A question of Pneumatics.

salmon said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.
Apart from the fact that if the pressure is low my thumb will deflect
the tread quite easily, I still wouldn't know whether I had got to the
optimum pressure. What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Without a gauge, you just have to use your own judgement.

You'll be able to press much harder into the tyre, therefore get a better
idea of the pressure, by pressing *both* thumbs into the *sidewall*, rather
than one thumb into the tread. Position both thumbs next to each other and
support the other side of the tyre with fingers, then dig thumbs in as hard
as you can. There should be some compression, but for road cycling at
least, it should be difficult, and painful after a second.

You do need a proper gauge to learn what the tyre manufacturer's
recommendation feels like, but you don't have to follow it. If you have
experience of what works best for you, then that's the "ideal" pressure and
the thumb test will let you reproduce it to within 15 psi. So you don't
need to know what the pressure is in psi, you just need to know it's about
the same as usual.

Note. On most bikes the rear tyre should be harder than the front because it
takes more weight. So you should be able to press your thumbs further into
the front tyre.

~PB

salmon said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.
Apart from the fact that if the pressure is low my thumb will deflect
the tread quite easily, I still wouldn't know whether I had got to the
optimum pressure. What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Thats what I picked up too, inflate till you can't push the tread in then let a
little air out so there's some give for when you cycle over rougher patches of
the road.

--
Stephen Patterson :: [email hidden] :: http://patter.mine.nu/
GPG: B416F0DE :: Jabber: [email hidden]
"Don't be silly, Minnie. Who'd be walking round these cliffs with a gas oven?"

Quoted message said:

What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Dunno, but one of the things that made cycling oh-so-much more pleasurable
was a cheapo track pump with a gauge. Tyres are pumped up in seconds.

Pete Biggs said:

salmon said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.
Apart from the fact that if the pressure is low my thumb will deflect
the tread quite easily, I still wouldn't know whether I had got to the
optimum pressure. What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Without a gauge, you just have to use your own judgement.

You'll be able to press much harder into the tyre, therefore get a better
idea of the pressure, by pressing *both* thumbs into the *sidewall*, rather
than one thumb into the tread. Position both thumbs next to each other and
support the other side of the tyre with fingers, then dig thumbs in as hard
as you can. There should be some compression, but for road cycling at
least, it should be difficult, and painful after a second.

You do need a proper gauge to learn what the tyre manufacturer's
recommendation feels like, but you don't have to follow it. If you have
experience of what works best for you, then that's the "ideal" pressure and
the thumb test will let you reproduce it to within 15 psi. So you don't
need to know what the pressure is in psi, you just need to know it's about
the same as usual.

It is my conclusion from threads on RBT that what you feel when you
squeeze a tyre like that is basically casing tension rather than
pressure-- in other words that fat tyres will feel harder at lower
pressures than thin ones. Therefore as a rule of thumb all tyres should
feel about the same ("good and hard"😉, whether they're fat MTB tyres or
thin racer tyres.

Anyone interested can see

http://tinyurl.com/2pehew
or
http://groups.google.co.uk/group/rec.bicycles.tech/browse_thread/thread/ec91d3709c1bf634/1bf12937a4e9c33b?hl=en#1bf12937a4e9c33b

and

http://tinyurl.com/2k4f5q
or
http://groups.google.co.uk/group/rec.bicycles.tech/browse_thread/thread/527b6e3202300638/43dbe855b4e86e64?hl=en#43dbe855b4e86e64

in message <[email hidden]>, salmon

(') said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.
Apart from the fact that if the pressure is low my thumb will deflect
the tread quite easily, I still wouldn't know whether I had got to the
optimum pressure. What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Until you know what your tyres feel like at the right pressure, there isn't
one. Once you do know what your tyres feel like at the right pressure,
then you want to get them to feel that hard. Go to your friendly local
bike shop and ask to borrow their track pump, which will have a gauge.
Pump your tyres up to the maximum recommended pressure shown on the
sidewall. Feel your tyres, and remember that feeling. Alternatively, buy a
track pump!

Generally speaking, for use on tarmac, the harder your tyres are the better
they'll roll and the less work you'll have to do. Tarmac provides
excellent grip and it isn't practically possible to get your tyres too
hard for good grip on tarmac. If you're mountain biking on loose or slimy
surfaces, then there is a compromise to be made between rolling resistance
and grip.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; Conservatives are not necessarily stupid,
;; but most stupid people are conservatives -- J S Mill

Simon Brooke said:

Generally speaking, for use on tarmac, the harder your tyres are the better
they'll roll and the less work you'll have to do.

True, but hard tyres aren't so comfy over the rough patches and
potholes you find in the real world. Unless you're going for ultimate
speed it's a compromise. Also, on some kinds of rough tarmac it feels
to me like harder work if the tyres are hard because of all the
vibrating, a slightly softer tyre rides more smoothly and the bike
feels easier to propel.

POHB said:

Simon Brooke said:

Generally speaking, for use on tarmac, the harder your tyres are the better
they'll roll and the less work you'll have to do.

True, but hard tyres aren't so comfy over the rough patches and
potholes you find in the real world. Unless you're going for ultimate
speed it's a compromise. Also, on some kinds of rough tarmac it feels
to me like harder work if the tyres are hard because of all the
vibrating, a slightly softer tyre rides more smoothly and the bike
feels easier to propel.

You may be right about that.

Rolling resistance is measured with smooth steel drums, and these tests
indicate that the higher the pressure the lower the RR. But tests on
real roads sometimes find different conclusions, although there is also
more possibility of error in the results.

Here's another recent RBT thread, which describes a test in Bicycle
Quarterly, one of whose findings was:

Tire pressure has only a small effect on the rolling resistance of
most tires. Narrow 23-mm tires seem to roll fastest at pressures of 105
psi (7.2 bar) or more. However, running these tires at 85 psi (5.8 bar)
for improved comfort increased the test times only 2%. Wider 28-mm
tires are as fast at 85 psi as they are at higher pressures.

http://groups.google.co.uk/group/rec.bicycles.tech/browse_thread/thread/e0a8bca86795ebb5/572ff48dadfc7d1a?hl=en&

Simon Brooke said:

in message <[email hidden]>, salmon

(') said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.
Apart from the fact that if the pressure is low my thumb will deflect
the tread quite easily, I still wouldn't know whether I had got to the
optimum pressure. What is the correct procedure for pumping up tyres
to the ideal pressure using a hand pump without the need for a
pressure gauge please?

Until you know what your tyres feel like at the right pressure, there isn't
one. Once you do know what your tyres feel like at the right pressure,
then you want to get them to feel that hard. Go to your friendly local
bike shop and ask to borrow their track pump, which will have a gauge.
Pump your tyres up to the maximum recommended pressure shown on the
sidewall. Feel your tyres, and remember that feeling. Alternatively, buy a
track pump!

Generally speaking, for use on tarmac, the harder your tyres are the better
they'll roll and the less work you'll have to do. Tarmac provides
excellent grip and it isn't practically possible to get your tyres too
hard for good grip on tarmac. If you're mountain biking on loose or slimy
surfaces, then there is a compromise to be made between rolling resistance
and grip.

and if on rocky ground, the possiblity of snake bites, and such at low
pressures, having a sprung bike helps for drops and such, but still a
possiblity on tight turns on rocky rooty areas.

you find what works for, you. i've allways liked mud tires, prone to
snake bites and poor traction on road, but they grip very well in loose
stuff.

roger

in message <[email hidden]>, Roger Merriman

(') said:

and if on rocky ground, the possiblity of snake bites, and such at low
pressures, having a sprung bike helps for drops and such, but still a
possiblity on tight turns on rocky rooty areas.

you find what works for, you. i've allways liked mud tires, prone to
snake bites and poor traction on road, but they grip very well in loose
stuff.

For mountain bikes, I very much like Velociraptors. Not the fastest or
lightest tyres and don't like wet roots, but cope well with mud, rock,
loose gravel - and don't p*nct*re easily.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Let's have a moment of silence for all those Americans who are stuck
;; in traffic on their way to the gym to ride the stationary bicycle.
;; Rep. Earl Blumenauer (Dem, OR)

Simon Brooke said:

Alternatively, buy a track pump!

Don't buy the red one from Halfords! (their own brand)

I got one today and it is awful. Above 100 psi, pushing down on the handle
lifts me off the ground - I don't know how I could get a skinny tyre upto
pressure, except perhaps if I bounced about on it like a pogo stick.

FWIW, my highest pressure tyres recommend 110-145 PSI. The pump is going
back for a proper one.

Jim Higson said:

FWIW, my highest pressure tyres recommend 110-145 PSI. The pump is going
back for a proper one.

Decathlon alloy one is brilliant. Can't remember how much it is though.
Not v dear...

Tony B

salmon said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.

To quote Schwalbe at
http://www.schwalbe.de/gbl/en/tech_info/luftdruck/?gesamt=39&ID_Land=38&ID_Sprache=2&ID_Seite=136&tn_mainPoint=TechnikInfos
"Use a pressure gauge to monitor inflation pressure. The widespread
thumb-test method is very inaccurate as all tires will feel
identically hard from a pressure of 2 bar up."
So buy yourself a decent track pump with a gauge - it should last a
cycling lifetime 🙂
Use the pressure range indicated on the tyre's sidewall: upper limit
for speed and improved puncture resistance, lower limit for comfort
and traction.

squeaker said:

To quote Schwalbe at
"Use a pressure gauge to monitor inflation pressure. The widespread
thumb-test method is very inaccurate as all tires will feel
identically hard from a pressure of 2 bar up."

Is that from their Advice for Arthritus Sufferers page?

~PB

squeaker said:

To quote Schwalbe at
http://www.schwalbe.de/gbl/en/tech_info/luftdruck/?gesamt=39&ID_Land=38&ID_Sprache=2&ID_Seite=136&tn_mainPoint=TechnikInfos
"Use a pressure gauge to monitor inflation pressure. The widespread
thumb-test method is very inaccurate as all tires will feel
identically hard from a pressure of 2 bar up."

So my being able to tell when my 100psi tyres have dropped to 70psi is
purely my imagination, is it?

Even when the gauge on the pump confirms it?

I'll file that gem of advice under "unalloyed [censored]".

Jim Higson said:

Simon Brooke said:

Alternatively, buy a track pump!

Don't buy the red one from Halfords! (their own brand)

heh think i have but i don't go behond 100 psi

Quoted message said:

I got one today and it is awful. Above 100 psi, pushing down on the handle
lifts me off the ground - I don't know how I could get a skinny tyre upto
pressure, except perhaps if I bounced about on it like a pogo stick.

i didn't have a problem there but then my highest pressure tired bike is
100psi

Quoted message said:

FWIW, my highest pressure tyres recommend 110-145 PSI. The pump is going
back for a proper one.

does sound unfit for the use you need.

roger

Simon Brooke said:

in message <[email hidden]>, Roger Merriman

(') said:

and if on rocky ground, the possiblity of snake bites, and such at low
pressures, having a sprung bike helps for drops and such, but still a
possiblity on tight turns on rocky rooty areas.

you find what works for, you. i've allways liked mud tires, prone to
snake bites and poor traction on road, but they grip very well in loose
stuff.

For mountain bikes, I very much like Velociraptors. Not the fastest or
lightest tyres and don't like wet roots, but cope well with mud, rock,
loose gravel - and don't p*nct*re easily.

mmm sure i had them a while back, don't think there is much that will
cope with wet roots bar studded tires possibly...

roger

squeaker said:

salmon said:

When I pump up my tyres, I check the pressure by grabbing hold of the
wheel and pushing my thumb into the tread. I don't know where I got
this method from and don't really know what it's supposed to prove.

To quote Schwalbe at
http://www.schwalbe.de/gbl/en/tech_info/luftdruck/?gesamt=39&ID_Land=38&ID_Sprache=2&ID_Seite=136&tn_mainPoint=TechnikInfos
"Use a pressure gauge to monitor inflation pressure. The widespread
thumb-test method is very inaccurate as all tires will feel
identically hard from a pressure of 2 bar up."

nonsense. I can gauge a difference between 9 bar and 7 bar quite
easily (although I cannot be that precise in absolute numbers

Quoted message said:

So buy yourself a decent track pump with a gauge - it should last a
cycling lifetime 🙂

That is good advice though

Quoted message said:

Use the pressure range indicated on the tyre's sidewall: upper limit
for speed and improved puncture resistance, lower limit for comfort
and traction.

Or feel free to go well above the recomended pressure. I never had a
problem runnign tyres rated for 85psi at up to 160psi before I
realised I was converting the units incorrectly. I still run 130psi
ok

best wishes
james

email hidden said:

Or feel free to go well above the recomended pressure. I never had a
problem runnign tyres rated for 85psi at up to 160psi before I
realised I was converting the units incorrectly. I still run 130psi
ok

The two times I have suffered a blow-out were on over inflated tubes.
Fortunately I wasn't riding either bike at the time, and wondered who
was firing a gun until I started to get on my bike for the journey
home.

Quoted message said:

Quoted message said:

So buy yourself a decent track pump with a gauge - it should last a
cycling lifetime 🙂

My Zefal track pump has got a broken compression lever at the valve
connector thingummy. 7 years of not particularly rigorous use, still
well worth the £20 though.

Is there a pedant in the house?