Tire Pressure Basics Part One – Cold Inflation Pressure

Talk to any riding instructor or track coach and you’ll hear an alarming number of stories of riders who don’t know what their motorcycle’s tire pressures should be.  Perhaps just as alarming is of the riders who do at least know how much air to put into their tires, they fail to understand that this recommendation is based upon a cold inflation pressure.  That is, the manufacturer’s recommendation is based upon a pressure while the tire is cold and before you’ve ridden.  You can check out the video we’ve created below, or read on.

If you remember back to basic science at school you should know that when gas is heated it expands.  It just so happens that air is made up of a bunch of different gasses, so as your tires get warmer, the air inside them expands.  Because there’s nowhere for this air to escape from the tire, pressure increases.

A basic rule of thumb is that for every 10 degree change in temperature, air pressure changes by 1 pound per square inch. Now imagine that you only ever had to put air in your tires once – it never leaked over time.  If you filled your tires to 32 psi in the dead of winter, come summer your tire would magically have an extra 4 pound of air inside.

Similarly, if you put air in your tires before a ride your tires pressure will increase quite dramatically.  Even in winter it’s not hard for a tire to increase in temperature by around 90 °F just from normal street riding.  This can be even more dramatic in the heat of summer when roads are particularly hot or if you’re really punishing the tires at the track.

Cold Inflation Pressure Temperature and Pressure Change

Reading this, you may see a problem arise for a motorcycle rider and perhaps you’ve been in the same situation before.  You’re in the mountains and have been riding for a good few hours.  As you pull into the gas station to fill the tank, you decide you’d better check tire pressures because it’s been a few weeks since you last did it.  Connecting the pressure gauge, you’re surprised to see that it’s reading 45 psi in the rear tire, when you know it’s only should be 36.  You then deflate the tires down to 36 psi and continue your ride.

Once this rider has gotten home, his tires cool down.  If that rider then checks his tires before leaving the house for his next ride, he will find them to be grossly under inflated.  That’s because when he deflated his tires during a ride, it was at a hot inflation pressure.   His pressures when he checked at the gas station were actually correct – it was merely showing 46 psi because the original 36 pounds per square inch of air had expanded during the ride.

Letting pressure out meant he was actually riding under inflated tires.  It is for this reason it’s essential to check and adjust tire pressures before a ride – a cold inflation pressure.

How to Change Your Motorcycle Grips

Learning how to change your motorcycle grips and putting new ones on your bike isn’t really high up on most peoples list of modifications, but there are reasons to do it – especially if you have an older bike where the grips are starting to wear down.  Newer, high quality grips can also improve feedback through the bars and reduce fatigue.  Different grips may also provide some riders with a bit of bling they’re looking for at a pretty cheap price.

If you’ve never done the job before it can be an extremely painful experience to remove the old grips, especially if you’re relying on sheer brute force. Some will even resort to cutting the old grips off with a Stanley knife.  But hold back on the sharp objects!  We can show you how to do it quickly and easily with the correct tools.

We’ve created a youtube video to show you the whole process, but you can also follow the instructions below.

The Tools

Obviously in addition to your new grips, you’ll need a tool to unscrew the bar ends from each bar.  Most modern bikes use some sort of bolt/screw that requires an Allen key to remove it, although some other bikes use a different type of bolt head.  This part of the job can actually sometimes be the hardest if a bolt is seized or was previously over-torqued.

Leverage will normally do the trick, so any tool that has a long length, enabling you to really push down on it (such as a long torque wrench) will help.  Another option may be an impact driver.  If you don’t own one, you can usually buy a manual impact driver (operated by hitting it on the back with a hammer) for around $10.  Before that though, employ some WD40 to see if that will coax it loose.

Changing Motorcycle Grips

Next on your list should be isopropyl alcohol (also called rubbing alcohol).  This is a great item for many automotive uses and should be in your garage anyway.  It works fantastic as a lubricant but also has the added benefit of evaporating very quickly, so you don’t lose time in waiting for it to clear.  It’s also cheap and unlike hairspray (which others sometimes recommend in removing grips), doesn’t smell.

Finally, a long flathead screwdriver and some rags for cleaning will be handy.

Old Grips

After you’ve removed your bar ends, get your long flat head screw driver and wedge it between the inside of the grip and the bar.  Push it along the bar as much as you can and leverage it up to create a gap, allowing you to spray the isopropyl alcohol onto the surface of the bar.

Repeat this all around the bar and do the same at the other end of it too, using the flathead screwdriver to create an opening to spray again.

Changing Motorcycle Grips

Hopefully with a bit of twisting and brute force, you’ll be able to pull the old grip off.  If it only budges a bit, use the screwdriver to pry the grip up off the bar and keep spraying the isopropyl.  It should eventually come free.

Once you’ve got them off, spray some more isopropyl on the now naked bars and clean up any old glue/adhesive on them.

Changing Motorcycle Grips

New Grips

Your new grips will come in two sizes.  The grip with the larger internal diameter (opening) is the one that goes over the throttle bar.

Changing Motorcycle Grips

Taking your isopropyl once more, spray again on the exposed bar.  Also spray inside the new grips.  Now place the end of the new grip on the bar from the opposite side of the bike – this way you will be pulling it towards you rather than pushing it away – a much easier task.

You again may need to employ your screwdriver here, pushing it under the new grip to help wriggle it on.  Keep spraying the alcohol on to help lubricate the grip and ease the process.  Just be careful with the grip on the throttle bar – ensure that the new grip is rotating on and off without issue.  Some may make the mistake of having it butt up against ignition switch housing – this may prevent, at best smooth throttle operation – at worse it will cause you to crash with a stuck throttle.

Changing Motorcycle Grips

You’ll notice that I haven’t made mention of using a glue or adhesive when putting the new grips on.  Personally, I feel that with the type of plastics used on the grips, they bond to the bars anyway.  If you want to change grips down the track, gluing them just causes pain in the future when taking them off.  However, others may disagree and feel gluing them is necessary.

Put your bar ends back on and you’re done.  Enjoy your new grips.