P
Phil Holman
Guest
<[email protected]> wrote in message
news:[email protected]...
> Phil Holman writes:
>
>>> How do tactics and strategy affect tire rolling resistance?
>
>> They don't, but tactics and strategy hugely overshadow tire rolling
>> resistance differences in mass start races.
>
> So why bring that up in this connection?
Because the rolling resistance difference between clichers and tubulars
is just didling in the noise. This thread is about the choice of
tubulars or clinchers for racing. I don't think rolling resistance is a
big enough factor to sway that choice, let alone some theoretical value
taken under test conditions that are nothing like actual road
conditions.
>
>> Also, the difference in rolling resistance measured under ideal
>> conditions does not necessarily translate to significant differences
>> under mass start road racing conditions. Has anyone run any tests on
>> anything other than a smooth roller?
>
> I think you don't understand rolling resistance. The losses are
> encountered by flexing the tread, tire casing, and tube, that are
> either elastomers directly or are bonded by ones. That flexing has
> hysteresis losses (does not return the same energy that was required
> to deform it). The rougher the surface the more tread deformation
> plays a role so the smooth drum is the standard by which tires are
> compared.
yada yada .....the fact that we let air out of our tires on chipseal
roads to go faster even though this increases rolling resistance; what
does this tell you? Rolling resistance is only one parameter to consider
when choosing the fastest wheel.
>
> Tread patterns cause tread squirm losses in addition to those from
> casing flex and these become worse with textured test surfaces, and
> higher inflation pressure. You can notice which tires in the RR
> curves at:
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
>
> have thicker tread with patterns because they cease getting better
> with increased inflation. This is even starker with MTB knobby tires,
> whose losses get worse with higher inflation pressure (even on a
> smooth surface) because individual knobs come under higher pressure
> and deform to barrel shapes.
>
> In order to compare rolling losses in tires, they must be run on
> smooth test surfaces. Other tests might be used to show other
> characteristics but the principal loss of interest is the one on a
> smooth surface that assesses losses internal to the tire. You would
> probably hear a howl of complaint if a rough gravelly drum were used
> because tread thickness of smooth tread would not even reveal the true
> character of the tire, quite aside from tires with thicker tread and
> tread patterns.
>
Very interesting. The next time I race on a smooth drum I'll take
notice. The measurement you talk about is a theoretical value taken
under conditions chosen for testing facility. Will I be able to finish
the race on the tire with the lowest RR? Is it the fastest on the road?
Phil H
news:[email protected]...
> Phil Holman writes:
>
>>> How do tactics and strategy affect tire rolling resistance?
>
>> They don't, but tactics and strategy hugely overshadow tire rolling
>> resistance differences in mass start races.
>
> So why bring that up in this connection?
Because the rolling resistance difference between clichers and tubulars
is just didling in the noise. This thread is about the choice of
tubulars or clinchers for racing. I don't think rolling resistance is a
big enough factor to sway that choice, let alone some theoretical value
taken under test conditions that are nothing like actual road
conditions.
>
>> Also, the difference in rolling resistance measured under ideal
>> conditions does not necessarily translate to significant differences
>> under mass start road racing conditions. Has anyone run any tests on
>> anything other than a smooth roller?
>
> I think you don't understand rolling resistance. The losses are
> encountered by flexing the tread, tire casing, and tube, that are
> either elastomers directly or are bonded by ones. That flexing has
> hysteresis losses (does not return the same energy that was required
> to deform it). The rougher the surface the more tread deformation
> plays a role so the smooth drum is the standard by which tires are
> compared.
yada yada .....the fact that we let air out of our tires on chipseal
roads to go faster even though this increases rolling resistance; what
does this tell you? Rolling resistance is only one parameter to consider
when choosing the fastest wheel.
>
> Tread patterns cause tread squirm losses in addition to those from
> casing flex and these become worse with textured test surfaces, and
> higher inflation pressure. You can notice which tires in the RR
> curves at:
>
> http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
>
> have thicker tread with patterns because they cease getting better
> with increased inflation. This is even starker with MTB knobby tires,
> whose losses get worse with higher inflation pressure (even on a
> smooth surface) because individual knobs come under higher pressure
> and deform to barrel shapes.
>
> In order to compare rolling losses in tires, they must be run on
> smooth test surfaces. Other tests might be used to show other
> characteristics but the principal loss of interest is the one on a
> smooth surface that assesses losses internal to the tire. You would
> probably hear a howl of complaint if a rough gravelly drum were used
> because tread thickness of smooth tread would not even reveal the true
> character of the tire, quite aside from tires with thicker tread and
> tread patterns.
>
Very interesting. The next time I race on a smooth drum I'll take
notice. The measurement you talk about is a theoretical value taken
under conditions chosen for testing facility. Will I be able to finish
the race on the tire with the lowest RR? Is it the fastest on the road?
Phil H