Is there a average psi or is it just the range printed on the tire?

[CanucksTraveller]

Aha!

Yeah sorry, I should have been clearer.

Ok my bikes a hybrid that's why it's got range of 40-65 psi

If it rains, I've heard it's better to have a lower psi to get more grip is this true or a myth?

Not sure that can be altogether true, you could probably more successfully argue that a higher pressure displaces water better... on balance I'd say that 45 PSI vs say, 55 PSI wouldn't materially affect rain grip to any huge extent... If the road is that slippy, it's slippy.


My town bike / hybrid thing is about the same pressure range and I ride them at the top end, rain or shine. But I carry a lot of weight with the shopping on board, and I'm fairly hefty too, so lower pressures may risk pinch flats. Depends on what your weight is and what your prefer. At least you're actively thinking about it and you know the range... you see some daft buggers riding around on BSOs with virtually flat tyres. Must be like riding through sand.

 

[Ming the Merciless]

In these days of supple casings and compounds for tyres the pressure does not affect real world rolling resistance as much a people think. So find a pressure in that range that is comfortable for you. Generaally you will have less weight on yhe front tyre so you want lower pressure up front. Higher pressures make it feel faster but unless you are on a oerfectly smoith road it will not be.

 

[Yellow Saddle]

In these days of supple casings and compounds for tyres the pressure does not affect real world rolling resistance as much a people think. So find a pressure in that range that is comfortable for you. Generaally you will have less weight on yhe front tyre so you want lower pressure up front. Higher pressures make it feel faster but unless you are on a oerfectly smoith road it will not be.

Road roughness is added over and above smooth-road rolling resistance. I other words, if a tyre in a batch has the lowest RR on smooth road, it will also have the lowest RR on rough road. Further, tyre pressure is always positively related to RR, no matter what compound or casing the tyre is made of.

 

[KnackeredBike]

My understanding, possibly imperfect, is the the reason why there reaches a limit in tyre pressure/faster ride is that the harder the tyre, the faster you jiggle around. And jiggling around 80kg or whatever of you requires energy too. The actual energy losses in rolling resistance in the tyre will improve, in theory, infinitely.

That's why track bikes can have solid wheels, because the surface is smooth so zero jiggling required.

 

[Yellow Saddle]

My understanding, possibly imperfect, is the the reason why there reaches a limit in tyre pressure/faster ride is that the harder the tyre, the faster you jiggle around. And jiggling around 80kg or whatever of you requires energy too. The actual energy losses in rolling resistance in the tyre will improve, in theory, infinitely.

That's why track bikes can have solid wheels, because the surface is smooth so zero jiggling required.

Something like that, but not quite. The Rolling Resistance (RR) doesn't increase infinitely. RR decreases with pressure and there is a point of diminishing returns which is slightly below the discomfort level. But it never turns back. In other words, harder and harder always produces less RR even if the improvement curve flattens out.

However, suspension losses kick in when the tyres are so hard that you start to jiggle. It has nothing to do with suspension as in springs and shocks, but bits of your body that jiggle around, as you said. The harder the bike shakes, the more energy is lost in shaking your body. Slack muscle is highly damped, in other words, it loses energy and doesn't return it on the rebound.

 

[User16625]

View attachment 376490

Based on my weight, thats 95 PSI for a 700cx25 tyre. Sounds about right.

 

[Yellow Saddle]

Based on my weight, thats 95 PSI for a 700cx25 tyre. Sounds about right.

You missed something in the third line, I think. I get 94.47 recurring.

 

[Randombiker9]

thanks guys

 

[confusedcyclist]

Ok, ok, if you can't tell us what the ideal pressure for every possible road surface condition and rider variable, can you answer me this...

What is your favourite colour?

 

[AndyRM]

Ok, ok, if you can't tell us what the ideal pressure for every possible road surface condition and rider variable, can you answer me this...

What is your favourite colour?

42.

 

[Brahan]

Tyre

 

[Profpointy]

What the hell Is that Maths. I have no clue how to work that out :P

I believe it's something to do with quantum physics , but don't quite know what. I recognise Paul Dirac's "bra" and "ket"notation ie the angled brackets, but don't know how this works. Doubtless it's in one of my many physics books that's a bit too hard for me

 

[LewisLondon]

You missed something in the third line, I think. I get 94.47 recurring.

Now, is that 94.47777777(etc), or 94.4747474747474 (etc)?

 

[Andy_R]

I'm surprised no one has mentioned to pump up the inner tube to the recommended PSI when it is out of the tyre....how lax of you lot.

 

[Edgy Dee]

There was a good article in Bicycle Quarterly on this subject, published here:
https://www.compasscycle.com/wp-content/uploads/2015/03/BQTireDrop.pdf