The 411 on thread locker:
Thread locking compounds, sometimes referred to as 'Loctite' despite it being a brand name, is an adhesive that can be applied to the threads of a fastener to keep it from loosening over time from vibration or shifting parts. This is especially useful on smaller bolts that require a relatively low torque such as rotor bolts, but can be put to use anywhere that a bolt can repeatedly loosen even though it has been properly torqued. Lubricating a fastener with grease, the swear-by for cycling mechanics, is done to allow a bolt or nut to be precisely torqued, and to ease removal down the road. Grease and thread locking compounds should never be mixed. While there are other ways to keep bolts from coming loose - cotter pins, lock washers and even safety wire - none of those methods are suitable for use on our expensive and lightweight mountain bikes. Thread locking compound is a thixotropic fluid, which means that its properties change under certain circumstances. For most types of thread locker, especially the blue colored version that is used on bicycle parts, this refers to a lack of oxygen that allows the fluid to set once the fastener has been tightened down to the correct torque. It is best to allow the locking compound a full 24 hours to fully set, although it will dry sooner than that.
Blue is your friend:
Thread locking compound is available in both a stick (left) and liquid (right) compound, and is used to keep bolts from backing off. It can be used in a number of places, including brake caliper and rotor bolts, or can come in especially handy on places like stem bolts if you spend your days doing hot laps in the bike park and want to keep your rig running safe.
Medium strength Loctite is most often blue in color and can be used on many places on a mountain bike to keep bolts from coming loose. It is thought of as being 'removable' in that it shouldn't require excessive leverage or heat to break free, and requires roughly 115 in/lb of torque to loosen a typical bike-part fastener. It is available in a squeeze bottle with a needle tip that allows you to apply it only where needed, but it can also be bought in a tube, similar to a glue stick, that is great for applying to places where you don't want it to run onto other surfaces (lever reach adjustment screws being a perfect example
). Blue thread lock is ideally used on any steel fastener that has repeatedly loosened despite having having been tightened to the recommended torque. Safety is a primary reason for thread locking compounds, and international standards specify that brake rotor and caliper mounting hardware are treated with it so there is little if any chance of an improperly torqued fitting rattling loose. Same goes for shock mountain hardware or any threaded fitting on a rotating part. Thread locking compound is also the go-to for press-in or threaded parts that tend to develop creaks over time (a touch of blue thread locker on some clean BB threads, for example
).What not to use:
Thread locker is available in different compounds and strengths that are usually color coded, although most are not suitable for use on a bike: red thread locker requires 230 in/lb to loosen and should be thought of as permanent, meaning that it will likely require a large leverage tool to remove the bolt. There is really no reason to be using the red colored compound anywhere on your bike. Green thread locker is best at penetrating into nooks and crannies, and can be used to hold sealed bearings in place (being careful to not get anywhere near the rubber seal
) if the bearing bore is oversized. The green compound needs roughly 90 in/lb to crack lose, and should be used very sparingly.
Start by removing the trouble making bolt and giving it a thorough cleaning with an alcohol based spray, being sure to remove any old grease or grime. Do the same to the threads that accept the bolt, using a Q-tip if needed to clean it properly. Let it air dry and take a minute to inspect the bolt's threads for damage or stretching that may have been caused by over tightening.
Apply a small amount, usually just one drop, to the threads on the bolt. There is no need to go overboard, too much will only make a mess.
Where to not use thread locker:
Thread the bolt back in, tightening it to the specified torque. Wipe away any excess thread locker that may be present. It is recommended to let the bike sit for 24 hours before riding to allow the compound to fully set.
Although blue thread locker can be put to use on many places, there are some where it shouldn't be applied. It should be avoided when working with titanium bolts, especially when they are being threaded into a dissimilar metal, such as steel or aluminum. Anti-seize is your best bet here because it will prevent galvanization, allowing you to easily remove the fastener down the road. We would also recommend that you skip using Loctite on aluminum bolts as well for the same reason, but it can also make removing fragile aluminum hardware difficult, leading to rounded or broken off heads. Here are some other places that shouldn't see thread locker:
• Chain ring bolts, especially aluminum versions (use grease to allow you to loosen them later on
• Most crank set bolts (grease used here allows it to attain the proper torque
• Pedal threads (pedals won't loosen due to their reverse threading, but using grease will eliminate creaks and make them easier to remove
• Axle threads on either front or rear thru-axles (grease here prevents the two aluminum surfaces from galling
• Any small hardware that hasn't repeatedly loosened (M3 sized bolts or smaller, such as those used to attach the adjustment dials of a fork. Using thick grease here will prevent loosening and make them easier to remove
) Are you an arm chair thread lock expert? Want to add to what Mike has to say? Do it below!
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