Scutle Shake

[Tim Crabtree]

Have an SL 320 2000. I have what I think is bad scutle shake, had shocs checked and they are fine. It's worse with the hard top off. Any ideas?

 

[Aussie Nick]

You need to describe the problem with much more detail.

 

[stumpy]

Sounds normal to me - our 129 was a bit wobbly without the roof on

 

[television]

Do you have the tyres too hard, mine was not bad, though it was a late one

 

[hairyg]

Sounds normal to me - our 129 was a bit wobbly without the roof on

Mine's the other way round, much more noticeable when the hard top is on.

Even then it is only when the road is badly potholed.

Tyre pressures first, then check anti-roll bar bushes. These are the only suspension component that has needed changing on mine after 107,000 miles.

 

[Gazzaj]

My brother has the same problem with his, its common with most convertables, struts can help it.

 

[moons]

Hi All.forgive me but what is scuttle shake exactly? my x used to have an SL 280. 1984 Model.the ride was nowhere near as smooth as our CE again 1984 model.

 

[stumpy]

Hi All.forgive me but what is scuttle shake exactly? my x used to have an SL 280. 1984 Model.the ride was nowhere near as smooth as our CE again 1984 model.

Scuttle shake is a tremor felt through the body of the car when hitting a bump in the road. Normally visible in the rear view mirror. I drove a Maserati GT Conv recently and not only did the mirror wobble, but the steering wheel moved an inch side to side too.
All this is caused by lopping the roof off a car.

 

[television]

The effects are as Stumpy says. On a saloon car the A pillars on the font join to the foof, this in turn joins to the rear of the car and it becomes whats called a shell.

On a soft top there is nothing joining the front of the car to the rear at roof level, so if you drive over a rough piece of road the front will move out of line from the rear, as there is only the bottom chassis holding the car together, and this is where the twisting takes place.

 

[DougCLK320]

Apparently, in the bad old days of BL, when they were prototype testing the Triumph Stag, it flexed so badly that they had to re-engineer the shell - introducing the steel hoop over the top behind the seats and tie it forwards to the middle of the windscreen header rail. This was the only way they could make it acceptably stiff for marketing.
I have never known a true 'open' car that didn't suffer some degree of scuttle shake. It is an impossibility to stiffen up the floor of any car and make it as stiff as a full monocoque (particualrly with bonded-in windscreens). Try a Megane convertable if you want to see how bad scuttle shake can be!!!
I'd agree with Malcolm and make sure you're tyres are inflated only to the minimum values stated in the manual. Other than that - just get used to driving around the worst of the potholes that infect seemingly every road nowadays...and enjoy the sunshine.
Doug

 

[television]

Apparently, in the bad old days of BL, when they were prototype testing the Triumph Stag, it flexed so badly that they had to re-engineer the shell - introducing the steel hoop over the top behind the seats and tie it forwards to the middle of the windscreen header rail. This was the only way they could make it acceptably stiff for marketing.
I have never known a true 'open' car that didn't suffer some degree of scuttle shake. It is an impossibility to stiffen up the floor of any car and make it as stiff as a full monocoque (particualrly with bonded-in windscreens). Try a Megane convertable if you want to see how bad scuttle shake can be!!!
I'd agree with Malcolm and make sure you're tyres are inflated only to the minimum values stated in the manual. Other than that - just get used to driving around the worst of the potholes that infect seemingly every road nowadays...and enjoy the sunshine.
Doug

Interesting that my SL 230 does not have any shake worth talking about

 

[DougCLK320]

Ah, but yours is a high quality car, relatively 'heavily' engineered' and with a comparatively short wheelbase.
Worst are these cheap folding tin tops with front wheel drive and huge rear overhangs. These have the high polar moments of inertia, particularly when the roof is stowed, exacerbated any flexing. MB's generally have short overhangs and the engines are set as far back as possible, moving the centre of gravity towards the centre and giving the low polar MOI essential for both reduced scuttle shake and quick, responsive handling. The smaller (lighter and shorter) engined models benefit most from the physics.
Doug

 

[television]

Ah, but yours is a high quality car, relatively 'heavily' engineered' and with a comparatively short wheelbase.
Worst are these cheap folding tin tops with front wheel drive and huge rear overhangs. These have the high polar moments of inertia, particularly when the roof is stowed, exacerbated any flexing. MB's generally have short overhangs and the engines are set as far back as possible, moving the centre of gravity towards the centre and giving the low polar MOI essential for both reduced scuttle shake and quick, responsive handling. The smaller (lighter and shorter) engined models benefit most from the physics.
Doug

I was not disagreeing in any way from your excellent write ups and explanations, just commenting on my car

 

[stumpy]

My TVR is very stiff but it has a separate chassis. The 6 series BMW is the stiffest 'monocoque' based convertible I've tried. Interestingly the original Mk1 Landrover Freelander was very wobbly, so much so that in extremis you couldn't open the door because the body had twisted so much.

 

[100%Bitch]

MInes not too bad either, although, there is a difference with the roof off compared to having it on.

 

[moons]

Hey,thanks everyone.been scratching my head about that for a long time.

 

[type49]

129s have a small metal brace between the steering column & bulkhead. It can get in the way if doing repairs etc in that area & can easily be disconnected at one end & pivoted out the way. Trouble is, it's then easy to forget when putting dash undertray back together. With this disconnected, scuttle shake is dreadfull.