Alfa Romeo Forums banner

1 - 20 of 39 Posts

·
Registered
Joined
·
891 Posts
Discussion Starter #1
Some state that reinforcing the attachment points of the trailing arms is abolutely necessary, others state that it is only needed for racing cars.

Is it necessay for normal street driving or not?

I have added some pics on this which I found on the web elsewhere
 

Attachments

·
Registered
Joined
·
1,169 Posts
My trailing arm mounts on the rear axle tube looked decidedly dodgy so I took some sage advice and reinforced them. It is not a difficult job and adds some peace of mind.
I only intend to use the car on the street.
Chris
 

Attachments

·
Super Moderator
Joined
·
11,559 Posts
It is not necessary for normal street driving unless roads are rough, corners are hard and at speed, or the brackets are seriously corroded. The reinforcements shown above are more than adequate for any normal street use.
These brackets almost always twist or distort before they break. If there is any apparent damage, reinforce them. If they are fine, and will not suffer unusual stresses, they will be fine from my experience.
 

·
Registered
Joined
·
891 Posts
Discussion Starter #5
Thx!

Anyone had problems with the original (not reinforced) brackets during normal road driving?

Just adding a couple of more examples
 

Attachments

·
Registered
Joined
·
142 Posts
Mine broke on the road

This summer I had a failure on one the left side of these brackets. I should maybe say that it was the second time I used the car since converting it to a 160hp 2L Engine! Now it is reinforced and no problem.
 

·
Registered
Joined
·
891 Posts
Discussion Starter #9
They get 2 types of load

Front and rear forces when accelerating and braking

Twists when the car is doing a turn. In a curve the car tilts to one side, while the rear axle stays flat on the road. The trailing arms then cause a twisting force on the attachment points.
 

·
Registered
Joined
·
7,741 Posts
All said, I have in fact seen them bent askew and have heard of failures with catastrophic results... I think, but not proven... that anytime you use non-stock fatter modern stiffer walled tires with profiles wider than 165 x15"s all bets are off. Stick to 155's. just my opinion.
 

·
Registered
Joined
·
57 Posts
To me, these brackets holding the trailing arms to the axle tube just look and feel flimsey. You would think that the triangle piece locating the center section would take all of the side to side forces and yet folded over brackets seem fairley common. On my Sprint I mig welded two pieces of 3/16" steel on each bracket, one in front and one in back leaving enough of a gap at the top for the limit strap and extending down to the botton of the bracket. This was pretty easy and I can corner fast with no worry. Dennie
 

·
Registered
Joined
·
1,348 Posts
They get 2 types of load

Front and rear forces when accelerating and braking

Twists when the car is doing a turn. In a curve the car tilts to one side, while the rear axle stays flat on the road. The trailing arms then cause a twisting force on the attachment points.
Indeed. On Giuliettas, the tubular trailing arms don't twist; the deflection of the rubber bushings is the only thing that should accomodate the relative body to axle rotation. There will be a significant stress in the axle brackets while cornering briskly with a stock suspension.

Paradoxically, on a racing car with stiffened suspension the car would not lean as much, which would result in lower stress in the brackets!

One thing that would increase the stress is the use of poly bushings instead of rubber. On a Giulietta with stock suspension I would simply not use them.

On 105 Alfas the stamped "Omega section" trailing arms will twist easily and this issue does not exist.
 

·
Super Moderator
Joined
·
11,559 Posts
Pictured below is my Ausca Guilia Spider rear axle trailing arms brackets. Note the originals have been replaced with solid plates. This car was raced with it's GTA engine, GTA CR transmission and GTA 5:12 partially locked rear axle less sliding block, but with the Ausca built rear sway bar. The car as pictured is currently in street trim. There was never any issues related to the trailing arm brackets, street or track.
 

Attachments

·
Registered
Joined
·
891 Posts
Discussion Starter #14
To me, these brackets holding the trailing arms to the axle tube just look and feel flimsey. You would think that the triangle piece locating the center section would take all of the side to side forces and yet folded over brackets seem fairley common. On my Sprint I mig welded two pieces of 3/16" steel on each bracket, one in front and one in back leaving enough of a gap at the top for the limit strap and extending down to the botton of the bracket. This was pretty easy and I can corner fast with no worry. Dennie
Hello Dennie,
Sounds like the modification proposed by alfaowner. Can you pls post a picture? Thx! Rafael
 

·
Registered
Joined
·
1,348 Posts
I seem to remember that Alfa beefed up these bracket over the course of Giulietta production. I just don't remember if it happened between 750 and 101 or between 101-1300 and 1600.
 

·
Super Moderator
Joined
·
10,599 Posts
On Giuliettas, the tubular trailing arms don't twist; the deflection of the rubber bushings is the only thing that should accomodate the relative body to axle rotation. There will be a significant stress in the axle brackets while cornering briskly with a stock suspension.

Paradoxically, on a racing car with stiffened suspension the car would not lean as much, which would result in lower stress in the brackets!

One thing that would increase the stress is the use of poly bushings instead of rubber. On a Giulietta with stock suspension I would simply not use them.
Three excellent points. It is ironic that street cars have a greater need for this reinforcement than race cars, but it makes sense. I suppose you could add a rear anti-roll bar instead of beefing up the trailing arm brackets!

I wonder if part of the problem is due to rubber bushings hardening with age. So a trailing arm-bushing assembly that could accommodate twisting in the 1960's can no longer do so today.

On 105 Alfas the stamped "Omega section" trailing arms will twist easily and this issue does not exist.
Yes, it does seem significant that Alfa changed the design from a tube to an "Omega section". They also increased the diameter of the bushings, allowing more rubber to more easily accommodate torsion.
 

·
Super Moderator
Joined
·
11,559 Posts
I believe it was more than once. 750's are different from 101 1300's, and 101 1600's are different from 101 1300's. Typically with Alfa's nothing happened all at once, so there is overlap.
 
1 - 20 of 39 Posts
Top