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I went and snapped my subframe - Doh!!!!

Alex

Nordschleife
Joined
6 Mar 2014
Messages
22,188
I've had an annoying knock I've had for some time now coming from the rear RH side. There was quite an amount of play in the lower control arm/fork that supports the coffin arm so I replaced that last month. Toe arm was replaced a few months back and coffin arm around 4 years ago. It wasn't a bad knock but every now and again, especially braking down a steep hill with an uneven surface, you'd hear it.

Anyway, the other day at work I was having a nosey around for the umpteenth time and noticed that my coffin arm eccentric bolt looked like it'd been moving slightly. I went to tighten it up and all of a sudden heard a 'ping'. Took a look at my subframe and instantly felt sick:

tFfTisw.jpg


DZQjbnC.jpg


Nw2loPK.jpg



My subframe snapped where the coffin arm bolts through it. Obviously something was seriously wrong here as the aperture there and the coffin arm bush are virtually size and size so that the subframe clamps the bush when the bolt is tight. This obviously wasn't the case otherwise it wouldn't have snapped.

Quick chat with some of the guys on here and MisterCorn (Legend) sorted me out with a replacement subframe from 9 Apart in Ramsbottom. So I stripped everything off it, dropped the subframe and shot off over to 9 Apart to collect it. Also sorted me out with a replacement coffin arm as I quickly realised that was the issue causing the subframe to snap.

Old subframe removed:

YQSrW86.jpg



Once back at work I set on with getting everything back together (as it's my daily and could really do with not having to drive the bird's mini). All back together with plenty of copper grease on the relevant parts and then setting the camber and toe - I've worked out a way of measuring and setting it myself at work that I'm confident with - who needs a Hunter :grin:

Car is now all back together and the annoying knock has now vanished!! Went for a 150 mile spin in it yesterday and all seems good.

Back to the problem that's caused all this in the first place. Been down my unit today to have a gander at the condition of the old subframe and coffin arm. Looks like over time the bush on the coffin arm has embedded itself into one side of the subframe, thus creating clearance between where it slots in. Then tightening the eccentric bolt and nut up has put that much force on the subframe that it's snapped it. You can see on both one side of the subframe and coffin arm how bad they were:

Subframe:

WpTyJ7B.jpg


qVbfBwn.jpg



Coffin arm:

ALb2M9I.jpg


4s27KYN.jpg


1O6GIH7.jpg


dV2C0Mr.jpg



Opposite faces of each didn't look too bad:

5MPYaN6.jpg


sP5fNB5.jpg



Bit of a rigmarole but happy it didn't snap whilst the car was in motion, or even worse - in motion in another country and also happy I've now got shut of an annoying knock.
 
Wow...that's not something you see every day - thankfully! :)

How old were the coffin arms?
 
4 years
 
Hi Alex,
I had a knocking from my front suspension shortly after the complete refresh by CG, turned out that the coffin arm bush was slightly too small and it was moving and knocking.

Pete and Chris were very careful not to tighten up the bolt as 'it will probably crack the subframe as the ally is very rigid with no give' and fitted a replacement coffin arm.
 

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