Hey all, 

 

I read a lot about tyre pressures for trials being in the range of 3-5 psi for the rear and 5-6 for the front. Obviously this depends wildly on terrain, rider weight, skill. But my question today is when do you actually check these pressures? I know that if I was to put 4 psi in my rear in the shade, after a quick ride in the sun this becomes 5 psi. Am I looking at setting the pressure to say a pressure and then just expecting that it will go up? Or am I suppose to ride it around then come back and adjust tyre pressures to the correct values? I guess in essence I'm asking is the tyre pressure a cold or hot measurement? If a rider says he/she runs 4 psi in the rear, are they really running 5 psi warm?

Edited July 5, 201511 yr by jml

The best answer is probably: It depens.

 

I always meassure them cold and expect it will go up a bit. But that just depends on what measurement you are aiming at/or talking about with friends.

 

 

 I usually check it right before I ride. If it`s a wet day, I set it on the low side. If it`s hot and dry, I keep a visual eye on the sidewall. World round in 1990, Globe Arizona. Jordi`s mechanic would check the tire pressure every time  he rode this big rock for the crowd. Like a dozen times!

Also you need to get a feel for it, setting it on a specific psi or bar only works if you know the right pressure to begin with.

 

Much sand, bit lower, try putting it wrong some times and see the difference! (once got a couple of fives because forgot that I. in a hurry did 1.5 bar and forgot to let it off again because I was helping others)

 

More sharp stuff, try keeping a bit harder.

Wtc minders as stated above check at every section I do it twice usually once before I start and again either a few sections in or when there is a slippery section etc.

Choice is yours but it won't change vastly unless temperature changes by 10 degrees

It's a hot measurement.

Once before the start, in between if in need.

 

After the trials I pump the tires up again they do roll easier up and down the trailer also the tires won't get flatten by the tie downs.

The best answer is probably: It depens.

 

I always meassure them cold and expect it will go up a bit. But that just depends on what measurement you are aiming at/or talking about with friends.

 

Let's say your aiming for the typical 4 rear, 6 front. Would you be putting in 3 psi expecting it to rise to the target of 4 psi, or would you be setting a cold temp of 4 psi and knowing it will rise to 5 psi?

 

It's a hot measurement.

 

So would you ride around first, come back and then check pressures?

Here's what I typically do.  Maybe over-kill, but, I like to keep it as close as possible to what feels right to me.  Unload and adjust pressure before I go for a little warm up ride.  Then adjust pressure just before my start time.  Adjust pressure before start of each additional loop.  Our events are usually three loops so I typically end up checking my tire pressure four times during the day.  I typically have to let a little air out each time I check it--but not always.  If I were riding a long single loop event, I would carry a gauge with me and check a few times during the day.  I like to run around 3.5 psi in the rear and 5.5 psi in the front with my gauge--your gauge may read differently or a little more or less air may feel right to you.

scottj that sounds like the kind of strategy I will take on-board. I've been setting pressures right after unloading the bike and then riding the rest of the event with those pressures. So this would atleast give me a better idea of what the tyres are doing throughout the event.

Or you can run nitrogen and set it and forget it ....

Mine hardly ever gets checked after a new tyre gets bedded in. Start with about 3.5 to4 ish and add a little when it starts to roll around too much on the sidewalls.

You'll soon get the feel of what its doing and what it should be doing. Experiment with between 3 and 6psi and find your happy medium as different pressures suit different riding styles.

Let's say your aiming for the typical 4 rear, 6 front. Would you be putting in 3 psi expecting it to rise to the target of 4 psi, or would you be setting a cold temp of 4 psi and knowing it will rise to 5 psi?

 

 

So would you ride around first, come back and then check pressures?

 

My point is that the measurement itself does not say that much. It must feel good, with good grip and results. Than measure, and try to learn yourself a good fealing. and than you will have (hot) measurements to refer back to in similar conditions.

Let's say your aiming for the typical 4 rear, 6 front. Would you be putting in 3 psi expecting it to rise to the target of 4 psi, or would you be setting a cold temp of 4 psi and knowing it will rise to 5 psi?

 

 

So would you ride around first, come back and then check pressures?

 

My point is that the measurement itself does not say that much. It must feel good, with good grip and results. Than measure, and try to learn yourself a good fealing. and than you will have (hot) measurements to refer back to in similar conditions.

I run 4 and 6 with nitrogen , If REALLY slippery , may go to 3.5 in the back ...

But I'm a old fart on a old bike . and she hooks up really good no matter what I do .

 Now my section ( my modern bike ) will be a learning experience , As I've got a new set of X-lites to mount on her to replace the rock hard dunlops ...

Right now at 3 psi in the rear you might as well have a slick on her ... When it gets traction , I'm gonna have to learn how to ride again ...

Glenn

 But play with pressure and see what your comfortable with , DON'T over think it ... learn to FEEL what works !