Lug nuts for wheels

[svcguy]

I am finally fitting my rear wheel extensions to my YM240D and wondering if someone out there knows if lug nuts are normal grade bolts or a grade 8 equiv. Interestingly, my lug nuts have a '17' in raised numbers on the bolt heads, a designation I am not familiar with. After rooting through my stock, I have found 12 suitable bolts (size), but they are normal grade. Not being an engineer, I would venture a guess that normal grade are fine, but that's all it would be is a guess.

Anyone out there have any definitive information on what grade bolts lug nuts are made of?

Thanks, Tom

 

[svcguy]

Sorry everyone. Realized I am calling these lug nuts, an old habit that obviously isn't very applicable. The rims on my 240D are fastened with bolts, not lug nuts, and the heads have a '7' on them. I need to type a bit slower.

 

[tmoritz]

I can tell you from experience that you definitely only want to use hardened bolts and lock washers. Softer bolts are not up to the strain. They eventually start to work themselves loose and come out completely, completely messing up the hub's thread. In my case this happened in mud on the front left wheel, while turning right. I was looking back at the work I was doing, and before I knew it (within five seconds or so), the entire front wheel was off, flat on the ground and slightly bent. Can easily be prevented by using hardened bolts and lock washers.

 

[svcguy]

Well, that experience works for me. I ordered new grade 10.9 bolts just to be on the safe side. Wouldn't want to see a rear wheel come off, it would be a long way to the ground!

 

[LMTC]

You also don't want bolts so hard that they are brittle enough to shatter when you use an impact wrench.

 

[svcguy]

Good point. 10.9 is the equiv to our grade 8. While I don't use an impact on my wheels, the next owner might. I have used the impact with other grade 8's though, and have not had any failures.

Shear shouldn't be in question, as both the rim and the extensions have a flange they mate to. Tension on the other hand will be an issue where the extension is attached to the axle. Grade 5 fasteners will actually fail before a grade 8 begins to yield, so they make sense with the application.

To be honest, I think the original rim bolts are 8.8 (grade 5). There is a 7 on each bolt head, but now that I noticed that, I see every single bolt on the tractor has a 7 on it. The old 240 is a tough tractor, but I doubt Yanmar used 10.9 spec bolts to assemble it.