Snapped u-bolt

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scottonthefen

scottonthefen

Well-Known Member
Posts
532
Location
England
Now I've started using my 2A on the road after a lot of work in the garage, and fitting new springs and u-bolts,I thought I should torque it all up properly.

I've read different opinions for u-bolts between 58ftlb and 65ftlb, so I got everything clicking ok at 50 and then went for 60. Snapped a u-bolt. It got noticeably easier soon after 55 ish which I thought was a bad sign and then it popped. One on the other side got easier too, which made me stop, so that one is now also suspect..

So.. do I look for the priciest OEM u-bolts I can find and try again. Or should I stop at 55ftlb? I was torquing them up with the vehicle stood at rest. Should I take the weight off anything while I do this?

Cheers.
 
I bought new ones for my s2 years ago off of ebay, bought the most expensive ones going figuring I dont want any aggro, first one snapped!
So bought the cheapest nastiest one going as I needed it asap, many years later its still on there.
As a get me going I cut a head off a bolt and welded the bolt shank to the side of the ubolt and drove it until the new one turned up.

No idea on torque value as I dont use them!
65ftlb is going some as most wheel bolts are in the area of 90 ftlbs and they are quite a bit bigger than the ubolts.
Dont forget if you greased/oiled them before fitting then you need less effort to tighen them as tightening to the torque spec will be to much for the fixing.
 
lynall said:
I bought new ones for my s2 years ago off of ebay, bought the most expensive ones going figuring I dont want any aggro, first one snapped!
So bought the cheapest nastiest one going as I needed it asap, many years later its still on there.
As a get me going I cut a head off a bolt and welded the bolt shank to the side of the ubolt and drove it until the new one turned up.

No idea on torque value as I dont use them!
65ftlb is going some as most wheel bolts are in the area of 90 ftlbs and they are quite a bit bigger than the ubolts.
Dont forget if you greased/oiled them before fitting then you need less effort to tighen them as tightening to the torque spec will be to much for the fixing.
Click to expand...

Luckily I had a spare which is on there now.. but not torqued up much yet!

I can't remember if I put copper slip on them when I fitted them as it's a couple years ago now but as it's only been in the garage until now that would still have been on there..
 
Steamwally says in his video here he had some snap at 58ftlb, so did them to 45 which was ok but he did get some evidence of movement on the base plates next time he had them off.



As I had them all clicking ok at 50lbft it looks like I might have to leave them at that unless someone can recommend a brand that they are confident will go up to 58+.?

All opinions welcome.. you've got me this far! :D
 
scottonthefen said:
Luckily I had a spare which is on there now.. but not torqued up much yet!

I can't remember if I put copper slip on them when I fitted them as it's a couple years ago now but as it's only been in the garage until now that would still have been on there..
Click to expand...


Most critical/fixings nowadays are the stretch type, ie it is not so much about how tight you do them, but how much clamping force they apply at any spcifiic torque figure, overtightening takes the fiixng from the elastic to the plastic stage, so even though it may be tighter it is applying less clamping force.
I should add this is how my non techy mechs mind undertsands it!

Bolts/nuts /fixings is a whole science lesson on its own, way beyond my attention span.
 
Have a read,

Obviously lubrication of threaded bolts has lots of benefits, but with it comes the overriding concern that the lubricant will change the torque required to develop proper tension on the bolt—and how that could affect the integrity of the joint. Some estimate that adding a lubricant could reduce the required torque reading by up to 40 percent!

Just like a stretched spring, which tends to pull back into its original shape, a stretched bolt tries to pull itself back to its normal state. It’s this pulling back force, called the “clamp force” that actually maintains the tightness of the joint.
So, torque isn’t the true measure of bolt tightness—it’s tension.

Both copied from here, http://www.smartbolts.com/insights/impact-lubricants-torque-readings/

Personally I lube everyhting , and preety much gauranteed overtighten everything!
 
I did notice it got strangely easier very soon before it snapped. Maybe this is where it crosses over from elastic to plastic, how you described it above - so the one on the other side that got easier and I stopped doing up is definitely suspect as if that's just happened on that one it's not trying to pull back to its original shape anymore is it its gone "plastic"...
 
scottonthefen said:
I did notice it got strangely easier very soon before it snapped. Maybe this is where it crosses over from elastic to plastic, how you described it above - so the one on the other side that got easier and I stopped doing up is definitely suspect as if that's just happened on that one it's not trying to pull back to its original shape anymore is it its gone "plastic"...
Click to expand...

Yes its prob knacked.

Yesterday I had a fine thread m12 nut strip its thread whilst I was winding it up by hand using a short spanner, defo cheap chinese siht!

Long term land rover ownership will teach you to buy more of what you need, ie keep spares for just about every repair you have done so far, you will need them!
So you dont just buy 8 u bolts you buy 10, A as you know one is going to fail as you fit them and 2 as spares for in service failure/use.
 
What's all this about torqueing up u bolts? Just do em tight with a socket and t bar. Within a week or two they will have rusted up anyway.

Col
 
845460FC-E557-4B69-97DC-65A73293A9F6.jpeg


I used coppaslip on U bolts just to stop em rusting so quick, although the old ones inside nut threads were fine
I could tell the quality of the LR part over the others I got didn’t think it was too expensive at time
 
Oh dear - some of you scare me!

There are certain parts of the vehicle - in particular U-bolts - imagine them coming off at any speed - that deserve a bit of respect

"Counting white knuckles" isn't always appropriate!
 
Stretch said:
Oh dear - some of you scare me!

There are certain parts of the vehicle - in particular U-bolts - imagine them coming off at any speed - that deserve a bit of respect

"Counting white knuckles" isn't always appropriate!
Click to expand...
Does that mean you are in favour of using a torque wrench to do them up?

Col
 
Colthebrummie said:
Does that mean you are in favour of using a torque wrench to do them up?

Col
Click to expand...
Oooo that sounds like a trick question Col!

You may use your fingers to wind on the nuts and then a normal (deep) socket and ratchet to start getting them tight (!)

[Oh the bright lights of interrogation!]

The important part is to make sure the torque is correct as specified - so that's when you need to get out the torque wrench

####

If you do get to the point "where things start to feel easier to turn" you have probably got a bit of cheapo rubbish that should NOT have been sold to you
 
If you check the axle to spring joint and see red rust dust thats a sure sign the u bolts are slack any issues with steering look at that location.
I have parabolic springs so needed shorter Ubolts bought them from GB Springs £48 full set, but they where good quality.
 

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Sorry - I don't like to be a pain - to come across like an internet warrior but =>

Cars tend not to have much in-built safety "redundency" designed into them unlike aircraft. Aircraft more often than not have a back up system although they tend not to have an extra set of wings these days...

...my point is that as a mechanic you always need to think about how important the part is you are fixing. Somethings might turn out to be embarrassing when they fall off whilst you are doing burnouts outside McDonalds but other things are much more related to the safety of yourself and others.

Those parts - such as U bolts - really ought to be torqued as specified. There is an implied responsibility when you fix your car just as a paid mechanic is as responsible when he / she fixes yours.
 
Stretch said:
Oooo that sounds like a trick question Col!

You may use your fingers to wind on the nuts and then a normal (deep) socket and ratchet to start getting them tight (!)

[Oh the bright lights of interrogation!]

The important part is to make sure the torque is correct as specified - so that's when you need to get out the torque wrench

####

If you do get to the point "where things start to feel easier to turn" you have probably got a bit of cheapo rubbish that should NOT have been sold to you
Click to expand...
Sorry, it wasn't meant as a trick question. It would seem to me that there are two types of mechanic, those like me that learnt spannering skills donkey's years ago that feel able to tighten a nut or bolt by feel and those that follow guidance in manuals to the enth degree. I haven't got a problem with using torque wrenches, I own a few but I couldn't swear they are accurate. I wonder how many of us trust torque wrenches that are several years old that have never been recalibrate or even wound back to zero after each use. On the rare occasion when I have used a torque wrench, I've often felt that whatever I was doing up was either too tight or not tight enough. I would like to mention that in almost 50 years of doing stuff up, I've never had anything come loose, unlike several so called skilled garage mechanics. I have had the odd bolt snap but that was more the fault of a crappy bolt than my ham fistedness.

Col
 
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