Walneck's Classic Cycle Trader - February 2009 - (Page 35) MONTHLY FEATURES the bolt head and add two. For example, no markings mean a grade 2, three markings a grade 5, and so forth. A lot of experts recommend nothing less than a grade 8 for anything expected to take a real beating, like Joe’s aforementioned shock bolts. Be advised that stainless bolts carry different markings. A 304 grade is roughly equivalent to a grade 5 plain steel bolt, and those wanting more strength can opt for stainless grade 316. There are numerous other grades and markings. What’s the big deal about different grades? Essentially strength and hardness. For example, one bolt company’s tech charts shows a grade 2 half-inch diameter bolt having a minimum tensile strength of 11,800 pounds and the same bolt in grade 8 recording 24,000 pounds, over twice as strong. Which one do you want to bet your safety on? “So you mean if I use only high quality nuts and bolts, I have nothing to worry about?” one might fairly ask. Ahh, if only life were so simple! The reality is that there are many other considerations, and even with these, wear and vibration always mean regular checks for bolt security are needed to assure everything’s tight. There are also other security precautions worth mentioning. Racers have long known, and been required in sanctioned events, to use safety wiring to make sure that nuts and bolts stay put. Since safety wiring isn’t necessary for most user applications, we won’t cover it here, and most street and trail riders will do quite well with the correct washer for each respective bolt and nut, and then using proper torque when tightening. Additional security can be gained by using modern self-locking nuts that are extremely reliable if not worn out from repeated disassembly. Thread locking cement like Locktite is also a good idea for many applications. And do fight the urge to skip using a proper washer as this discrepancy very frequently results in the nut working loose. It pays to remember that the original manufacturer tried to build the bike to make a profit and installed washers because they were needed not because they were superfluous. If they were, they wouldn’t have been used to make a higher profit. Had I learned this earlier, I wouldn’t have lost a boxful of mufflers, pipes, taillight brackets, mirrors and other doodads I distributed along various highways and byways. With respect to correct torque, figures based on bolt size and grade would be a handy reference, but specific torque can’t always be reduced to a simple answer or reference table. Many variables determine the correct answer-fastener surface finish, coating, plating, class of screw, thread fit, etc. Solution? Check the tech books for your bike or the bolt source when building specials or replacing stock hardware. OK next month we take a look at hydrogen embrittlement, thread pitch, and more stuff that’ll drive ya nuts. MOTORCYCLE TIPS Six marks and the manufacturer’s logo mean this is a grade 8 good for high stress applications. This bolt came out of one of my parts bins. It’s most likely off an old Brit, but I’m not sure. I also have a lot of old military aircraft fasteners with many different markings that don’t follow modern marking standards but are still high quality fasteners made under government specifications. This is a stainless steel bolt. These use a different marking system. Regardless of what sort of bolt you use, washers and locking nuts are wise insurance. WALNECKS.COM I WALNECK’S CLASSIC CYCLE TRADER® | February 2009 35 http://www.WALNECKS.COM
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