krichbaum

Folks, I'm looking around for a 951 and I've been focused on '87 and later cars because I know there are some differences in the suspension. I'd like to find out exactly what the differences are, so I can further investigate the '86 cars and what extra cost might be needed to update one. I know there are some advantages to a '86 as compared to others, such as no airbags and slightly lighter weight. So maybe I should more seriously consider the '86s.

Keep in mind, I'm an experienced track/racecar driver and I'm most worried about the performance in that environment. It will be a street car but will also get track time just for fun. What I'm looking to find out is what kind of physical differences there are, such as the spindles, control arms, etc. Also, what are the resulting geometry differences. I'm sure things like scrub radius, ackerman, possibly even camber curves are affected? What are the difference, both front and rear?

Also, how hard is it to find the required parts to update the suspension? Are the parts readily available, and does anybody know what they'll cost?

BTW, I did try searching for some of this info, but didn't really find exactly what I was looking for. If finding the answers are as easy as pointing me to particular threads, I'd appreciate it if you'd do so.

Gary

Charlotte944

Gary:

I have an '86 951 and an '87NA, and the only suspension differences I'm aware of are the wheel offsets.

Cars prior to '87 have a 23mm offset, while later cars have a 52mm offset.

As I understand the situation, to convert from early to late offset you need to change front control arms, spindles and rear trailing arms. If you want better information, try talking to either Skip or Jason at Paragon Products.

Ski

86 control arms are shorter, as are the rear axles simply because of the different offsets for ABS which was offered in 87+MY. The 87 - 88 non ABS cars do not have the ABS sensors on the spindles so if you want ABS, get a car already equipped with it. I think by the time you purchased the hubs, spindles, control arms for offset for more choice of wheels, etc...buying a 87+ you would see no difference in $$ in the end. As far as geomerty, lowering any of the MY cars is going to result in a slight change of geometry. Rennbay offers a longer ball jt pin to correct this and the serious track cars usually go to an aftermarket arm, castor block, ball jt pin and then you have to machine the spindle to match the 19mm pin of say the Charlie arms.

Sam Lin

Just to clarify, both the Charlie and Fabcar arms have a 17mm pin availabie, no machining is necessary on the spindle unless you want the added strength insurance.

Sam

Ski

Sam the guy who bought the Charlie arms off the track car called the manufacturer and he said NO to 17mm pin on the Charlie arm, this was 8 months ago, which is the reason he went ahead and bought the spindles too. Has he started making them now, 17mm pin?

macnewma

I have heard that he has started making 17mm ball joints too, but I haven't confirmed. I have a set ready to go in my car with 19mm. I asked Paragon if they had 17mm ones and they weren't aware of them and suggested using the 19mm for the extra strength.

How much did the machine work on the spindle cost you?

Max

Sam Lin

Bret, last I heard was that 17mm was available for them, but that was even longer ago than 8 months, so perhaps he stopped making them by the time you asked? I'm pretty sure I've seen a 17mm pin on a Charlie. Come to think of it though, I don't know if perhaps the user machined the 19mm pin down to 17mm, and it wasn't purchased that way.

Sam

pk951

From what i hear the front spindles on 87 are stronger than 86, turbo S spindles are even stronger much better for track use.

Ahmet

Then there's other improved items such as strut mounts, hub design, front calipers, tie rods, I believe brake booster and master cylinder as well.

The car later cars have preferable camber curves compared to the older set up. I believe caster is not affected much. Bump steer is vastly improved. Subjectively ride seems better with a later model car as well.
Ahmet

Matt Sheppard

'87 and later "stock brakes" have a 2mm larger leading piston on the caliper than the '86.

If your going to track it, you may want to just find an S. Better control arm design, S4 braking and THE ultimate spindle/hub combo. A decent driver can get later non-M030 cars to fade at say Willow Springs. The "S" or M030 caliper is such that you have enough brake for anything your likely to see. I upgraded my red car to those brakes and ended up going back to stock '87 brakes, mainly because in a parking lot daily-driver situation, no matter how I modulated them, they were almost digital so when you applied them you "STOPPED". Embarrasing, dangerous and annoying - but boy can they scrub speed like a race car should! It just depends on what your after.

pk951

--------------------------------------------------------------------------------Quote

It is funny that no one has mentioned the REAL reason the ball joints fail on alloy arms. It is really important to know this because is sets the stage for something you are going to have to deal with throughout your whole 944 racing career:

On cars built prior to -87, NONE of the front end parts are strong enough for the loads involved in racing. Every part in the front suspension can and eventually will fail catastrophically.

It is all metal fatigue. Yes, in unusual cases the ball joints can get bent over by over travelling. I doubt they would snap off instantaneously, but being bent over does nothing good for the fatigue life.

The harder you work thse parts, the shorter the fatigue life. On 225/50 15 tires and stock brakes, your parts are probably going to last a while, maybe a few seasons. On 285 slicks on 10.5 inch wheels, you will be lucky to complete a race weekend.

The reason Fabcar and Charlie arms are effective it is that the strength of the ball joint pin is so high that the loads involved are below the fatigue limit of the part. Of course if your car gets really fast, you might just start incurring loads that are above the fatigue limit, which means these parts WILL eventually fail.

The design of the factory ball joint pin is pretty inexcusable. The 360 degree groove pretty much guarantees a failure at the bottom of the groove. The ball joint's play-free life span is incredibly short on a race car as well. Despite this, I am not really in favor of steel arms, modified or not, on GT-type 944s. They are not stiff, and will eventually fail near the inner bushing hole. I am sure they are fine on cars with smaller tires.

Once you overcome the ball joint issue you move on to hubs, spindles, and steering knuckle pinch bolt failures. The real solution is to change to Turbo S hubs and spindles which are probably twice as strong and almost strong enough for a decent GT car. This is inconvenient and expensive of course, and even these parts break when they get enough miles on them.

In short, the pre 87 parts are unacceptable for anything but a very limited car like a 944 spec, and the post 87 parts are decent for anything but a full blown GT. In any case, regular inspections are a must.

Chris Cervelli
Premier Motorsports

krichbaum

Thanks for the replies so far. It sounds like I'll need the 'S' parts at a minimum. Rather than spend the money on as S, Maybe it would still be better to buy an '86 if it saves some money, then go straight to the $$$ control arms and the associated bits. It really doesn't make much sense for me to get an S because I'll also be upping the power output quite a bit (aftermarket turbo, etc). Of course, there are other things to consider yet, like brakes.

I have to say, I am a bit disappointed that the Porsche engineers didn't do a better job with certain aspects of the car. But its still a good platform to build on.

M758

pk... I was about to mention Chris's View on this subject. Then saw your post.

Sounded just like Chris... Then I read that it was Chris! LOL


Anyway for those that don't know Chris has pretty extensive history racing 944 Turbos including some high hp cars on huge tires. So he knows well of what he speaks.

The basic probelms is that Porsche never engineered these cars for racing at the highest levels. It does seems that what was learned from Turbo Cup racing made it in to production the 944 Turbo S models. Remember it takes a couple years for racing to generate data on the weak points and then time to change production. By then it was the middle of 88 and Time for Turbo S model. 89 Turbos also have these changes.

Not sure what parts were used on the later S2's or 968's.