18"x10" wheels with 275 rubber all round definitely helped with that problem.
Why would Porsche Homologate the 968 turbo RS with anything but the optimal wheel widths?
It's hard to know. We can only guess. They were so rear engine centric that perhaps they just assumed to use a wider rear than front? Perhaps less sophisticated damping was available back then and a square setup with quite a lot of negative camber tramlined too much for them? At normal road speeds it wouldn't matter so much. At high speeds and on the track, there's too many people that have run successfully with a square setup for it to be just subjective.
I think it's over simplifying it to say that Porsche with all their resources, couldn't work out the best way to set up their competition cars. Perhaps they decided the extra weight of the wider front wheels and tyres wasn't worth the trade off, when they could control understeer with camber, anti roll bar and damper set up. And perhaps it's all the drivers that run wider front wheels and tyres that are cutting corners on setup.
Perhaps perhaps perhaps...We'll never know. But remember, the factory also said not to go over what, 16" wheels? Clearly 18" wheels work fine despite the extra unsprung weight with bigger wheels, rubber and braking systems. Also, despite the factory homologating the 968 t RS were they really serious about that car? Many compromises were allowed. Namely 8v engine. By that stage they could have explored and developed the 16v turbo for much greater results. (Would have rendered obsolete many a thread in the forums too). It would seem that they had no real ambitions for that car vs 911 or prototype based models. The Carrera RS was the preferred option for the race teams too. As for cutting corners with the sqr setup (pun intended?) alluding to some perceived lazyness, I think you're off the mark there. I can only speak for myself but I know what we went through to improve my car back then. If the sqr setup showed an immediate improvement then so be it. Isn't the idea of racing to decrease one's lap times?
Yes the pun was intended . I could mention that there were optional extra 18" road wheels for the 968. And Porsche were probably serious about the 16v 924 LeMans cars that didn't run a square setup AFAIK. I think the 968 S/RS came with a pretty serious price tag too. But anyway, 15 years ago when I put KW's on my turbo, I used some 968 track day settings for the bump and rebound, and had the geo set up by one of the best guys in the country. Combined with good tyres, it's pretty neutral if it does slide, though my Mrs isn't a fan of the ride on bumpy roads, and wont get in the car. So I think for a road car at least, square is just playing at Race car.
Yes the pun was intended . I could mention that there were optional extra 18" road wheels for the 968. And Porsche were probably serious about the 16v 924 LeMans cars that didn't run a square setup AFAIK. I think the 968 S/RS came with a pretty serious price tag too. But anyway, 15 years ago when I put KW's on my turbo, I used some 968 track day settings for the bump and rebound, and had the geo set up by one of the best guys in the country. Combined with good tyres, it's pretty neutral if it does slide, though my Mrs isn't a fan of the ride on bumpy roads, and wont get in the car. So I think for a road car at least, square is just playing at Race car.
It was largely due to the UK chaps who had anointed the KWs that I followed same path. I actually went for the 2 way race versions rather than the V3s which were in vogue back then. Even with all the stock rubber bushings/bearings changed for metal and monoball, plus riding on 18" wheels with lower profile R specs, I never felt they were unbearably firm or unforgiving on the street. To be fair, I didn't switch to a sqr setup for a few years. I did run some pretty serious -camber for the track and usually couldn't be bothered to switch it back for the street. I don't remember thinking the sqr setup on the street was any more or less liveable when I finally 'graduated'. Realising that my story is subjective and anecdotal I would still consider the fact that quite a few people have run something similar to good effect enough to believe the hype. Nonetheless it is not mandatory.
Of the 24k miles that I've done in my turbo, on the KW's and 18" wheels, at least 23k of those have been done on the same 100 mile back road route. It's a great route that a bike and a car magazine used to use for their road tests. I've also done over 40k miles down there on bikes over the last 30 years. Track day KW settings on that road are fine. Perhaps you have better roads over there, because I've driven on roads here that made the ride very uncomfortable.
Whether a wheel fits depends on how much negative camber you want to run.
Even though common knowledge says it wont fit, its easily possible to run early offset wheels on a late offset car for instance... if one runs enough negative camber (in this case around -2 degrees which also gives some very good performance benefits).
That said, I think the 9 inch rears should easily fit the front
07-21-2023, 03:48 PM
. I could mention that there were optional extra 18" road wheels for the 968. And Porsche were probably serious about the 16v 924 LeMans cars that didn't run a square setup AFAIK. I think the 968 S/RS came with a pretty serious price tag too. But anyway, 15 years ago when I put KW's on my turbo, I used some 968 track day settings for the bump and rebound, and had the geo set up by one of the best guys in the country. Combined with good tyres, it's pretty neutral if it does slide, though my Mrs isn't a fan of the ride on bumpy roads, and wont get in the car. So I think for a road car at least, square is just playing at Race car.
