Jobst Brandt vs. Tire Glue

[[email protected]]

On Aug 8, 8:58 pm, dvt <[email protected]> wrote:

> The "CotonTech+" looks like a very high performance tyre in that case.
> Expensive, too.

http://www.fm-boyaux.fr/index.htm

I had figured out that the angle was measured from vertical last
February but forgot to make a specific note of it in my data file. I
did notice that that there was a surprising difference between the
Vittoria Rubino Pros in 23mm and 25mm sizes, so I sought one out to
buy. It wasn't until my ride this afternoon that I looked down and
realized I had a 25 on, so I went back to look at the article.

 

[[email protected]]

On Aug 8, 11:13 am, [email protected] wrote:
> On Aug 7, 4:19 pm, dvt <[email protected]> wrote:
>

> > >>>http://anonymous.coward.free.fr/rbr/lecycle.png

>
> ****! I had the slip.angle.wet backwards. It's measured from
> vertical, not horizontal, so -->LOWER<-- slip.angle.wet implies better
> traction. The rain tires generally do have better traction than plain
> tires.

You mean it's measured from horizontal, right? So a tire
with a high slip.angle.wet of 60 slips when the wheel is
at 60 deg to the ground, or 30 deg to the vertical. That
would be poor traction performance.

The tires have slip.angle.wet of about 45 to 60 and the
rain tires have lower slip.angle.wet. The values of
45 to 60 are why I think it's measured from the horizontal.
If the test approximates real conditions, 45 deg from
vertical is outrageously good in the wet. I don't think
you can lean a bike over at 60 deg from vertical even in
dry weather without sliding out.

Ben

 

[[email protected]]

On Aug 9, 3:04 am, "[email protected]" <[email protected]>
wrote:
> On Aug 8, 11:13 am, [email protected] wrote:
>
> > On Aug 7, 4:19 pm, dvt <[email protected]> wrote:
>
> > > >>>http://anonymous.coward.free.fr/rbr/lecycle.png
>
> > ****! I had the slip.angle.wet backwards. It's measured from
> > vertical, not horizontal, so -->LOWER<-- slip.angle.wet implies better
> > traction. The rain tires generally do have better traction than plain
> > tires.
>
> You mean it's measured from horizontal, right? So a tire
> with a high slip.angle.wet of 60 slips when the wheel is
> at 60 deg to the ground, or 30 deg to the vertical. That
> would be poor traction performance.
>
> The tires have slip.angle.wet of about 45 to 60 and the
> rain tires have lower slip.angle.wet. The values of
> 45 to 60 are why I think it's measured from the horizontal.
> If the test approximates real conditions, 45 deg from
> vertical is outrageously good in the wet. I don't think
> you can lean a bike over at 60 deg from vertical even in
> dry weather without sliding out.
>
> Ben

Ugh. This is why I was confused. They didn't change the angle of the
bike: the bike was held vertically and they tilted a slab of wet
asphalt relative to it.

 

[[email protected]]

On Aug 9, 12:52 am, [email protected] wrote:
> On Aug 9, 3:04 am, "[email protected]" <[email protected]>
> wrote:
>
> > You mean it's measured from horizontal, right? So a tire
> > with a high slip.angle.wet of 60 slips when the wheel is
> > at 60 deg to the ground, or 30 deg to the vertical. That
> > would be poor traction performance.
>
> > The tires have slip.angle.wet of about 45 to 60 and the
> > rain tires have lower slip.angle.wet. The values of
> > 45 to 60 are why I think it's measured from the horizontal.
> > If the test approximates real conditions, 45 deg from
> > vertical is outrageously good in the wet. I don't think
> > you can lean a bike over at 60 deg from vertical even in
> > dry weather without sliding out.
>
> Ugh. This is why I was confused. They didn't change the angle of the
> bike: the bike was held vertically and they tilted a slab of wet
> asphalt relative to it.

Give me a lever and a place to stand, and I shall
move the earth.

Ben

 

[[email protected]]

someone sniped anonymously:

>>> He's correctly pointed out that glue types on tubulars have an effect
>>> on the issue that does not seem to be recognized in the survey's done.

>> There has been no discussion of using shellac -- it's all road glue
>> because that's what people use. If he or anyone want to test with
>> shellac, go ahead, but that's sort of testing stuff that is not used.
>>

> I don't believe the original supposition included that specifier (road
> or track).

>>> In addition, the road surface issue is a consideration. If you're
>>> measuring resistance to a surface, then the type of surface is a major
>>> issue in the tests.

>> There is no indication why this would effect one sort of tire and not
>> another.

> Sorry, suggesting that we can _assume_ that there would be a linear
> relationship between resistance against a smooth surface and
> resistance against a road simulated surface is so far outside of
> scientific that I'm not even sure how to comment.

Oh! Can you explain what you believe causes RR? Until now it has
been elastomeric hysteresis (rebound of rubber not being the same a
compression). That the cords of a tire casing being fully encased in
elastomeric binders and the tube and tread being rubber, RR is well
understood. For that reason tire tests are performed on smooth steel
drums that cause the casing, tread and tube to flex consistently.

If you insist on a rough surface, how rough? How do you then compare
tires?

Your statement suggests there are mysterious unrecognized causes for
these losses. As was mentioned, adding surface roughness affects
tires equally except that patterned tread squirms more than slick
tread and causes even greater differences between tires but does not
change the order

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html

In the RR curves I listed, the curves are a family of nearly identical
curves, one being the multiple of the next, except that the one with
tread patterns do not fall off as much with higher inflation pressure.
and cause slight differences in slope.

Jobst Brandt

 

[[email protected]]

someone snipes:

>>> He's correctly pointed out that glue types on tubulars have an
>>> effect on the issue that does not seem to be recognized in the
>>> survey's done.

>> There has been no discussion of using shellac -- it's all road glue
>> because that's what people use. If he or anyone want to test with
>> shellac, go ahead, but that's sort of testing stuff that is not
>> used.

> You're missing the point. The point is that if there is a
> difference between shellac and other glues, why not amont road
> glues? In fact there is a difference between Conti and Mastik in
> some of the data referenced by Fogel. It follows that without
> quantifying this variable, you don't really know whether the glue
> that is used for tests is optimal.

So your point is that glue doesn't affect RR or what is it? How much
better a glue that can be used for road riding (change of tire) is not
in your assessment as I see it, so why not use hard glue and be done
with it?

>>> In addition, the road surface issue is a consideration. If you're
>>> measuring resistance to a surface, then the type of surface is a
>>> major issue in the tests.

>> There is no indication why this would effect one sort of tire and
>> not another.

> Again, you miss the point: the evidence is that smooth drums
> exaggerates differences. Reporting a wattage difference between
> tires based on smooth drum testing is misleading.

Oh! Explain what a smooth drum does to exaggerate differences and how
this adversely affects tire evaluation?

>>> Lastly, the selection of tubulars by pro teams is a major point:
>>> Considering the lengths that they go to for a mild advantage, it
>>> seems logical that they'd have studied the issue in great depth
>>> and concluded the tubulars hold an advantage. There are
>>> advantages to tubulars beyond rolling resistance.

> But none that outweigh RR for a supported pro, IMO.

The "IMO" doesn't get you off the hook. How about elaborating on the
reasons for this "outweigh"?

Jobst Brandt

 

[[email protected]]

Tim McNamara <[email protected]> writes:

>>>> so if you're using clinchers with butyl tubes, your RR is higher
>>>> than using a top tubular.

>>> And if you lowered the pressure in the clinchers to 60psi and kept
>>> the tubulars at 110psi, the clinchers would probably be slower too.
>>> Another flaw in the research.

>> Hardly. It's black and white: according to that research, if you're
>> using butyl tubes with a top clincher, you're giving up watts to
>> those using top tubulars. It's that simple.

> But it's not that simple, since various bits of research do not provide
> clear concordance.

>> People are not generally lowering their tire pressure to make
>> themselves go slower, but I bet a lot of people are using butyl tubes
>> in their clinchers and think they are still assured of better RR than
>> people on tubulars. I seem to remember Jobst himself talking about
>> why he uses butyl tubes.

> They hold air better is the reason Jobst gave, IIRC. However, tests
> conducted by Jan Heine at Bicycle Quarterly suggested that latex tubes
> were slower than butyl tubes, which is contrary to lore.

I don't believe that is possible, other factors being held constant.
Where did the extra energy go? That butyl rubber has greater losses
than latex has been known for a long time. That latex tubes are
generally thinner than butyl is also known. I think there was a major
error in that test.

Jobst Brandt

 

[[email protected]]

John Forrest Tomlinson writes:

>>>> Are you sure that it's not, at least in some circumstances? Do
>>>> you think the pro teams would publish the fact that they are
>>>> using shellac for TT bikes or anywhere else?

>>> I'm not sure but I look at that stuff kind of stuff online and
>>> (rarely) in person a lot -- have had a pro world champion in my
>>> apt, ridden with pro nat champs, etc. and a couple of my buddies
>>> used to get tons of hand-me-down stuff from arguably the top
>>> domestic pro team. I try to keep my eyes open and never heard nor
>>> read about that. Seen some weird stuff that was not obvious in my
>>> day (steel fork on a team OCLV frame is an example).

>>> I haven't been at a top-level TT though .

>> Did you ever just ask a pro mechanic what type of glue they use?

> No.

I asked many riders and mechanics over the years why they used track
glue and none could tell me, that information having apparently been
lost in dead time during WWII, after which bicycle racing was no
longer held a leading interest in sports. The answers I got did not
make sense but were often repeated, just like the reasons given for
holes in brake disks found mainly on cars that suggest racing
abilities.

Tire tests done by IRC for Avocet (the curves shown below), finally
answered for me what the effect of track (hard) glue was. When I saw
these curves, it was obvious what caused the poorer performance of the
two tubulars among these tires, known of good performance in
durability, cornering and light weight. I might have come upon this
otherwise just from the wear characteristics of tubular tire base tape
that in some cases wore through to the casing from movement.

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html

Jobst Brandt

 

[Zog The Undeniable]

[email protected] wrote:

> This is not a debate! If you talk to those who ride tubulars, their
> belief is based on reasonable evidence. Good tubulars are lighter,
> have thinner casings and tread that naturally have lower RR than a
> heavier tires and tubes.

Isn't the real benefit with tubs that the *rims* are much lighter,
because the outer wall of the box section is, in fact, the outside of
the rim? A box section clincher rim has to have all this, plus a bead seat.

 

[Hobbes@spnb&s.com]

On Sun, 02 Sep 2007 18:22:33 +0100, Zog The Undeniable <[email protected]>
wrote:

>[email protected] wrote:
>
>> This is not a debate! If you talk to those who ride tubulars, their
>> belief is based on reasonable evidence. Good tubulars are lighter,
>> have thinner casings and tread that naturally have lower RR than a
>> heavier tires and tubes.
>
>Isn't the real benefit with tubs that the *rims* are much lighter,
>because the outer wall of the box section is, in fact, the outside of
>the rim? A box section clincher rim has to have all this, plus a bead seat.

That's a benefit.

I think it's mostly the effectiveness of the tire at providing rim protection
and a good ride. The ratio of effective to overall volume in a sewup is so great
that there's really nothing you can do in the design of a clincher that can
match it.

Ron

 

[[email protected]]

On Sep 1, 7:40 am, [email protected] wrote:
> I haven't seen any.

You're a day (or so) late and a dollar short.