Hello all as a complete 911 newbie I am just after a bit of advice on improving the handling of my 3.0 litre sc. The problem is the massive understeer I am getting while cornering.

Is this just part and parcel of 911 ownership or can I minimise it somehow?

Thanks in advance

Jay.

Hi Jay -

Welcome to the forum.

I'll kick things off but i'm sure others will chime in.

Despite their reputation for oversteer the 911 actually tends to understeer.  Oversteer normally happens when a driver lifts off the throttle when cornering.

Anyway to your understeer problem.  There is plenty you can do to get your handling like a dream.  When set up well the older 911's handle fantastically IMHO.

The first thing to do it get it corner weighted and balanced and then have the geometry set correctly.  Given you have had a few changes to your car i.e. light wieght plastic bumpers stripped interior etc I would suggest you first corner weight the car with you in the driver seat. If you dont get the front to rear balance and cross weights right the handing will be off as well as braking.  Tyre wear will also be off.  You also won't get heat into all of the tyre width and you'l lose grip.

Next I would suggest alignment.  Getting camber caster and toe right is essential for proper handinling.  If its going to be primarily a track car then I would suggest dialing in a couple of degrees of +ve camber on the front although it can be tough to pull the struts in.  A strut brace can help here.  You then need to think about the toe.  Porsche suggest 0 degree to Plus half a degree (ish).  Toe out like this will give you a little straight line stability.

Then when all of thhis is done you can think about your front and rear roll bars.  Do you know what size you are running?  This will effect the tendency for over/understeer.

Quote: Pete at Apr 15, 2009 8:10:44 pm

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Then when all of this is done you can think about your front and rear roll bars.  Do you know what size you are running?

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Thanks for the welcome and the advice Pete! I have read about corner weighting before not sure who to go to in the South west though. As far as the roll bars go not sure what its running to be honest.

I am sure it is just a set up issue with mine I would love to get it corrected though as understeer is a nightmare. I have some track time booked at Castle combe a week on Saturday shame it wont be sorted before then!

We will get your car sorted no problem.  Gwynsms is man.  He has all the laser equipment and scales.  I've been in cars that he has sorted and they are a totally different drive after that.  Get a rule out and measure the diameter of your roll bars.  Meantime have a chat with Gywn.  I'm sure he'll see this thread and join in.

Ideal I am sure it has the potential to be a very compotent car! I will get it on the ramp tomorrow and have a look at the roll bars. 

Quote: JK at Apr 15, 2009 8:36:32 pm

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Ideal I am sure it has the potential to be a very compotent car! I will get it on the ramp tomorrow and have a look at the roll bars. 

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Did you measure the diameter of your roll bars?

I totally forgot mate I am back at work tomorrow so I will do it then.

No problem.

Here's a link to the effect of ARB's on handling.911 ARB Handling

Im changing my ARB's at the moment.  I had 20mm front and 18mm rear.  Im changing the rear to a 20mm turbo one as it helps me get over gearbox clearance issues.  It will be interesting to see how she handles with a 20/20 setup.

Turns out the handling isn't as bad as I had first thought took the 911 to Castle combe yesterday and found it more than competant even against the awd stuff!

Awesome JK.  Sounds like you bought a good one. 

How was your laptimes?  You'll have to post your thoughts of the circuit over in the 'ciruit lowdon' section.

Any pics or video of your day?

No idea on my lap times to be honest they could be hours but it was so much fun! The 911 is a real challenge to drive fast but so rewarding! I do have a few pictures and video I will get them uploaded asap. I have a nice clip of me spinning it at Quarry on my last lap!

Checked my anti roll bars today 20mm front 20mm rears

Interestingly thats what Im running.  Its not a combination that the factory produced for their 911 variants.

Here's a list of ARB's for the carerra's: ARB's for 84 - 89 911's

Normally the rear is slightly smaller than the back to give the car slightly more understeer.  But give your car isnt original it may have been chosen to counter the efeect of lighter front and rear bumpers etc.

you could also think about turbo tie rods , this gives a dam sight better feel on the steering  if not already fitted and possubly a bump steer kit as the car is lower than standerd . i would get the turbo tie rods done before your alignment
done ,

+1 for turbo tie rods.  make sure you get lenforder and nothing else or they will wear out.....

I fitted turbo tie rods and gives it a much better feel at the front end.  Definitely need to do it before you get the alignment done.....