Air pressure

orfeo said:

I was just reading through that pump post, and i saw most ppl talking about having tyre pressures
of 100+ psi (i assume). On my tyres it has a
psi rating of 45-60, which seems a bit low as i can still indent them with my thumb. What
pressures do most ppl pump their tyres up too? I'm riding a trek 970 with slicks with grooves
for the water to run off (not sure on the brand obviously). Do different tyres have different
pressure ratings?

Yes. Fat tyres require lower pressures than skinny tyres. Yours is an mtb with fat tyres, so don't
pump them up to 100psi, they might blow them off the rim if you did.

hope this helps GK

Quoted message said:

and is it better to have a higher pressure (assuming you not subjecting your tyres to large impact
forces).

orfeo

orfeo said:

I was just reading through that pump post, and i saw most ppl talking about having tyre pressures
of 100+ psi (i assume). On my tyres it has a
psi rating of 45-60, which seems a bit low as i can still indent them with my thumb. What
pressures do most ppl pump their tyres up too? I'm riding a trek 970 with slicks with grooves
for the water to run off (not sure on the brand obviously). Do different tyres have different
pressure ratings? and is it better to have a higher pressure (assuming you not subjecting your
tyres to large impact forces).

orfeo

AFAIK you shouldn't exceed the rating printed on the tyre (every tyre has this, I guess the narrower
the tyre, the higher the pressure). I'd say road tyres are typically inflated at 100-120 psi. Track
bikes might be even higher (given these bikes are in theory only ever ridden on perfect surfaces and
don't need the shock absorption qualities of a road tyre).

If you're a bigger guy like me (over 90kg) on a road bike, it's important to keep the tyres at their
upper limit, otherwise you puncture more easily and if the pressure's low enough, you can damage
your rims when you hit a pothole.

HTH,

&roo

All tires have different pressure ratings. These are set by the maker and are the safe range. Too
low and you risk pinch flats, too high and risk the tire blowing off the rim.

Having said that, the makers generally are conservative in their ratings, but the safer answer if
you want to run higher or lower pressures is to get another tire.

I have a set of wheels with 40psi MAX tire pressures, and another set with 135psi MAX - different
tires, different pressures for different uses.

(Also, at bicycle speeds the grooves for the water to run off is all marketing.)

Megan

orfeo <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

I was just reading through that pump post, and i saw most ppl talking about having tyre pressures
of 100+ psi (i assume). On my tyres it has a
psi rating of 45-60, which seems a bit low as i can still indent them with my thumb. What
pressures do most ppl pump their tyres up too? I'm riding a trek 970 with slicks with grooves
for the water to run off (not sure on the brand obviously). Do different tyres have different
pressure ratings? and is it better to have a higher pressure (assuming you not subjecting your
tyres to large impact forces).

orfeo

Quoted post said:

Originally posted by Megan Webb


(Also, at bicycle speeds the grooves for the water to run off is all marketing.)

Megan

ohhh...really, interesting, can anyone recommend some mtb slicks which are weight friendly? and not too expensive.

orfeo

"orfeo" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

ohhh...really, interesting, can anyone recommend some mtb slicks which are weight friendly? and
not too expensive.

Vredestein S-Licks are a bit on the expensive side but they are damn light and damn fast on the
road! $50-$60 each. They also come in RED!! :-D There was another thread on mtb slicks recently.
When I ever get spare time I'm going to create an online list of mtb slicks for us aussies. If you
want the info I've got I can email it to you.

hip

ohhh...really, interesting, can anyone recommend some mtb slicks which
: are weight friendly? and not too expensive.
:
: orfeo
:
:
I have specialized fatboys. 1.25" ~3.1cm. They are slicks with no grooves. They are pretty good.
There are reviews over the web of these tyres. I think Cycling Australia reviewed them sometime over
the last year. Cost about $40 a tyre.

Peter

orfeo <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Megan Webb said:

(Also, at bicycle speeds the grooves for the water to run off is all marketing.) Megan

ohhh...really, interesting, can anyone recommend some mtb slicks which are weight friendly? and
not too expensive.

orfeo

On this, there check out the thread on hydroplaning. The link below also explains

sheldonbrown.comtyres.htmlOpen ↗

Scoll up the page and read the rest on tires.

I can't help with makes/models tires as on the mtb, the slicks I use on my mtb comutter are whatever
el'cheapo ones that are going. Haven't found any problems with this yet..

Megan Webb said:

On this, there check out the thread on hydroplaning. The link below also explains

sheldonbrown.comtyres.htmlOpen ↗

You know something...I'm not convinced by this (doesn't mean it ain't true...I just smell a rat).

For bike tyres it says:

"Bicycles can NOT hydroplane because..."

This is a big statement to make. That is, under all circumstances, no bike can hydroplane.

"A bicycle tyre has a curved road contact. Since a bicycle leans in corners, it needs a tyre with a
rounded contact area, which tends to push the water away to either side."

The same would apply to Motorbikes. They too have rounded contact areas, and lean into corners. But
no motorbike rider in their right mind uses a slick, unless its on a track on a dry day.

"A bicycle tyre is narrower, so not as much water is in contact with the leading edge at once."

Sounds fair to me, but I'm not sure if this totally rules out aqua-planing.

"The high pressure of bicycle tyres is more efficient at squeezing the water out from under."

Not quite true. Mountain bike tyre pressures are often the same as that off a car.

"Cars go much faster than bicycles, again leaving less time for water to escape. At high
bicycle speeds, hydroplaning is just possible for car tyres, but is absolutely impossible for
bicycle tyres."

Note sure about this. Bikes go quite fast, and cars can aquaplane at fairly low speed.

Does anyone have comments? Has the web site conclusively proved its point, or is it
somewhat lacking?

Mike

Slicks for MTB's are also high pressure - 70 to 110psi, which makes them still 3 times car tyre
pressure. A big difference. Offroad tyres are lower, but still almost double that of cars, but they
have tread anyway.

I'll start conjecturing now:

Considering a bike tyre's contact patch is the size of a single tread block on a car, you would need
triple the speed on a bike to aquaplane than a car. (Based on the fact bikes are pushing down on the
road 3 times the force than a car per sq.inch)

How much speed do you need to drive a car (with treaded tyres) through a puddle to aquaplane? 80,
90km? That means 240 or 270kmh on a bicycle..

Hope this helps GK

Mike Doyle said:

Megan Webb said:

On this, there check out the thread on hydroplaning. The link below also explains

sheldonbrown.comtyres.htmlOpen ↗

You know something...I'm not convinced by this (doesn't mean it ain't true...I just smell a rat).

For bike tyres it says:

"Bicycles can NOT hydroplane because..."

This is a big statement to make. That is, under all circumstances, no bike can hydroplane.

"A bicycle tyre has a curved road contact. Since a bicycle leans in corners, it needs a tyre with
a rounded contact area, which tends to push the water away to either side."

The same would apply to Motorbikes. They too have rounded contact areas, and lean into corners.
But no motorbike rider in their right mind uses a slick, unless its on a track on a dry day.

"A bicycle tyre is narrower, so not as much water is in contact with the leading edge at once."

Sounds fair to me, but I'm not sure if this totally rules out aqua-planing.

"The high pressure of bicycle tyres is more efficient at squeezing the water out from under."

Not quite true. Mountain bike tyre pressures are often the same as that off a car.

"Cars go much faster than bicycles, again leaving less time for water to escape. At high
bicycle speeds, hydroplaning is just possible for car tyres, but is absolutely impossible for
bicycle tyres."

Note sure about this. Bikes go quite fast, and cars can aquaplane at fairly low speed.

Does anyone have comments? Has the web site conclusively proved its point, or is it somewhat
lacking?

Mike

puddle to aquaplane? 80, 90km? That means 240 or 270kmh on a bicycle..
:
: Hope this helps GK
:

I agree...

There is much more applied physics evidence on the net if this is not enough.

Peter

Specialized Fat Boys are the slick to get. Thin as you can get them.

I have used them for years. They are fast and don't puncture often.