Almost every fastener on a production bike is medium-carbon or alloy steel, heat-treated to a property class. Steel makes complete sense when you're building bikes in the tens of thousands, because it's strong, cheap, predictable and easy to work with at volume.

The problem is that steel rusts, so it needs a coating to survive being outside. Usually that's zinc plating, and it's the coating keeping the corrosion off rather than the bolt itself. Any coating has a finite life. Round the edge of it with a spanner, catch it with a stone off the road, or just leave it out through a few British winters, and eventually the steel underneath gets corroded.

The word titanium on its own doesn't tell you much. Grades 1 to 4 are commercially pure, which means soft and ductile and no use whatsoever in a loaded fastener. Then you get the alloys, and Grade 5, properly called Ti-6Al-4V, is what you need. It's titanium with roughly 6% aluminium and 4% vanadium alloyed into it, and it accounts for most of the titanium used for fasteners, for the simple reason that it's the strongest.

All titanium we source and supply is Grade 5, and we lead with that because the grade is the whole basis of this comparison. A Grade 2 titanium bolt will be worse than the steel fastener you've just taken off.

That third line catches people out. Titanium is about half as stiff as steel, so a titanium fastener stretches more under the same load and takes up movement in a joint rather than resisting it flat. For the sort of fasteners we supply that's fine, and in a few places it's an advantage, but it's the reason titanium is a bad idea in a handful of applications we've listed further down the page.

This is the easy one to check and we'd encourage you to do it. Put the OEM bolt on a set of kitchen scales, put the titanium one next to it, and you'll get around 40% lighter than OEM steel for the same fastener. That comes straight out of the density of the material, so it isn't something we can take credit for.

Where people get carried away is expecting to feel it. One bolt is a few grams and nobody has ever noticed a few grams, so if weight is your reason for spending the money rather than looks, it's worth being a bit choosy about which bolts you start with.

Unsprung and rotating mass counts for the most. Caliper bolts, disc bolts, sprocket bolts. Weight the suspension has to control, or that has to be spun up and stopped again every time you use the brakes, does more harm per gram than weight bolted to the frame. It's the same thinking behind spending serious money on wheels.

After that, go where there are simply a lot of fasteners. Fairing and bodywork, engine case covers, sump, bellypan. Individually they're nothing, but as a set they add up to something you can put on the scales.

Anything beyond that you're doing for how it looks and how it holds up, which is a perfectly good reason to do it. We'd just rather not sell you weight savings you'll never notice.

Rust is iron oxide, and there's no iron in titanium, so there's nothing available to rust. That isn't a coating doing the job either, so there's nothing to wear through. Titanium grows its own thin oxide layer the moment it meets air, and if you scratch that layer off it re-forms straight away.

For a bike ridden in this country that's the part that matters. Salted roads through the winter, weeks of rain, and the chemicals in whatever you clean it with. Come back to the same fasteners a few years in and they look like they did the day you fitted them.

The dissimilar metals problem

There's a second corrosion issue that gets talked about less and probably matters more day to day. Bolt steel into aluminium threads, add water, and you've effectively built yourself a small battery: the two metals sit a long way apart on the galvanic scale and the aluminium corrodes away around the fastener. That's why steel bolts seize solid into alloy engine cases, yokes and calipers, and why getting them out years later involves heat, penetrating oil and a fair bit of swearing.

Titanium and aluminium sit much closer together electrochemically, so that reaction is far less aggressive.

Threads are where a fastener gives itself away, and it's the thing you notice most once you've got the old ones off and something better sat next to them.

Rolled threads, not cut. A cut thread is machined by removing material, which severs the grain of the metal. A rolled thread is formed by pressing the material into shape instead, so the grain follows the profile and the surface ends up harder and smoother. Rolled threads hold up better under fatigue and engage more cleanly, and it's why everything we supply is rolled. On a fastener going into an expensive alloy casting, that's not a detail worth saving money on.

Then there's thread fit. A fastener held to a tighter tolerance engages properly down its whole length rather than binding on high spots, so the torque you put in goes into clamping the joint instead of fighting friction.

And the head. Undersized hex sockets, shallow drives and flange diameters that aren't quite right are all common at the cheap end, and a shallow socket is a rounded bolt head waiting to happen.

Further up we said that on an OEM fastener the coating is the part that gives up first. We supply three finishes and none of them has that problem, though for three different reasons. It's worth knowing which is which, because it changes how they age on the bike.

Polished is bare titanium

Nothing on it at all, just the metal finished to a shine, and that's the natural colour of titanium. There's no finish to fail because there is no finish. The one thing to know is that bare titanium colours up by itself when it gets hot enough for long enough, so polished fasteners sitting close to a header can pick up a gold or blue tint over the years. It's the same effect as anodising, happening in exhaust heat rather than in a tank, and it does nothing to the fastener.

Bronze is an anodised oxide layer

The colour isn't dye, ink or powder, and nothing is added to the surface at all. Anodising thickens the oxide layer the titanium already has, and because that layer is transparent, light bouncing off the metal underneath interferes with light bouncing off the oxide surface and you see a colour. Alter the thickness by a few nanometres and the colour changes with it.

The upshot is that it can't chip, peel or flake, because it isn't sitting on top of anything. It is the surface. There's no edge for a spanner to catch and nothing to lift, and it adds no measurable thickness either, so fitment and thread engagement are unaffected.

Black is PVD

Physical vapour deposition. The coating material is vaporised inside a vacuum chamber and deposited onto the fastener a few atoms at a time, so it bonds to the metal at atomic level rather than sitting on it as a film. That's the real difference between PVD and plating or paint, both of which are layers laid over the top with an interface underneath them waiting to let go.

What you end up with is a coating a few microns thick, thin enough that fitment and thread engagement are unaffected, and considerably harder than the titanium underneath it. It's the same process used on fork stanchions, cutting tools and high-end watch cases.

The conversation usually gets framed as titanium against OEM, but there's a third option sitting between the two and it's the one that causes most of the trouble. Budget aftermarket fasteners come in steel, aluminium and titanium of an unstated grade, they all can look much the same in a listing photo, and the price is the only thing telling you which is which.

Why we don't sell aluminium nuts and bolts

Aluminium is all over the budget market and it's easy to understand why. It's cheap, it anodises in every colour going, and it's lighter than titanium. We don't supply aluminium nuts and bolts, and we're not going to.

It's considerably weaker than either steel or titanium, and the threads deform and strip far more readily. The bigger issue is fatigue. Steel and titanium have a fatigue limit, meaning that below a certain load they'll take the cycles indefinitely. Aluminium doesn't work that way. It accumulates damage under repeated loading no matter how lightly it's loaded, so with enough time it will eventually let go.

So for anything with a thread on it that's actually being torqued up and holding something together, we'd rather you left the OEM steel where it is than went to aluminium.

Washers are a different question

We do supply aluminium washers, and we'll happily put them on load-bearing applications. Exhaust mounts are where ours see the most use.

That isn't us contradicting ourselves, because the loading is nothing like a bolt's. A bolt is stretched and cycled in tension, which is precisely the condition aluminium is worst at, and it has to carry thread engagement on top of that. A washer only ever works in compression, spreading clamp load across a wider area and protecting the surface underneath the fastener head. None of the failure modes that rule aluminium out of a bolt apply to it. Different job, different material choice, and there's no reason to pay for titanium where aluminium does the job properly.

The drilling is purely to take weight out. The material comes from the parts of the washer that aren't in the load path, so what's left still carries the clamp load exactly as it should. That's another thing you can do to a washer and can't do to a bolt.

Leave stretch bolts alone. Some fasteners are deliberately torqued past their yield point so that they stretch and hold clamp load that way, which makes them single-use by design. The manual will tell you to fit new ones on reassembly. Cylinder head bolts are a common example, and depending on the bike you'll also find them on flywheel and crankshaft bolts and some primary drive fasteners. They're engineered around the behaviour of one specific material, and a titanium substitute isn't a like-for-like swap.

Fitting them properly

There isn't much to it, but it's worth doing in order. Titanium can gall, which means the surfaces can micro-weld under load if they're run dry.

Put a copper or nickel-based anti-seize on the threads. Nickel is the better choice anywhere hot. Silicone spray and light lubricants won't do the job here, because they won't survive assembly torque and they do nothing about galling.

Start every fastener by hand and make sure it's running true before a tool goes near it. Titanium galls when it's forced, and cross-threading an alloy casting turns a ten-minute job into an expensive afternoon.

Torque to the figure for the fastener you're replacing, using a torque wrench rather than going by feel.

And clean the threads in the receiving component first, because dirty threads give you a false torque reading every time.