Alfa Ricciardi: How much force goes through the lower trailing arm mounts?

[tjb0274]

But i dont think its acceleration/braking thats started the cracks. It looks to me like the trailing arm is twisting the bracket off the chassis. THis twisting along with the stress concentration at the top edge is the problem. The solution is to remove the stress concentration where the cracks originate by a simple redesign of the brackets.

What bushes do you have in the trailing arms?

Agreed on the bracket design. It's hard to know when the crack first started - the driver's side brackethas no discernible cracks. Could be from long-term cumulative stress (the chassis is 25 years old), or it could have been a specific high-stress incident - the axle was hopping under hard acceleration at Broadford, and I was hitting the curb hard through the esses.

The TA bushes are standard rubber items.

[giulia_veloce]

All good Divano Veloce.

As said before,,this thread became very confusing to many people and there were lots of opinions,,including mine.
Keep up the good work guys,,and the modifications.
Some  mods are interesting.
Some make great reading.
And there will always be opinions.

[Doug Gould]

Its pretty hard to see from the photo's, but the nut side looks like a weld quality problem. Once one side started to fail, the other side would follow due to increased loads.

Ordinary road loads are pretty easy to calculate, but that's not what causes problems. It will be impact loads from corrugations / potholes, etc that do the damage and these are nearly incalculable. Car companies use real world testing or rig testing based on data collected from real world driving for this.

The other thing that can cause loads sufficient for failure can occur at full suspension travel (ie full droop) if there is any misalignment of the linkages.

Simply re-welding it is not really adequate because of the fatigued parent metal and heat affected zone from the original weld. Either cut out a section and do it again, or re-weld the crack then add some gussets.

[Evan Bottcher]

I think this thread has served its purpose, enlightened some, puzzled others, even an insult or two. Closing it now. Thanks!

Also: "Remember it's all just opinions"!