Suspension/Tire Issues - need advice from the experts (flash968)

[Tidybuoy]

Some History:

1) I added Koni Struts all 4 corners on my 1988 n/a - ride was very stiff and I didn't really like it for street driving. Had 215/60/15's.

2) Added 968 M030 Swaybars F&R and the ride became perfect. All the bumpyness went away with the new swaybars.

3) Just added Turbo Phonedials 16's 7&8's with Bridgestone Potenza RE71 225/50's all 4's

Now the ride is back to very stiff and the steering jerks when going over small bumps as slow speed (almost like driving on street car tracks).

In addition, the steering is much easier with the 16's than it was with the 15's. I would have thought going with a slightly wider/lower profile tire would have made the steering stiffer - but the tires (although both Potenza's) are different performance levels.

My thoughts: I should have gone with 225/55's or 205's in the front. Possibly the Bridgestones are too stiff for the street - they corner fantastic.

I'm thinking that maybe I should switch back to the 15's and only use the 16's when I go on Porsche trips with my local PCA as I did all of this to keep up with the Boxters on the twisty roads.

I also have a set of 200lb lowering Weltmeister front springs sitting in a box that I have not installed and I thought that maybe this would help. The ride is perfect with the 15's but the car will definately slide out in a hard turn much more easily than the 8" 16's.

Any advice would be great. I find it hard to believe that the factory Turbo would ride like my car does. it's too rough of a ride. I'm also not sur of what is factory stock tire sizes (which is what I want). My owners manual states 205/60/15 but the sticker on the gas cap says 215/60/15 - why the difference.

Flash968 - you've give me good advice before, what should I do. I'm looking for improved performance but not to the level of a track car.

Thanks in advance.....................Vern

[Makis]

This is the penalty you pay for going lower profile tire. You feel more of the road. 50 profile although smaller then 60 is not that small on a 225 tyre. Try different adjustments on your Koni struts and also play with the tyre pressure. Not sure if the M030 sway bars can be used succesfully with the standard springs. You may need uprated springs in the front and at the rear. Getting the 944 suspension right is quite tricky unfortunatelly.

[Techno Duck]

Original size was 215/60/15 . Not sure where you are reading 205/60/15..as my '88 owners manual makes no reference to that.

The widths do not make a difference in the ride of the car. The RE070 (i am assuming RE71 is a typo) are a high performance summer tire, so they likely have a very stiff sidewall. What tires were you using previously? The 16's also have a slightly smaller sidewall than the 15's, so another reason for the more 'edgy' ride.

The 200lb springs will only make you feel more of the road..

[Tidybuoy]

Sorry, I mis-spoke. The original tire size (per the dealer sales brochure not owners manual) states 195/65/VR 15 but the sticker on the inside of the gas cap states 215/60/15.

Yes, I meant RE070 & my previous tires were Potenza G 009.

The ride on the 16's is not horrible but I don't like the feeling like I'm driving on railroad tracks. The slightest bump and the steering wheel jerks (mostly at slow speeds). The handling on turns is great but I think I may have preferred a less performance tire for ordinary driving - which I have with my 15's.

I guess what I'm wondering is can I do anything - like when I added the 968 M030 bars, the bumpyness of the Koni's went away (even though sway bars really only effect turning, it also had and effect on straight driving as some bumps are on one side and not the other and therefore the sway adds a tiny amount of additional stiffness - but smoothed out the ride). I was thinking that maybe the 200lb springs may do the same - but me thinking isn't always a good thing.

Thanks for your comments.

The same dealer sales brochure states that the turbo's came with 205/55/VR16 fronts & 225/50/VR16 rear

[924Sman]

Assuming the wheels were realigned? If not, camber/caster issues will cause tramlining(darting about over bumps/grooves) in the road surface and will be more noticable at low speeds. At high speed the tramlining is reduced and not as easy to "feel" but still there. Too high of tire pressure can contribute or exagerate this issue also.

Running a 16" in appropriate profile should not cause this but will add weight and make the front "feel" stiffer(heavier steering) to a small degree.

Here is the story on Tramlining......
The term "tramlining" is being used to describe when directional control is disrupted by the vehicle's tendency to follow the longitudinal ruts and/or grooves in the road. It's name could be compared to the tram or trolley driver who does not steer because his vehicle follows the path established by the tracks.

Any vehicle can exhibit tramlining on certain areas of the highway because of uneven pavement or severe rutting. And all vehicles tramline to some degree rather than obediently following the driver's steering input. For example, there's usually at least a small change in steering resistance felt through the wheel when crossing an uneven expansion joint or asphalt junction during lane changes.

Noticeable increases in tramlining are frequently uncovered when drivers living in the snowbelt make the seasonal changeover from winter tires to summer tires, or when any driver upgrades the performance of their tires using either the same size or going to a "Plus Size" tire and wheel package. The reason that it becomes more pronounced then is because neither the typically narrower and softer handling winter tires nor the Original Equipment tires generate as much grip or responsiveness as the higher performance summer tires. Since the vehicle's suspension works as a complete package, a higher performance tire will also uncover any previously unnoticed looseness in the rest of the suspension.

Components

Tires have the most direct influence on tramlining because they are the part of the vehicle that comes into contact with the road (and the longitudinal ruts and/or grooves that exist there). Unfortunately anything that increases a high performance tire's responsiveness also increases its willingness to tramline.

High performance tires with short sidewalls that develop lots of cornering power at lower slip angles will be more susceptible to tramlining than standard All-Season passenger tires that develop less cornering force until their slip angle increases. A wider treaded tire will encounter more longitudinal ruts and/or grooves in the road than a narrow treaded tire. A tire with large tread blocks that transmits the driver's input to the road with great precision will also transmit the road's imperfections back to the vehicle's suspension. And because tires become more responsive as their tread depth wears away (which is why tires are shaved for competition and track use), a tire will become more likely to tramline as it wears.

Wheels can influence tramlining as well. Installing wider tires or a "Plus Size" tire and wheel package usually requires using wheels with a different offset then the vehicle's original wheels. In some cases, the new wheel will have slightly less offset than the original and in other cases, slightly more. It all depends on the vehicle's suspension design and available wheelwell clearances. You will even find that Original Equipment manufacturers often use different wheel offsets for their different diameter tire and wheel packages.

Usually the amount of offset change is kept to a minimum and vehicle tracking remains relatively unchanged. However it the offset is significantly different, it will alter the way the road forces are transmitted through the tire and wheel to the suspension. Therefore, large changes in wheel offset will increase the likelihood of tramlining.

Suspension bushings, ball joints and shock absorber mounts have a direct influence on tramlining as well. As miles are driven and the years go by, the suspension's wear parts will deteriorate as they age. This often happens so slowly that it isn't very noticeable. Over time the ever-increasing suspension wear permits play that eventually allows the tire to be directed by the irregularities of the road rather than be controlled by the suspension.

Imagine a worn suspension that allows a front wheel and tire to swing between the recommended 1/16-inch of toe-in and 1/16-inch of toe-out when it encounters a rut in the road. This 1/8-inch difference in the direction that the tire is pointed will result in the vehicle tramlining. Replace the worn part to remove the play and you will significantly reduce or remove the tramlining. Many drivers with higher mileage cars have reported that replacing worn suspension components has eliminated tramlining and made the car drive like it is new again...which I guess it essentially is!

Service Adjustments

Using higher tire pressures than recommended by the vehicle manufacturer for your driving conditions will unnecessarily stiffen the tire and make it even more willing to cause tramlining. If you are running higher tire pressures than necessary, simply dropping the tire pressures to those recommended by the vehicle manufacturer will help reduce tramlining.

Alignment settings can be key as well. The "camber" and "toe" settings both play a role in vehicle stability and the propensity for tramlining. Extreme positive or negative camber settings will make a vehicle more sensitive, especially when only one wheel encounters a longitudinal rut and/or groove at a time. Even if all the tires are "aimed" straight ahead when the vehicle is in motion, a tire that is "cambered" wants to turn. This is the result of the "camber thrust" generated by a leaning tire (it is also part of the explanation of how motorcycles turn). A vehicle suspension using lots of negative camber for competition or the track will experience more tramlining on the street.

Additionally, the drivers who use additional toe-out settings to encourage their vehicle to turn into corners better also encourage tramlining because the extra toe-out will reduce vehicle stability in a straight line.

In the case of the competition driver who uses non-factory alignment settings, the amount of tramlining that is acceptable has to be left up to the driver. For only street-driven cars, getting them aligned with negative camber and toe settings within the factory's specifications is an important first step.


Dal

[Aufenbahn]

Exactly - I ran into this this fall when I replaced some old hard tires with newer stickier ones and suddenly my car was darting all over the place. Now that I have my snow tires on all four corners I don't notice this at all. In the spring I'll have to deal with it - I'm thinking of first checking my ball joints. I've copied out your recomendations for future reference.

[Tidybuoy]

Thanks for the good replys. 924SMAN, that explains a lot. I haven't checked the tire pressure since the tires were mounted but I will do that tonight. As far as alignment, I had it aligned about 3 months ago - that was with the old tires still mounted. I'm not sure if the settings would change just because of new tires & wheels. As far as changing offset, etc...I stuck with factory Phonedials with the 52.3 offset for this car.

Another thing, the steering wheel is vibrating at 70mph and I took the wheels back for re-balancing but nothing changed. It's possible that my bearings need tightening. I recently re-packed the bearings but I really was not sure how tight to tighten and the Clarks Garage writeup was a bit vague.

As I said in a previous post, the ride is not horrible but I definately notice a difference. Maybe I will just have to get used to it. I'm taking my 15's into the powder coater and after that, I may switch back (or back & forth). Anyway, thanks for the input guys.

[924Sman]

To get the bearings right, get the wrench on the nut and spin the wheel as fast as you can, as it is spinning tighten the nut until you feel or see the wheel take a sudden drop in revs, then back the nut off a 1/4 turn or until the spin is free and no wobble checking the top and bottom by hand. Then tweak the nut to align the cotter pin and re check the free spin.

The offset is of no bearing as is the tire width . I do not feel the rim size here is a reason because you have 1 inch larger rim and a 50 profile. Stock is 15 and 60 profile so if you measure the circumfrence, you will get almost the same figure.

I am assuming all the other components of the suspension are in good condition? A arm bushing/caster block, tie rods, b joints etc.

Dal

[angelny911]

lot's of info joining in ..thanks Angel

[Tidybuoy]

Yeah, I'm going to re-do the bearings based on the advice above. The suspension is in good shape - the car only has 30k miles and although old, it's been well kept and everything seems tight.

I suppose this whole thing is me getting use to the 50's. I just feel that I had gotten it perfect after the Koni's and the 968 sway bars, the suspension felt very tight and handling was much improved over bone stock. Personally, I don't really like the low profile look on this car but then again, it might look better with the front end dropped a tad. Currently the car sits level most of the time but sometimes the rear looks like it is about 1/2 inch lower. There is definately more space over the front wheels vs. the rear. I've seen many of the members on this board where their cars have lower profile tires and they look good - but on my car, I think there is too much space over the front wheels.

Since I'm good at wasting money, I'm looking for another set of 16's to get powdercoated - I don't like the silver that I used for my current wheels and I just found out they have a powder called German Wheel Silver - which I should have gotten the 1st time. On round two, I may get a set of less performance tires (or touring) for daily use. We'll see how the budget looks over the next few months.

[flash968]

ok - let's start with the simple stuff

what tire pressures are you running?

what are the strut and shock settings?

[924Sman]

I had to think a bit but I do recall when I only had my Koni's, 968 bar on and using my 16" race wheels and the ride did get a bit harsher, this perhaps is what you are feeling. Lowered profile makes for a more rigid ride is all.

I assume you know if your tires are worn in an odd way by sight, but have a look to clear any alignment questions.

Dal

[Tidybuoy]

Originally Posted by flash968

ok - let's start with the simple stuff

what tire pressures are you running?

what are the strut and shock settings?

1) My Tires are set at 29lbs front & 36lbs rear.

2) Front Struts are Koni's and are currently set to full soft.

3) Rear Shocks are Koni's and I beleive I set them to one turn from soft. The rears are different as you must set them before installing and can only be set off the car (or disconnected at the bottom).

I'm coming to the conclusion that my issue is just the tires that I chose. Looking at the reviews on Tire Rack last night, there were several negative reviews stating the tire being harsh and noisy (I agree with this review).

As previously stated, everything was perfect with the 15's, Koni's, and 968 bars. But, when I switched to the 16's, the ride got harsh (albeit, the cornering inproved). I was wondering if stiffening the springs would help because when I initially added Koni's the ride was harsh until I added the 968 bars. It seems that little things like the 968 bars have helped and maybe slightly stiffer springs could do the same.

[Tidybuoy]

Originally Posted by 924Sman

I assume you know if your tires are worn in an odd way by sight, but have a look to clear any alignment questions.

Dal

Yeah, the tires are brand new so there are no wear issues. I had the car aligned about 3 months ago so that should be good as well.

This weekend I will re-do my bearings and see if I can get rid of the 70mph vibration. I think it's the combination of these "little" issues that's bugging me.

Thanks......................Vern

[angelny911]

vern how low is the car did you install a bump steer kit ?

[924Sman]

First things first, fix that vibration and you may cure the other ride issue! No sense diagnosing the ride until all the components are happy. Tires may work out after too!

Dal

[Tidybuoy]

Originally Posted by angelny911

vern how low is the car did you install a bump steer kit ?

Completely at stock height. I would like to drop the front a tad as the rear sits about 1/2 lower than the front. I have a set of 200lb Weltmeister lowering springs but I have not installed them.

[flash968]

well, i would start by setting the tire pressures to those specified on your door, and work from there - 36 may be too high, and 29 is very likely too low

is the harshness fore or aft or both?

the konis have a built in gas pre-load that tends to make things jouncy - they also only have adjustment in bounce, and not compression - hydraulics are much better, but more expensive

bridgestones do tend to be stiffer in the sidewall, so they will result in more jounce than say a michelin, which is one of the softest sidewall designs - the upside is that the bridgestone will stay put better, giving you better control, whereas the michelin will squish and snap back, which makes for a better ride, but less control

[Makis]

29 lbf front and 36 lbf rear for the 16 inch wheel is not right. I have the same size wheels as you on my S2 and I am using 34 lbf front and 34 lbf rear and have my 225/50/16 front and 245/45/16 rear.

[Tidybuoy]

Originally Posted by Makis

29 lbf front and 36 lbf rear for the 16 inch wheel is not right. I have the same size wheels as you on my S2 and I am using 34 lbf front and 34 lbf rear and have my 225/50/16 front and 245/45/16 rear.

Thanks, I was going by the sticker inside the fuel door but that is for the 15 inch wheels.

Another thing...At lunch, I decided to turn the Koni's to full firm. I had done this before and it was terrible - But, that was before I had installed 968 swaybars. Today, it seemed to help with my problem and did not make the car bouncy as in the past. Of course it was raining today and sometimes that makes cars ride a little smoother as you float on the water barier.

I will definately check the tire pressure and adjust for the 16's. Thanks for the tip.................Vern