Don't overlook the tire thing. There have been more than one set of bad tires sold over time. I'm not a fan of Kumhos. The limited slip diff will exagerate any differences in the rear tires from side to side with accel/decel as you describe. Make sure the tires are the same size, if directional-mounted in the right direction, proper pressures, etc. (note the psi recommendations from the factory aren't as much a function of year built as compensation for oversteer tendency and Porsche trying to protect idiot drivers)

Try the side to side swap, as recommended.

As whale notes, systemic evaluation of all components and rehab of them is a real possibility. As I went through Ruby in the day, I'd spend a grand or two in parts, and do the rear end. Or the front end. Or upgrade the entire brake system. To me, that is half the fun with these cars.

 

I did check all that. It seems it may have had a problem in the past as new mounts were welded on in 2000 - a job the receipts show being sub'd out. It's been very neatly done and there's no play.

The tires are directional and installed on their correct sides. I'm gonna double check everything again but I was kind of thinking it might be the shocks - is there a usual service life for rear shocks? They must get pretty pounded?

 

Thanks Ed, Thanks everyone. I presume it is ok to swap the tires and have them going against their rotation for the purposes of a brief test?

 

Probably not. I'd go to your tire shop and say the car is doing weird stuff with the new tires and want them swapped. They should do it at n/c.

 

Really? I was under the impression that the direction on most tires had more to do with wet performance than anything else. I have never investigated it, but I have certainly seen ham fisted mechanics install wheels in the wrong position with directional tires.

 

I'll throw in my $02 here as I had the same problem you described. The car would pull right under hard acceleration and back left when letting off the gas. This was after a complete suspension rebuild with new bushings, shocks, tires, wheel bearings, etc, etc.

It turned out to be an alignment/corner balance issue and was solved with a second and more exact wheel alignment.

The problem you describe could be caused by corner balance that is way off; was the car lowered at some point? Also difference in caster from left to right could cause this too. I would not suspect the rear shocks.

My suggestion is to verify correct tire pressures then take the car to an alignment shop that is familiar with the 911 and have them check it out for you.

Let us know what happens.................

 

TT Oversteer, the reason I didn't suspect alignment is because the tires that have been on there for 7,000 miles are worn really uniform. Also, on a straight road it tracks perfectly - no pulling, no shakes. Would this be the case if my alignment was off?

I think I'm going to pull the rear wheels and take them back to the shop to have the tires swapped to the other side. If the problem is reversed or if the shop finds an issue I'll know it's the tires. Then, when it's off the ground I'll have a good nose around underneath.

As far as I know the car is at stock ride height - is there an easy way to check?

 

You can swap directional tires for a test. In the dry there is no risk. This is an easy test and will prove or disprove a tire problem. We swap directional tires on race cars in the dry to even out wear on practice tires.

 

I would start by having the alignment checked. If it hasn,t been done for 10 yrs it,s long overdue even if the tires are wearing evenly.A readout without any adjustments will cost less than replacing one rear shock or swapping 2 tires from rim to rim with a new balancing. I suspect corner balance and alignment will be the root cause. Corner balance can be way off on these cars after years of driving. Most shops including some P car dealers don,t even understand what corner balance is. I was visiting a new Pcar dealership last week and the Hunter alignment reps were there and showed me the new $50000 alignment machine just installed. I asked about corner balance as no one in this town has scales. The reps and service mgr. didn,t even know what I was talking about. There is a simple" tripod method" of checking if it is close but real accurate setup requires scales. Simple corner balance check. Measure fenders to floor heigt at 4 corners. Lift car at centre rear engine seam. Measure fronts again if one side is now lower than other the low corner is soft. Repeat from front at centre of ctossmember and check rears .Either a front or rear corner can be soft. The car can still sit level with all on the ground. I have often seen 911s with a premature front one side brake lock issue which is caused by corner balance and on off torque steering can also be the result

 

I agree with having the alignment checked - but I had almost the exact same issue and it was Rear Wheel Bearings. Unnerving was the exact comment I used to describe the feeling........ And it only happened when loading and unloading the suspension in turns........

 

If I were trying to truly define or eliminate a problem, I think I'd try to do it right. But, who knows, maybe not.

You bring up a good point.....I remember on Pelican a few years ago where someone had new tires installed, and they put the 6's on one SIDE and the 7's on the other-or whatever the size was, the rears on one side, fronts on the other. I know it is silly, but stuff happens.

 

The limited slip/tire issue is one I've experienced. I lost a tire @ TMS going into turn 2 (talk about fun) at a DE. I had to get a replacement, same size, but new. The car did the angle to one side on accel, return on decel that you describe, which I attributed to the limited slip on Ruby and some difference in diameter from a tire with miles and a new one. Two new tires at the rear solved the issue.

 

I've seen it to many times to count. 928 cars always had them swapped after some bonehead "rotated" the tires.

I'm sure a close inspection will find the culprit here. Shocks will not last forever, the miles and (more importantly) the age would dictate new ones in this case I suspect. All the suspension bushings including top mounts at the front should all be closely inspected along with a good corner balance and alignment. This may require a little coin, but it will make the biggest differance in the cars behavior now, and in the long run.
You may want to start talking to shops in your area.

 

Ok, I think we spill the beans now. None of us think these cars are worth a darn, and they don't handle very well even when well-sorted. We just want you to keep spending.

This forum is just a conspiracy planted by the Obama administration to stimulate the economy.

 

BWAHAHAHAH. You think this is bad...go jump in the 944 forum, social engineering at its best.

and Ed, poor handling...well you should know, a Targa with a 915...sheez. just don't drive flatout for fear of catching on fire.