Most of the roads here in my part of Texas suck. A bit like driving on a washboard. Sadly, I feel more confident when it comes to traction and handling driving around in my 1990 Jeep Comanche pickup than in my 1994 968. Going around a mild washboard bumpy turn in my Jeep I feel completely confident that I'll still be on the road when I get through the turn. On the other hand and going through the same turn, I find myself wondering on every bump when I am going to slide off the road! My gut feel here is that this is not the tires, since the tires on my Jeep are about the cheapest I could buy. But that IS a gut feel.

Am I just noticing this more in my 968, or it is something else?

 

My only guess is in these turns sometimes the 968 is somewhat "tramlining" if that's the proper term, getting pulled around by grooves in the road.

 

Tramlining generally caused by the car's steering, without any driver input, following a groove in the same direction as car travel - often caused by the overlap of different tarmac surfaces. Tyres quite happy to 'drop' in the groove and go with it.

Washboard bump type surfaces, typically on dirt roads, result from other vehicles 'bouncing' at speed gradually and creating a 'dip' over time. If it's a road surface type the 968 will spend most of its time on then a spring and damper spec change would be the call.

 

I asked Duck.ai to further define Tramlining:

"Tramlining is a phenomenon that occurs in vehicles, particularly in cars, where the vehicle tends to follow the grooves or ruts in the road surface. This can lead to a feeling of instability or wandering, as the vehicle may pull to one side or the other, making it difficult for the driver to maintain a straight path. Tramlining is often more pronounced in vehicles with wider tires or those that have a stiffer suspension setup. It can be influenced by factors such as tire pressure, alignment, and the condition of the road."

That does describe the sensation I am being plagued with! I have recently had a full alignment and I check my tire pressure often so these being out of spec is probably not the cause, I don't have any control (pun intended) of the road conditions.

@LM964 , can you point me to any further information about the spring and damper spec change? I would like to learn more about what is involved to address this specific issue by these changes and learn details of how these adjustment might be incorporated.

Anyone else that has done this and with success?

 

There are two different experiences for two different scenarios here; one being the the car's steering wanting to follow a different line and the other being driving and steering on an undulating surface of ridges and troughs (from what I can gather from your post lead).

I had a few different 928 models in the past and the later S4 loved to tramline on fast open motorways and dual carriageways where there were lane differences in road surface material - e.g. concrete vs different tarmac densities. With wide tyres the S4 was quite happy to pick up a groove line and very gently veer away from staying central and straight and in the line of travel. Nothing I can do about that other than small geometry tweaks (or just bring it back on line).

I assume you were referring to 'washboard' as the bumpy road surface running across the line of travel. For smoothing the ride and steering on this kind of surface it's a mix of spring rates and damper settings. Again, depending on what you want and driving style, it would be an idea to ask around for recommendations. Me personally I have CS springs, adjustable Konis all round and original M030 option sway bars and castor mounts. But that's about me wanting a setup for twisty sprints and hill climbs. If you're driving Texan washboard dirt roads then it's probably a setup closer to rally spec and a ride height to suit. Can't really suggest anything more tbh. You'll need to seek recommendations form specialists in your area. Maybe others will chip in with their experiences and ideas.

 

Dang it. I forgot to hit "Send Reply" again!
I was going to ask how are your shocks? Worn shocks can wreak all sorts of havoc.

FWIW, The "trammeling" described here was much worse when I went to 17" Cup II wheels, vs the OEM base 16" wheels, especially if your TP is a little bit low. (Due to the width, not the circumference) I notice it most on tarmac surfaces, where heavy trucks have created two "ruts" in the surface. The tire catches the side of those ruts and wants to climb out of it. Makes me constantly think I'm out of alignment. Also happens on off camber surfaces. Tires want to follow the low side, which seems like "pulling."

 

Could be more than tramlining e.g. washboard surface. First think to try is different tires, what do you have on right now? The Conti Sport 02's are known for ride quality.

Shocks/Struts - Have been reading reviews on the KW V2 Comfort that KW has developed mostly for the BMW market, the reviews are quite favorable, much better ride despite higher (linear) spring rates, so overall improved handling. I wonder if we could get a dozen or two 968 owners with interest to approach KW, the V3's are more track oriented.

 

Could be more than tramlining e.g. washboard surface. First thing to try is different tires, what do you have on right now (and diameter/size)? The Conti Sport 02's are known for ride quality, just bought a pair.

Shocks/Struts - Have been reading reviews on the " KW V2 Comfort " that KW has developed mostly for the BMW market, the reviews are quite favorable, much better ride despite higher (linear) spring rates, so overall improved handling. I wonder if we could get a dozen or two 968 owners with interest to approach KW, the V3's that are available for the 968 are more track oriented.

 

Well I was certain I had written and posted an excellent response but it would appear that I followed @dlearl476 and didn't actually upload it. But from memory I believe I mentioned 2 things.

One was that my use of "washboard" was a feeling observed on paved roads, no off-roading

Two was a note that my shocks are original, mileage around 85k. I have looked at the posts here about the Koni modified strut solution and it is tempting, except that I think that job is above my pay grade. I did mention it to the service rep at the local Porsche service center when I was there last time. They didn't flat out say no, but, they are not fans of modifications and don't generally install non-OEM parts. After scanning my memory cells, I don't seem to recall this being an issue for the full 30 or so years of ownership, just more recent, so that could support the idea that this is an issue with something, like shocks, wearing out. Replacing these is on the list, perhaps it needs moved up.

Tires, I hear ya!. Wish I knew a way to try various tires before buying them, that would be great! (I know Discount Tire ads in the past did suggest you could bring tires back if you were not satisfied, even after hours....). But I note the possibility that tires could be contributors to the problem and I'll be sure to at least try to find a tire with tramlining resistance will be a goal, especially if I don't get some kind of successful fix before the new set is needed (maybe 20k-30k miles from now).

Oh what I have at the moment are Mich Pilot Sport All Season.

 

When my struts failed, I did the Bilstein inserts. Purchasing the adapters is straightforward, and the instructions included make it very easy to cut the existing housings. I had a shop TIG weld the adapters on, then had the entier assemblies powder coated prior to installing the inserts. I still need to replace the summer tires, waiting on availability of Conti 02's, supposedly by later in June. Not really a fan of all-season tires, end up being compromised in all situations.

 

Oops, forgot to include the size. Front is 225/45 ZR17 and rear 255/40 ZR17.

 

I would first recommend that you (or have a shop) inspect all of the suspension components thoroughly - ball joints, wheel bearings, sway bar bushings, both control arm bushings, upper strut mounts, bolts connecting the strut to the hub and lug nuts. I would do that first before going down the path of buying new components or making any assumptions. Any odd vibration or movement in the suspension or wheel indicates something might be loose or broken/disconnected.

 

Good to know I'm not the only one!

It was about 85K that I did my shocks/struts. I won't tell you what the tech told me, but suffice it to say my "dampers" stopped damping miles prior. The seals had gone in the FR and there was no fluid left in there.

The dilemma I faced was that while I'm a big fan of Bilstein dampers, everything I read said "increased stiffness." I have no pretentions and like the Cab as a well-rounded touring car, so I opted for the originals Sachs dampers. As luck would have it, Gaudin in LV saved me $100s* over any Koni or Bilstein option, even Sachs OEM and they were right there in LV where I was having the work done. Pick em up, dropped them up at the shop, and $600 install and the rest is history as they say.

Immediately left on a 1.000 mile jaunt around the four corners area and couldn't have been happier with the result.

FWIW, the #1 symptom I experienced prior to replacing the original damper at 85K was that every time I hit a bump the front end would shudder, sometimes almost jerking the wheel out of my hands.
FWIW II: The other day when I was perusing Porsche Classic world, I saw the original Boge/Sachs front shocks listed, but not the rear struts. No idea if they're NLA or not, maybe I just didn't make it to that page.

*~$100 per corner over even ShockWarehouse prices, forget about Pelican, FCP, etc.

 

I had Pilot Sport AS on my car before. Granted, they were worn, but I replaced them with Hankook Ventus V2 Evos and I couldn't be happier. 1/3 the cost of Pilots and IMO just as "handle-y." I'll be mounting my 3rd pair of rears next month.

 

Not much of a datapoint, but when I bought my 968 from the third owner it had newer Boge/Sachs on the front and adjustable Koni's on the rear. Been meaning to take one or both off to see which rebound setting it has.