tyre pressure?

Simon Grant said:

Hi all,
Im a new cycle commuter(abt 6 weeks)and i have been concerned
about running with correct tyre pressure so i have been and bought a
raleigh gauge.The recommended psi on my tyres is 65 however i have
tested the pressure with the gauge and they are about 40 at the
moment and they feel solid.Im quite scared of blowing the tube any
more to get to 65?

You will be unlikely to burst a tube, or force a tyre off a rim.

Sheldon Brown has an article on the subject (as with most bicycle
subjects!).
http://sheldonbrown.com/tyres.html#pressure

Schwalbe (tyre maker) have a few tips on appropriate pressures in their
guides:

http://www.schwalbe.co.uk/shopdata/files/tech-info.pdf

1 bar = 14.5 psi

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Simon Grant said:

Im a new cycle commuter(abt 6 weeks)and i have been concerned about
running with correct tyre pressure so i have been and bought a raleigh
gauge.The recommended psi on my tyres is 65 however i have tested the
pressure with the gauge and they are about 40 at the moment and they feel
solid.Im quite scared of blowing the tube any more to get to 65?

If the tube blows at less than the recommended tyre pressure, you have a
dud tube and/or tyre and ought to get it replaced anyway.

A higher-pressure tyre will give you a ride that's faster for the same
effort, but also that's a bit more bumpy. Try it and see what you like.

I run all my bike tyres at the maximum recommended pressure, and trailer
tyres about 10psi below the maximum.

Roger

--
After your first day of cycling, one dream is inevitable. A memory of
motion lingers in the muscles of your legs [...] You ride through
Dreamland on wonderful dream bicycles that change and grow.
-- H. G. Wells, /The Wheels of Chance/

In article <[email hidden]>, Simon Grant
[email hidden] says...

Quoted message said:

Hi all,
Im a new cycle commuter(abt 6 weeks)and i have been concerned about
running with correct tyre pressure so i have been and bought a raleigh
gauge.The recommended psi on my tyres is 65 however i have tested the
pressure with the gauge and they are about 40 at the moment and they feel
solid.Im quite scared of blowing the tube any more to get to 65?

Any advice would be appreciated

As long as the tyre is correctly fitted, and both tyre and rim are
undamaged, you should be able to easily exceed the masimum rated
pressure without any fear of explosion. :-) Many people fail to
inflate their tyres properly, and this can cause damage to the tyre, the
rim and the tube. You don't /have/ to run at the rated pressure,
depending on your weight and the sort of riding you do a little under
may be fine, but you should try it and see how it feels.

On 22/12/2007 16:37, Simon Grant said,

Quoted message said:

Im quite scared of blowing the tube any more to get to 65?
Any advice would be appreciated

Like wot others have said! But... I don't ever fit a tyre and pump it
all the way up in one hit. Go up to about 25-30psi, stop and check all
around both sides to make sure the tyre is seated evenly. Then you go
up to full pressure! You might find that at some point the tyre "pops"
slightly - that's just it seating itself and nothing to worry about.

--
Paul Boyd
http://www.paul-boyd.co.uk/

Simon Grant said:

Hi all,
Im a new cycle commuter(abt 6 weeks)and i have been concerned
about
running with correct tyre pressure so i have been and bought a raleigh
gauge.The recommended psi on my tyres is 65 however i have tested the
pressure with the gauge and they are about 40 at the moment and they feel
solid.Im quite scared of blowing the tube any more to get to 65?

Any advice would be appreciated

It depends what you're doing. If riding on the road on narrow road tyres,
then at this time of year you want about 100psi, in summer about 110 or
120 - serious racers go up to 180psi (using 'tubs' - tubular tyres -
because conventional 'clincher' tyres may blow off the rims at that
pressure). If riding a mountain bike with fatter tyres on very loose and
difficult surfaces, you want to go as low as 30psi, in which case you
definitely want tubeless tyres because conventional tyres will pinch-flat
at that pressure. All other cycling is between those extremes.

But if you're using conventional tyres at 40psi, not only are you
working /much/ harder than you need to, but you're also at extreme risk of
punctures. If you're riding on the road go for the maximum rating printed
on your tyres, or a little above it. You might run your tyres a little
softer at this time of year because of ice, but 40psi is almost certainly
too soft.

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

;; may contain traces of nuts, bolts or washers.

Quoted message said:

Simon Grant said:

running with correct tyre pressure so i have been and bought a raleigh
gauge

Maybe also consider a track pump (aka floor pumps) they come with an
integral pressure gauge. Use it before you leave home. It's a lot
easier to pump your tyre to the correct pressure. Wiggle do loads of
them. Keeping your tyres pumped up to the correct pressure is
worthwhile.

--
Nige Danton

Quoted message said:

Im a new cycle commuter(abt 6 weeks)and i have been concerned about
running with correct tyre pressure so i have been and bought a raleigh
gauge.The recommended psi on my tyres is 65 however i have tested the
pressure with the gauge and they are about 40 at the moment and they feel
solid.Im quite scared of blowing the tube any more to get to 65?

Any advice would be appreciated

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred. If
you can deform the tyre with your thumb - it's too low.

Duncan

Duncan Smith said:

Quoted message said:

Im a new cycle commuter(abt 6 weeks)and i have been
concerned about running with correct tyre pressure so i have been
and bought a raleigh gauge.The recommended psi on my tyres is 65
however i have tested the pressure with the gauge and they are about
40 at the moment and they feel solid.Im quite scared of blowing the
tube any more to get to 65?

Any advice would be appreciated

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred.

100 psi is likely to be way too much if the manufacturer's recommendation is
65. Ok, manufacturers are conservative sometimes, but not /that/
conservative. The tyre is probably not very narrow, and wider tyres need
less psi to be equaly hard as narower ones with more psi. You should not
make a specific pressure recommendation until you know the exact size of the
tyre (at least).

The front tyre should be a bit softer than the front as well - as it takes
less weight.

Quoted message said:

If you can deform the tyre with your thumb - it's too low.

For road riding, a person with average strength (for an adult male) should
be able to deform a tyre slightly by pressing both thumbs together into the
sidewall as hard as possible.

For off-roading you might want it soft enough to deform more easily.

~PB

Thanyou everyone who has given me advice,the tyres are 26x1-3/8th for
information and the bike is a comfort bike that i use for commuting daily on
roads only.distance is 6miles each way
"Pete Biggs" <[email hidden]> wrote in
message news:[email hidden]...

Quoted message said:

Duncan Smith said:

Quoted message said:

Im a new cycle commuter(abt 6 weeks)and i have been
concerned about running with correct tyre pressure so i have been
and bought a raleigh gauge.The recommended psi on my tyres is 65
however i have tested the pressure with the gauge and they are about
40 at the moment and they feel solid.Im quite scared of blowing the
tube any more to get to 65?

Any advice would be appreciated

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred.

100 psi is likely to be way too much if the manufacturer's recommendation
is 65. Ok, manufacturers are conservative sometimes, but not /that/
conservative. The tyre is probably not very narrow, and wider tyres need
less psi to be equaly hard as narower ones with more psi. You should not
make a specific pressure recommendation until you know the exact size of
the tyre (at least).

The front tyre should be a bit softer than the front as well - as it takes
less weight.

Quoted message said:

If you can deform the tyre with your thumb - it's too low.

For road riding, a person with average strength (for an adult male) should
be able to deform a tyre slightly by pressing both thumbs together into
the sidewall as hard as possible.

For off-roading you might want it soft enough to deform more easily.

~PB

In article <cd549d43-1173-40e2-aab9-
[email hidden]>, Duncan Smith
[email hidden] says...

Quoted message said:

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred. If
you can deform the tyre with your thumb - it's too low.

Is the wrong answer. He made no mention of tyre size or loading, and
the thumb test is pretty useless (different people have different size
and strength thumbs, and different ideas of how hard they're pressing,
different tyres have more or less rigid sidewalls).
The rated pressure on a tyre is a guide to maximum inflation. Heavy
loads as encountered on expedition bikes and tandems may require
exceeding the rating, but make the tyre more likely to blow off the rim
if bead/sidewall/rim are damaged/worn/low quality or just not a good
fit. Very low pressures will increase the risk of sidewall/rim damage
and pinch punctures from kerbs/potholes/debris and cause squirmy
handling. Anywhere between the two extremes is a compromise between
comfort, puncture resistance, rolling resistance and grip. Generally I
reckon a safe range to try is 1/3 under to 1/4 over the rated pressure,
depending on use and as long as tyre and rim are reasonable quality and
condition, so the OP's tyres are probably OK for 40-80PSI.

Simon Grant said:

Thanyou everyone who has given me advice,the tyres are 26x1-3/8th for
information and the bike is a comfort bike that i use for commuting
daily on roads only.distance is 6miles each way

That size equates to 35mm - which is pretty fat. I suggest 50 to 70 psi for
an average-weight load. (That's the rider plus luggage:-)

~PB

Rob Morley said:

In article <cd549d43-1173-40e2-aab9-
[email hidden]>, Duncan Smith
[email hidden] says...

Quoted message said:

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred. If
you can deform the tyre with your thumb - it's too low.

Is the wrong answer. He made no mention of tyre size or loading, and
the thumb test is pretty useless (different people have different size
and strength thumbs, and different ideas of how hard they're pressing,
different tyres have more or less rigid sidewalls).
The rated pressure on a tyre is a guide to maximum inflation. Heavy
loads as encountered on expedition bikes and tandems may require
exceeding the rating, but make the tyre more likely to blow off the
rim if bead/sidewall/rim are damaged/worn/low quality or just not a
good fit. Very low pressures will increase the risk of sidewall/rim
damage and pinch punctures from kerbs/potholes/debris and cause
squirmy handling. Anywhere between the two extremes is a compromise
between comfort, puncture resistance, rolling resistance and grip.
Generally I reckon a safe range to try is 1/3 under to 1/4 over the
rated pressure, depending on use and as long as tyre and rim are
reasonable quality and condition, so the OP's tyres are probably OK
for 40-80PSI.

To that right answer I would add:--

Another disadvantage of low pressure is increased wear rate.

Another advantage of high pressure is lower rolling resistance (higher
speed) on smooth surfaces.

~PB

In article <[email hidden]>, Pete Biggs
[email hidden] says...

Quoted message said:

Rob Morley said:

Anywhere between the two extremes is a compromise
between comfort, puncture resistance, rolling resistance and grip.

^^^^^^^^^^^^^^^^^^

Quoted message said:

Another advantage of high pressure is lower rolling resistance (higher
speed) on smooth surfaces.

:-)

Roger Burton West said:

Simon Grant said:

Im a new cycle commuter(abt 6 weeks)and i have been concerned about
running with correct tyre pressure so i have been and bought a raleigh
gauge.The recommended psi on my tyres is 65 however i have tested the
pressure with the gauge and they are about 40 at the moment and they feel
solid.Im quite scared of blowing the tube any more to get to 65?

If the tube blows at less than the recommended tyre pressure, you have a
dud tube and/or tyre and ought to get it replaced anyway.

A higher-pressure tyre will give you a ride that's faster for the same
effort, but also that's a bit more bumpy.

There's an upper limit to this, otherwise
we'd all be riding rigid tyres.

But, yeah, most people's tyres (who aren't on this group ...)
are too soft.

BugBear

Quoted message said:

Quoted message said:

Don't worry anout what the max says: get hold of a track pump and put
in at least 80psi - when you're comfy with that go to a hundred. If
you can deform the tyre with your thumb - it's too low.

Is the wrong answer. He made no mention of tyre size or loading, and
the thumb test is pretty useless (different people have different size
and strength thumbs, and different ideas of how hard they're pressing,
different tyres have more or less rigid sidewalls).

I think you're correct - it's probably unwise to advise others against
recommended limits - but for me, my Dutch Perfects (700x32) and
Michelin Slicks 622-35 both had low a MAX. 65 and 80 respectively if
my memory serves me well, but they've both been fine in the ~100-120
psi range (so far).

Duncan

In article <539789e3-29a6-429e-a1cf-5945a41dd587
@x69g2000hsx.googlegroups.com>, Duncan Smith
[email hidden] says...

Quoted message said:

I think you're correct - it's probably unwise to advise others against
recommended limits - but for me, my Dutch Perfects (700x32) and
Michelin Slicks 622-35 both had low a MAX. 65 and 80 respectively if
my memory serves me well, but they've both been fine in the ~100-120
psi range (so far).

Is there a good reason for running them that hard?

Duncan Smith said:

Quoted message said:

Quoted message said:

Don't worry anout what the max says: get hold of a track pump and
put in at least 80psi - when you're comfy with that go to a
hundred. If you can deform the tyre with your thumb - it's too low.

Is the wrong answer. He made no mention of tyre size or loading, and
the thumb test is pretty useless (different people have different
size and strength thumbs, and different ideas of how hard they're
pressing, different tyres have more or less rigid sidewalls).

I think you're correct - it's probably unwise to advise others against
recommended limits - but for me, my Dutch Perfects (700x32) and
Michelin Slicks 622-35 both had low a MAX. 65 and 80 respectively if
my memory serves me well, but they've both been fine in the ~100-120
psi range (so far).

Unless carrying an elephant and using special wheel rims, 120 psi in a 35mm
bicycle tyre is ridiculous. You won't be getting decent suspension and
grip, the rims are in danger of exploding, and the tyres are in danger of
blowing off.

(Cue festive blow-off jokes)

~PB

Pete Biggs said:

Duncan Smith said:

Quoted message said:

> Don't worry anout what the max says: get hold of a track pump and
> put in at least 80psi - when you're comfy with that go to a
> hundred. If you can deform the tyre with your thumb - it's too low.

Quoted message said:

Quoted message said:

Is the wrong answer. He made no mention of tyre size or loading, and
the thumb test is pretty useless (different people have different
size and strength thumbs, and different ideas of how hard they're
pressing, different tyres have more or less rigid sidewalls).

Quoted message said:

I think you're correct - it's probably unwise to advise others against
recommended limits - but for me, my Dutch Perfects (700x32) and
Michelin Slicks 622-35 both had low a MAX. 65 and 80 respectively if
my memory serves me well, but they've both been fine in the ~100-120
psi range (so far).

Unless carrying an elephant and using special wheel rims, 120 psi in a 35mm
bicycle tyre is ridiculous. You won't be getting decent suspension and
grip, the rims are in danger of exploding, and the tyres are in danger of
blowing off.

(Cue festive blow-off jokes)

~PB

It's not as bad as you think. The 'close to' 120 was on the 700c
which is used for commuting to work with panniers. The 622-35 road
slick goes to 100 - but again, in that guise, it's also used for
commuting to work - and is suprisingly nippy for an MTB - not all that
much different from a road bike.. Maybe I'll take them down to 90
next time.

Thanks,

Duncan

In article <f0516131-66b1-4d34-af4d-270a73fc78c1
@l32g2000hse.googlegroups.com>, Duncan Smith
[email hidden] says...

Quoted message said:

It's not as bad as you think. The 'close to' 120 was on the 700c
which is used for commuting to work with panniers.

I'm about 17 stone and 90PSI is fine in a rear 700x28, maybe a bit more
with loaded panniers.

Quoted message said:

The 622-35 road slick goes to 100 - but again, in that guise, it's
also used for commuting to work - and is suprisingly nippy for an MTB
- not all that much different from a road bike..

622-35 is 700C - is this a hybrid?

Quoted message said:

Maybe I'll take them down to 90 next time.

That should be plenty. OTTOMH: A tyre deforms until its footprint
matches the load it has to support, e.g. a tyre run at 100 PSI loaded
with 100lb. needs a square inch of contact. Rolling resistance on a
smooth flat surface is caused by this deformation, so the more flexible
the tyre casing, or the higher its pressure, the less rolling resistance
occurs. A wider (or larger diameter) tyre needs to deform less than a
narrow one because its tread surface has a shallower curve, and
inflating it to a higher pressure has the effect of reducing "suspension
travel" so that small road bumps are transmitted to the bike and rider,
effectively presenting you with a tiny hill that has to be climbed each
time you ride over a bump. A narrow flexible tyre at high pressure on a
smooth surface deforms less in the sidewall, relative to the contact
area, when compared with a wider tyre, so overall rolling resistance is
less, but the high pressure doesn't reduce the suspension effect as much
as with a wider tyre, so better contact/comfort is maintained.
(I expect someone from rec.bicycles.tech will be along in a bit to tell
me that Jobst says different, or something ...)