1 reply to this topic

[Ipod]

How do you check to see if the front knuckle joint is worn, where it sits in the upper suspension arm?

Can this be checked in situ?

 

1999 Mpi by the way, not that it makes any difference I'd thought, only that there is an upgraded one on minispares from 1990 onwards.

 

http://www.minispare...ic/GSV1264.aspx

 

Cheers

Edited by Ipod, 05 October 2013 - 04:57 PM.

[tiger99]

If you knew the dimensions, i.e. the distance from the flange that abuts the trumpet to the face of in it the cup, you could jack the suspension till the knuckle was at right angles to the arm, for a good measurement, and see how far in it has sunk. So when you get new knuckles you cam measure them and keet the figures for future reference.

 

But as for now, it is difficult to tell. Considering the low cost of knuckles, and the high cost of replacing the upper arm if it is damaged by the knuckle cup wearing through, I tend to replace then every time the suspension is dismantled, or 60k miles. If you have a cone compressor it is a relatively minor job.

 

I have been thinking about the possibility of a knuckle wear indicator, which would work something like a brake pad wear indicator. The trumpet is insulated from earth so you would take 12V from the white ignition controlled circuit, through a line fuse to a lamp, and from there to a tag fitted over the knuckle shank before it is pushed into the trumpet. Earth would be via the top arm bearings, but as that is damaging to roling element bearings, even at the low current of a warning lamp, and as the subframe is not relaibly earthed, I would fit a tag to the damper to top arm bolt and take a very flexible wire from there to earth on the inner wheel arch. It would need a small hole drilled into the bottom of the knucle cup, and a small piece of brass inserted, so that electrical contact was made while some small thickness of the nylon cup still remained.

 

I have not proved if that idea will work, as it may be difficult to obtain any sort of electrical contact because of the grease in the cup.

 

However, you could try measuring electrical resistance between the shank of the knuckle, where it abuts the trumpet, and the arm. If there is continuity, the cup is definitely worn through, and needs to be changed immediately. Don't measure from the body of the trumpet, as the ever-present aluminium oxide may insulate it completely from the knuckle.

 

I will be very interested to know the results if you are able to do that test. If it works it will be useful to others.