1988 Carrera front end vibration

[Raulg]

My 88 Carrera has 90K miles. The front end has developed a vibration at about 55-60 mph and above.
It has been like this for a while now. I took it to an INDY and was told the front tires were out of balance. They balanced them. Minor improvement. They said the front end was tight.

The vibration continued and I took the front wheels to get re-balanced.
The vibration is still present.

The control arms bushings have never been replaced, nor have the swaybar bushings.
1. Should I start with the swaybar bushings? I looked for a procedure on Youtube but could not find one.
2. Should I consider replacing the control arms? I have seen them for $400 or so per set including the ball joints.

I would appreciate any pointers in this respect. This is a nice car but the vibration has taken the fun out of driving it.
Thank you
Raul

[Mr. Merk]

1. Sway bar bushing would not cause a vibration whatsoever.

2. Control arm bushings and ball joints wouldn't directly cause a vibration, but could cause improper tire wear.

Seeing as it is specific to highway speeds I would definitely lean towards something tire or wheel related. Improper tire wear could cause vibration. Bent wheels could cause vibration (and is likely repairable.) They could still be "balanced" but as a long time technician co-worker once said; "you can balance a square peg but it won't roll very well."

[Pedro '84 Coupe]

How old are the tires?

[aj88cab]

Originally Posted by Pedro '84 Coupe

How old are the tires?

I once has a set of old tires that developed tread separation and would vibrate as speed increased.

Also had a new bad out of round tire that did the same thing.

Switch wheels front to back and see if the vibration goes away or moves to the back. That will help determine if issue is in the tire/wheel or suspension.

[PFNog]

Does the vibration go away at higher speeds? 70? 75?... if so it's likely a tire or wheel. Rotational imbalance will cause harmonic resonance that will be worse at some speeds and hardly noticeable at others.
As others have mentioned, sometimes tires develop issues you can't see, but definitely feel. The other problem could be with the wheel/rim. Long ago I had a vw that had the front wheel shake at 65... couldn't get rid of it with tire balancing or changing. Finally bought new wheels and viola.
See if your mechanic has a pair of good wheels & tires he can slap on there for a test drive. Easy enough to eliminate that possibility w/o having to start buying parts.

[spoke]

My '86 930 has some steering wheel shake at times caused by the front calipers not releasing completely. Thus I'm getting brake judder even when not pressing on the brake peddle. Are your rotors heating up excessively or unevenly side to side?

[Lyle O]

Originally Posted by PFNog

Does the vibration go away at higher speeds? 70? 75?... if so it's likely a tire or wheel. Rotational imbalance will cause harmonic resonance that will be worse at some speeds and hardly noticeable at others.
As others have mentioned, sometimes tires develop issues you can't see, but definitely feel. The other problem could be with the wheel/rim. Long ago I had a vw that had the front wheel shake at 65... couldn't get rid of it with tire balancing or changing. Finally bought new wheels and viola.
See if your mechanic has a pair of good wheels & tires he can slap on there for a test drive. Easy enough to eliminate that possibility w/o having to start buying parts.

^^This. Also make sure the vibration is at a certain vehicle speed, rather than a certain engine RPM.

[GH85Carrera]

My 85 911 is super sensitive to wheel imbalance. The ONLY way to get it right is with the road-force balance, and weights on the inside and outside as necessary.

One simple test is find a friend with a similar car and swap the front wheels and for for a drive.

And 55-65 MPH is the magic speed my car would get the vibration from wheel balance. Roadforce balance fixed it.

[spoke]

Originally Posted by GH85Carrera

...road-force balance...

I go to a shop in Pittsburgh that does road-force balance. There's nothing like it. Smooth as silk.

One other thing to check is to make sure the rims are not dented. On new cars this mostly happens on the inside of the wheel when the webbing is near the outside of the wheel. I had an older Audi with all 4 wheels bent on the inside. You can easily check this by lifting the car up and spinning the wheel and check for dents on the inside of the wheel.

[Trackrash]

I would jack up the front and spin the tires. Easy to see a tire that does not spin true. You would be surprised how often this can happen, especially with old tires. Could also be flat spotted. My AX tires are flat spotted and vibrate at those speeds.

If they spin true, have them balanced on the car. I have found that those modern spin balance machines don't play well with Fuchs.

[Raulg]

Thank you all for your advice.
I raised the front end and found the two front tires out of round.
I also found the passenger side front caliper sticking. I was able to push the caliper pistons in and out several times and it appears not to stick anymore.
My records indicate that the tires are more than 5 years old. I will buy new tires however I am having a difficult time finding replacements especially for the rear.

The rear brakes were fine and the tires seem to still be round although they are as old as the front tires.
I hope the placement tires improve the ride, i think there is still something else amiss.
Thank you for al your help.
Raul

[Trackrash]

I had kind of a weird vibration in the front of my 911 AND sticking calipers.

Turned out to be old rubber brake hoses. They will swell inside causing all sorts of weird problems.

[jlex]

My RF caliper was sticking a couple of years ago, and I temporarily fixed it as you did... moving the piston in and out a few times. Found out that's just a temporary fix... you really need to overhaul the calipers or it'll start sticking again.
Too bad they don't use tire truing machines anymore... just throw out of round tires away and sell you new ones. If a tire is out of round, no amount of balancing will fix it. Are you sure the out of round condition isn't just temporary from the car being parked all winter? Mine work out the flat spot after a few runs in the Spring.

[Raulg]

Update.
There are very few options on 16" tires.
I got new Hankook tires. The fronts were mounted on the rims and balanced.
I test drove the car and the vibration is gone.
I am in the process of changing the rears now.
I bought all 4 tires together but took the fronts to a tire shop first then the rears.
The old tires were Nexen 3000, they look nicer than the Hankooks but Nexen does not make 245-45-16s anymore.
Thank you for the advice. I will order brake hoses soon.
RG

[Mr. Merk]

What Hankook did you find? The only thing I can find they make in that size are slicks with a single rib.

[Raulg]

Mr. Merk,
I bought Hankook Ventus V2 H457s.
Fronts: 205-50-16.
Rears: 245-50-16 ( The previous tires were 245-45-16 but series 45 were not available)
I got them from atw-tires through ebay. My car has 16x9 rear wheels (after market).
Not as good looking as the old Nexen but they are doing the job.

Jlex asked about the out-of-round condition. I have experienced the bumps/flat spots before and after a couple of miles they would go away.
In recent weeks apparently the out-of-round seemed to go away but there was vibration from 55 mph so to 75 mph. I didn't venture faster because of the vibration.
The vibration appears to be gone with the new tires.

Thank you all for the advice
Raulg