the flyin' scotsman

I've noticed a few times now that when cruising for a few km's at 160kph the car develops this vibration that comes and goes repetitively. I dont hear or feel it when accelerating or slowing down.

I did the flex plate pinch bolt last autumn and saw a 3mm movement.

Thoughts?

marton

from the front or the back?
Definitely speed related

Any vibration coming thro the steering?

Marton

Bill Ball

I had a subtle vibration at 85-95 MPH, not below or above that speed range, that had a period of about 10 seconds. Vibrate, calm, vibrate. Proved to be rear wheel balance. Happened to me twice with new tires. Both times, one rear wheel was off an ounce when rechecked.

the flyin' scotsman

Thats a possibility Bill, the PS2s are a couple of k kms old now so perhaps a rebalance would be in need. at least its a cheap fix.

BTW the vibe seems to be coming from the rear; no shaking from the steering wheel at all, straight and true, recently aligned 4 wheel.

Bill Ball

The other observation with mine is that the vibration varied with road surface. On asphalt I didn't notice it, but on concrete I did. Weird. I'm glad it was wheel balance because it was rather puzzling.

bigs

When Nicole was passing through SLC, she reported a very similar problem of vibration at speed. The SLC Motorsport guys found out that both of her rear rims were very slightly out of round. She musta dinged them on a pothole at one point in time. So you might want to have your rims checked.

AO

If you get them road force balanced they will check the roundness and truness of the wheel and shoud there be a variance in the tire they will match it to the weel for the best ride. It's the only way to get them balanced in my book.

Bill Ball

Yep, that's what Nicole had done (Hunter road force) in SLC and it smoothed things out despite her bent rims. I think balance was the main cause of her vibration, but she needs those rims trued too.

perrys4

When I saw the thread title I thought to myself...he's bitching about a little vibration at 160 mph?? The I saw KPH....guess I better pay more attention.

the flyin' scotsman

Perry............160 kph is 100 mph and with wide open roads I can do it for kilometers; oops miles (other than the Brits who else has miles anyway? wait they're different miles aren't they, no thats gallons, **** this is turning into a Python sketch, another Brit thing)

The wheels are new also, turbo twists which I know doesn't guarrantee trueness but I'll have them checked.

IcemanG17

A good balance (road force is best) makes all the difference in 928's.....I had a slight vibration with my old 16's around 95mph...but the new (road force balanced) 18's are totally smooth!

Rob M Budd

FWIW.
Several years ago when I still had the original engine I had a vibration at certain speeds I thought was drivetrain related.
By accident I discovered it was the AC compressor. When the AC was shut off it went away completely. With it on, the vibration would come and go.

Sab

I just got rid of a vibration at around 100 MPH. The tires where simply not balanced right. Most shops will simply throw the wheels on the balancer and apply the weights once. The tires will stll be out of balance. This time around I watched the guy do it over and over again until all wheels showed 0 / 0 on all tires. And sure enough no vibrtions at all up to 130 MPH.

Bill Ball

Sab:

I agree.

the flyin' scotsman

I'm on the balance thing guys; thx. Hopefully it resolves the vibes and there's nothing more serious.

With all the recent TT/TC brg discussion and drive shaft issues one wonders when that time will come................with all the experience out there now is there any thought to PM on these brgs before they break?