Negative Camber - Understeer - Stiffened ARB

[scam75]

Afternoon All

I am suffering from understeer, a lot worse in the wet currently. I run a bit of negative camber and the front ARB is stiffened with poly bushes and triangular ARB supports. Car is lowered about 60mm also. Is this to be expected? Turn in is very sharp and understeer is exagerated when already cornering and applying more steering.

I currently have pretty well worn Toyo T-1S's on the front which are getting a but tracked on the inside. Anyway I have just ordered a set of Uniroyal Rainsport 3's to chuck on. This tyre seems to be pretty soft and seems to give excellent wet and dry grip, only trade off being they wear quite quick.

I assume I will only get 5k miles out them maybe however I am hoping they make a difference to my current understeer issue.

Any thoughts?

Cheers

Stuart

 

[944 man]

Received wisdom, frequently repeated says that you should stiffen the rear anti-roll bar. What youre doing though is saying that I have insufficient front grip and I will make this less noticeable by decreasing rear grip too. Received wisdom is frequently boll*cks repeated on the internet by people who don't really know what theyre talking about... []

Id suggest trying to find the missing front grip. Too fat a rear tyre? Too firm a front ARB? Too little front compliance? Im presuming that it only does this because you have changed something. Further Id expect that you have only changed something because you believe that t will be an improvement. Probably best to remove the last 'upgrade' first and see how it goes from there.

Apologies for brevity.

 

[scam75]

Cheers Simon

I have only really noticed this since I chucked on pretty worn and knackered Toyo T-1S's as a stop gap when a front Conti developed a sidewall bubble. The issue was there with the Conti's (Premium Contacts) but not as severe.

I had started putting on harder rubber on the front as my last 2 pairs of Toyo T-1R's wore down quite quickly on the inside edges, being directional I could rotate them and get a bit longer, but grip has been worse on the harder compounds although lifespan of rubber is longer! I suppose this is common prevelance.

I have made no suspension changes for a number of years, just different rubber, so I am hoping to see a good improvement on the brand new Rainsport 3's which seem to be getting good reviews. However I accept that not being directional, and being soft, I may be replacing again in the not too distant future. If desired grip levels return though I suppose I can't complain.

Edit to add I still run grippy T-1R's on the rear and am using standard width tyres on CS wheels, 245 rears, 225 fronts. If the soft new rubber does not have the desired effect my next move is removing the triangulation brackets from the front although I do like the car set up with a smidge of understeer, just not enough to put me into a field! [&:]

Cheers

Stuart

 

[edh]

Sounds like your front tyres are rubbish. Sounds like you are expecting more grip than they can give, adding steering angle & exceeding the friction circle & washing out

A standard car will understeer a bit - it's how they are set up. Tyres first, then maybe some more caster?

or....how about some part worn P6000's for the rear? []

 

[TTM]

At the risk of repeating myself, these triangular ARB stiffeners are rubbish.
My car understeered pretty much like a barge full of sand during the short while I had them on.
Porsche designed the suspension so that the brackets could flex.

 

[scam75]

Thanks edh and Thom!

I think the front tyres are rubbish and I think that combined with the triangulation brackets is what is causing my current sand barge handling, much more so in the wet. We will see what difference nice, new soft rubber makes and if I'm still not happy the brackets become door stops!

Will give the worn P6000's a miss for the rear thanks! Incidentally when I bought my car it had 10 year old P6000's on the front with about 7mm left. That was not a great introduction to driving a 944 turbo considering I had to drive it 500 (mostly wet) miles home!!

Cheers

Stuart

 

[JagdHamster]

I have always understood that a too-firm front ARB increases understeer.

So a firmer rear ARB would help (certainly transforms fast Audis.....), but I'd soften the front first.

Russ

 

[944Scott]

Did you find one of your triangulated brackets hard to get on? I did. when the suspension was set up they struggled setting up the castor one side and I wonder if this is preventing adjustment, I intend to remove it, elongate the holes and refit with a view to improving the castor.

 

[scam75]

Nah Scott, mine went on no bother.

Stuart

 

[944Scott]

ORIGINAL: scam75

Nah Scott, mine went on no bother.

Stuart

Lucky beggar, hopefully modifying mine will allow me to tweak the castor.

 

[Diver944]

ORIGINAL: edh

how about some part worn P6000's for the rear? []

Worn P6000's????? Now there is an oxymoron if I ever I heard one []

It does sound to me like your worn out front tyres are the cause of the problem and it's not helped by a slightly stiffer front end.

 

[ChasR]

If I am honest I have never been all that impressed by the grip of T1 tyres (well, the T1-Rs and Ss) on other cars I have bought. Worn out examples cannot be helping (a few do reckon that Toyos do go 'off' in their grip upon approaching the legal limit of tread.

Whilst the ARB stiffeners probably do not help I would be tempted to see what happens with the new tyres being fitted . On mine it certainly helped albeit it was not terrible previously (my fronts were a little tired and an advisory on the MOT).

 

[Neil Haughey]

This times x1000. I had them on my race car since 2010. NineX who have been looking after my car since the winter advised to take them off as they can cause the bushings to bind. They freed everything up front and rear resulting in a car which cornered more quickly at 5 c in February on Dunlop road legal tyres then it did last summer on slicks. Just don't waste your time and money on these trash American suspension mods. The brackets on the front have to flex to stop the bushes from binding just as the rear trailing arm bushes have to flex to step the rear suspension from binding up. The cars in race form will pull 1.4g repeatedly on bone stock bushes and suspension components apart from springs and shocks so why does anyone feel the need to ruin their 944 with aftermarket bodged up rubbish.

ORIGINAL: TTM

At the risk of repeating myself, these triangular ARB stiffeners are rubbish.
My car understeered pretty much like a barge full of sand during the short while I had them on.
Porsche designed the suspension so that the brackets could flex.

 

[Neil Haughey]

Whilst we are on the subject something is very much amiss if the understeer is worse in the wet. I have always found things to be the opposite in that a setup which seems very tiring in terms of steering load and understeer in the dry can suddenly feel pretty hairy and loose in the wet. Its the tendency for the rear tyres to want to let go in the wet just takes all the weight out of the steering and kills a lot of the understeer mid corner and exit. Fun though until you get carried away and crash.

 

[944 man]

ORIGINAL: TTM

At the risk of repeating myself, these triangular ARB stiffeners are rubbish.
My car understeered pretty much like a barge full of sand during the short while I had them on.
Porsche designed the suspension so that the brackets could flex.

In hard use they cause failures too.

 

[scam75]

Thanks for all your input chaps. I think my current tyres could be graded as fubar'ed after inspecting them this morning. Dry grip 2/10, wet grip 0/10. New rubber arrives today, hopefully get a chance to fit them this evening. Will see how they go once scrubbed in.

Interesting all the comments on the stiffening brackets. I actually liked how they tightened the front in and gave me noticeably sharper turn in. I suppose this is contributing to my current issue with gubbed rubber. I was also under the impression they prevented roll bar drop links snapping. Either way my car will understeer somewhat more than Porsche intended with a poly bushed and stiffened front ARB and f all done with the rear bar! Am I right in thinking an MY90 has the slightly thinner rear bar?

Anyway, I will reserve further judgement till my new rubber is mounted and scrubbed in and then see how she handles and if it's to my liking or not.

I am also thinking of moving from Toyo's on the rear, although currently I have fairly fresh T-1R's on. The issue here is choice. I cannot get Rainsports in 245/45/16. Toyo's, Conti's, Falken's, Bridgestone's seem available. Any others?

Again, thanks for all your varied and intersting comments. Lot's of food for thought.

Stuart

 

[TTM]

When I bought the turbo it had the 968 M030 (30mm) front ARB with Delrin bushes, and perhaps I lost a bit of precision when replacing them with standard rubber bushes, but nothing to write home about. Then I tried these stupid brackets and noticed my mistake.
Yes the drop links flex and may break eventually... but my turbo has now 205k miles and although the drop links could do with a sanding & repaint, they do not look like they want to crack.

Normally your car came with the 16mm rear ARB. The 968 M030 rear ARB (19mm) has 3 settings which should help you adjust oversteer nicely.

 

[scam75]

Ok, update today. Tyres on, problem gone. All steering compliance returned on fresh new, soft rubber. It seems I had been driving on tyres with all the rubber qualities of concrete. I knew they were not too clever but never thought they were just that bad!

Lesson to me: don't scrimp on rubber, even as a stop gap! The difference is night and day and the car is totally transformed!

Happy days

Stuart

 

[edh]

Good result

(although I still think the P6000 fix would have worked..)

 

[Hilux]

Weltmeister ARB`s are a good upgrade but you need good tyres and suspension and a slightly agressive set up as body roll is very well controlled so when grip goes it goes without warning (on road tyres)