Reply With QuoteThe shear strength of a cheese stick would almost be ok for towing 500Kg. I'd usually use grade 8 as these are standard fare from my local engineering supplies, but almost anything woukd do IMO.
Master
SubscriberI have a Hayman Reece type towbar bought recently second hand for a W202 Mercedes sedan. It's the flat tongue type with 50mm towball. I have the tongue bolts.
It came without the chassis mount bolts washers and nuts- just a 1m length of 2 3/4 inch tube with 3mm angle steel welded on the ends- two bolts each side are all that is needed apparently.
So I rifle through my bolt collection, find a 70mm length grade 8.8 hex bolt, 1.5 thread, 12mm shaft. Just one.
At the local engineering hardware, I locate four grade M12 bolts of appropriate size.
Load rating for the Hayman Reece towbar is nominal 1250kg.
Vehicle specification is a bit higher (1500kg braked) if you use the OE towbar which is hens teeth.
Unbraked towing capacity is 500kg or 1950 GCM.
With a Braked trailer is 2950kg.
With this Hayman Reece tow bar, braked towing capacity is 1250kg + 1450kg (vehicle kerb weight).
Is that grade M12 bolt washers and nut suitable for the job at hand?? It'll only be towing a 8x5 box trailer- 500kg all up anyway.
I only mention the above specs to outline the limits of the set up, not that I will be asking it to do.
Advice welcomed.
Cheers steu
Super Moderator & CA manager
SubscriberThe shear strength of a cheese stick would almost be ok for towing 500Kg. I'd usually use grade 8 as these are standard fare from my local engineering supplies, but almost anything woukd do IMO.
If you need to contact me please email homestarrunnerau@gmail.com - thanks - Gav.
AT REST
Grade 8.8 is ideal as it can be tightened enough to stop the bar moving around yet tough enough to absorb large shock loadings. Softer bolts can't be tightened enough and harder bolts could in theory snap under repeated strain. Even a 3500kg D1 towbar is only held on with 4 of those plus two M10 bolts.
Wizard
Do you have grade 8 bolts, or class 8.8 bolts? Class 8.8 bolts are about the same as grade 5 bolts. For a towbar mount, I personally would use grade 8 or the metric equivalent.
Aaron
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