wheel shake at 70- 72mph

stu12345_2

I did say to the garage even on old  or new tyres  and when the tyre pressures are equal and you take your grip of the wheel the car tries to move towards the kerb
I wasn't sure if it's the road camber as roads are designed to drain water from the centre to the gutter 

no judder from brakes, just judder from steering wheel as if it's a certain speed that creates the resonance through the steering wheel 

LightFlare

even the individual wheels were balanced it might not be the case where the two together are -- especially if tyres have been fitted at different times and have different wear -- possibly even different make/tread pattern could cause it

stu12345_2

same make fitted 3 weeks apart, still got shake despite being balanced 
don't want to hassle the tyre fitter, it's a one man band, local guy with good reputation.he knows how his stuff 
guess next thing is tracking .
I mean his machine showed up balanced when he gave me new tyres, but it has always shook at that speed 

it's just I live rural and rarely go on dual carriageways

badmemory

Tracking, did it pass its MOT?

stu12345_2

yes easily

Goudy

Worn wheels bearings can cause a bit of judder or shake at speed but you often hear a shuddering, pulsing whooping noise first.

I know that sounds a bit odd, but rather than feel a shudder or shake through the car, you hear a juddering, pulsing whooping noise.
When a bearing is really bad if might feel like the car is shaking as the whooping noise can be quite overwhelming.

Warped discs usually cause judder when braking but you can get a bit of shudder if the discs haven't been fitted flush, ie dirt or rust between the disc mount face and hub.

If all four wheels are balanced properly and you're getting a specific judder at a certain frequency/speed, then it could be the driveshaft joints are worn.

As the speed increases any wear in the inner or outer joints on either driveshaft will cause them to run out out of true and they will shudder and shake, it'll transmit the shudder through the car just like if a wheel balance was out.

I think one driveshaft on these Astra's, (the offside) is longer than the other and has a carrier or support bearing half way along, that can be prone to wearing out and again allow the shaft to run out of true and the car to judder/shudder.

Another common issue is a out of round tyre.
If a car has been stood a while it can develop a flat on the tyre where it was parked and stood with all the weight on it.
This will give you the same result as a unbalanced wheel.

born_again

stu12345_2 said:

same make fitted 3 weeks apart, still got shake despite being balanced 
don't want to hassle the tyre fitter, it's a one man band, local guy with good reputation.he knows how his stuff 
guess next thing is tracking .
I mean his machine showed up balanced when he gave me new tyres, but it has always shook at that speed 

it's just I live rural and rarely go on dual carriageways

If it done this pre change of tyres, then the issue is elsewhere.
So just how long has this been going on for?

Any advisories on MOT?

Goudy

Here's a test.
Find a stretch of quiet fast straight road, with a down hill slope if possible. Perhaps a quiet bit/time on the motorway.

Take it up to the speed it shakes at and then slip it out of drive into neutral for a second or two.

If the vibration eases when not under power (in neutral), it's likely a driveshaft/gearbox problem.

If it's still vibrating as bad not under load, it's wheels/hubs/tyre problem.

stu12345_2

it has been doing this for 3 years, it has never failed or had reports of drive shaft problems etc in the MOT.
I have never had the car tracked since I've owned it.
 the discs are smooth and perfect, there is no rumble from wheel bearings.
I think this as I said happens at a certain resonance at precisely 70 to 72 and not a mile an hour above or below that speed.
I rarely go on dual carriageways at speed, I'm in a rural county,  hence I don't experience the shake often  through the steering wheel. I aver 3000 miles a year, the car is used daily .

it changes gear beautifully  no bangs or thuds, note the only odd thing I get is when I'm going down a steep hill say at 60 and I touch the brakes the car shifts into gear 3 by itself until the hill levels off then it goes back into gear 4 , top gear in the auto. 
thought it was just  a safety gear breaking characteristic of a torque converter auto astra

no other auto cars I've ever owned does this.

that's the only odd thing it does apart from steering wheel shake at 70 to 72

Goudy

An MOT won't test the wheels for balance and will only visually test that the driveshaft rubber CV joint covers are secure and not split.

Something is causing the car to shake at a certain frequency/speed.
It's either in the drivetrain (driveshafts/gearbox) or at the wheels/tyres/hubs.

If it's at the wheels/tyres it will do it at this frequency/speed if it's under engine power or not.

If it's in the drivetrain it will be worse under engine power than not under engine power.

This is why I suggested testing it by slipping into neutral for a second or two at the specific frequency/speed.
If the shaking reduces, it's more than likely in the drivetrain as removing engine load altogether is effecting the shaking.

If it continues to shake as badly not under engine power (in neutral)  it's likely the wheels/tyres/hubs as the engine powering/not powering the drivetrain is having no effect on the shaking.

Certain cars have uneven driveshaft lengths.
One is longer than the other. It's not usually a problem for everyday models but it can cause sportier, higher powered models to torque steer a bit. (steer one way by itself under hard acceleration) 

On some models the longer shaft has a support bearing in the middle to stop the shaft whipping out of true when under high load.
These support bearings are prone to wear and allow the shaft to whip out of true under power.

Some car models are more prone than others and certain Vauxhalls do suffer this as they have a longer shaft with a support bearing (and the Fiat Panda 4x4 is notorious for the centre support bearing failing on the prop shaft to the rear axle)

If these shafts are allowed to whip out of true, you'll get the effect described above, they'll shake at a certain frequency/speed under engine power but won't (or won't as badly) when there is no engine power transmitted down them (like in neutral).