Safety Alert Ford Sierra Compression strut problems

[cabrioman]

Interesting findings Paul.

I tend to feel the ARB mount is a bit flawed in its design and could have done with being more substantial, especially the surface area of the mounting plate.

I will have to stick with struts, but I think I may look to fabricate a mount bracket that goes round the edge of the chassis. My thoughts are to add an additional mounting bolt to pass through the chassis side to side to remove any posibility of twisting, which looks to have possibly been the cause of the weld failure.

At least by modyfying the bracket rather then the chassis this will allow me to trial a solution, before I resort to a welding torch on my nice new shiny chassis🙂

[danny_nelson]

To my knowledge Dave clutterbucks car is the only one reported with a failure with a standard ARB. With due respect to Dave I don't think his car can be compared to any of the above. Daves car was subject to years of neglect left in a roofless garage with a tree on top, and in a sad state. The car was then bought and done up before Dave bought it. Dave will tell you that the tops of the rear turrets (shock absorber mounting) Rotted through as well, and had to be welded. So I think this one can be put down to neglect. The first pictures Paul has posted are of the ex Simon Gregory car!!

[milliemarlin]

It might not be practical to fit the ARB to beamers but could a cross brace be fitted. I have in mind something like this which is intended to fit between the tops of rally car suspension legs to provide bracing. Perhaps mounted under the compression strut bracket or even part of it.

I blagged these pictures from carrepairmart.com and bmrsuspension.com hope they don’t mind.

Suspension strut.jpg BMR brace.jpg

[cabrioman]

To my knowledge Dave clutterbucks car is the only one reported with a failure with a standard ARB. With due respect to Dave I don't think his car can be compared to any of the above. Daves car was subject to years of neglect left in a roofless garage with a tree on top, and in a sad state. The car was then bought and done up before Dave bought it. Dave will tell you that the tops of the rear turrets (shock absorber mounting) Rotted through as well, and had to be welded. So I think this one can be put down to neglect. The first pictures Paul has posted are of the ex Simon Gregory car!!

Quite concerning Danny to hear those pics are of Simons car, it can’t have done hardly any mileage I wouldn’t have thought, as it wasn’t road worthy when Simon took it on.

A cross brace could help matters Paul but I can’t help feeling a mount that bolted round the chassis leg like a large U shape would be the best option as done like that I can’t see how it could possibly rotate/flex to cause the damage seen, the welds on the strut mounting lugs would have to be well done though to make sure it didn’t just transfer the failure to the bracket itself. The joys of kit cars eh.

It a good job the owner of Simons car spotted it before it let go as it could have been quite a catostrophic failure with both sides showing the same damage.

[A_Hogg]

I thought that the intention of any ARB was to impose a motion on the TCA . The 'D' mounts offer fore and aft location but allow the ARB to essentially pivot within them. So as one wheel/suspension arm moves upwards that energy is imparted to the other side thereby stiffening the suspension . A compression strut, as I see it, only offers fore and aft location and nothing else.

[cabrioman]

I thought that the intention of any ARB was to impose a motion on the TCA . The 'D' mounts offer fore and aft location but allow the ARB to essentially pivot within them. So as one wheel/suspension arm moves upwards that energy is imparted to the other side thereby stiffening the suspension . A compression strut, as I see it, only offers fore and aft location and nothing else.

Exactly right Alan, the rally bods use group A anti sway blade kits in conjunction with the compression strut to stiffen up the suspension as removing the ARB and just using struts actually softens the suspension. Sure the caster location is much improved but it introduces more roll without an ARB.

I wasn’t too concerned about the roll aspect as a few people, Marlin included had sugesseted the car didn’t really need anti roll control and would be fine without an ARB if it wasn’t for the need to lock the fore aft movement of the TCA.

So if there is a solution to stabalise the mount and continue to use the struts I would be happy with that as the ARB is not really needed from a roll perspective on the Marlin.

The other option is a custom ARB to go round the engine, there are a couple of firms in sheffield that can custom build sprung ARB’s so I intend to give them a ring to get a price. It could of course be cost prohibitive and digging out the welder might be the best option.

[milliemarlin]

I thought I ought to point out that this only affects Cabrios. The Sportster suspension is a different design. One day I dream of finishing mine when I stop fixing up Millie.
Paul

Sportster.jpg

[milliemarlin]

Having the front wheels independent of each other does improve the ride. The ARB is intended for a much heavier car with a higher centre of gravity.

I have to admit without the rubber bushings rolling over cattle grids, cats eyes and the like is harsher. I almost lost three fillings after the fourth cattle grid on Monday’s jaunt.
Paul

[ggrum]

Just to try and bring this issue into perspective, only 5 BMW based Cabrios were produced by Marlin, 2 as kits and 3 factory built. Any others were modified and re-engined by the owner. Although it is unclear if any cars with the standard ARB set up are affected it is certainly worthwhile taking the time to check. As already mentioned by milliemarlin the Sportster is not affected by this issue as it has a completely different design of front suspension.

[dave_clutterbuck]

My ARB mounting had split similar to pictures in the thread and had not been welded previously, on this occasion corrosion was not an issue in this area.
I am keeping an eye on the offside ARB mounting as this has been welded previously, not to Dave Billings quality though as pointed out when he did the major shock absorber mount fabrication and welding.
Time flies Danny, it is nearly five years since we A framed it to Dave's workshop.