Lots of people want to order quality replacement bolts for there motorcycle but don't understand how they're measured and which materials are best.
Bolt sizing is pretty straightforward. Modern Japanese motorcycles all use metric bolts. The most important thing is the shank diameter – that's the distance across the main threaded shaft of the bolt. It's measured in millimeters and they're generally preceded by an 'M', which stands for metric. The common sizes on a motorcycle are M5, M6 and M8. The shank length is often given in millimeters too.
Bolt heads mainly come in two forms. Traditional hex heads are measured in millimeters, again from flat side to flat side. The common sizes used on motorcycles are 8mm, 10mm, 12mm, 13mm, 14mm, 17mm, 19mm. Quite a lot of motorcycles use some Allen bolts. These are measured by the width of the hexagonal hole, flat to flat. The common sizes are 4mm, 5mm and 6mm. Some bolts head have a star drive – these are generally ones you're not meant to tamper with. Threads vary in their pitch (the distance from the crest of one thread to the next) but metric bolts have a standard thread pitch for each size. M4 are typically 0.4mm, M5 0.5mm, M6 1.0mm, M8 1.25mm M10 are often sold with a 1.5mm thread but most motorcycle bolts are finer – generally 1.25mm. One common exception is side-stand bolts on Italian motorcycles, which are generally M10 with a 1.5mm thread pitch. You get the odd reverse-tread, too, but usually only on gear linkages – otherwise it'd be difficult to tighten both ends.
Bolt materials vary. Aluminum is popular, as it's fairly cheap and light. Anodizing it can provide a fairly corrosion resistant coating in loads of colors. There are different grades of stainless steel – some are stronger and/or more corrosion-resistant than others. Weaker ones shouldn't be used in high-load applications like footpegs and brake mountings. You can buy stainless bolts that are strong enough for these uses. Titanium is the most expensive but is very light and corrosion-resistant. It's particularly crucial to use a torque wrench when fitting titanium bolts, though, as they can easily be damaged by too much force (you should also inform the mechanic at your motorcycle dealership that you have titanium bolts).Tag: ScrewsFastenersReplaceMaintenanceRepairBoltsMaterialsStainless Steel