Tyre pressure checking for the complete novice.

I’ve watched new and experienced bikers try this comparatively simple task and fail repeatedly, so here’s number one in a series of basic maintenance tasks for beginners: a walk through of one of the most vital pre-ride safety checks there is… 

Preconditions:

You’ll need a pressure tester (I talk about testers here) and your bike’s tyres should be measured cold. They mustn’t be hot from a ride or have been left in the sun all day. Why is this? Because tyre pressure changes with temperature is why. If you measure your tyres at 31psi while they’re hot, they will fall below this reading when they cool. Underinflated tyres can be dangerous, not to mention the fact that they’ll make your normally sprightly steed feel like a wheelbarrow full of gravel – so learn the good habit of checking tyres in the morning before a ride.

Also it seems obvious but try and habitually do this when you have access to a pump, like at a garage or when you have a retro footpump handy (remember them?) If you need air or balls this up, you’ll need that pump.

Method: 

Check your manual to find your pressures. They differ front and rear and the rear is always higher. Sometimes tyre pressures are also placed on a sticker under the seat like this:

under seat tyre pressure label BMW
Very handy for people who lose owner’s manuals

As you can see, you’ll need to decide if you will be generally riding one up, with a pillion or with a pillion and luggage. Rear tyre is on the left, front on the right.

Next check your units. Does your manual give you info in PSI (pounds per square inch) or BAR? Low numbers like you see on the sticker above (2.5, 2.7, 2.9 etc) are in metric BAR. If your manual gives a higher number like 32 or 36 for example, it will be in PSI (sometimes confusingly written as lbf/in2). Just make sure you have an appropriate gauge that you can measure with.

Now take off your dust caps and don’t lose them.

schrader motorcycle valve and dust cap

Dust caps are important especially if you ride off road. They include a seal which keeps dust out of the clever ‘Schrader’ valve mechanism which, rather amazingly, was designed in the late Nineteenth century. Old tech is good tech as they say.

Next the tricky bit. To check the pressure you must place your chosen tester squarely against the top of the valve and push down sharply and firmly against the valve to make a seal between the valve and the tester. When you do this, a small shh of air will escape (this is normal) which must cease immediately as you push down further so you get an accurate reading of pressure.

If you apply the tester skew-wiff, you’ll just get air coming out continually and you have to blow the tyre up again. If you don’t press down firmly – the same. Air will escape continually as you fiddle and you will have to pump up your tyre again. So here we go in pictures:

analogue tyre pressure tester
Here’s a typical analogue tester. It has both scales – imperial and metric.
analogue tyre pressure tester head
…and here’s the business end of the tester which you apply to the valve.

Your aim will be to apply the end of the tester to the valve. When you do, the little nodule in the end of the tester you can see will open the tyre valve and allow air to rush momentarily into your tester. The circular rubber seal around this nodule connects with the valve head as you push and stops air escaping into the atmsophere.

pen gauge tyre pressure tester head
Here’s the end of a pen gauge – exactly the same design. Little piece in the middle which pushes down the valve and a rubber sealing ring around it.
schrader valve
Here’s a detail of the top of a schrader valve with the valve mechanism visible in the centre. This is what you’ll push the tester against. When that bit in the centre is depressed, air will rush into your tester to give you a pressure reading.
tyre pressure check 2
So apply your tester and Aieee! What are you doing?! I said SQUARELY
tyre pressure check 1
You had one job!
tyre pressure check 3
Ahhh. Happy endings.
tyre pressure check 4
Push down squarely and firmly. There will be a quick hiss then no more air should escape as your gauge reader registers the pressure (If you’re using a pen gauge like I am here, make sure the piston that shoots out and gives a reading doesn’t hit you in the hand and give you a false result). Remember, don’t fear that brief shh of air – it’s normal. Air continually escaping is called a ‘cock up’. We are not at home to Mr Cock up.

Now take a look at the reading and see if you need to adjust. Here’s a gauge from a pen reader as an example. Analogue ‘clock face’ gauges are more simple to read. Pen gauges are read at the interface of the piston and pen barrel. This one says 36psi.

reading a tyre pressure gauge pen

If you need to top up, do so with a garage pump in short two second blasts then re-check.  Fitting the garage pump head is the same process – squarely and firmly. Ask help if you need – it’s no big deal and no one was born knowing these things, even smug gits. If you need to reduce pressure, just use the tip of your ignition key to press down the valve centre to remove air. Again, a short blast is all you need to adjust up or down a few psi.

That’s it newbie mechanic. Learn this well. It’s one of the most important safety checks you can do for your bike.

Final Money-Saving Tip: If you ever discover your tyres going slowly flat and find the valves are leaking after putting a bit of fairy liquid over the top of the stem and seeing bubbles appear, don’t let a tyre fitter tell you that you need new tubes/have to pay to have your tubeless tyres to be de-rimmed to fit new valves. Just have them replace the valve inners – they screw out easily with the correct tool and cost just a few pence each.

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