Need to Improve Handling - Suggestions Please

[nervy]

I would be grateful for some advice.

I have recently purchased a 1996 Targa, it had an aero1 rear spoiler fitted when the previous owner acquired it - but no front dam.
He had it lowered using a set of progressive 30mm lowering springs by H&R and Bilstein HD shocks fitted, plus one KLA strut brace.

She corners beautifully but is still 'twitchy' at the front in a straight line especially if it is windy.
So I have a few questions on how best to remedy the situation.

If I leave the suspension as is:
1. Will fitting an Aero1 front dam do it ?
2. Will removing the rear Aero1 spoiler and replacing with an original retractable spoiler do it ?

If I put the suspension back to the normal height:
1. Will fitting an Aero1 front dam do it ?
2. Will removing the rear Aero1 spoiler and replacing with an original retractable spoiler do it ?

Or do I need to do something completely different ?

Also, how much will adding a front dam reduce road clearance ?

Thank you for any suggestions.

 

[clubsport]

Assuming the suspension is in good condition, including wishbone bushes etc...it sounds more like a set up issue,,are the tyres evenly worn?

There is an age old rule often used on 911 that apparently you have to fit a corresponding front spoiler to match the rear,,,,I am sure there is something to this,,but doubt you would notice much difference under 100-120mph.... I have seen a few mismatched spoiler combos over the years and unless the drivers are actually gods, they have managed to keep them on the roads.

Depending on the speed at which you are experiencing these effects, I would be very surprised if it is solely down to the aerokit.

 

[nervy]

Hi Clubsport,
thanks for your response.

Most parts on the front end are fairly new. New steering rack and gator, track rods and wishbones etc replaced Oct 08. Tyres are almost new all round.
Car has done 2,500 miles since then.

In France the twitching happened at around 80-90 mph. 2 days ago in Suffolk it was at 60.mph. Both windy days.


I also have a '78 S.C. targa which has a whaletail and front dam. No problems with that one, up to 130 mph in Germany.

 

[burrow01]

Most likely to be suspension setup, do you have any details of the alignment that was performed when the suspension work was done by the previous owner?

Pete

 

[nervy]

Hi Pete,
sorry no information on the suspension set up apart from the information posted in reply to Clubsport, is that any help ?

If not, what do I need to do ?

Alan

 

[topcats993]

I dont know about suspension but Porsche recomend if aerokit is fitted it should be front and rear together on a 993 be it rs or other A rear tail is much larger then the standard spoiler so much more downforce

 

[clyde]

As clubsport said I doubt you would notice uneven effect of mis-matched spoilers below 100mph or so. I would definately get the suspension geometry checked. About a year or so after I first got my C4 it started "wandering" at speed on motorways. It felt really unsettled and wasn't very nice to drive at all, requiring constant steering adjustment to keep in a straight line. But wasn't really that noticable on A and B roads, probably because of the lower speeds and the fact that they tend not to have two or three mile long straights[][]. Suspension geometry adjustments sorted it and I now have it checked and adjusted on an annual basis.

 

[topcats993]

Having had my C2 without the front RS splitters on while they were re painted
I put the origials back on and ran the car just with the rear RS tail and trust me anything over 85 did not feel right the went light at the front and all over the place

To th OP see if you can borrow a standard bootlid and grill before you start shelling out lots of money on other stuff would be my advice

 

[i_sabberton]

Hi Nervy,

I have the H&R with Bilstein suspension set up on a 993C4, it has been lowered in excess of 30mm. The 20mm deep rubber splitter which is beneath the front PU (Turbo front) has been removed and I haven't noticed any difference in handling - the splitter removes itself due to the height of the car, I've given up riveting it back on.

The handling is great, but it, and especially the bumpsteer is sensitive to wheel size, tyre choice, and tyre pressures. I've run the car on both 17" and 18" wheels, and also on a set of non-standard 18" 8.5J fronts.
Is your car on 17", or 18" wheels?
Do the wheels have the optimum width and offset (as specified by Porsche)?
Does the car have a steering brace (noticeable improvement with 18" wheels)?

Ian.

 

[jboult]

Nervy,

Can't help with your problem - but maybe you can help with mine!

I'm looking to sort the handling on my '96 Targa out, and have been thinking for a while of going down the Bilstein HD/H&R route. The only thing that's stopped me so far is the worry that this might be too firm for the Targa, and exacerbate any scuttle shake, create more noise from the roof trim, squeaks, etc. Apart from the specific problem you have, how do you find the suspension set-up otherwise? I've been putting this off for a while and it's my last major project, so want to get it right.

Cheers/John

 

[iver rek]

Bit late into this, but here goes. I bought a car last year, with a kit as you can see. I wouldn't describe it as 'twitchy', when I bought, it but it certainly wandered at speed and picked up road imperfections easily. This year I had new Powerflex front suspension bushes fitted and a 4-wheel alignment carried out. Result; transformed. It now feels like the man in the factory expected.

ps. It's on 18 inch wheels, which are by all accounts more sensitive.

 

[nervy]

Hi John

I don't know how much better or worse the set-up is from the original, because it had already been changed before we bought it. The previous owner said that it was a vast improvement on the original.
The car is on it's original Targa wheels (17") I have been told that Targa's can't take 18's?

There are squeaks from the roof seals but when it's not raining I always drive with the wind deflector up which stops the noise immediately. I have heard that glycerine rubbed along the seal stops it for a while, but I want to make sure that it wont affect the rubber before I try it.

The cornering is great. The ride comfort is a bit bumpy (almost like a sports car) but better than my 78 S.C.

As I have already said, the front end twitchiness is only apparent when there are blustery crosswinds.
I took it out this morning, (winds light to variable) and had no problems at all.

Regards
Alan

 

[jboult]

Alan,

Thanks for the update. I think I'll try the bushes first then look at the rest of the suspension components. It needs doing, so I may as well take the plunge.

On the squeaking seals thing, most Targa owners go through the same, and most try some sort of lubricant (I've heard everything from olive oil to furniture polish!). I couldn't stand the noise in mine - I think I used a rubber/vinyl polish in the end and that cures it for 6 months or so at a time.

Cheers/John

 

[ubertub]

not sure what you mean by twitchiness, but if it's only in wind it sounds like you are referring to the need to react to the car being steered off course by wind... and the unexpected result of your corrective steering. I've got similar setup to you - HDs and H&R and the only issue I have is too much understeer for my liking... which Robin at 9M sorted to an extent.
I'd go with the majority and re-check wishbone bushes, but worn wishbone bushes should be very noticable under breaking into corners as you'd experience toe-out.. ( I think) so unless that's the issue ???
Erm... Maybe it is just a need for a good geo set-up.. and the removal of the rear spoiler.
good luck.

 

[nervy]

Hi Everyone,

Thank you for your suggestions.

I have recently taken off the Aero 1 rear spoiler and replaced it with the original type of rectractable spoiler. So far so good, much better in a straight line even when windy.

I didn't want to fit an Aero 1 front dam as she is low enough already, so that may have been another answer to the problem.



Cheers

 

[Porker993]

I too have had this twitchiness recently - two new rear "wishbones", a control arm and 4 wheel alignment sorted it 100%. At 104,000 miles I don't think that is too bad.

A well sorted 993 is a joy to drive, should be rock steady at speed, even with cross winds, uneven road surfaces etc.


I

 

[geolab]

the problem could be sorted with a simple alignment machine.
what you have to adjust is the toe-in toe-out. the exact measure is -1* / side. for sport chassis and 18" it is -1*45'
It is a bit hectic to adjust this with the steering wheel straight. As I do it myself on my car, I get it right after three to four trials.
There is no correlation with front bumper, spoilers, etc. these go into effect at above 180 km/h