Tyre pressure query

[Paultr]

Apologies as this thread is not strictly related to electric bikes other than it concerns my bike which is electric.

I have a Cannondale hybrid bike which I have put a motorised rear hub on. I am looking for puncture options so have recently bought a spare inner tube to carry around with me.

My question is that my tyres (Panaracer Comet Hardpack 700 x 38C) have a stated tyre pressure on them of 44psi - 3 bar but the new inner tube (Specialized 700 x 28-38C) says 15psi - 1 bar on the packaging.

Can I and should I ignore what the inner tube says and follow the tyre recommendations or have I got the wrong type of inner tube ?

 

[Gubbins]

Could the 15psi be a minimum perhaps?

 

[Paultr]

Could the 15psi be a minimum perhaps?

I have never been very good with these type of graphics but this one seems a bit obscure - any Idea what they mean ?

 

[JPGiant]

I think that means - a minimum of 15 psi is required to properly seat the tyre bead on the rim.

 

[Paultr]

Could the 15psi be a minimum perhaps?

Yes, bingo - you are right. Looking at the graphic again (I hate these instructional graphics) it seems to say it is the minimum pressure to maintain a seal.

 

[Paultr]

I think that means - a minimum of 15 psi is required to properly seat the tyre bead on the rim.

Thanks - our posts crossed - see my photo of the graphic on the box.

 

[JPGiant]

You're welcome, nice to see other members on the forum so early in the day.

 

[Fat Rat]

At least they could have been more accurate
1bar = 14.5psi

 

[seosamh1977]

I reckon you'll need much more than 15psi to seat a tyre properly. on my continental xkings i usually need to hit at least 50psi to seat them properly, then deflate to my required pressure(usually 32psi rear(2.2in tyre), 27psi front(2.4in tyre)). On my 1.75 Vittoria Rubino slicks, i usually need to hit about 80psi to seat the tyre properly, then i'll deflate to 60psi rear and 55psi front for those.

Essentially just keep pumping till you hear the tyre pop on, it might take a few pops. Then visually check the tyre is even all the way round on both sides.

Max psi, always go with what it says on the tyre and work backward from there to your desired psi(you don't really want to run max psi tbh, how low you need will vary on the conditions you ride). Lower pressures mean more grip and comfort. (don't go too low, you'll start risking pinch flats.)

Tubeless is another option some people swear by these days, too much flaff for me though.

 

[Paultr]

.....
max psi always go with what it says on the tyre and work backward from there on you desired psi(you don't really want to run max psi tbh, how lo you need will vry on conditions you ride). lower pressures mean more grip and comfort. ( don't go too low, you'll start risking pinch flats.)
.....

Is what is stated on the tyre the maximum pressure and not the optimum/recommended one ?

I realise it is trial and error but when you say work backwards from the max pressure what sort of values are typical - my max is 44psi so would say 35 psi be a good starting point ?

 

[Fat Rat]

Is what is stated on the tyre the maximum pressure and not the optimum/recommended one ?

I realise it is trial and error but when you say work backwards from the max pressure what sort of values are typical - my max is 44psi so would say 35 psi be a good starting point ?

Only your going to know what pressures to run
Rider weight
Bike (tyre and wheel size)
Type of terrain
Style of riding
All makes a difference just whatever you choose stay in manufacturers specs and you will have no issues .

 

[seosamh1977]

Is what is stated on the tyre the maximum pressure and not the optimum/recommended one ?

I realise it is trial and error but when you say work backwards from the max pressure what sort of values are typical - my max is 44psi so would say 35 psi be a good starting point ?

Yes, the maximum is exactly that, the top of the range(don't go higher. You can just to seat the bead but running pressure when out should always be below the stated pressure ). A tyre will usually run pretty harsh at that full whack. 35psi on that tyre is a good starting point, yes, depends what kinda riding you do though. As mentioned above, your weight etc will affect things. If off road, you could go lower, if on road could maybe go higher. It's really just a case of finding a sweet spot that you like. So experiment a wee bit. Lower pressures smooth out the bumps and allow your tyre to deform around them, so the bumpier the ride, lower pressure will make it more comfortable and will give you more grip.

Tyre pressure isn't really a constant, once you get to know a tyre, you can tailor the pressure to the type of ride you are doing.

Just be careful of going too low, ie sub 25psi on those tyres, you'll start risking pinch flats below those pressures. Again that's dependant on your weight, lighter riders can go lower, and it also depends on how aggressive you ride and on what terrain.

Every tyre is different though, the higher volume the tyre the lower the max psi will get. Ie on road bikes, with skinny 23mm tyres, will probably be having psi's of 100+. Fatter tyres much less so, volume means max rating on tyres will be lower. For example, 4 inch fat bike tyres can be run under 10psi.

So really, it's something you just need to investigate and get to know, you'll get it after a while.

Generally too, lower pressures mean more rolling resistance(ie slower), but there's a sweet spot for a particularly journey. But it's not always the case that higher pressures are always faster. If a tyre is nicely deforming over the bumps in your ride, it's actually faster than if it's too high a pressure.

Also check your tyre pressures regularly, air will seep out over time.

 

[mike killay]

This is of course one of the major disadvantages of the various solid tyres on the market.

 

[Gubbins]

This is of course one of the major disadvantages of the various solid tyres on the market.

I have solid tyres.. or at least it sometimes feels that way on the MP's....

 

[flecc]

I have solid tyres.. or at least it sometimes feels that way on the MP's....

Yes, they are what I'd call semi-solids. As shown here:


.

 

[Gubbins]

Yes, they are what I'd call semi-solids. As shown here:
View attachment 25424
.

Can't see your clipboard image but yes they are hard if you blow them up! I generally have them around 30 psi and I assume I am still safe from pinch flats.

 

[flecc]

Can't see your clipboard image but yes they are hard if you blow them up! I generally have them around 30 psi and I assume I am still safe from pinch flats.

That's odd, it's an ordinary small file *.jpg. I've reinserted it with a rename to see if that works for you.
.

 

[Gubbins]

That's odd, it's an ordinary small file *.jpg. I've reinserted it with a rename to see if that works for you.
.

That's odd! Both show as a small broken square.
I wonder if it's my phone that needs some permissions after an update.
Will look on pc later..

 

[Gubbins]

Can't see your clipboard image but yes they are hard if you blow them up! I generally have them around 30 psi and I assume I am still safe from pinch flats.

clearly its my phone.. and yes I know about the construction.. Trade away Grip and Flexibility for puncture protection..

 

[Paultr]

Yes, the maximum is exactly that, the top of the range(don't go higher. You can just to seat the bead but running pressure when out should always be below the stated pressure ). A tyre will usually run pretty harsh at that full whack. 35psi on that tyre is a good starting point, yes, depends what kinda riding you do though.
.....
.....

No wonder I am feeling every bump as I have mine at the max pressure ! I could have also saved myself a few quid as I had to go out and buy one of those stirrup type pumps as putting 44psi in with my little bike pump was too much of a tall order. First job of the day is to reduce them and I am looking forward to a softer ride.