Kinkajou

I was driving and when I was going through a speed bump, very slowly I heard loud noise, like something broke and then I could hear something dragging.

Got off, looked around and found out that the rear spring leaf was hanging completely. After taking a closer look I found that the bolt that holds this in place was broken. I found a cople of feet away the parts.
A little bit of bolt with the threaded end and a castle screw and some kind of rubber dampening part.

I now know that this part is the one that holds the spring in place and in tension. And that if you use a longer bolt the ride hight will increase and a smaller one will give you a low ride.

It is a peculiar bolt. Very long: 9" head included and about 1/2 inch in diameter.

I have looked around and it seems to be a difficult part to come by here in Mexico.
I have found a screw that is 1/2 inch diameter and 8" long. But is grade 5. I believe it is not strong enough.

Do you know what grade is the original? Could this be strong enough or not really?

Thanks for the advise in advance.

The car is a 1994 C4 with standard transmission. Almost stock with little mods like stainless steel brake lines, Turn one pump, Optispark changed for Dynaspark, and some other modifications that make it more reliable.
This car is sometimes used for track days so it is not really a garage queen.

jaa1992

Find a 10" long bolt to replace it with - grade 8 would be best, a 5 should work
You'll want to double nut it so it doesn't back off.

Bill32

I strongly disagree James.

I've seen grade 8 bolts break under load and cause wrecks. Especially the crappy ones that you can get at Home D, etc.

At least a grade 5 will bend a bit.

To do it right, get an AN bolt. They're not that expensive.

mgarfias

what bill said

trackboss

I agree with the above, but a 1/2" (or even smaller) grade 8 bolt should not break in such an application. The stresses are under tension and dampened by the rubber bushings. I think something may have caused bind. In any case, VBB sells replacements.

Bill32

Yea, I agree on this particular application. But I won't use a grade 8 on any suspension application as a general rule.

Shrek

Just the opposite! Longer bolts will lower ride height.

trackboss

It's a bit like rod ends. Those that don't know complain about poor quality rod ends not realizing that they will bend in an impact and save what they are attached to rather than transmit the force. I've seen lower end 3/4" rod ends on control arms bend a full 90* right where the rod ends transitions from threaded shank to rod end and not break. Essentially, a $20 part instead of a $50 or more part saved a $700 part and nearly a grand in labor.

Kinkajou

So the longer the bolt within reason , the lower the ride.

And a grade 5 bolt instead of the grade bolt will protect more expensive parts of the suspension. I imagine that the grade 8 is very rigid and that stiffness will transmit to suspension parts.
Did I get it right?

And any suggestions on mounting back the bolt? I intend to use a second jack to elevate the rear spring leaf until it is in alignment so I can insert the bolt. Protecting the leaf with a big piece of wood. Or is there a better way?

Crepitus

http://www.vbandp.com/auto-parts/c4-...ategory_id=114

froggy47

yep

Slalom4me

A castle nut is intended to be retained by a cotter pin. Was the pin
still in place on the end of the bolt?

A cause of failure reported in the past has occured where, instead
of replacing the OEM bolts with longer ones to lower the rear of the
vehicle, someone has just removed the cotter pins and backed the
nuts down the threads past the hole intended for the cotter
pins. Tensile load capacity of the bolt on the far side of a cotter pin
hole is much less than it is on the head side of the hole.

.

the blur

I may have some factory bolts in my basement.

froggy47

[QUOTE=Kinkajou;1585550049]
And a grade 5 bolt instead of the grade bolt will protect more expensive parts of the suspension. I imagine that the grade 8 is very rigid and that stiffness will transmit to suspension parts.
Did I get it right?

QUOTE]

Not really, unless you are measuring to the tolerance of a space shuttle, the bolt rides on rubber & then there is the SPRING so don't count on the flex in a bolt to do anything.

IMO put the same GRADE bolt back in.