MB dealer nuts and bolts - whats the difference

[SilverSaloon]

hi

I had to cut off a suspension arm nut to remove it on my W124.

So, I have two options:

(1) go to dealer and spend £9.00 on a new nut & bolt as per correct part numbers

or

(2) go to local hardware shop, get same length, thickness of bolt for less than £1.00

I've actually gone to the dealer and spent £9 this time, but what differs the dealer bolt from the hardware shop's bolt? Dealer bolt is heavier and is grey matt in colour. Hardware shop bolt is shiney metal

I assume the dealer bolt is high strength for suspension? whats the code/type/name of the type of bolt so i can seek elsewhere for cheaper?

cheers!

derek

 

[Druk]

Tensile strength of bolt might be cast on head. 8.8 or 10.9 are high tensile and 12.9 being the top grade.

Grey appearance is zinc plating. Dealer bolt might have threadlok already on but big deal on that. Bottle of Loctite and it's sorted.

 

[R2D2]

Why would you take a chance on a bolt that holds your suspension together. £9 is a small price for the peace of mind surely!

 

[BTB 500]

£9 is a small price for the peace of mind surely!

£8, if the non-M-B one costs £1 anyway

 

[Stratman]

Aint no such thing as 'just a bolt'.

 

[SilverSaloon]

Why would you take a chance on a bolt that holds your suspension together. £9 is a small price for the peace of mind surely!

Don't dispute that but £8 is a lot for a bolt if the same type of bolt can be purchased elsewhere - it would become very expensive if u needed to renew a few of them

 

[DSM10000]

I would look at it this way Derek:

The MB supplied bolt will have been designed, manufactured and tested to meet the loads and stresses that the suspension undergoes, unless you can find these design specifications and then satisfy yourself that another manufacturer and supplier meets all of the required standards would you really want to risk it?

Just because a part appears to be simple in design and without obvious fancy features does not mean that it has none.

Compared to the cost of other suspension components is £9 not rather good value?

The fact that the two bolts you compared, whilst seeming to be the same in size had differing mass shows that the materials are clearly very different.

 

[SilverSaloon]

indeed but i suspect a site such as:

Hexagon Bolts

may be worth looking at. You can get >10 bolts for the price of 1 MB bolt, of the same strength spec.

 

[GordonTarling]

Would you really want a front suspension bolt shearing off at an inconvenient moment? Forget the inconvenient moment, I wouldn't want one shearing at all! Just bite the bullet and fit the correct bolts.

 

[SilverSaloon]

as i stated in my 1st post, i have fitted the correct bolts, from the $tealer this time.

All i wanted to know is what type of bolt they are, so in future i can look at alternative sources, which are of the same style/strength/type of bolt.

why pay more than you have to for the same thing?

 

[IanMSpencer]

The chances are that the MB bolt is sourced from any old quality bolt manufacturer so in principle you can buy generic bolts rather than branded bolts however to do this you need to understand the specification of the bolt. You also need to know not just the length and width, but the thread pitch - not all metric bolts use the same pitch.

There are different grades of steel and treatments which have different properties, and it may be that one bolt has to be good at twisting forces, another might get occasional shocks. The designer will have considered this.

Also, materials are important, differences in material can cause electrolytic reactions, steel bolts into aluminium for example.

If you are an experience engineer, you'd be able to assess the task of the bolt and either identify an exact generic equivalent or have a reasonable idea of a sound alternative.

Consider it £8 for expert advice from a Merc engineer.

 

[V12]

As you have cut the old bolt off you'll know how hard they are compared to the majority of the hardware shop lurpak bolts.

Lots of sound advice above!

 

[NOMONEYBUTAMERC]

As Druk says , the tensile strength is marked on the head of quality bolts. I always look to save money in every area that I can , except Safety. The saving of £8 on a bolt is not the last thing you want going through your mind just as a detached wheel starts working its way up your ars*e!

 

[WDB124066]

The MB bolts generally have their threads rolled [i.e. forged] as opposed to a straight out machine cut, their shape and design minimises stress raisers, they are a nice piece of engineering all on their own. Washers should be the through hardened type, not the soft ones you'll pick up cheaper, as they do not transmit torque as evenly or hold the bolt tension as well as the through hardened types.
The things that can go wrong with bolt manufacture would surprise you, especially when you are heat treating them. Accountants just love to try and cut corners on starting material and heat treatment processes.

How would the Insurance Co's deal with a car that has non-genuine bolts installed in critical locations - are they concerned about this at all...??

 

[gazz]

There is also the issue of counterfeit bolts. There are some dodgy things floating about that come in on the same flights as rubber dog poo and fake vomit. They are often stamped on their heads with the same 8.8 or 10.9, but yield strength way lower. Why take the chance with your life and, potentially, the lives of others?

 

[Dieselman]

Why take the chance with your life and, potentially, the lives of others?

I thought he was talking about bolts, not firing a bullet into his head?


Lynne Faulds-Wood alert.

A Potential Death trap...

 

[gazz]

I thought he was talking about bolts, not firing a bullet into his head?


Lynne Faulds-Wood alert.

A Potential Death trap...

Do you have an opinion, or prefer to belittle that of others?

 

[hotrodder]

MB bolts generally have their threads rolled

For the typical sizes found on cars and the like virtually all commercially made bolts have rolled threads. Once you get into really large diameters and/or oddball sizes threads may be cut but pretty much everything else has rolled threads because it's cheaper (faster than cutting threads and chipless so no waste) as well as better. About the only time i come across cut threads on commercially made fasteners (and the difference is typically obvious to the naked eye) is with studs and even then you have a choice unless you want grade 8.8 or higher in which case it's typically rolled threads only

For the vast majority of things i fabricate i use flutess thread rolling taps over conventional straight or helical flute cutting taps. Half the time the extra strength of the rolled thread is immaterial, i use 'em for speed and lack of chips/swarf in any compatible material for sizes under M10

MB don't make bolts and in most cases probably won't design anything either, why bother when you can select a spec that'll do the job and is available off the shelf
Sometimes the fasteners that OEMs use are harder to find elsewhere but often the difference is something that only mattered when the car was made, things like this

long thread lead-in which is about making the fastener almost impossible to cross thread for example
Occasionally you come across a weird grip length i.e. the bolt has an odd length shank in relation to it's total length. That can make a difference on suspension bits as the nearest 'off the shelf' thing that'll physically work results in a portion of the threaded section being subjected to bending loads when the fastener is used in double shear instead of tension. Last saw that one on an old aircooled VW, a grade 12.9 cap screw that does double duty functioning as a pinch bolt and a cotter pin on a ball joint. With generic 12.9 cap screws the grip length is wrong and some of the threaded portion ends up being used as the cotter pin

If the grade, overall and grip length can be matched then pretty much the only risk of buying a generic bolt is counterfeit cheapnese tat (as already said) and if buying from somewhere reputable i'd say the risks of that are probably no higher than going to MB and paying several times the going rate
The electrolytic corrosion thing is rarely an issue as most manufactures use plain ol' BZP, yellow passivated or black oxide fasteners which are a lot easier to find than uncoated. Not relevant to a suspension bolt but as magnesium castings become more popular for weight saving reasons the corrosion thing does come into play with not only aluminium bolts being used but weird flavours too instead of the more common 7075-T6... http://www.kamax.com/fileadmin/user_upload/dokumente/veroeffentlichungen/alu_fast_for_magn_comp.pdf

 

[WDB124066]

Agree with most of this but MB do make bolts AFAIK, as soon as they put their logo on it regardless of who actually physically made it. In other words legally AFAIIA MB are deemed to be the manufacturer once their logo is on it. Rest assured there will be MB specs for bolts that the makers will need to comply with before the logo may be applied.
When people start buying their own hardware for critical applications they need to know what they are buying, cut threads are a bit of a no no, as are the qualities listed above. Stick with the Genuine part - you know you are getting it right first time, most of the time.

 

[markjay]

Unapproved bolts is a serious issue for airlines - several aircarfts have crashed in the past due to industrial bolts being passed off as approved aviation parts to unsuspecting (and potentially incompetent) airline buyers.