does size matter?

[vk2icj]

Ok I have a 60 series that has a TJM bullbar on it. (steel) I went to put on my winch (which is another problem because it didn't fit) and in the process decided to replace all the bolts because the ones used were not clearly marked. I went to bunnings with one in my pocket and bought 8 new M10 High tensile bolts 8.8. Ok now the old bolts I think were actually M12 because they are slightly larger than the ones I bought. I put the M10 bolts in and before tightening there was a bit of slop. Does it matter that the bolt holes have slightly smaller bolts in them? They are high tensile and there is 8 of them.

Thanks

Chris

[berad]

They'll be fine, all the load is on the bullbar its self, the bolts are more to locate the winch and fairlead.

[STIKA]

what brand of winch is it?

If it a warn it will probably be 3/8

[Gwagensteve]

In practice, maybe not.

In theory, yes. bolts are rated for their tensile strength. They're much weaker in tension than in shear, and if there is slop, you have the potential for a shear load to be introduced.

The idea is that bolts clamp things together tightly enough that the bind between the two faces prevents shear.
That's kinda an answer as to why you might be OK (If you have enough tension on the bolts) and why why what you've done isn't ideal (as the bar can move a bit before the bolts go into shear, allowing a large shock load to be generated.

Steve.

[Struth]

I wouldn't do it, just imagine putting 6mm bolts in there, it's a big exageration of the difference between 12mm and 10mm going down to 6mm is 50% the bolt that a 12mm is in size, probably only 10% the strength of a 12mm though.

So 10mm is only 83.5% of a 12mm size and maybe only 65% 0f it's strength. A good mechanical engineer could do the maths properly.

You have weakened the bullbars mounting to the vehicle and introduced excessive clearance to all the bolt holes.

My 2c

[LuxyBoy]

Do it once, do it right.
Fantastic motto

[vk2icj]

Yeah I better go get some bigger bolts. Maybe another bunnings run

I may have confused some. These bolts are the ones to the chassis that holds the bullbar to the chassis.

It's a different problem but since some asked. My winch is an X9 superwinch. When I try to get aligned with the holes the motor of the winch buts up hard to the plate of the bullbar with about 5 mm to clear the holes for the bolts that mount the winch (different problem than above) My only thought is to drill new holes but I think new holes close to the old holes would weaken the bullbar. I'm stumped for today

Chris