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MTB 29*2.20 65 PSI



 
 
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  #1  
Old October 10th 18, 11:02 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default MTB 29*2.20 65 PSI

Today I had the first flat tire with the
29*2.20 MTB. This presta valve stuff is
obviously alien to me at this point, but
I managed to make it full again.

1) Some people say you don't even need an
adapter, you can just use
a Dunlop interface.

2) But of course I do have an adapter, only it
wasn't a pleasant thing fiddling with it
back and forth. I'm getting a quality pump
soon, God willing.

3) On the tire, it says 65 PSI. This must be
some theoretical possibility in a lab
setting with all brand new stuff, right?
Like when you buy a tent for three persons,
which is barely big enough for yourself to
sleep comfortably in?

4) Tires are 29*2.20 or 57-622. What is a good
PSI for going on asphalt ~98% of the time?

5) Is there a difference what PSI one would
like in the front and rear tires?

TIA

--
underground experts united
http://user.it.uu.se/~embe8573
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  #2  
Old October 10th 18, 11:33 PM posted to rec.bicycles.tech
Roger Merriman[_4_]
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Posts: 143
Default MTB 29*2.20 65 PSI

Emanuel Berg wrote:
Today I had the first flat tire with the
29*2.20 MTB. This presta valve stuff is
obviously alien to me at this point, but
I managed to make it full again.

1) Some people say you don't even need an
adapter, you can just use
a Dunlop interface.

2) But of course I do have an adapter, only it
wasn't a pleasant thing fiddling with it
back and forth. I'm getting a quality pump
soon, God willing.

3) On the tire, it says 65 PSI. This must be
some theoretical possibility in a lab
setting with all brand new stuff, right?
Like when you buy a tent for three persons,
which is barely big enough for yourself to
sleep comfortably in?

4) Tires are 29*2.20 or 57-622. What is a good
PSI for going on asphalt ~98% of the time?

5) Is there a difference what PSI one would
like in the front and rear tires?

TIA


3 yes that’s the maximum pressure, unwise to go beyond it really, though
since most pumps will give slightly different readings..

4 my commute bike is mostly on tarmac and 40psi seems to work, in that it’s
firm enough for my and commuting gear with out being rock solid.

5 depends on use I generally don’t alter the pressures F/R since being a
old MTBer I tend to shift my weight around so the % over each wheel differs
depending on the moment.

Roger Merriman

  #3  
Old October 11th 18, 07:50 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default MTB 29*2.20 65 PSI

Roger Merriman wrote:

3 yes that’s the maximum pressure, unwise to
go beyond it really, though since most pumps
will give slightly different readings..


What I meant was, I understand if it says 65psi
then that is the max, *but* is this to be
understood as a digit obtained in a controlled
lab setting with a brand new tube and tire, or
do people actually put in 65psi and use it?

5 depends on use I generally don’t alter the
pressures F/R since being a old MTBer I tend
to shift my weight around so the % over each
wheel differs depending on the moment.


Despite this being a MTB I use it as a
utility [1] to get stuff from the shop, go to
they gym, visit all my girlfriends etc. So
it is no rocks, no jumping, no slope/hills
(never use the small chainring for example).
Does that mean the same PSI front and rear?

[1] And I'm sure no one else ever got that
idea

--
underground experts united
http://user.it.uu.se/~embe8573
  #4  
Old October 11th 18, 10:57 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Posts: 8,785
Default MTB 29*2.20 65 PSI

On Wednesday, October 10, 2018 at 11:02:45 PM UTC+1, Emanuel Berg wrote:
Today I had the first flat tire with the
29*2.20 MTB. This presta valve stuff is
obviously alien to me at this point, but
I managed to make it full again.
1) Some people say you don't even need an
adapter, you can just use
a Dunlop interface.


You need a pump either with two holes in the head, one for Dunlop, one for Presta, or with a specially made head that self-adapts to the valve -- I've never had one of the latter that works better than a two-hole type.

2) But of course I do have an adapter, only it
wasn't a pleasant thing fiddling with it
back and forth. I'm getting a quality pump
soon, God willing.


Of the two-hole types, the SKS Rennkompressor is the undisputed champion but it is a garage pump, not a carry-along, it is pricey, and if you wear spectacles the dial is far away and the divisions small; on the other hand, all those racing mechanics who use it can't all be wrong, and the thing is rebuildable only forever.

3) On the tire, it says 65 PSI. This must be
some theoretical possibility in a lab
setting with all brand new stuff, right?
Like when you buy a tent for three persons,
which is barely big enough for yourself to
sleep comfortably in?


It's a joke. Why should you ever wish to pump up a tyre 2.2in in width to 65psi? That kills all the comfort. I run an always laden bike (my painting gear, often shopping) under my 95kg or so on 2.35in wide tyres at 2 bar/28psi and a casual bit but definitely under 30psi and down to 1.6 bar with no ill effects and all the comfort a bike can give

4) Tires are 29*2.20 or 57-622. What is a good
PSI for going on asphalt ~98% of the time?


2 bar, unless your tyres' sidewalls are incompetently designed or manufactured.

5) Is there a difference what PSI one would
like in the front and rear tires?


Depends on the geometry of your bike and how you would like it to react to steering inputs and road irregularities. My own bike was chosen for lazy, relaxed geometry and a long wheelbase, and I inflate the tyres front and rear the same, to preserve that predictable understeering characteristic because downhills over which I often touch 50kph+ too often have road surface surprises, which on a twitchy bike can hurt or kill you even if you still have reflexes as fast as mine. On the other hand, my study and studio are both at home, so I have no need to duck in and out of rush hour traffic, for which one might want a bike with "faster" geometry and slightly harder fat tyres (still not 65psi! -- maybe 33 to 40psi, nothing over 40psi). My everyday bike is fitted with both a Rohloff hub gearbox and a motor/battery combo chosen for high instant torque, and I'm a retired jock and a masher, four factors that all contribute quick reactions in traffic, so there's more than enough power in the rear wheel to drive nippy behavior if I want it, but I'm assuming yours is a derailleur bike and powered only by your legs. You could try a few pounds differential first at the rear and then at the front, and see how the bike behaves, but I think the difference will be subtle. When I was an automobile racer at a time when the sidewall construction of the tyre set the limits of inflation pressure, I discovered in a set of high-speed tests that only a few millimeters in contact width made much more difference than front-rear pressure differentials in the car's handling (handling being what happens when the driver exceeds the car's native capability which is called roadholding...), which is why, especially in midengined cars the rear wheels started wearing much bigger tyres than the front wheels..

Andre Jute
Oh, nostalgia!
  #5  
Old October 12th 18, 05:25 AM posted to rec.bicycles.tech
Tosspot[_3_]
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Posts: 1,200
Default MTB 29*2.20 65 PSI

On 10/11/18 8:50 AM, Emanuel Berg wrote:
Roger Merriman wrote:

3 yes that’s the maximum pressure, unwise to
go beyond it really, though since most pumps
will give slightly different readings..


What I meant was, I understand if it says 65psi
then that is the max, *but* is this to be
understood as a digit obtained in a controlled
lab setting with a brand new tube and tire, or
do people actually put in 65psi and use it?


I run mine over the max PSI at the rear, and can comfortable get 100 PSI
into them. Exploded one once, poor fitting tbf.


  #6  
Old October 12th 18, 12:37 PM posted to rec.bicycles.tech
Sepp Ruf
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Posts: 217
Default MTB 29*2.20 65 PSI

Tosspot wrote:
On 10/11/18 8:50 AM, Emanuel Berg wrote:
Roger Merriman wrote:

3 yes that’s the maximum pressure, unwise to
go beyond it really, though since most pumps
will give slightly different readings..


Even more inconvenient: If you fill the tire with CO2 and ride
Joerghian-style, leading wild lions out of a suddenly burning forest, the
pressure will rise like a hockey stick, and the tires' inevitable explosion
will damage the vulnerable ecosystem!

What I meant was, I understand if it says 65psi
then that is the max, *but* is this to be
understood as a digit obtained in a controlled
lab setting with a brand new tube and tire, or
do people actually put in 65psi and use it?


Maybe with very high loads or (more likely) in a desperate attempt at
lowering a noisy knobby tire's rolling resistence.

I run mine over the max PSI at the rear, and can comfortable get 100 PSI
into them. Exploded one once, poor fitting tbf.


Contis are supposed to be rated at half the (mean?) explosion pressure, but
exceed Schwalbe's max PSI at your and your blast-proof bike shed's own risk.
  #7  
Old October 12th 18, 10:10 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default MTB 29*2.20 65 PSI

Andre Jute wrote:

[...]


Thank you!

--
underground experts united
http://user.it.uu.se/~embe8573
 




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