Narrowly avoided disaster - what locking nut for adjustable rear camber arms?

[Newbers]

Driving home yesterday I heard a small bang then a scraping noise. I guessed it was the exhaust and as I was very close (200m) to home I carried on and made it in to the drive. Turns out it wasn't the exhaust:

(Sorry - not sure why that is upside down) I just had the Powerflex adjustable control arms fitted and it would appear the OEM bolts don't lock with these (unless the garage didn't tighten them up properly).
Having done about 70 miles at speed I am amazingly lucky this happened at very low speed and so near to home - it could have been catastrophic. As it is the wheel is a bit scraped up and I've lost all the wheel weights.
I'll get the garage to sort it out but meanwhile any thoughts about the best nut/bolt? OEM bolt has the adjuster cam (which I don't need so I'll replace that with a 10,9 high tensile) but the OEM nut is a serrated flange I wonder if I'd be safer with a Nyloc nut.

 

[Jakg]

You can get flanged nyloc nuts.

Bear in mind that the nut, too, has a tensile strength (expressed as a Class - e.g. Class 8).

 

[R60BBA]

Which garage fitted your arms mate?

 

[Newbers]

Local independent in St Albans. I'm not getting on very well with garages at the moment - OEM or independent. Four out of four of my last bookings (Mercedes, BMW, Merc specialist and independent) have all required revisits after very routine work.

 

[R60BBA]

Local independent in St Albans. I'm not getting on very well with garages at the moment - OEM or independent. Four out of four of my last bookings (Mercedes, BMW, Merc specialist and independent) have all required revisits after very routine work.

Get them to fix it (free of charge of course) and then never take your car there again.

Evolve Automotive in Luton are solid BMW specialists and aren’t far from you. Might be worth giving them a try next time you need to book the car in.

 

[enuff_zed]

Local independent in St Albans. I'm not getting on very well with garages at the moment - OEM or independent. Four out of four of my last bookings (Mercedes, BMW, Merc specialist and independent) have all required revisits after very routine work.

Get them to fix it (free of charge of course) and then never take your car there again.

Evolve Automotive in Luton are solid BMW specialists and aren’t far from you. Might be worth giving them a try next time you need to book the car in.

Plus free wheel refurb and re-balance

 

[Newbers]

You can get flanged nyloc nuts.

I can only see these in stainless steel which is not going to work. Having Googled a bit it appears that other adjustable control arm kits come with nuts/bolts and all appear to have flanged nuts. It did also occur to me that you don't really see Nyloc nuts on cars. When I assemble nuts and bolts that are going to be in a corrosive environment I often use nutlock. If nothing else it keeps the crud out of the threads so I'll probably do that.

Evolve Automotive in Luton are solid BMW specialists

- Thanks for the tip, I'll give them a buzz next time it goes in, they're just up the road from Specialist Cars (BMW) where I've been get my services done for the last 19 years.....

Plus free wheel refurb and re-balance

Absolutely. They're lucky I won't be claiming for serious damage (or at least clean pants!).

 

[Liam22]

The OEM arms use very thin steel where they meet the ball joint. Aftermarket arms are thicker and the OEM bolt is too short (does not allow full engagement of the nut. If the garage tried to reuse the OEM bolt then they gave you the car back in an unsafe condition.

Really the new arms should come with new fixings.

Fit a bolt the right size. Since when did this becomes a specialist activity?!

 

[Newbers]

The OEM arms use very thin steel where they meet the ball joint. Aftermarket arms are thicker and the OEM bolt is too short (does not allow full engagement of the nut. If the garage tried to reuse the OEM bolt then they gave you the car back in an unsafe condition.

I read this and went straight down for a measure! The ears (?!) either side of the bushing measure about 67mm externally. OEM bolt is M12 x 1.5 x 81 - 10.9. (not sure what the 1.5 is. perhaps something to do with the length of the threaded port or the flange?) This would just about be adequate without washers....

Looking at the other side: . It seems there is no thread to spare but the problem seems to be the eccentric washer. Assume the nut is serrated it needs to engage with metal that is not going to move in order to lock. I'm guessing the washer has slipped allowing the nut to work loose. That said no serration on the bolt flange so not sure what would stop that end slipping.....

 

[enuff_zed]

In my 23 years on military aircraft we always worked on the understanding that a minimum of 1.5 threads needed to protrude through the nut to be 'in safety'.

On a similar vein, you could consider wire-locking them? Or split-pinning?

 

[Liam22]

The nut is not fully engaged which means it is not possible to torque correctly.

1.5 is the thread pitch. Here is a suitable BMW OEM bolt. Flange nuts are easy enough to find on eBay.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F171468469056

 

[Jakg]

You can get flanged nyloc nuts.

I can only see these in stainless steel which is not going to work. Having Googled a bit it appears that other adjustable control arm kits come with nuts/bolts and all appear to have flanged nuts. It did also occur to me that you don't really see Nyloc nuts on cars. When I assemble nuts and bolts that are going to be in a corrosive environment I often use nutlock. If nothing else it keeps the crud out of the threads so I'll probably do that.

Some drop links come with flanged nylocs.

You can get non-stainless ones - eg https://www.ebay.co.uk/itm/NYLOC-LOCK-NUTS-BZP-NYLON-INSERT-LOCKING-CLASS-8-M3-M4-M5-M6-M8-M10-M12-M16-M20/323767145623?hash=item4b62069497:m:md7cDOJGhrbnU_e603vjYSQ

 

[Newbers]

Here is a suitable BMW OEM bolt. Flange nuts are easy enough to find on eBay.

Thanks for your help - I've bought two of those + OEM flanged nuts. Rather expensive but hopefully that will sort it. I couldn't find anything similar in small quantities unfortunately.

Now I can get back to trying to figure out what's up with the handling (that led me to fitting these in the first place)....

 

[Newbers]

For the record I got this back from Powerflex today:

> On 30 October 2019 at 15:48 POWERFLEX - World Leaders in Polyurethane Suspension Bush Technology <[email protected]> wrote:
>
>
> Hi Nick,
>
> It's the adding of the eccentric washer that's the reason for the bolt coming undone.
>
> It's not allowed the nut to tighten up probably. This washer is no longer required because the geometry adjustment comes by way of the arm.
>
> I've actually got our development set on one of my cars from when we first launched these years and I've never had an issue - that washer wasn't re-fitted however.
>
> Kind Regards
>
> James Bourn ~ Sales Director