Thread: Are High Tensile Bolts Needed?

Yes Ht bolts should be used.

Michael.

I clicked # 3

what you should put in there is what the rated design asks for in your particular circumstances...

a 4 tonne rated hitch has different requirements to a 2 tonne rated hitch :P

you could have 1/2" high tensile bolts or 1" low mild steel bolts or ????? depending on what the engineered design is...

i have fitted engineered hitches specifing use of 1/2" mild steel bolts to fit the unit to the chassis.

and i have fitted hitches with 1/2" grade 8 bolts as the specified fastener...

then you get to find out whether they want a fine thread or a coarse thread on the fasteners :P

I voted yes, but it is really an open ended question, depending on the design of the tow bar and fittings. I suspect the original Landrover tow bar was not designed to use high tension bolts, as these would have been rare in 1948.
In fact, since the Series tow bar is designed to be attached with galvanised (not zinc plated) bolts, and these are not readily available even today, there could be a good case for not using them. On the other hand, high tensile bolts undoubtedly make the installation stronger, and the later tow bar installations are almost certainly designed with high tensile bolts in mind, suggesting that these should be used. The same would apply to the NATO hitch on Series military cross members, as the attachments are closer together and smaller diameter holes are used.

John

Originally Posted by JDNSW

I voted yes, but it is really an open ended question, depending on the design of the tow bar and fittings. I suspect the original Landrover tow bar was not designed to use high tension bolts, as these would have been rare in 1948.
In fact, since the Series tow bar is designed to be attached with galvanised (not zinc plated) bolts, and these are not readily available even today, there could be a good case for not using them. On the other hand, high tensile bolts undoubtedly make the installation stronger, and the later tow bar installations are almost certainly designed with high tensile bolts in mind, suggesting that these should be used. The same would apply to the NATO hitch on Series military cross members, as the attachments are closer together and smaller diameter holes are used.

John

Short answer is YES - ALWAYS use high tensile bolts (Class 8.8 in metric or grade 5 in imperial MINIMUM).

John - you always have to complicate things. Galvanised bolts are readily available in Grade 5 (3 radial lines on head) - which are equivalent to the Class 8.8 metric bolts which are the ubiquitous "high tensile" bolts.
What makes you think high-grade bolts were rare in 1948???

Bolting a series tow bar on with standard bolts can be dangerous. When I was yound and silly I did just that (4x hardware shop 3/8 gal bolts), and luckily it didn't fail on me (handled a few recoveries offroad too - but I try to use minimal force when doing a snatch recovery). BUT - the SCARY part - when I went to remove the bolts and replace them with grade 8 bolts - 2 or the 4 snapped rather than undid Whick means they must already have plastically deformed/fatigued, and were on the point of complete failure.

Does using high tensile bolts create the potential for damage to the chassis?

Everything needs a weak point and if the bolts will not stretch, the chassis could be damaged as the tow bar is of thicker steel than the chassis.


Jeff

For some reason I thought that HT bolts had to be black....but Ive had a look at trhe bolts Ive just used, and they have 8.8 stamped on the head but are silver.....

In my case the bar is rated to 3000kg

Originally Posted by isuzurover

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What makes you think high-grade bolts were rare in 1948???
...........

Rare is perhaps not the right word - but remember that the 1948 Landrover was designed to be used by farmers, and I think you will find that in 1948 the average UK farmer would be very unlikely to have any in their stockpile of bolts - mostly they were probably wrought iron.

I have just checked the oldest (S2) chassis I have with an attached tow bar.

The upper 3/8 bolts holding the drop plate have three radial lines as indicated - the lower drop plate (1/2") bolts and the ones holding the towing jaw are not so marked, but just have the manufacturer's name (Rubery Owen), which I suspect is the tow bar manufacturer, suggesting these are original.

John