Smooth tyres

Quoted message said:

Sheldon has a decent enough starting point for experimentation, with
suggested pressures:

http://www.sheldonbrown.com/tyres.html#pressure

Thanks for the link. Unfortunately the table he gives all revolves around
something called 'wheel load', but he gives no definition, nor can I find
one. How do you work out what your wheel load is? (I'm assuming it can't
just be weight, since his figures are for 100lb and 70 lb - not adult people
weights, to say the least.)

Quoted message said:

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

spokes said:

Quoted message said:

http://www.sheldonbrown.com/tyres.html#pressure

Thanks for the link. Unfortunately the table he gives all revolves around
something called 'wheel load', but he gives no definition, nor can I find
one. How do you work out what your wheel load is? (I'm assuming it can't
just be weight, since his figures are for 100lb and 70 lb - not adult people
weights, to say the least.)

A quick guess would be weight of (bike + rider) divided by two.

However the rear wheel will probably carry more weight than the front
wheel.

Martin Dann said:

spokes said:

Quoted message said:

http://www.sheldonbrown.com/tyres.html#pressure

Thanks for the link. Unfortunately the table he gives all revolves
around something called 'wheel load', but he gives no definition,
nor can I find one. How do you work out what your wheel load is?
(I'm assuming it can't just be weight, since his figures are for
100lb and 70 lb - not adult people weights, to say the least.)

A quick guess would be weight of (bike + rider) divided by two.

However the rear wheel will probably carry more weight than the front
wheel.

Correct. Or one could crudely estimate a stationary bike+rider by measuring
each wheel on bathroom scales.

I start from half rider weight on each wheel, then add a bit to the back,
subtract a little from the front.

I'm mainly concerned to stop the "pump it to the maximum on the sidewall"
mentality, which I think is flawed.

- Nigel

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

On 8 Oct, 22:09, "spokes" <[email hidden]> wrote:
How do you work out what your wheel load is? (I'm assuming it can't

Quoted message said:

just be weight, since his figures are for 100lb and 70 lb - not adult people
weights, to say the least.)

FWIW CTC reckon 65/35 for the rear/front load ratio, though my SWB
recumbent is ~50/50 (and the tadpole trike 32/2x34). Any many adults
(esp. females) weigh less than the 140lbs used by Sheldon.... (We are
not all lard arses - yet.)

Quoted message said:

I start from half rider weight on each wheel, then add a bit to the back,
subtract a little from the front.

I'm mainly concerned to stop the "pump it to the maximum on the sidewall"
mentality, which I think is flawed.

Hmmm. Yes indeed. The initial impetus for following up the post was that
I've been plagued by punctures lately, and I've been tending to 'take it to
the max' on pressure, partly for performance, but partly also from a dim &
distant memory that hard tyres helps prevent punctures. Now I discover on
Sheldon that over-inflation can actually *increase* problems with punctures,
so I'm thoroughly baffled. Care to expand on 'flawed'?

Quoted message said:

FWIW CTC reckon 65/35 for the rear/front load ratio, though my SWB
recumbent is ~50/50 (and the tadpole trike 32/2x34). Any many adults
(esp. females) weigh less than the 140lbs used by Sheldon.... (We are
not all lard arses - yet.)

Thanks for that. So according to CTC at least, my rear wheel load is 65% of
my weight; my front wheel load 35%, yes? Give or take....

Quoted message said:

spokes said:

Quoted message said:

I start from half rider weight on each wheel, then add a bit to the back,
subtract a little from the front.

I'm mainly concerned to stop the "pump it to the maximum on the sidewall"
mentality, which I think is flawed.

Hmmm. Yes indeed. The initial impetus for following up the post was that
I've been plagued by punctures lately, and I've been tending to 'take it to
the max' on pressure, partly for performance, but partly also from a dim &
distant memory that hard tyres helps prevent punctures. Now I discover on
Sheldon that over-inflation can actually *increase* problems with punctures,
so I'm thoroughly baffled.

Low pressure reduces punctures because the tyre is able to "tent over"
sharp stones etc. without them going in. I didn't really believe it at
first but remember being convinced that it is true by Carl Fogel.

High pressure might mean fewer punctures though because since the
contact patch is a bit smaller you have a better chance of avoiding the
nail in the first place.

spokes said:

Quoted message said:

I start from half rider weight on each wheel, then add a bit to the
back, subtract a little from the front.

I'm mainly concerned to stop the "pump it to the maximum on the
sidewall" mentality, which I think is flawed.

Hmmm. Yes indeed. The initial impetus for following up the post was
that I've been plagued by punctures lately, and I've been tending to
'take it to the max' on pressure, partly for performance, but partly
also from a dim & distant memory that hard tyres helps prevent
punctures. Now I discover on Sheldon that over-inflation can actually
*increase* problems with punctures, so I'm thoroughly baffled. Care
to expand on 'flawed'?

"flawed" in the sense that...

If you are chasing outright cycle speed, then very high pressure and very
narrow light weight tyres may be the right choice (c.f. professional cycle
racers).

If you are riding your bike a fair distance (100km/day+ rides or touring),
then a bit more comfort might well be better than absolute speed; you'll
ride further before your backside or hands give up due to the vibration*.

If you are commuting/shopping over relatively short distances, then comfort
and low puncture rates may well be a higher priority than the last seconds
of speed.

It seems obvious to me that the appropriate tyre pressure is related to the
weight carried (rider + luggage + bike).

Another document covering the area is published by Schwalbe (cycle tyre
maker).
http://www.schwalbe.co.uk/shopdata/files/tech-info.pdf

(*) and a logical extension of this argument can takes one to either
suspended touring bikes such as Moultons, or to recumbents.

- Nigel

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

Thanks for that. Interesting. Bafflingly tho', the Schwalbe guide at that
link says:

The higher the inflation pressure, the lower the rolling resistance and
higher pressure also reduces the likelihood of a puncture.

....which had always been my understanding, till I read Sheldon's:

An overinflated tyre is more prone to damage from sharp rocks and similar
road hazards.

I'm about 11 stone and have been running Schwalbe Speziales @ about 115psi,
but have now given up on them after my third (rear wheel) puncture in a
fortnight (ie, about 150 miles of city riding). They were sold to me as
having kevlar in, but I find that very hard to believe. but maybe it's my
fault because I've been riding them at their max pressure. (Then again, 11
stone's not exactly heavy)

In short, I'd happily trade off comfort for speed, but if I could
significantly reduce my puncture risk by running at, say, 100 rather than
115psi, that *would* be worth it.

Quoted message said:

"flawed" in the sense that...

If you are chasing outright cycle speed, then very high pressure and very
narrow light weight tyres may be the right choice (c.f. professional cycle
racers).

If you are riding your bike a fair distance (100km/day+ rides or touring),
then a bit more comfort might well be better than absolute speed; you'll
ride further before your backside or hands give up due to the vibration*.

If you are commuting/shopping over relatively short distances, then
comfort and low puncture rates may well be a higher priority than the last
seconds of speed.

It seems obvious to me that the appropriate tyre pressure is related to
the weight carried (rider + luggage + bike).

Another document covering the area is published by Schwalbe (cycle tyre
maker).
http://www.schwalbe.co.uk/shopdata/files/tech-info.pdf

(*) and a logical extension of this argument can takes one to either
suspended touring bikes such as Moultons, or to recumbents.

- Nigel

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

spokes said:

Thanks for that. Interesting. Bafflingly tho', the Schwalbe guide at
that link says:

The higher the inflation pressure, the lower the rolling resistance
and higher pressure also reduces the likelihood of a puncture.

...which had always been my understanding, till I read Sheldon's:

An overinflated tyre is more prone to damage from sharp rocks and
similar road hazards.

Yes, it does seem contradictory.

The CTC page on the topic suggests minimum pressures for various sections of
tyre and weight of rider.
http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3802

Quoted message said:

I'm about 11 stone and have been running Schwalbe Speziales @ about
115psi, but have now given up on them after my third (rear wheel)
puncture in a fortnight (ie, about 150 miles of city riding). They
were sold to me as having kevlar in, but I find that very hard to
believe. but maybe it's my fault because I've been riding them at
their max pressure. (Then again, 11 stone's not exactly heavy)

In short, I'd happily trade off comfort for speed, but if I could
significantly reduce my puncture risk by running at, say, 100 rather
than 115psi, that *would* be worth it.

I've no idea of the section of the tyre you quote.

I weigh about 10st10lbs, and run my audax bike with 28mm tyres at about
80psi on Panaracer Pasela TG.
If I push the bike to 90 they give a much harsher ride. These have had one
puncture in 2500 miles.

My tourer (also on 28mm) tends to run at about 75psi. This bike has
Continental Gatorskins in summer (until they wear out), Schwalbe Marathon at
other times, and, as I now have the audax machine, I might increase the
section to 32mm when next replacing tyres. No punctures in last year (~3000
miles?)

Digging up URLs has caused me to think a bit more, and perhaps I should
experiment with a bit less pressure in the front.

My wife's bike has Schwalbe CityJets in 1.5in section. These have been
puncture free for several years. So infrequent are punctures, that the
spare tube which rattles around in the rack-pack developed abbraision holes
and had to be thrown away this summer !

For regular urban riding to avoid punctures, I'd try something like Schwalbe
Marathons, or maybe the Marathon Racer if you prefer light weight tyres. Or
similar weights/designs from other makers of choice.

- Nigel

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

In article <[email hidden]>, spokes
[email hidden] says...

Quoted message said:

Quoted message said:

Sheldon has a decent enough starting point for experimentation, with
suggested pressures:

http://www.sheldonbrown.com/tyres.html#pressure

Thanks for the link. Unfortunately the table he gives all revolves around
something called 'wheel load', but he gives no definition, nor can I find
one. How do you work out what your wheel load is?

Stick one wheel on your bathroom scales, support the other wheel at the
same height and sit on the bike in your normal riding position - support
yourself with an elbow against a wall. Repeat with scales under other
wheel.

Thanks. Now how am I going to get my bike in the bathroom..
"Rob Morley" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>, spokes
[email hidden] says...

Quoted message said:

Quoted message said:

Sheldon has a decent enough starting point for experimentation, with
suggested pressures:

http://www.sheldonbrown.com/tyres.html#pressure

Thanks for the link. Unfortunately the table he gives all revolves around
something called 'wheel load', but he gives no definition, nor can I find
one. How do you work out what your wheel load is?

Stick one wheel on your bathroom scales, support the other wheel at the
same height and sit on the bike in your normal riding position - support
yourself with an elbow against a wall. Repeat with scales under other
wheel.

In article said:

Thanks. Now how am I going to get my bike in the bathroom..

Although they are called "bathroom scales", they won't actually
stop working if you take them out to the bike instead of the
bike into the bathroom :-)

Quoted message said:

Quoted message said:

Stick one wheel on your bathroom scales, support the other wheel at the
same height and sit on the bike in your normal riding position - support
yourself with an elbow against a wall. Repeat with scales under other
wheel.

Um...yeah...it was what my Dad used to call a jo-oke
pretty feeble admittedly, but..
"Alan Braggins" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article said:

Thanks. Now how am I going to get my bike in the bathroom..

Although they are called "bathroom scales", they won't actually
stop working if you take them out to the bike instead of the
bike into the bathroom :-)

Quoted message said:

Quoted message said:

Stick one wheel on your bathroom scales, support the other wheel at the
same height and sit on the bike in your normal riding position - support
yourself with an elbow against a wall. Repeat with scales under other
wheel.

In article <[email hidden]>, spokes
[email hidden] says...

Quoted message said:

Um...yeah...it was what my Dad used to call a jo-oke
pretty feeble admittedly, but..

Stick a ;-) after it and people will be in no doubt that what you say is
funny, otherwise we might think that you're another "Alan Holmes". ;-)

In article said:

In article <[email hidden]>, spokes
[email hidden] says...

Quoted message said:

Um...yeah...it was what my Dad used to call a jo-oke
pretty feeble admittedly, but..

Stick a ;-) after it and people will be in no doubt that what you say is
funny, otherwise we might think that you're another "Alan Holmes". ;-)

I think you'll find that doesn't always work. Check the post he was
replying to ;-)

In article <[email hidden]>, Alan Braggins
[email hidden] says...

Quoted message said:

In article said:

In article <[email hidden]>, spokes
[email hidden] says...

Quoted message said:

Um...yeah...it was what my Dad used to call a jo-oke
pretty feeble admittedly, but..

Stick a ;-) after it and people will be in no doubt that what you say is
funny, otherwise we might think that you're another "Alan Holmes". ;-)

I think you'll find that doesn't always work. Check the post he was
replying to ;-)

Just because it's there doesn't mean that he knows what it means. I'd
probably have noticed it if he hadn't top-posted. :-)