[patkeefe]

I don't use the 968 much, and it is neglected, to a point. I do use it maybe once a week or so, more in the summer. Every time I get in it I can't help but notice how harsh the ride is. Bumps are transmitted back up the wheel, it rattles and shakes a bit, and it really darts around following the low spots in the road. It's the wifey's car; she loves it but hardly drives it because it has become so beastly.



Now that I just about have the 911 back together, it's time to do some maintenance. I'm going to examine the type of shock absorbers I have, I think they're Koni's, as the <acronym title='previous owner'>PO</acronym> is rumored to have changed them all 60K miles ago.This 968 is a Cab. Tires don't seem to make much difference on the car when it .comes to handling or ride, with the exception of the current Yokohamas are terribly noisy. I haven't looked over the bushings or the control arms yet.



I don't get a lot of rear to front pitch on braking in a straight line, nor a lot of pitching up on acceleration. The dampers don't seem worn by common measure. I had two bolts missing from the front crossmember, but replacing them did not cure the problem.



Aside from my venting, can anyone suggest things I should be on the lookout for?

TIA

Pat

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[flash]

yeah - konis can ride rough. what setting do you have them on?



tramlining as described is usually worn caster blocks.

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[mylz87]

PK's post sounds like a car I test drove -

What are caster blocks, where are they located and do you need a lift to fix them?



Thanks

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[mbardeen]

Castor blocks attach to the back of the front control arms. You can replace them with the car on jack-stands (which I recently did).

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[banditsc]

What size rims are on there?

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[patkeefe]

Thanks for the suggestions. banditsc, I have 17's. I have to look and see the width and offsets. I do have 5mm spacers in the front, which I put in over the winter, as the front left tire rubbed on the inner wheel well. The spacers had no effect on the ride quality.

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[flash]

the first thing to do is find out what setting you have the shocks (and i presume struts) on. people frequently set them too stiff for their springs, mistakenly thinking that it will stiffen the suspension and make the car handle better. in reality it only causes jacking.

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[mbardeen]

I actually had a question about that (sorry to thread jack).. what are the recommended settings for Koni yellows on our cars? I left mine as they were set from the factory (full soft, I think). The struts are pretty easy to change, but it seems that the rear shocks have to come out of the car to get set. I haven't yet torqued the bottom bolts down, so it would relatively easy to change them now, as opposed to later.

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[flash]

it depends on the springs. the stiffer the spring, the more you increase the rebound setting. compression is fixed on koni yellows.



the rear shocks indeed must be removed to set them. you also must remove the foam insert in the top of the shock. this will allow you to compress the shock, engage the stop at the bottom, and then be able to turn them. reinsert when finished.



for stock springs in the front, set the struts at a maximum of 1 turn from full soft. the strut adjuster turns counter clockwise to firm up.



for stock torsions in the rear, set the rear shocks at either 1/2 turn from full soft, or 1 turn from full soft. unfortunately there is no setting in between. 1/2 turn may be too soft for some and 1 turn may be too firm. i recommend erring on the soft side. the car plants better, even though it feels like it droops a bit.

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[patkeefe]

I did read a bit of information on the 968 suspension before I posted this; a few of the Flash posts were quite informative (well, all the ones I read were). I got to wondering if I have ever seen adjusters on the shocks, and I don't remember seeing the dials on top of the front struts. I will check tonight when I get home. I'm going to try and get some numbers off the rears and the struts in front.



I had changed the right side caster block some time ago, as the original had been eroded by leakage from the power steering system, which has been repaired. Are there any special tests to perform on the control arms, other than to just shake the crap out of them and look for play?

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[flash]

there are no dials on the shocks, and only the struts have an external adjuster. you adjust the shocks off the car.

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[patkeefe]

I took out the right rear. It is a yellow Koni, sport adjustable.With the internal bump stop in, I could compress it with a little effort. I went back to extended on its own in less than five seconds. I pushed and pulled the bump stop out to full compress, and engaged the adjuster. It is two full turns from lock to lock. So, I suppose one turn is halfway. I think they were on full counterclockwise when I took them out. I think the shock is beat, at least relative to what I think the bump and rebound forces should be.

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[flash]

5 seconds on full soft is about right. but, if they resist going in and out, or slip at spots, or are "notchy" then they are toast.



the rear shocks are clockwise to full stiff. only the struts are backwards. if yours was at full counterclockwise they were on full soft. if that is still too stiff, i would recommend getting a hydraulic shock.

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[patkeefe]

Thanks! I could feel a bit of internal clunkiness ("notchy") on rebound when the shock was down near full compression. It definitely had a rough patch there. I put that shock back in at 1/2 turn clockwise from full soft. I'll get the other rear tomorrow.



I guess these Koni Sports are not hydraulic? I thought they were. Time for some research!



Edit: Inside of both rear tires are worn out. I must have put a bit of negative camber in there when I last had the car at the track.

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[flash]

nope - gas



the rear of this car doesn't respond well to gas shocks. the compound angle of the suspension complicates things and gas makes the back twitchier than hydraulic. unfortunately, other than OEM, there isn't an inexpensive hydraulic option. there is a really good one, but not nearly as inexpensive as the gas options.



lol - at least they aren't bilsteins. that valving is really stiff. helps on the track, but beats you up on the street.

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[patkeefe]

My 911 turbo rear shocks are at Bilstein now getting revalved...they weren't harsh enough!



I did set the left rear shock to soft plus 1/4 turn, which is where it was. The rear tires are corded on the inside, so I ordered two new Yokohama tires to replace the corded ES100's that were on there. I will see what kind of difference the tires make and take it from there. BTW, the fronts show minimal wear, and they were installed when the rears were. All the Porsches we have eat rear tires.

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[Cloud9...68]

[quote name='patkeefe' timestamp='1366856261' post='141846']

All the Porsches we have eat rear tires.

[/quote]

I've read that a lot, but it seems so strange to me. I always wear my fronts out (back in the distant past when my car ran, anyway) much faster than my rears. These cars are so modestly powered that I don't understand how their rear tires can wear faster than their fronts, which take most of the cornering and braking force, and yet many people report that their rears wear faster, so I can't dispute it. I've just never experienced it.

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[Langley968]

My last set of rear tires wore out WAY before the front, but that was because the wheel aligment was out. Now there seams to be regular wear happening.

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[Cloud9...68]

Yeah, I was wondering if fast wear of the rear tires isn't alignment related, because it just doesn't make any sense to me in a car with the 968's layout, staggered wheel widths, and modest weight-to-power ratio. It isn't like these cars routinely burn rubber or anything. Full disclosure - I'm sure my car's tendency to wear out its front tires MUCH faster than its rears is mostly due to all the track time I was putting on it, but when I wasn't tracking it, the wear seemed to be pretty even all around.

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[flash]

tire wear is alignment and setup related. many people put too much negative camber on their car, mistakenly thinking that it will help them in the corners. while it does flatten out the outside tire, it puts the inside tire on an edge, which decreases the net contact patch area, and thereby puts more load on the outside tire, which heats it up more, and actually increases wear on that tire.



the answer for track (which is very different than what you do for autocross) is to decrease roll, and put more weight on the inside tire, and not try to rubber band and bubble gum the cornering power with negative camber.



as for shock valving, many people mistakenly think that stiff shocks make their car handle better. shocks are there for one reason and one reason only. there are there only to slow down the spring. how stiff a shock needs to be is determined entirely by the springs chosen.

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