Lowered 944s and shattered ball joints

[John Sims]

Ah, but individual packages might not attract duty where as a big package most certainly will.

In years gone by you would be able to get them from ProMax by now - they had a knack of picking up on a good idea from the States and then distributing it in the UK.

I'm out to the shed to hunt out my redundant wishbones today (if it stops raining).

 

[Hilux]

You are not just correcting the binding issue on the ball joint but you are correcting the
suspensions geometry. Since the control arm moves in an arc and not a
vertical line, the further up it goes the more it pulls the wheel in towards
the car. This is a progressive motion, meaning, the further it moves from
center line the more it pulls in per mm of movement. By having it start
(standard pins) in an already elevated position you are having much more
pull in during suspension compression. By making the control arm flat again
(GCK pins) it makes the pull in ratio the least that it can be.

BTW, the more the wheel pulls in the more positive camber the wheel is
given. This is called the "camber curve."

I`m not sure you'll dial this out at all with a lowered car. The wishbone will move in a prescribed (fixed) arc with the steering arm above it moving in a similar/longer arc. Porsche will have set this at the optimum arc so as to prevent the wheel moving inwards as it moves up (primarily) and down.

Lowering the suspension must change the relationship with this arc as the steering arm will be lower relative to the wheel. It must increase `bump steer` which can be muted by adjusting the settings but never dialled out completely unless the steering rack is raised to compensate.

Ergo lowering the car will have an effect in that it must alter the wheel track/arc.

Looking at the design closely I am convinced that it is limiting body roll that is key BUT I also consider that the ball joint limits are finite front and back with more play available sideways as the wishbones do move in that plane relative to the car thereby increasing the tolerance.

Bl**dy interesting discussion, keep it coming.............................[]

 

[John Sims]

I agree that it may increase bump steer, however is it not also possible that the reduced compression arc my help? [8|] Perhaps not as the wheel isn't coming in shortening the distance.

There must be some advantage in the steering knuckle and wishbone being in different planes (as this would be the only way to avoid bump and roll steer).

Have just doodled the change, and see exactly where you are coming from. [] Buttocks! Ideally you want to lower the steering ball joint as well so that it's relationship is the same as original.

The thing is we don't know how Porsche designed the suspension in the first place - one assumes they included allowances for roll steer - so lowering and stiffening completely lashes that up as well. []

However, reducing ride height isn't new to 944's - M030 makes provision for it - so Porsche must have made some calculations to that effect (or more likely did a suck it and see). Surely the 944 Cup cars would have lashed their ball joints if it had been an issue? So the big question is now does the extended ball joint help or hinder, or is one better sticking within the Porsche design envelope.

I am becoming less concerned over the standard ball joints as I have convinced myself that Peter's broke because his Leda struts didn't have appropriate bump stops. This could be complete nonsense but works well as a head in the sand solution.

Aren't McFearsom struts a pain in the bum - double wishbones are so much easier to work out.

I might get a wheel off today and have a bit of a measure up - at least we can then see exactly what is happening.

 

[Peter Empson]

ORIGINAL: Indi9xx

Peter,

What camber and caster angles were you running?

How much lower than stock is your ride height?

Sorry for the slow reply, spent hours stuck on the A4103 near Worcester last night, seems they forgot to grit it. [][][] Total mayhem, also got properly stuck in the snow twice, it just isn't my week!

The suspension settings I had JZ use were posted on Titanic a while back, and I might be wrong but I think they may have been ones you suggested once? I've got the print out at home so can check the camber, but it wasn't particularly extreme.

The ride height is a dificult one, I'd guess 15mm lower. There was plenty of space between the top of the wheel and the arch if that gives you a guideline. Once its got a full compliment of wheels back on I'll try to find out.

I'll have a proper read of this thread when I'm back home tonight, but I like the way it's going and the Rennbay options seems quite appealing to me too.

 

[Peter Empson]

Just checked and the basic settings were what you recommended a while back, which was "1.5 degrees of negative camber on the front, about 1 degree of negative camber on the rear, and set the caster to between 3.5 and 4.5 degrees".

I've attached a pic of the side profile so you can see the ride height. It actually looks quite low here as you can't see where the tyre finishes. It's always had that slight nose down stance so maybe that's a factor too.

 

[John Sims]

ORIGINAL: Peter Empson
.........

You seem to have reversed into the front of Beaky []

 

[Hilux]

However, reducing ride height isn't new to 944's - M030 makes provision for it - so Porsche must have made some calculations to that effect (or more likely did a suck it and see). Surely the 944 Cup cars would have lashed their ball joints if it had been an issue? So the big question is now does the extended ball joint help or hinder, or is one better sticking within the Porsche design envelope.

I agree entirely and stated such earlier in this thread but it fell on silent ears [].........................

Also to be noted is the fact that Mo30 is fully adjustable and can be adjusted considerably lower than the normal ride height so Porsche wouldnt have equipped the Mo30 cars with adjustable suspension that took the cars past their design parameters?

 

[sawood12]

Then the question is did the cup cars run the same lower wishbones than the road cars or were they modified in some way. They must have had some sort of fix in place as you cannot get away from the fact that several people around the world on different suspension systems have had problems with ball joints on lowered cars.

 

[dlknight]

ORIGINAL: Peter Empson

Sorry for the slow reply, spent hours stuck on the A4103 near Worcester last night, seems they forgot to grit it. [][][] Total mayhem, also got properly stuck in the snow twice, it just isn't my week!

Hi Peter,

Were you in your 944 ? I was trying to get back to Worcester from Henley-in-Arden, after spinning in the country lane by work (attempting to climb a quite steep ungritted hill) then 20mph up the M40 as that wasn't gritted either ! got to the M5 which was completely empty and snowless as luckily it had been gritted. I heard that 250 cars were abandoned on the A4103 as Froomes Hill had been closed

Regards

Dave K.

 

[Guest]

ORIGINAL: John Sims

ORIGINAL: Big Dave UK

John
As far as im aware Peters car is on LEDA,S.????
Are you having a "senior" moment.[][][][][].....

Yes, but you see where I am coming from.

TBH I do see Leda as a bit of a cottage industry, so wouldn't be surprised if they hadn't done that calculation in respect of limiting travel.

I would expect KW to get it right.

John,

Now whhhoooo. Leda are one of the worlds formost manufacturers of race suspensions. They have a lot more world race and rally championships on the shelf than KW. And before anybody flames me yes i know KW are a newer company. They are definately no Cottage Industry. In the US where they have access to all the major suppliers (moton, ohlins, bilstein, koni, leda, kw etc etc) and provide most of the development. Which shock manufacturer consistantly wins? Leda. Speak to Racers Edge, Scott Gomes, Chris White, Albert Broadfoot or even John Milledge for their views on Leda and you certainly will get a positive responce as they have all used the product. Ledas are available in several lengths depending on what you state the car is being used for. If you order standard length that is how they come. If you order for lowered car with limited travel you will get appropriate length pistons. I know KW supplies a good product but there is no need to belittle what is a great product and English to boot. Certainly not a cottage industry!

 

[John Sims]

ORIGINAL: sawood12
........ several people around the world on different suspension systems have had problems with ball joints on lowered cars.

I'm wondering if it is because they are using "different" suspension. I am still now of the opinion that they fail because bad bump stop provision allows the suspension to compress beyond the design tolerance of the ball joint. As noted previously, this is a convenient "head in the sand" stand point.

It would be interesting to remove the springs and anti roll bars to find out how far the ball joint will go.

I have e-mailed Rennbay for their comments on what effect their extended ball joints will have on bump and roll steer. After some hours of searching (and swearing) I found my redundant wishbones so I am now awaiting the arrival of my Rennbay kit. I didn't strip the balljoints today as I I'm going to have the wishbones sand blasted first. [8D]

 

[John Sims]

ORIGINAL: Hilux

I agree entirely and stated such earlier in this thread but it fell on silent ears [].........................

Also to be noted is the fact that Mo30 is fully adjustable and can be adjusted considerably lower than the normal ride height so Porsche wouldnt have equipped the Mo30 cars with adjustable suspension that took the cars past their design parameters?

Sorry Paul.....I will try to pay attention. []

It is comforting that we are thinking along the same lines (seemingly) independently. []

 

[John Sims]

ORIGINAL: tommo951

John,

Now whhhoooo. Leda are one of the worlds formost manufacturers of race suspensions. They have a lot more world race and rally championships on the shelf than KW. ....

Well they have been at it long enough. They are an Essex company, and I had them fit a set of springs on one of my Capris probably 25 years ago, so I certainly bear them no malice.

However, if they are so wonderful in sorting suspension settings, as you suggest, why is it they supplied Peter with a system that allowed him to shear a ball joint?

 

[Peter Empson]

ORIGINAL: John Sims

You seem to have reversed into the front of Beaky []

Lol!
Well no wonder the rear looks a little high then []

 

[John Sims]

ORIGINAL: Peter Empson

ORIGINAL: John Sims
You seem to have reversed into the front of Beaky []

Lol!
Well no wonder the rear looks a little high then []

That wouldn't have been quite so bad if you hadn't stood on his bonnet to open your tail gate. []

 

[Peter Empson]

ORIGINAL: dlknight

Hi Peter,

Were you in your 944 ? I was trying to get back to Worcester from Henley-in-Arden, after spinning in the country lane by work (attempting to climb a quite steep ungritted hill) then 20mph up the M40 as that wasn't gritted either ! got to the M5 which was completely empty and snowless as luckily it had been gritted. I heard that 250 cars were abandoned on the A4103 as Froomes Hill had been closed

Regards

Dave K.

Hope you survived the spin intact, it was really treacherous.

I was in a VW Transporter which is hopeless in the snow. Really eventful drive home. It didn't start well, got stuck outside the hotel at Hay-on-Wye and it took me a good 20mins to get up the hill, then followed my satnav down a road that turned into a single track country lane [], couldn't stop as I knew I'd never get moving again and ended up on some farm land. I was totally stuck and a huge ravenous dog (don't know breeds, so lets call it a St Bernard Matthews) came up and made me decide to stay inside the cab []

After a few minutes the farmer appeared and the pee'd off rifle touting yocal I expected was in fact the nicest guy imagineable, he offered me a tea and towed me out not once but twice. First time he got me back on the flat but there still wasn't enough grip to even pull away so he had to do it all over again to get me back to the main road [].

Then in trying to keep momentum up on the A4103 (which was almost solid ice in places) I slowly rounded an uphill bend to find the road dropped down steeply, in the middle distance was a long queue of traffic and right after the brow a woman was blocking the road doing a three point turn [] Somehow I stopped in time by using the verge and then spent the next few hours waiting till the road opened. It was appalling and easily avoidable if they'd bothered to grit the road. Some people were stuck from 1pm till 8pm and abandoned cars and lorries were everywhere. Getting home took 6 hours, covering 120 miles.

Sorry for the OT (but at least no cameras were mentioned []). I feel better now for venting that []

 

[Guest]

ORIGINAL: John Sims

ORIGINAL: tommo951

John,

Now whhhoooo. Leda are one of the worlds formost manufacturers of race suspensions. They have a lot more world race and rally championships on the shelf than KW. ....

Well they have been at it long enough. They are an Essex company, and I had them fit a set of springs on one of my Capris probably 25 years ago, so I certainly bear them no malice.

However, if they are so wonderful in sorting suspension settings, as you suggest, why is it they supplied Peter with a system that allowed him to shear a ball joint?

Did Leda fit the shocks? Were they given a spec sheet? What springs were used in conjunction with the shocks? Were Leda aware of the spring rates? Had the balljoints ever been exchanged? Were they dry or was there grease in the cup? There are a lot more componants and scenarios that can lead to ball joint failure than shocks. All they do is provide rebound compression and a degree of latitudual rigidity . How dare Porsche build a car that can develop componant failure at 15 to 20 yrs old. Remeber you are a respected member of the Porsche comunity and this is a public board. Your comments can influence others. You are single handedly blaming Leda for Peters balljoint failure. What is your qualification? As I remeber (and apologies if my recollections are incorrect) initially you thought it was the strut itself that had broken and titled the thread to that effect. The thread then reverted to the title it now bears.
Please if you can evidence an engineering based reason for the balljoint failure attributed to the Leda shock perhaps you can let us all know. Otherwise I think you owe Leda an apology. I have raced on Leda for years after having a shock made by a manufacturer of predominantly Red Shocks blow out on me coming out of the dip at Oulton Park in an XJS in 1988 to very expensive consequences. I have always found Leda helpful and prepared to work with you to seek further developments. Hence why I feel your comments are unfair

 

[Peter Empson]

ORIGINAL: tommo951


Did Leda fit the shocks? Were they given a spec sheet? What springs were used in conjunction with the shocks? Were Leda aware of the spring rates? Had the balljoints ever been exchanged? Were they dry or was there grease in the cup? There are a lot more componants and scenarios that can lead to ball joint failure than shocks. All they do is provide rebound compression and a degree of latitudual rigidity . How dare Porsche build a car that can develop componant failure at 15 to 20 yrs old. Remeber you are a respected member of the Porsche comunity and this is a public board. Your comments can influence others. You are single handedly blaming Leda for Peters balljoint failure. What is your qualification? As I remeber (and apologies if my recollections are incorrect) initially you thought it was the strut itself that had broken and titled the thread to that effect. The thread then reverted to the title it now bears.

I don't wish to get involved in a debate about Leda as such, but I would like to add I've been very happy with my suspension and their customer service. However I think John is just trying to think through the scenarios that might have caused this failure to help prevent anyone going through the same thing.

Personaly I think my failure was probably caused through fatigue, my setup is pretty stiff and I do drive as hard as I'm happy to when on track. This ball joint had been subjected to many such track days, not counting the many pot holes and speed bumps also covered on the roads. It's entirely conceivable that this was the original one fitted to the car 20 years/190K ago.

Not that I feel it's related at this time, but just FYI the suspension was setup by JZ to fairly conservative settings, was used with Leda supplied Eibach springs with a setup recommended for me after Leda spoke to the Racers Edge. The car is very well maintained mechanicaly and is checked over regularly.

As for blaming the strut failing, well I think that was my fault []. At the time my car was burried in the gravel trap (that's how quickly this all happened) so nothing was visible and given that another 944 owner did experience a rear strut failure on his 944 a while back we did (not unreasonably in my opinion) discuss this as a possibility. Only later on when the car was dug out did Rick confirm the Balljoint failure.

 

[John Sims]

ORIGINAL: tommo951
..... I have always found Leda helpful and prepared to work with you to seek further developments....

If they knew everything about everything they wouldn't have to would they?

I'm not slating Leda, or bigging up KW, or anybody else. I made the point that limiting travel may/is important to ensuring components don't wreck themselves. My perception of Leda is that they might not have been aware of the ultimate tolerance issues on a 944.

As you quite rightly point out, they deal with a great many cars. 100's & 100's of different types of cars. You also noted that they discuss their products with the owners with a view to improve the product or adapt it to suit a particular owner. This is laudable, I am very much in favour of personal service. However, it is unlikely you would find the likes of Koni or Bilstien paying such attention to an individual owner. It is for this reason that my perception of them, in comparison to Koni or Bilstien, is of a cottage industry.

A number of people I know, and respect, have chosen Leda suspension over others. I respect their choice. I don't decry Leda for working with them. I like to be personally involved in the development of my car and I like to work with people who will listen to me - that doesn't mean either of us is infallable.

The reason Leda are used on racing cars is Leda make bespoke suspension components. This is great if something isn't available off the shelf or if, as you say, you want something tailered to suit your specific requirements. The thing with anything bespoke is it is its own prototype.

We will probably never know what ultimately lead to the failure of Peters suspension. But the whole point of a forum is that we can suggest and speculate and consider others comments.

 

[dlknight]

ORIGINAL: sawood12

Then the question is did the cup cars run the same lower wishbones than the road cars or were they modified in some way. They must have had some sort of fix in place as you cannot get away from the fact that several people around the world on different suspension systems have had problems with ball joints on lowered cars.

Hi Scott,

As far as I am aware they used different bushes (brass?) within the control arm and also the thicker 19mm ball pins.

http://www.ssiauto.com/product_info.php/cPath/21_25/products_id/28

Regards

Dave K.