Torquing control arm

[VenomX]

According to Haynes etc. It is best to torque the thrust arm at 80Nm + 120degrees.
However, some people say you can just torque to 120Nm.
Car is a C240 W203

Which way is best ? Photo diagram attached..


Thanks

 

[BlackC55]

80 plus 120 degrees is correct.

 

[BlackC55]

Fundentally. Really tight!
It must be done with the car on the floor too.

 

[VenomX]

Fundentally. Really tight!
It must be done with the car on the floor too.

Thanks, yeah I know it must be ground level when torqued. What I tend to do is jack up the axle and make it "ground level" so the arm sits at the same angle as it would be on the floor - and then torque.

 

[ALFAitalia]

I do the same.

 

[VenomX]

Is there any difference between doing 80Nm+120deg as opposed to just 120Nm ?

 

[jasonh]

80Nm +120deg gets the correct amount of stretch into the bolt. It also tells you that the bolt is a stretch bolt and is therefore usually a one time use.

However if you apply 80Nm + 120 deg then try a torque wrench on it you'll probably find it clicks at 115Nm but the nut moves a smidgen at 125Nm so the bolt is actually around 120Nm.

I've found this on some Mini subframe bolts and I just go for the 120Nm because you get essentially the same result with less fuss.