Dennis K

Just did a track day at Laguna Seca yesterday. About halfway through the day I started getting some nasty steering wheel shake in Turn 9. It only happened at peak g at the exit of the turn. It also happened to a much lesser degree at the exit of Turn 6. Both turns 6 and 9 are left handers. It would not happen anywhere else or on the first two or three laps, but after that the problem would get progressively worse.

I checked the right front wheel bearing play and tightened it a quarter turn, but that did not help. I'm suspecting the wheel bearing is toast or the race in the hub is loose. I'm wondering what else I should check. Any other things to look at?

BC

My rack bushings are all oily, and that makes the car jiggle in a high G turn. There is too much play in the stock front end.

Bill Ball

Dennis: Really need to look at the rack and all attached parts. Want to bring it over next Saturday? We can pop it up on the lift and take a close look.

heinrich

Fluid full?

blau928

Hi Dennis,

I guess the fluid fill did not fix it.. I would suspect the rack bushings, ormaybe the tie rods, or even the upper ball joints.. 6 is an uphill, and 9 is a downhill.. It's only happening on left turns, so maybe there is a leak from a bad seal in the rack somewhere..?

I remember feeling it in 9... BTW, did the fluid level go down after you filled it..? If so, I'd suspect the rack.. If not, then I'd look at bearings and ball joints... I had my left upper ball joint go out before the right side...

Thanks a million for the hot laps, great fun...!

Alan

Did you already check your tires carefully for tread separation??

Alan

FBIII

I second a tire problem. Maybe the cords are breaking down within the tire. I'd rotate the front tires and see if the symptom moved.

peanut

In a high G turn the load is coming off your inside front wheel and I suspect a shimmey is starting due to slight play somewhere . You need to check all your linkage as suggested, track rod ends, rack bearings but also suspension and mountings. It could be the play is more evident when the wheel that is not under load has dropped. Try jacking up the car under the ball joint on one side only then use a decent length of iron bar to test for play in the unsupported wheel bearing and associated suspension/steering componants

blau928

Guys,

The tires are pretty new, I remember chatting about tires with Dennis, as he was running Pirelli Corsa's. They were not corded etc., a bit round on the shoulder, but I think because the fronts are 263/35-18 on 10 inch rims..

HTH,

Dennis K

Thanks guys. I'll have some stuff to look at tonight. I checked the pwr strg fluid between session and it was low. Refilled it, but the shake came back. Actually shake doesn't really describe it accurately. It's more violent than that . . . like hitting a series of potholes with the right front wheel. It feels like it's trying to rip the wheel out of my hands.

Hadn't thought of the tire cord thing . . . I wish I had done the tire swap at the track because there is nowhere on public roads where I'd feel comfortable pushing hard enough to replicate the problem.

Bill -

Thanks so much for your offer. I have track days scheduled at Sears Point from Fri-Sun otherwise I'd take you up on it. I'm going to look at the hub tonight, if that's not it then I think I'll give it to Devek to wrestle with. If things don't work out and I have to cancel my track days, I may still take you up on it.

BC

Thast the exact thing I had happen to me, and I know its the rack bushings and maybe the tierods, but not so much. Violent, and exagerated by the bumps in the turn. It did this getting on the highway at about 75 or 80, hard right sweeper, downhill a bit I think.

Jim bailey - 928 International

two or three laps before it starts....so possibly heat related and very violent but only under extreme side loads only in left turns. Right wheel loaded left unloaded. I wonder if the brakes caliper rotors wheels are moving around hitting ?

Bill Ball

Dennis: If you want to come over Wednesday night, that would be OK, if DEVEK can't get to it quickly.

jheis

Might also be a bad shock.

I experienced something similar at an autocross and some of the spectators told me that my left front wheel & tire were bouncing up and down violently. Didn't have any noticeable affect in normal driving - other than a slight stutter step if I hit something like a Botts dot in the middle of a corner

James

peanut

yep this is my guess too.
eitherthe shock or possibly mountings if the car has been run up a kerb or struck something . Miss-alignment maybe.possibly incorrect a-roll settings ,bushing knackered

Ok lets start a poll my guess is suspension specifically the shock