Rick Johnson

One point not mentioned about low pressure in mud - the flexing of
the tire casing works to eject the mud as it returns to a round
profile after being flattened by contact with the ground. The effect
can be pronounced in sandy or gritty mud, much less so in clay or
other tacky material.

The effect appears very dramatically with snow in very cold
conditions.



Rick



On 10/7/2011 2:51 PM, Shane Gibson wrote:

Anyway you slice it ... my experience indicates to me ... that
less pressure in the sloppy stuff is better, and my tires don't
slip and slide as much ... and more pressure on the dry means
faster results.  That's the way I'm gonna roll!  :) 

~~shane

--

"Opportunities multiply as they are seized."   - Sun Tzu

On Fri, Oct 7, 2011 at 2:49 PM, don
person <don.person@gmail.com>
wrote:

In soft conditions, the ground conforms to the tire.

On hard surfaces you need the tire to conform to the ground.

That is why tires have (or do not have) tread in the first
place.



Even so, I was running 45-50psi in the 28mm 'cross clinchers
we used

during my heyday.



-shiggy

On Fri, Oct 7, 2011 at 2:30 PM, Shane Gibson <sygibson@gmail.com>
wrote:

>

> I disagree on the more pressure in the mud issue.
 I believe you want less

> pressure, so the tire deforms/conforms to the
ground more, and you get MORE

> tread blocks in the ground gaining traction.  In
firm/dry courses, you don't

> need as much traction - so you can run higher
pressure, and have less

> rolling resistance.

> ~~shane

> --

> "Opportunities multiply as they are seized."   -
Sun Tzu

>

>

> On Fri, Oct 7, 2011 at 2:27 PM, don person <don.person@gmail.com>
wrote:

>>

>> Well, there can be a "firm" bottom to the mud.
For 'cross if there is

>> no bottom forget floatation. Get off and run.

>> I tend to use higher pressures for the rideable
mud to better support

>> the tread blocks for mechanical traction.

>> -shiggy

>>

>> On Fri, Oct 7, 2011 at 1:57 PM, Ryan <rlsone@gmail.com>
wrote:

>> > While I'm writing my thesis I could whip
out a CFD model real quick if

>> > you want ;)

>> >

>> > On a more serious note, since when in
Oregon do we have a "hard bottom"

>> > to grab onto? Over concrete and the like
sure, but from my (limited)

>> > experience, it goes from wet mud to
slightly less mud.

>> >
_______________________________________________

>> > OBRA mailing list

>> > obra@list.obra.org

>> > http://list.obra.org/mailman/listinfo/obra

>> > Unsubscribe: obra-unsubscribe@list.obra.org

>> >

>>

>>

>>

>> --

>> Don Person (shiggy)

>> mtbtires.com

>> Google Voice: 541.414.3434

>> _______________________________________________

>> OBRA mailing list

>> obra@list.obra.org

>> http://list.obra.org/mailman/listinfo/obra

>> Unsubscribe: obra-unsubscribe@list.obra.org

>

>







--

Don Person (shiggy)

mtbtires.com

Google Voice: 541.414.3434

_______________________________________________

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obra@list.obra.org

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Unsubscribe: obra-unsubscribe@list.obra.org

Shane Gibson

Anyway you slice it ... my experience indicates to me ... that less pressure
in the sloppy stuff is better, and my tires don't slip and slide as much ...
and more pressure on the dry means faster results. That's the way I'm gonna
roll! :)

~~shane

--
"Opportunities multiply as they are seized." - Sun Tzu

On Fri, Oct 7, 2011 at 2:49 PM, don person wrote:

> In soft conditions, the ground conforms to the tire.
> On hard surfaces you need the tire to conform to the ground.
> That is why tires have (or do not have) tread in the first place.
>
> Even so, I was running 45-50psi in the 28mm 'cross clinchers we used
> during my heyday.
>
> -shiggy
>
> On Fri, Oct 7, 2011 at 2:30 PM, Shane Gibson wrote:
> >
> > I disagree on the more pressure in the mud issue. I believe you want
> less
> > pressure, so the tire deforms/conforms to the ground more, and you get
> MORE
> > tread blocks in the ground gaining traction. In firm/dry courses, you
> don't
> > need as much traction - so you can run higher pressure, and have less
> > rolling resistance.
> > ~~shane
> > --
> > "Opportunities multiply as they are seized." - Sun Tzu
> >
> >
> > On Fri, Oct 7, 2011 at 2:27 PM, don person wrote:
> >>
> >> Well, there can be a "firm" bottom to the mud. For 'cross if there is
> >> no bottom forget floatation. Get off and run.
> >> I tend to use higher pressures for the rideable mud to better support
> >> the tread blocks for mechanical traction.
> >> -shiggy
> >>
> >> On Fri, Oct 7, 2011 at 1:57 PM, Ryan wrote:
> >> > While I'm writing my thesis I could whip out a CFD model real quick if
> >> > you want ;)
> >> >
> >> > On a more serious note, since when in Oregon do we have a "hard
> bottom"
> >> > to grab onto? Over concrete and the like sure, but from my (limited)
> >> > experience, it goes from wet mud to slightly less mud.
> >> > _______________________________________________
> >> > OBRA mailing list
> >> > obra@list.obra.org
> >> > http://list.obra.org/mailman/listinfo/obra
> >> > Unsubscribe: obra-unsubscribe@list.obra.org
> >> >
> >>
> >>
> >>
> >> --
> >> Don Person (shiggy)
> >> mtbtires.com
> >> Google Voice: 541.414.3434
> >> _______________________________________________
> >> OBRA mailing list
> >> obra@list.obra.org
> >> http://list.obra.org/mailman/listinfo/obra
> >> Unsubscribe: obra-unsubscribe@list.obra.org
> >
> >
>
>
>
> --
> Don Person (shiggy)
> mtbtires.com
> Google Voice: 541.414.3434
>

don person

In soft conditions, the ground conforms to the tire.
On hard surfaces you need the tire to conform to the ground.
That is why tires have (or do not have) tread in the first place.

Even so, I was running 45-50psi in the 28mm 'cross clinchers we used
during my heyday.

-shiggy

On Fri, Oct 7, 2011 at 2:30 PM, Shane Gibson wrote:
>
> I disagree on the more pressure in the mud issue.

Shane Gibson

I disagree on the more pressure in the mud issue. I believe you want less
pressure, so the tire deforms/conforms to the ground more, and you get MORE
tread blocks in the ground gaining traction. In firm/dry courses, you don't
need as much traction - so you can run higher pressure, and have less
rolling resistance.

~~shane

--
"Opportunities multiply as they are seized." - Sun Tzu

On Fri, Oct 7, 2011 at 2:27 PM, don person wrote:

> Well, there can be a "firm" bottom to the mud. For 'cross if there is
> no bottom forget floatation. Get off and run.
> I tend to use higher pressures for the rideable mud to better support
> the tread blocks for mechanical traction.
> -shiggy
>
> On Fri, Oct 7, 2011 at 1:57 PM, Ryan wrote:
> > While I'm writing my thesis I could whip out a CFD model real quick if
> you want ;)
> >
> > On a more serious note, since when in Oregon do we have a "hard bottom"
> to grab onto? Over concrete and the like sure, but from my (limited)
> experience, it goes from wet mud to slightly less mud.
> > _______________________________________________
> > OBRA mailing list
> > obra@list.obra.org
> > http://list.obra.org/mailman/listinfo/obra
> > Unsubscribe: obra-unsubscribe@list.obra.org
> >
>
>
>
> --
> Don Person (shiggy)
> mtbtires.com
> Google Voice: 541.414.3434
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

don person

Well, there can be a "firm" bottom to the mud. For 'cross if there is
no bottom forget floatation. Get off and run.
I tend to use higher pressures for the rideable mud to better support
the tread blocks for mechanical traction.
-shiggy

On Fri, Oct 7, 2011 at 1:57 PM, Ryan wrote:
> While I'm writing my thesis I could whip out a CFD model real quick if you want ;)
>
> On a more serious note, since when in Oregon do we have a "hard bottom" to grab onto? Over concrete and the like sure, but from my (limited) experience, it goes from wet mud to slightly less mud.
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>

--
Don Person (shiggy)
mtbtires.com
Google Voice: 541.414.3434

Ryan

While I'm writing my thesis I could whip out a CFD model real quick if you want ;)

On a more serious note, since when in Oregon do we have a "hard bottom" to grab onto? Over concrete and the like sure, but from my (limited) experience, it goes from wet mud to slightly less mud.

Chris Cortez

Well played, and wow.

On Oct 7, 2011, at 12:08 PM, Sarah Tisdale wrote:

> You're either trying to "cut through" the mud to get to the hard
> bottom (narrower tires, higher pressures). Or, if there's no hard
> bottom, you're trying to "float on" the mud (wider tires, lower
> pressures).
>
> Choosing between the two involves highly complex fluid dynamics. I
> personally believe every CX setup is incomplete without a
> viscometer, and perhaps a rheometer. Otherwise, one cannot
> accurately gauge reynolds number and laminar flow. One can debate
> the merits of a shear-rheometer versus an extension-rheometer, but
> I'm a fan of the newer native stress-controlled instruments.
>
> Where is Cobra Kai when you need him?
>
>
> On Thu, Oct 6, 2011 at 9:15 PM, Jason A. Skelton > wrote:
> In very wet, muddy conditions like we had at the Blind Date on
> Wednesday night, does lowering the tire pressure make it easier to
> ride through the mud? I know in sand lower tire pressure helps with
> traction and I wonder if there is a similar situation in mud.
>
> thanks
>
> Jason
>
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>
>
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org

Sarah Tisdale

You're either trying to "cut through" the mud to get to the hard bottom
(narrower tires, higher pressures). Or, if there's no hard bottom, you're
trying to "float on" the mud (wider tires, lower pressures).

Choosing between the two involves highly complex fluid dynamics. I
personally believe every CX setup is incomplete without a viscometer, and
perhaps a rheometer. Otherwise, one cannot accurately gauge reynolds number
and laminar flow. One can debate the merits of a shear-rheometer versus an
extension-rheometer, but I'm a fan of the newer native stress-controlled
instruments.

Where is Cobra Kai when you need him?

On Thu, Oct 6, 2011 at 9:15 PM, Jason A. Skelton wrote:

> In very wet, muddy conditions like we had at the Blind Date on Wednesday
> night, does lowering the tire pressure make it easier to ride through the
> mud? I know in sand lower tire pressure helps with traction and I wonder if
> there is a similar situation in mud.
>
> thanks
>
> Jason
>
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org
>
>

Jason A. Skelton

In very wet, muddy conditions like we had at the Blind Date on Wednesday night, does lowering the tire pressure make it easier to ride through the mud?