Interesting info about HF trailer bolts

[lmh222]

Hello, I've heard a lot of talk about whether or not to replace the bolts on a HF trailer with higher grade or stainless bolts.

I seem to have discovered some interesting info that may be helpful to others...

I decided to purchase new, grade 8, bolts for my HF 1175lb capacity trailer just to be absolutely sure that they were high quality fasteners. My plan was to use new grade 8 bolts with the Nylock nuts that came with the trailer. I went out to Home Depot and cleared out their drawer of 3/8" diameter (per the parts list that came with my HF trailer) grade 8 bolts.

I came home very excited to get started on my trailer assembly but found that the nylock nuts provided with my trailer DO NOT fit the new 3/8" bolts correctly (the nut wiggles around on the threads of the bolt). No, this is not a coarse vs fine thread count issue, the 3/8" bolts seem to be a smaller diameter than the bolts supplied with the HF trailer.

I went on the web and found this site: http://www.boltdepot.com/fastener-infor ... Chart.aspx and noticed the my HF bolts have the numbers 8.8 printed on the top of all of them just like the diagram of the METRIC high quality bolts. I did a little bit more research and it seems that grade 8.8 is only used to describe metric fasteners.

Ok, so that means two important things... first, 8.8 grade bolts are high quality and do not need to be replaced (YAY!) and second, anyone who does replace their bolts needs to replace the nuts too (or purchase metric bolts). The fit was "close" but there was definitely a lot of slop in the connection... I'm REALLY REALLY glad that I happened to notice that something didn't seem quite right. A poor fitting between the nut and the bolt would probably be WAY more dangerous than using the standard fasteners.

My guess is that either HF had a problem with their fasteners at some point and just switched them out without changing the instruction manual or, whoever wrote the manual thought that mm should just be "translated" into inches for us crazy Americans who like to use inches instead.

In any case, I thought that some others who are just starting on their tear project may find that information useful.

Lindsey

[JunkMan]

I always thought that you were supposed to use grade 5 bolts on something like a trailer, that grade 8 was too brittle. Seems like that was something I was taught in the military many many years ago.

[ceebe]

Since the US is the only inch holdout in the world, and the HF trailer is an import, the whole thing is likely to be metric with the possible exception of the hitch assy.. BTW, most auto racing hardware articles suggets grade 5 bolts over grade 8 . Aircraft hardware is also very similar to grade 5 in composition. I'd rather have a bolt deform but stay in place than break!

[lmh222]

Yeah - I think that you're right. The more that I learn about bolts the more relieved I am that I did not replace mine.

The grade 8 bolts are stronger but their VERY brittle so there are actually situations where a grade 5 bold would bend but the grade 8 would snap. How something fails is sometimes more important than the fact that it failed.

The good news about the HF bolts is that the website that I referenced above says that grade 5 is actually the exact same strength as class 8.8. Oh, and I believe that I called is "Grade 8.8 before" but it is actually called "Class 8.8".

So far, it sounds like I would have been much worse off with my replacement bolts. I'm really glad that I took the time to research it. I was really anxious to get started but it would have been really depressing to figure this out a month from now.

[ceebe]

Failure mode is why large aircraft are held together with a lot of little bolts rather that a few big ones. Just back off on the impact wrench a bit and the stock bolts as supplied oughta last forever.
I have to tell myself daily that i'm not building a rolling bomb shelter or a space shuttle but just a damn camper.

[bdosborn]

I always thought that you were supposed to use grade 5 bolts on something like a trailer, that grade 8 was too brittle. Seems like that was something I was taught in the military many many years ago.

It depends on how you're using the bolt. A grade 5 is stronger than a grade 8 in shear. A grade 8 is stronger than a grade 5 in tension. The bolts that were included with my trailer were cheap ungraded crap. I replaced them all with grade 5 bolts and nyloc nuts since it seemed to me that most of the bolts were in shear. Also, every bolt has 2 washers now; they only included about half as many as was needed. I always use nylocs because lock washers always seemed to rattle loose in my jeep. I assembled the trailer with the bolts they supplied and didn't like how floppy it was. It was *much* stiffer after I replaced them. Its good to hear that they're including graded fasteners with the trailer now.
Bruce

[TomS]

The Red Trailer came with grade 8.8 bolts.

[ceebe]

Putting large area washers under both the bolt head and nut is the best advice you can get with a bolt together trailer. They will spread the load over a greater area and eliminate any gouging of the structure which could lead over time to a crack.