I.D. help w/ Mystery part: Like a tiny trailing arm?

[dantye]

On my '81, there is tiny trailing arm-like link from a bracket on the driver side of the rear axle housing to the body (it's about 10" long?) The tiny bushings in the ends are shot, so it is a rattle source.

Is this important, and, if so, where can I get one, or could I just remove it?

Can post photo if needed,

[Fi8spider]

That would be your brake balance bar if I'm understanding correctly, which is connected to your rear brake proportioning valve.

Under braking the cars nose want to naturally tip forward and the rear end lift up.
When this happens the distance between the differential and the body increases in the rear end and basically that's not good for a cars braking stability, especially under hard sudden braking.

The balance bar puts pressure on the proportioning valve when the rear end lifts under braking which inturn adds more pressure to the rear brakes so the car sits flatter thus making it safer.

I made my bushes by filing down some small nolathane bushes I picked up at the local suspension specialist. A little bit fiddly but they fit nice and being neoprene they should last a bit longer.

Even without the bushes the system still works, obvioulsy not the way it was intended but the valve still operates.

[maytag]

Are we sure he's not talking about the upper trailing arm?

Fi8Spider probably has ya correctly. But just in case: the upper trailing arm will look just like the other one on the passenger side. and it is outboard.
the brake compensator rod that was described is inboard; closer to the center of the pumpkin, and there's only one.

[dantye]

That would be your brake balance bar if I'm understanding correctly, which is connected to your rear brake proportioning valve.

Under braking the cars nose want to naturally tip forward and the rear end lift up.
When this happens the distance between the differential and the body increases in the rear end and basically that's not good for a cars braking stability, especially under hard sudden braking.

The balance bar puts pressure on the proportioning valve when the rear end lifts under braking which inturn adds more pressure to the rear brakes so the car sits flatter thus making it safer.

I made my bushes by filing down some small nolathane bushes I picked up at the local suspension specialist. A little bit fiddly but they fit nice and being neoprene they should last a bit longer.

Even without the bushes the system still works, obvioulsy not the way it was intended but the valve still operates.

THANKS! I think you nailed it. I will take it off and fab some new bushings. I think the shot bushings have been one of my few remaining "Mystery Noises." since the noise happens upon braking.

Checked, and autoricambi.us has them for $1.60 each - 4 required. Small price and very easy job to eliminate one more rattle. They surmise that 80 percent of the cars out are driving around with these bushings completely shot!

They call the item:
"Brake Compensator Linkage Rod Bushing."

[akavinn1]

Anyone have a pic of the part under the car ? I am not sure but I think that's what I need too

[dantye]

Anyone have a pic of the part under the car ? I am not sure but I think that's what I need too

The pic is with it OFF the car, but Here is a thread that should help:

http://fiatspider.com/f08/viewtopic.php ... age#p86158

The pic is in the 2nd post in the thread.

[RoyBatty]

I have a different understanding of the operation of the rear brake compensator.
As it was explained to me, the weight transfer of hard braking will cause the nose to dive and the rear to rise. When the aft of the car rises in this situation, the linkage on the brake compensator works to limit the braking action at the rear wheels to help prevent rear wheel lockup.

[Fi8spider]

I have a different understanding of the operation of the rear brake compensator.
As it was explained to me, the weight transfer of hard braking will cause the nose to dive and the rear to rise. When the aft of the car rises in this situation, the linkage on the brake compensator works to limit the braking action at the rear wheels to help prevent rear wheel lockup.

Yes-yes, thank you for the correction Roy.
May I also add another correction to my post, making the car sit flatter under braking is achieved through stiffer front springs, silly me. Speaking of which I have just put a set in the 131 last week and it's off to the track I go tomorrow with a bunch of Fiat buddys.

[dantye]

Follow-up: Installed the bushings mentioned above from Autoricambi and it got rid of more annoying noises!
Perhaps the easiest and least expensive rattle to fix. Can't see the change in braking yet - except one less "clunk."

[bradartigue]

Follow-up: Installed the bushings mentioned above from Autoricambi and it got rid of more annoying noises!
Perhaps the easiest and least expensive rattle to fix. Can't see the change in braking yet - except one less "clunk."

Something that hasn't been said, at least now your rear brakes work. That little rod and those bushings are what controls the amount of fluid that the rear brakes get under hard braking. In an emergency it will keep the ass end of your car from becoming the front end of your car. Always inspect them when doing a brake job and replace when worn.

[dantye]

Something that hasn't been said, at least now your rear brakes work. That little rod and those bushings are what controls the amount of fluid that the rear brakes get under hard braking. In an emergency it will keep the ass end of your car from becoming the front end of your car. Always inspect them when doing a brake job and replace when worn.

Ah Ha! Since I will be on Interstate Highways in it for about 500-700 miles in the next few days, I guess that just proves that it pays to be picky, even if you aren't sure what you are being picky about! THANKS!

[akavinn1]

Someone just told me that the early spiders in Italy were lower and didn't have it

[bradartigue]

Someone just told me that the early spiders in Italy were lower and didn't have it

Someone was wrong!

This equipment is shown in shop manuals dating to the very first 124 series cars. I'm looking at it now, figure 321 of the Brake System page (218) of the manual called "124."

Generally speaking all of the Spiders got taller over the years to meet bumper height requirements. FIAT's biggest market for the Spider, and in some years the ONLY market for the Spider, was the USA, so there were very few Europe-only parts. The myth of camshafts being debunked we defused years ago; the carburetors were different only on the 1608 and 1438 Spiders, after that they all got the same carburetor; the springs were not apparently any different except on the show cars (they were always lower); the gauges were different; the side markers were different; the pininfarinas were called "spidereuropa" over there and "azzura" over here. A few other things, but nothing major. I don't think Europe ever got non-injected Spider 2000, lucky them.