C70: scuttle shake

[burgess]

Hi guys, I have a 2001 2.0 LPT C70 convertible with dynamic suspension setup, never noticed scuttle shake, neither driving alone or with four adults in the car.
So I'm wondering if a softer suspension setup contributes to scuttle shake.

[ITSv40]

An interesting question, but I feel difficult to answer unless you can experience two similarly maintained cars driven over the same road to do a direct comparison.

My own car is factory spec and maintained as it should be with the correct tyres inflated to the correct pressures. Comfort suspension with a strut brace fitted. The strut brace did make a difference, but not massively, it went from 'alarming' to 'just having character'.

I do find the road surface has a big impact, where driving on a well maintained dual carriageway it drives tight and without any shake. Turn off onto a potholed country lane and it will shake over rough surfaces.

I do think the geographical location will make a difference. You are in Wales so your roads are built on rock which is stable and you should have good even road surfaces. Here in Northamptonshire we are on clay and the roads do subside and move about with the resulting surface deteriorating and becoming uneven. The hot dry summer of 2022 seems to have had a devasting effect on the substructure of the roads and they have become more uneven than previously.

[burgess]

Thanks for responding ITSv40. Under what conditions dose the strut brace make a difference, straight-line or cornering and bends?

You have Comfort suspension. Indicating a phase shift in energy imparting into the chassis after the initial impact from the terrain surface, plus the interval between the front then rear suspension actions. Comfort suspension, springs and shocks moving more than the dynamic setup does.

I've driven on various terrains, Motorways to cart tracks through woods in Shropshire, but never noticed anything I would relate to scuttle shake.

[ITSv40]

Originally Posted by burgess

Thanks for responding ITSv40. Under what conditions dose the strut brace make a difference, straight-line or cornering and bends?

You have Comfort suspension. Indicating a phase shift in energy imparting into the chassis after the initial impact from the terrain surface, plus the interval between the front then rear suspension actions. Comfort suspension, springs and shocks moving more than the dynamic setup does.

I've driven on various terrains, Motorways to cart tracks through woods in Shropshire, but never noticed anything I would relate to scuttle shake.

It is more over rough surfaces at 'normal' road speeds. I don't tend to drive fast through corners or push it round bends, more leisurely cruising with the roof down. When I first bought the car - without strut brace - at 50,000miles the shaking was quite alarming to the point where, when I went over rough surfaces, I wondered how many bolts had dropped out on the road. Now with the strut brace it will still shake but not as much - and confident all bolts are still in place.

I have only driven two other convertibles: My sons '89 XR3i Cabriolet - fully restored to concours and that shakes alarmingly. You can see the dashboard shaking from side to side in relation to the floor mounted gear lever - and a '73 R-R Corniche Drophead. The Corniche was really floppy in comparison to the C70. Not shaking as such, just floppy on the soft compliant suspension. It felt it needed a double dose of Viagra to stiffen things up.

Obviously three very different cars, but I would say the C70 gives the nicest middle of the road driving experience.

[Chris1Roll]

I only kept my '04 C70 2.0T for six months as I simply couldn't put up with the scuttle shake.
No strut brace.
As ITSV40 says, I also found on a decent surface it was fine. When I test drove it (in Wales, coincidentally) I didn't think it was too bad. Unfortunately I live right next to the biggest engineering project in the UK and all the lorries, bits of nuclear reactor, and buses to transport the workers have destroyed all the roads that I have cause to drive on regularly.

I think some people can cope with it and others can't, and where you live and the state of the roads could have a big impact on where that point is for you.

Way back in the history for mine, there was one guy who old owned it for just 8 weeks when it was ~1 year old. There is a main dealers invoice smack bang in the middle of that 8 weeks:
"Checked all steering and suspension components, no faults found. Test drove vehicle and drives normally for a C70"

[burgess]

Thanks for responding Chris1Roll.
Interesting comments, was your 04 fitted with the comfort suspension setup?

[Dippydog]

While I'm not a soft top person[I wouldn't have one by choice]my step daughter has one.I must say that I've never felt alarmed or anything by any scuttle shake.I take it when people speak of strut braces they're on about the bar type thing that some fit from suspension top to suspension top under the bonnet? That being the case her car doesn't have one of those it does have a "V" shaped brace underneath the front half of the car and it has a tow bar[minus the ball or any electrical sockets so I don't know if it's ever been used for towing]fitted under the back end.What if any difference that makes I've no idea.

[ITSv40]

Originally Posted by Dippydog

While I'm not a soft top person[I wouldn't have one by choice]my step daughter has one.I must say that I've never felt alarmed or anything by any scuttle shake.I take it when people speak of strut braces they're on about the bar type thing that some fit from suspension top to suspension top under the bonnet? That being the case her car doesn't have one of those it does have a "V" shaped brace underneath the front half of the car and it has a tow bar[minus the ball or any electrical sockets so I don't know if it's ever been used for towing]fitted under the back end.What if any difference that makes I've no idea.

The V shaped brace under the front subframe is standard on the convertible. As are solid mounts in the subframe to body. Folks fit a towbar as there is a school of thought that it stiffens the car and improves handling.

[Dippydog]

Yes I had assumed the underbody V brace was just for convertibles as my V70 for instance doesn't have one. I had read that some fit a towbar in the belief that it "stiffens things up" how true this is neither I nor step daughter can say as her C70 is the only one of its type that either of us has driven.

[burgess]

Well thanks gents for your answers. As I said, mine has dynamic suspension springs and shocks as OEM setup and no strut top brace.
Had an assortment of tyres but no adverse effects.
When I got the car in 2015, it had a mixture of tyres (225x45x17) Landsale on the from and Michelin Perlli on the rear, all aging.
In early 2016 changed to full set of Three As MS P606.
January 2018, changed the fronts to Maxxis HP5.
Driving in Mid-Wales and North Wales, especially on country road with no white lines, rally cross comes to mind. So maybe, dive it like you stole it and you'll not notice scuttle shake.