Spring plate bolts

[Mike Andrew]

Just had my suspension refreshed by a local shop and have a question.

Spring plate bolts were frozen necessitating the use of an oxy torch to cherry heat them and break them loose to finish adjustments. The bolts. locking and eccentric, were reused and not replaced. Problem or not with heat and possible metallurgical changes? They seemed to think it was not an issue. My only concern is failure at an inopportune moment

If an issue, can I change them myself and not induce any changes in ride height rather than dragging the car back to them for this? Both sets of bolts are readily available from Elephant/our host. Suggestions to do so, if required??

[Lyle O]

Heating the steel to "cherry red" definitely changes the metallurgy (not for the better in terms of modulus; it will be weaker). If I were you, I would replace the ones which were "superheated". But that is me...

[AlBackus36]

No one here is going to know how hot your shop got the bolts unfortunately. Cherry can mean slightly red to almost orange. Temperature can affect mechanical properties, but I wouldn't assume your parts are now prone to failure if they had to heat them up.

You can replace things one bolt at a time without risk of movement. I would recommend checking alignment if you remove and replace the camber or toe adjuster.

On the adjustable plates, the two large forward bolts and the three (including camber) aft bolts carry the load between the torsion bar and the trailing arm. I wouldn't worry about the toe adjustment.

[Mike Andrew]

I will order eccentric and locking bolts for each side to replace the questionable heated bolts. The Toe, Camber bolts were not heated according to the shop and responded to PB Blaster soaking.

Suggestions for replacement procedure? I am leaning toward lifting car to remove weight, placing a block under the wheels to support that weight and replacing one at a time and torquing to spec. My assumption is that the Eccentric can just be installed in the same position as the suspicious bolt and locked down with no height change. Then do the locking bolt and repeat on other side. Measure ride height at wheel arch before and after to ensure that has not changed.

Flaws or oversights in my plan? Bentley of no help for this task other than for torque values.

Thanks in advance for any help.

[AlBackus36]

The lock and eccentric up front are big torques. Like 190ft-lbs. I think it's 32mm for their heads on the body side of the plate. You need a thin bicycle or similar slim wrench on my car to hold them. I use my 250ft-lb capable torque wrench.

Support half of car worked on or all of car on jack points.
Allow suspension to hang. Tightening these will rotate the spring plate differently per side.
Mark location of plate relative to arm (not needed if only doing front two bolts)
Note position of spring plates relative to eachother.
Remove one bolt.
Replace one bolt.
Repeat.

This will be a ***** and is up to you if it's worth it. Those are like 1/2" bolts at the front of the plate. Each one will have a shear strength of something like 18kips which is ~6.5 times the weight of the car. You have two per side. Cut the properties in half and you're still safe.

Did you ask if you've ever seen one of these bolts fail? I haven't but maybe a racer or long tooth mechanic has.

[Shaun @ Tru6]

Why were the bolts heated? Only nuts should have been and those are easily replaceable through Belmetric.

[AlBackus36]

I take it back. You aren't replacing the bolts with the plates on the car.

Replacing the bolts will require full removal of the spring plate assembly.

Replace the nuts like Shaun is saying and move on... Or just forget it. Mechanics are heating nuts/bolts all over the country every day.