Tagged: 6mm

We Need To Torque About Bolts

(from left to right) US 1/4″, large-head 6mm, regular (hollow) 6mm, and a crank bolt for comparison…

Read: A Rough Guide To Making Your Bolts Last Years Rather Than Months.  Excuse the appalling pun I chose for the main title… it makes more sense if you say it in an Estuary English accent.

Rusty, rounded-out allen heads, dirty, greasy, snapped bolts and stripped threads; when most people think of working on their bike in any form they tend to cognitively leap to these nightmare scenarios before thinking twice about the whole affair and kicking their tool box back into the dark, spider-infested abyss.  Being the ragtag bunch we are, a lot of riders don’t really think about bolts much further than a. getting a new component and b. tightly bolting it as quickly as possible to your bike so you can get out and ride but hold up there, slugger, your bolts are the only things holding the lumps of metal you call a bike together.  Furthermore they’re the only thing stopping you landing on your teeth.  Bolts deserve our uninhibited love and respect.  So how can you bolt parts onto your bike in a fashion that prevents the bolts from turning terracotta in 6 months time and binding with the strength of a thousand pickle jars?

The answers to all bolt related problems are simple enough, I’ll try and keep it snappy as I’m very aware of the fact I’m trying to make an article about fucking bolts interesting.

So before we start, what tools are you using? And how are you using them?  Rusty tools are something you should avoid like the plague, because rust spreads like such.  Rust will transfer from your tools to any exposed metal on your bolts so always keep your tool clean, dry and rust-free.  A bit of WD-40 and some wire wool is good for getting rid of superficial amounts of rust if it does build up however.  Next up, it’s always good practice to have a good amount of leverage in your tools for the job at hand.  Sure, trying to undo your rusty-ass cranks with a tiny 3 inch long allen wrench by stamping on it might indeed work… but it could easily enough put you in hospital.  A shorter allen key will almost certainly be a cheaper allen key with sharper edges- stick with something either a little longer or use something with a proper handle ie. a multitool.  Lastly, is that allen key seated properly before you turn it?  You sure?  Wiggle it a little, push it down and repeat until you’re absolutely certain.  Rounded bolt heads are literally the worst.  While we’re on the subject of rounding things off, are you still doing up your wheels with a spanner head when there’s a socket or ring spanner to hand?  Stop dat.  A spanner head only has 2 points of contact where a ring spanner or socket have 6, spreading the load more efficiently.  Your wheel nuts will last much longer.

A US Imperial 1/4″ stem bolt (left) and a ‘large-head’ 6mm stem bolt (shown right) look very similar side-by-side but use two different sized allen wrenches and two different thread pitches. They do not fit the same stem.

90% of bike mechanics is cleaning shit no one thought to clean; and this is no different.  Let’s focus on the stem for now as it’s the component with highest concentration of bolts and it’s the easiest to fuck up.  First step is to take a 6mm allen key (or a 1/4″ if your stem is American- there is a difference) and unbolt your bars.  If you’re installing new bars then it’s never a bad idea to use some glass/sand paper to sand any paint off the knurling if it hasn’t been masked off during powdercoating.  If it’s an old stem, it’s probably absolutely filthy under the stem plate, body, and bar clamping area so grab a whole load of loo roll/ paper towels and clean all that stuff away.  Do the same with the steerer tube/clamping area.  Spray some WD-40 or some degreaser to help clean stubborn dirt away if need be.  Just like your Mum told you when using the toilet for the first time, ‘Keep wiping until there’s nothing left on the paper.’  Repeat this process with the bolts and threads until everything is dry and clean.  You can just use a parts washer if you’re a flash cunt.  It’s very important to clean any dirt away, any debris left in between two parts acts as a lubricant allowing your bars and/or steerer to slip.

Now everything is dirt free you can inspect the parts for wear and damage.  If your stem plate and body have significant scratches gorged into the clamp area from slipping, this could prematurely damage any new bars you put on them and may have reduced clamping power due to having uneven clamping surfaces.  By all means, use damaged parts at your own risk if you have no other option but if they continue to slip, I highly recommend replacing.  The same goes for your bars, if they’ve been slipping about to the point the knurling on the clamp area has been ground smooth, it might just be time for some new ones.  It’s always worth checking the holes in your stem face plate for burrs caused by over-tightening (more on that later)  These burrs will make putting the bolts through them and installing your bars an extra hassle as the bolt threads will ‘catch’ on the faceplate.  This can be remedied slightly by filing them with a round file.  Prolonged over-tightening of those bolts will warp the faceplate creating further burrs and warping until it eventually fails and takes your face with it…

Lets say everything is gravy with your bars and stem, before you go and bolt them back on, pop a little of that thin ‘3-in-1’ type oil onto your bolt threads to keep them from oxidising over long periods of time and making it a pain to undo them again.  Grease of varying kinds works well too but takes longer to clean when it becomes dirty.

This paragraph will seem to many like I’m stating the obvious, but you don’t know until you know… and plenty don’t.  Most stems will have four stem plate bolts and they’ll have one of a few ways of fastening them.  The most common and traditional way is to tighten the four bolts incrementally and evenly in an ‘X’ pattern, another is occasionally used on top load stems and involves tightening two shorter front bolts fully against the stem so the plate and body are touching before tightening the two rear bolts to tighten everything in place.  Sometimes the plate will be on a hinge, sometimes in two pieces, this changes stem-to-stem so it’s always best to check with the shop from where you bought it or the manufacturer website if completely unsure.

Over-tightening is something we’ve all been guilty of at one point or another, particularly when it comes to stems, and yet is probably the easiest way to kill a part.  I understand the reasoning behind it, it’s the logical thing to do in most people’s heads; if your stem’s slipping wrench the shit out of the bolts with a long ass allen key to clamp it tighter! The only thing you’ll find is it puts totally unnecessary amounts of stress on your parts (sometimes to the point the pinch bolts at the back cause the two sides of the stem to touch, or the bars and steerer get crushed out of shape) and still your stem will slip about like a greased up pig in a Vaseline factory.

Example of a large torque wrench- 12-60Nm


In MTB and road cycling, manufacturers often print torque settings onto their parts so you know exactly how tight to do up each bolt.  Contrasted against BMX, most people couldn’t tell you what a torque wrench even was…  mainly because they cost a small fortune and are far from essential.  Even I don’t own one of my own.  A torque wrench is essentially a standard ratchet wrench with a built in mechanism that clicks when you reach a desired tightness in a nut or bolt to indicate when to stop.  Getting your hands on a torque wrench and working with one for a while can teach you to gauge what kind force to put into bolts just by feeling them.  In this section I’ll approximate and describe to the best of my ability what each kind of bolt requires in the way of force, as well as the rest of the bolts on your bike as a comparison.

  • Wheel bolt/nut- 55 N m+ (Pretty much as hard as you can tighten it without shitting/ hurting yourself, you don’t want a saggy chain every time you do an ice pick do you?)
  • Crank bolt- 40-50 N m (Pretty damn tight, not putting your entire weight into it, but most of it- stopping when you feel a lot of resistance)
  • Pedal spindle- 30-35 N m (You don’t want to be using a ton of force- stop when you begin to feel increasing resistance in the pedal spanner)
  • Pivotal seat- 25-30 N m (Pretty much the same as above- just with an allen key, so there’s less leverage involved)
  • 1/4″ and large-head 6mm stem bolts– 20-27 N m (Tighten until you feel the threads slow you down, then tighten by an extra 1/8th of a turn or so.  You should feel like you’d be able push the bolt round a fair bit more if you put some elbow grease into it… don’t though.)
  • Standard 6mm stem bolt– 15- 19 N m (Simply tighten until you start feeling resistance, then stop.  It’s best to stick to the lower end of the Nm scale if your bolts are also hollow)
  • Seat clamp- 7-15 N m (lightly tighten until you feel the bolt becoming a little harder to turn but not fully resisting- you can test by trying to turn the seatpost)
  • Brake hardware- 3-6 N m (brake hardware uses smaller bolts and needs less in the way of torque, just enough to stop the bolt moving when the calipers are pivoting)

The overwhelming voice in some people’s heads will scream, ‘It’s not tight enough! Tighten it more! Tighter is safer!’ but it’s hardly ever the case.  Your first port-of-call should always be to clean the affected component before you try torquing your bolts any tighter than you already have.  Bike mechanics often work under the cautionary mantra of ‘try the least dramatic fix first’ even if that fix is simply to break out some clean toilet roll and give everything a good ol’ scrub.