308 High speed wobble

I took my 85 qv for a drive the other day, when i got above 75 the front end started to
Shake alot. When i got below 75 the shaking went away. The tires only have about 200 miles on them. I have the original qv metric wheels. The wherls are not bent and the ballance is good. I was wondering it any one else has had this problem and any fix.

 

That could be your fron wheels not balance. Out of balance wheels can usually be felt at 70mph. Have them check and have your suspensions check thoroughly too.

 

I would also have said wheel balance but if you know that's OK...

How long was the car sitting, what was the tire pressure while doing so, and what was the temperature outside?

In addition to the items mentioned in the previous post, the tires can flat-spot and cause what you are describing. It usually disappears after driving a while, once the tires can warm up to "normal" operating temps. THe colder it is, the more pronounced will be any flat-spotting and the longer it will take to disappear.

My tires will do it if the car sits for only a few days but only slightly and it disappears quickly. Over the winter, when the car sits for 6 months, it will do it quite noticeably and doesn't completely disappear for a couple of days, sooner if I do a 50-60 mile run.

The lower the tire pressure and colder the temps, the more pronounced the flat-spotting will be. Again, with modern tires, it's temporary and they will true out with driving.

(I put 50PSI of air in the tires for over-wintering to help reduce the resulting flat-spotting)

 

It probably wouldn't hurt to re-balance the front wheels again.

 

Excessive toe will cause the tyres to hop at speed and the feed back can be a shimmy. Lost

 

I had that with the 16" repros before putting in the hubcentric rings.

 

Steering rack wear...check that.

 

He's still on the metric rims...

 

oops, didn't know that.

 

It's almost always one of two things:
-tire balance
-problem with a tire (like a sidewall bulge or tread issue). Both can be addressed by going to your local tire retailer.

If neither of these are your issues, you just need to get the car in the air and start tugging on the wheels to check the bearings (check for wobble), using a pry bar to check for excessive play in bushings and check for any play in one wheel in steering.

Still, I'd bet on tires. It's common to throw a weight or have a tire change from sitting and require a rebalance.

 

tire balance. if you go to one of the "discount" places you will invariably wind up with a poorly balanced wheel(s).. rebalance and they will go away. It's amazing what an 1/4 oz will do at 70 MPH...

if its steering shake the whole rack will be bouncing up and down... same for toe and camber adjustments. usually under HARD braking.