Hard braking down hill blowouts

[Jay Beattie]

On Mar 28, 11:59 am, Hank <[email protected]> wrote:
> On Mar 28, 9:30 am, Jay Beattie <[email protected]> wrote:
>
>
>
>
>
> > On Mar 28, 8:26 am, Marz <[email protected]> wrote:
>
> > > On Mar 28, 3:49 am, Ben C <[email protected]> wrote:
>
> > > > On 2008-03-28, Ben Kaufman <[email protected]> wrote:
>
> > > > > Is it normal to have blow-outs on a road bike from prolonged hard
> > > > > braking going about one mile down  a  steep hill  or should superior
> > > > > wheels and tires be able to deal with the generated heat?  I have an
> > > > > old panasonic but keep the tires and tubes up to date (PerfomanceBike
> > > > > GT2 Kevlar, rated at 105 lbs, 26TPI,  which are not the best in the
> > > > > world but  a heck of a lot better than what my LBS sold me. It is a
> > > > > 27 inch rim and I could not find any better quality tires).  Butis it
> > > > > the tire/wheel quality at issue?  I have been thinking about getting a
> > > > > new bike rather than trying to  upgrade this one for a number of
> > > > > reasons (I don't think it's even possible to switch to the current
> > > > > wheel size) but  the blow-outs are my biggest justification of
> > > > > expenditure to my wife.
>
> > > > Some math I did earlier:
>
> > > >http://groups.google.co.uk/group/uk.rec.cycling/msg/991d32532f671264
>
> > > > It's probably all wrong off course, but my tentative conclusion fromit
> > > > is that the rims act as heat sinks-- they can soak up quite a lot of
> > > > energy, enough for most purposes, but they can't really cope with
> > > > sustained braking.
>
> > > > Disks on the other hand have much less heat capacity (because they're
> > > > smaller) and probably work hotter, so I reckon they might get up to
> > > > temperature quite quickly and then dissipate more because of the bigger
> > > > temperature difference with the surrounding air. This would mean they
> > > > should be better for continuous braking. In any case they won't makethe
> > > > tyres pop off.
>
> > > Disk brakes have their own problems with heat and can 'fade' (fail) on
> > > long downhill sections.
>
> > > From hayes...
>
> > > "Brake Fluid Fade - This type of fade occurs when the brake fluid
> > > inside a hydraulic caliper boils.  An important characteristic of
> > > brake fluid is that it is incompressible.  When a brake fluid boils,
> > > gas is formed within the system that is compressible and any lever
> > > stroke available goes toward compressing the gas instead of generating
> > > brake power.  Interestingly enough, when a fluid is under pressure, it
> > > is very difficult for the fluid to boil.  If a brake system is under
> > > pressure, the fluid temperature can rise above the boiling temperature
> > > without the fluid actually boiling.  Once the pressure is released,
> > > the fluid will instantly boil and fade will occur."
>
> > > A common practice for long downhill sections when using disk brakes is
> > > to brake hard and release as opposed to constant braking to control
> > > speed. The idea being, that when you release you allow the disk to
> > > cool slighty.
>
> > > I've experienced disk brake fade more often than rim brake blow outs
> > > and that the disk brake fade occurs quicker during a descent than a
> > > rim brake blow out. But, the offroad trails I ride are on average alot
> > > steeper than the roads I ride and also require alot more braking.
>
> > I think that is an important point -- road versus trail.  I have done
> > long road descents on my mechanical disk equiped cross bike without
> > any brake fade.
>
> Well, yeah - if it's mechanical, the fluid definitely won't boil!- Hide quoted text -

My cables boil! I was thinking of friction material fade. I totally
glossed over the brake fluid boiling issue. It would seem to me that
you could divert brake fluid heat in to a radiant loop to power a
steam generator for the ride up the other side of the hill. Carl can
probably find a filed patent for that. -- Jay Beattie.

 

[Jay Beattie]

On Mar 28, 11:59 am, Hank <[email protected]> wrote:
> On Mar 28, 9:30 am, Jay Beattie <[email protected]> wrote:
>
>
>
>
>
> > On Mar 28, 8:26 am, Marz <[email protected]> wrote:
>
> > > On Mar 28, 3:49 am, Ben C <[email protected]> wrote:
>
> > > > On 2008-03-28, Ben Kaufman <[email protected]> wrote:
>
> > > > > Is it normal to have blow-outs on a road bike from prolonged hard
> > > > > braking going about one mile down  a  steep hill  or should superior
> > > > > wheels and tires be able to deal with the generated heat?  I have an
> > > > > old panasonic but keep the tires and tubes up to date (PerfomanceBike
> > > > > GT2 Kevlar, rated at 105 lbs, 26TPI,  which are not the best in the
> > > > > world but  a heck of a lot better than what my LBS sold me. It is a
> > > > > 27 inch rim and I could not find any better quality tires).  Butis it
> > > > > the tire/wheel quality at issue?  I have been thinking about getting a
> > > > > new bike rather than trying to  upgrade this one for a number of
> > > > > reasons (I don't think it's even possible to switch to the current
> > > > > wheel size) but  the blow-outs are my biggest justification of
> > > > > expenditure to my wife.
>
> > > > Some math I did earlier:
>
> > > >http://groups.google.co.uk/group/uk.rec.cycling/msg/991d32532f671264
>
> > > > It's probably all wrong off course, but my tentative conclusion fromit
> > > > is that the rims act as heat sinks-- they can soak up quite a lot of
> > > > energy, enough for most purposes, but they can't really cope with
> > > > sustained braking.
>
> > > > Disks on the other hand have much less heat capacity (because they're
> > > > smaller) and probably work hotter, so I reckon they might get up to
> > > > temperature quite quickly and then dissipate more because of the bigger
> > > > temperature difference with the surrounding air. This would mean they
> > > > should be better for continuous braking. In any case they won't makethe
> > > > tyres pop off.
>
> > > Disk brakes have their own problems with heat and can 'fade' (fail) on
> > > long downhill sections.
>
> > > From hayes...
>
> > > "Brake Fluid Fade - This type of fade occurs when the brake fluid
> > > inside a hydraulic caliper boils.  An important characteristic of
> > > brake fluid is that it is incompressible.  When a brake fluid boils,
> > > gas is formed within the system that is compressible and any lever
> > > stroke available goes toward compressing the gas instead of generating
> > > brake power.  Interestingly enough, when a fluid is under pressure, it
> > > is very difficult for the fluid to boil.  If a brake system is under
> > > pressure, the fluid temperature can rise above the boiling temperature
> > > without the fluid actually boiling.  Once the pressure is released,
> > > the fluid will instantly boil and fade will occur."
>
> > > A common practice for long downhill sections when using disk brakes is
> > > to brake hard and release as opposed to constant braking to control
> > > speed. The idea being, that when you release you allow the disk to
> > > cool slighty.
>
> > > I've experienced disk brake fade more often than rim brake blow outs
> > > and that the disk brake fade occurs quicker during a descent than a
> > > rim brake blow out. But, the offroad trails I ride are on average alot
> > > steeper than the roads I ride and also require alot more braking.
>
> > I think that is an important point -- road versus trail.  I have done
> > long road descents on my mechanical disk equiped cross bike without
> > any brake fade.
>
> Well, yeah - if it's mechanical, the fluid definitely won't boil!- Hide quoted text -

My cables boil! I was thinking of friction material fade. I totally
glossed over the brake fluid boiling issue. It would seem to me that
you could divert brake fluid heat in to a radiant loop to power a
steam generator for the ride up the other side of the hill. Carl can
probably find a filed patent for that. -- Jay Beattie.

 

[SMS]

Ben Kaufman wrote:
> Is it normal to have blow-outs on a road bike from prolonged hard braking going
> about one mile down a steep hill or should superior wheels and tires be able
> to deal with the generated heat?

It's normal. Pump your brakes rather than having them on all the time,
and stop occasionally to let them cool. That said, it does vary with rim
and tires. It's not the air in the tube expanding because of the heat
that causes the blow out, it's the rim getting too hot.

Are your rims straight side or hook edge? What kind of bead does the GT2
tire have (steel or kevlar)? Sheldon's shop sells some 27" steel bead
tires. See "http://www.sheldonbrown.com/harris/tires/630.html"

Also, for a good and amusing tutorial by Sheldon about folding steel
bead tires, see "http://www.sheldonbrown.com/video/tire-folding.html".
Remember, red is the only color that works, LOL.

On tandems, there was (or is) often a drum brake to use as a drag break
when descending steep hills. A disc brake doesn't work well as a drag
brake, as the rotor will warp and the pad will quickly be worn down.

I have an old panasonic but keep the tires and
> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
> not the best in the world but a heck of a lot better than what my LBS sold me.
> It is a 27 inch rim and I could not find any better quality tires). But is it
> the tire/wheel quality at issue? I have been thinking about getting a new bike
> rather than trying to upgrade this one for a number of reasons (I don't think
> it's even possible to switch to the current wheel size) but the blow-outs are
> my biggest justification of expenditure to my wife.

It's a good justification. Get a road bike with disc brakes. It will
eliminate the blow outs, but if you ride with the brakes constantly on
you'll go through a lot of pads and rotors.

 

[SMS]

Jay Beattie wrote:
> On Mar 28, 8:26 am, Marz <[email protected]> wrote:

>> I've experienced disk brake fade more often than rim brake blow outs
>> and that the disk brake fade occurs quicker during a descent than a
>> rim brake blow out. But, the offroad trails I ride are on average alot
>> steeper than the roads I ride and also require alot more braking.
>
> I think that is an important point -- road versus trail. I have done
> long road descents on my mechanical disk equiped cross bike without
> any brake fade. In fact, in the rain, the disks are far better than
> my rim brakes. There is a local 14 mile descent that I did in the
> rain/snow on my cross bike with good stopping all the way to the
> bottom -- which was a good thing because my hands were frozen, and I
> couldn't generate much force on my levers. -- Jay Beattie.

Yeah, the problem with disk brake fade is more common with hydraulic
disk brakes than mechanical disk brakes. Always use non-hydraulic disk
brakes if retro-fitting, and look for mechanical disk brakes on new
bicycles as well.

 

[SMS]

Jay Beattie wrote:

> My cables boil! I was thinking of friction material fade. I totally
> glossed over the brake fluid boiling issue. It would seem to me that
> you could divert brake fluid heat in to a radiant loop to power a
> steam generator for the ride up the other side of the hill.

I use the steam to power a generator that operates by lights.

 

[[email protected]]

On Fri, 28 Mar 2008 12:15:25 -0700 (PDT), Jay Beattie
<[email protected]> wrote:

>My cables boil! I was thinking of friction material fade. I totally
>glossed over the brake fluid boiling issue. It would seem to me that
>you could divert brake fluid heat in to a radiant loop to power a
>steam generator for the ride up the other side of the hill. Carl can
>probably find a filed patent for that. -- Jay Beattie.

Dear Jay,

Alas, re-generative braking systems are notoriously inefficient, so
early inventors concentrated on worthier steam-powered bicycles:

http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/steambike/steambike.htm

The Michaux steam velocipede is the epitome of elegance and good
looks, but the Roper was far more efficient.

Details on the Roper, whose inventor died while riding it:
http://motorcyclemuseum.org/classics/bike.asp?id=3

Movie with exciting sound track of a Roper replica chugging along:
http://www.lindsaybks.com/gallery/Jorg/cycle/Jorgbike.mov

Cheers,

Carl Fogel

 

[Michael Press]

In article
<04d83991-8e34-4954-9882-dd742be9b56a@f63g2000hsf.googlegroups.com>,
Marz <[email protected]> wrote:

> A common practice for long downhill sections when using disk brakes is
> to brake hard and release as opposed to constant braking to control
> speed. The idea being, that when you release you allow the disk to
> cool slighty.

Yes. The idea is to heat the disc quickly and very
hot. The convective cooling to the air is faster at
higher temperature. The heat transfer to the hub and
brake assemblies is reduced because the disc can cool
to a lower temperature before it is heated again, and
the brake assembly can also cool.

--
Michael Press

 

[jim beam]

Marz wrote:
> On Mar 28, 9:03�am, jim beam <[email protected]> wrote:
>> [email protected] wrote:
>>> Ben C? wrote:
>>>>>> Disks on the other hand have much less heat capacity
>>>>> Nor do they exchange heat with the tyre.
>>>> Indeed. �I wonder if they ever melt the grease in the hub though.
>>> Most bicycle disks are mounted on support spiders so flimsy that heat
>>> conduction to the bearings is insignificant.
>> "flimsy"??? �is that stanford parlance for "stainless [disk] steel is a
>> poor conductor"? �or is it presumptive nonsense from someone that
>> doesn't know what they're talking about?
>
> Disks are very flimsy and are not constructed to resist side to side
> forces. They're only 'stiff' in the direction of the rotating wheel.
> And not all disks are contructed with stainless steel spiders (see
> Hope).

stiffness has absolutely nothing to do with thermal conductivity. or
surface thermal transfer to air.


>
> For example you could poor water on a hot rim to cool it, but the same
> action on a disk may (and has for me) warp the bloody thing.
>
> laters,
>
> Marz

 

[jim beam]

Ben C wrote:
> On 2008-03-28, Marz <[email protected]> wrote:
>> On Mar 28, 3:49 am, Ben C <[email protected]> wrote:
>>> On 2008-03-28, Ben Kaufman <[email protected]> wrote:
> [...]
>> Disk brakes have their own problems with heat and can 'fade' (fail) on
>> long downhill sections.
>>
>> From hayes...
>>
>> "Brake Fluid Fade - This type of fade occurs when the brake fluid
>> inside a hydraulic caliper boils. An important characteristic of
>> brake fluid is that it is incompressible. When a brake fluid boils,
>> gas is formed within the system that is compressible and any lever
>> stroke available goes toward compressing the gas instead of generating
>> brake power. Interestingly enough, when a fluid is under pressure, it
>> is very difficult for the fluid to boil. If a brake system is under
>> pressure, the fluid temperature can rise above the boiling temperature
>> without the fluid actually boiling. Once the pressure is released,
>> the fluid will instantly boil and fade will occur."
>>
>> A common practice for long downhill sections when using disk brakes is
>> to brake hard and release as opposed to constant braking to control
>> speed. The idea being, that when you release you allow the disk to
>> cool slighty.
>>
>> I've experienced disk brake fade more often than rim brake blow outs
>> and that the disk brake fade occurs quicker during a descent than a
>> rim brake blow out. But, the offroad trails I ride are on average alot
>> steeper than the roads I ride and also require alot more braking.
>
> I have heard of fluid fade affecting bicycle brakes before. It is
> shocking in my opinion because that's the easiest kind of fade to fix--
> you just need brake fluid that doesn't boil, which exists. There's no
> tradeoff or anything, it's a win-win no-brainer. Cars haven't suffered
> from fluid fade for years with modern decent brake fluid.
>
> I mentioned this before and someone said it's because bicycle brakes use
> crappy brake fluid because it doesn't strip the paint. My advice: use
> proper car brake fluid in your bike brakes but pour it in carefully and
> don't spill it.

or if you do, wash it off immediately with water. wash, never wipe.

 

[Ben Kaufman]

On Fri, 28 Mar 2008 12:29:10 -0400, Hobbes@spnb&s.com wrote:

>On Thu, 27 Mar 2008 22:06:48 -0400, Ben Kaufman
><[email protected]> wrote:
>
>>Is it normal to have blow-outs on a road bike from prolonged hard braking going
>>about one mile down a steep hill or should superior wheels and tires be able
>>to deal with the generated heat? I have an old panasonic but keep the tires and
>>tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
>>not the best in the world but a heck of a lot better than what my LBS sold me.
>>It is a 27 inch rim and I could not find any better quality tires). But is it
>>the tire/wheel quality at issue? I have been thinking about getting a new bike
>>rather than trying to upgrade this one for a number of reasons (I don't think
>>it's even possible to switch to the current wheel size) but the blow-outs are
>>my biggest justification of expenditure to my wife.
>
>Actual blow outs or is the tire moving on the rim and tearing the stem?
>
>Just asking because the latter is more common but the former more often blamed.

No, the tire stayed on the rim. I heard the bang but at first could not tell
which tire had blown - fortunately, I was going under 10mph at the time. The
location of the failure on the tube was about 1/3 of the way around from the
stem and was a 2 inch appearing "slit." In other blowouts I have felt a tell
tale "thump thump" before it blew, and usually in those the tire is taken off
the rim, which makes the tube replacement process that much faster

Ben

 

[Ben Kaufman]

On Fri, 28 Mar 2008 12:47:50 -0700, SMS <[email protected]> wrote:

>Ben Kaufman wrote:
>> Is it normal to have blow-outs on a road bike from prolonged hard braking going
>> about one mile down a steep hill or should superior wheels and tires be able
>> to deal with the generated heat?
>
>It's normal. Pump your brakes rather than having them on all the time,
>and stop occasionally to let them cool. That said, it does vary with rim
>and tires. It's not the air in the tube expanding because of the heat
>that causes the blow out, it's the rim getting too hot.
>
>Are your rims straight side or hook edge? What kind of bead does the GT2
>tire have (steel or kevlar)? Sheldon's shop sells some 27" steel bead
>tires. See "http://www.sheldonbrown.com/harris/tires/630.html"

Wow, I see they do still have some name brand 27" tires. Thanks.
>
My rims are straight. The tire has a wire bead, I just checked the specs.
When I get them from performance they were "folded" but they spring back when
unleashed. The tires that my LBS put on were terrible. I think they were Kenda
brand and they would unseat and blow without provocation.


>Also, for a good and amusing tutorial by Sheldon about folding steel
>bead tires, see "http://www.sheldonbrown.com/video/tire-folding.html".
>Remember, red is the only color that works, LOL.
>
>On tandems, there was (or is) often a drum brake to use as a drag break
>when descending steep hills. A disc brake doesn't work well as a drag
>brake, as the rotor will warp and the pad will quickly be worn down.
>
> I have an old panasonic but keep the tires and
>> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
>> not the best in the world but a heck of a lot better than what my LBS sold me.
>> It is a 27 inch rim and I could not find any better quality tires). But is it
>> the tire/wheel quality at issue? I have been thinking about getting a new bike
>> rather than trying to upgrade this one for a number of reasons (I don't think
>> it's even possible to switch to the current wheel size) but the blow-outs are
>> my biggest justification of expenditure to my wife.
>
>It's a good justification. Get a road bike with disc brakes. It will
>eliminate the blow outs, but if you ride with the brakes constantly on
>you'll go through a lot of pads and rotors.

I didn't know they made road bikes with disk brakes, I was thinking of something
like a Giant OCR C3..hmm I will have to look around some more. It is only this
one steep hill that gives me problems because of the hazards that I must keep
speed down, and of course I tend to keep it braking even harder for fear of
going too fast if I do have a blow out. My assumption, based upon the square of
velocity for kinetic energy is that it would generate less heat if I kept the
speed down to 10mph rather than 20mph (i would be going close to 50 mph without
braking).

Ben

 

[Ben Kaufman]

On 28 Mar 2008 05:35:01 GMT, [email protected] wrote:

>Ben Kaufman wrote:
>
>> Is it normal to have blow-outs on a road bike from prolonged hard
>> braking going about one mile down a steep hill or should superior
>> wheels and tires be able to deal with the generated heat? I have an
>> old Panasonic but keep the tires and tubes up to date
>> (Performance Bike GT2 Kevlar, rated at 105 lbs, 26TPI, which are not
>> the best in the world but a heck of a lot better than what my LBS
>> sold me. It is a 27 inch rim and I could not find any better
>> quality tires). But is it the tire/wheel quality at issue? I have
>> been thinking about getting a new bike rather than trying to upgrade
>> this one for a number of reasons (I don't think it's even possible
>> to switch to the current wheel size) but the blow-outs are my
>> biggest justification of expenditure to my wife.
>
>This is a traditional problem, so much so that bicycles are prohibited
>down certain roads in the Alps. Zirlerberg above Innsbruck is a
>classic with six runaway escape ramps for brake failures of trucks.
>The Würzen Pass from Slovenia to Austria has a long 18% grade.
>
>Locally in the Santa Clara Valley we have several tire blow-off
>descents on Metcalf Road and Hicks and Almaden Roads, each of which
>has had fatalities on descents. Tandems are noted for this problem,
>especially if the driver isn't careful to use front and rear brakes
>equally. For this reason tandems used for mountain touring are best
>equipped with hub brakes (drums or disks).
>
>In the days of tubular tires, that were glued onto rims, glue melted
>allowing tires to creep and tear off the inflation stem causing rapid
>deflation. I experienced that effect in the alps ans later had
>clincher blow-offs on the same stretch of the Gotthard Pass.
>
>I instrumented a wheel with pressure sensor and temperature
>thermocouple to monitor a blow-off but was unsuccessful getting the
>tire to separate even though temperature reached 150 degC and pressure
>125 psi. The mechanism for blow-off is still unclear but it seams the
>bead material softens and creeps of the hooked bead of the rim.
>
>On steep descents after riding through water, I have generated steam
>that came hissing out of the rim from around the stem as I braked for
>successive hairpin turns on the Nufenen Pass in the Alps.
>
>Jobst Brandt

Darn, I may just have to avoid this hill in warmer weather

Ben

 

[[email protected]]

Ben Kaufman wrote:

>>> Is it normal to have blow-outs on a road bike from prolonged hard
>>> braking going about one mile down a steep hill or should superior
>>> wheels and tires be able to deal with the generated heat? I have
>>> an old Panasonic but keep the tires and tubes up to date
>>> (Performance Bike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
>>> not the best in the world but a heck of a lot better than what my
>>> LBS sold me. It is a 27 inch rim and I could not find any better
>>> quality tires). But is it the tire/wheel quality at issue? I
>>> have been thinking about getting a new bike rather than trying to
>>> upgrade this one for a number of reasons (I don't think it's even
>>> possible to switch to the current wheel size) but the blow-outs
>>> are my biggest justification of expenditure to my wife.

>> This is a traditional problem, so much so that bicycles are
>> prohibited down certain roads in the Alps. Zirlerberg above
>> Innsbruck is a classic with six runaway escape ramps for brake
>> failures of trucks. The Würzen Pass from Slovenia to Austria hasa
>> long 18% grade.

>> Locally in the Santa Clara Valley we have several tire blow-off
>> descents on Metcalf Road and Hicks and Almaden Roads, each of which
>> has had fatalities on descents. Tandems are noted for this
>> problem, especially if the driver isn't careful to use front and
>> rear brakes equally. For this reason tandems used for mountain
>> touring are best equipped with hub brakes (drums or disks).

>> In the days of tubular tires, that were glued onto rims, glue
>> melted allowing tires to creep and tear off the inflation stem
>> causing rapid deflation. I experienced that effect in the alps ans
>> later had clincher blow-offs on the same stretch of the Gotthard
>> Pass.

>> I instrumented a wheel with pressure sensor and temperature
>> thermocouple to monitor a blow-off but was unsuccessful getting the
>> tire to separate even though temperature reached 150 degC and
>> pressure 125 psi. The mechanism for blow-off is still unclear but
>> it seams the bead material softens and creeps of the hooked bead of
>> the rim.

>> On steep descents after riding through water, I have generated
>> steam that came hissing out of the rim from around the stem as I
>> braked for successive hairpin turns on the Nufenen Pass in the
>> Alps.

> Darn, I may just have to avoid this hill in warmer weather

I didn't mention it but this was with tubular tires on socketed rims,
so a rim strip had no part in this. Evaporative cooling is so fast
that as soon as the brake was released, the hissing steam ceased. At
first I thought I had a puncture and I was hearing air escaping from
the tire.

The lesson learned here is that there is much kinetic energy going
into the rim from braking. That it can produce steam reveals how hot
rims become even in cold weather. Water got into the rim crossing the
San Giacomo pass walking and sliding in deep snow and crossing a creek
to get on the plowed Nufenen Pass, the San Giacomo pass was still
snowed shut from winter.

http://www.goyellow.de/map/?lon=8.38788&lat=46.47754&z=14&mt=aerial

Passo della Novena := Nufenen Pass

Jobst Brandt

 

[datakoll]

On Mar 27, 10:06 pm, Ben Kaufman <spaXm-mXe-anXd-paXy-5000-
[email protected]> wrote:
> Is it normal to have blow-outs on a road bike from prolonged hard braking going
> about one mile down  a  steep hill  or should superior wheels and tires be able
> to deal with the generated heat?  I have an old panasonic but keep the tires and
> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI,  which are
> not the best in the world but  a heck of a lot better than what my LBS sold me.
> It is a  27 inch rim and I could not find any better quality tires).  But is it
> the tire/wheel quality at issue?  I have been thinking about getting a new bike
> rather than trying to  upgrade this one for a number of reasons (I don'tthink
> it's even possible to switch to the current wheel size) but  the blow-outs are
> my biggest justification of expenditure to my wife.
>
> Thanks.
>
> Ben

How many times do you bake from X to Y ? and how long are the times
from braking point A to BP B?

I wrote the following last night. Sidewall dirt at the bead is
relatively invisible under normal shop conditions.
a thorough all surfaces cleaning before reassembly helps (and before
disassembly) then pull and push nipple in and out to seat and pinch
pinch pinch sidewalls inward thoroughly all around before and then
maybe during the first pounds going in.
once in a while when placing a new tube in, I'll soap, soak and brush
sidewalls clean. I cover the sidewalls with FL teflon wax on the bead
then overspray the area with belt conditioner as brake prep so the
dirt is on that surface, floats away when soaping. after it gets
beaten with a stick.

 

[datakoll]

On Mar 27, 10:06 pm, Ben Kaufman <spaXm-mXe-anXd-paXy-5000-
[email protected]> wrote:
> Is it normal to have blow-outs on a road bike from prolonged hard braking going
> about one mile down  a  steep hill  or should superior wheels and tires be able
> to deal with the generated heat?  I have an old panasonic but keep the tires and
> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI,  which are
> not the best in the world but  a heck of a lot better than what my LBS sold me.
> It is a  27 inch rim and I could not find any better quality tires).  But is it
> the tire/wheel quality at issue?  I have been thinking about getting a new bike
> rather than trying to  upgrade this one for a number of reasons (I don'tthink
> it's even possible to switch to the current wheel size) but  the blow-outs are
> my biggest justification of expenditure to my wife.
>
> Thanks.
>
> Ben

btw. BEN, do you know what reconditioned Panasonics are fetching on
Ebay?

 

[Michael Press]

In article <[email protected]>,
Ben Kaufman <[email protected]> wrote:

> On Fri, 28 Mar 2008 12:47:50 -0700, SMS <[email protected]> wrote:
>
> >Ben Kaufman wrote:
> >> Is it normal to have blow-outs on a road bike from prolonged hard braking going
> >> about one mile down a steep hill or should superior wheels and tires be able
> >> to deal with the generated heat?
> >
> >It's normal. Pump your brakes rather than having them on all the time,
> >and stop occasionally to let them cool. That said, it does vary with rim
> >and tires. It's not the air in the tube expanding because of the heat
> >that causes the blow out, it's the rim getting too hot.
> >
> >Are your rims straight side or hook edge? What kind of bead does the GT2
> >tire have (steel or kevlar)? Sheldon's shop sells some 27" steel bead
> >tires. See "http://www.sheldonbrown.com/harris/tires/630.html"
>
> Wow, I see they do still have some name brand 27" tires. Thanks.
> >
> My rims are straight. The tire has a wire bead, I just checked the specs.
> When I get them from performance they were "folded" but they spring back when
> unleashed. The tires that my LBS put on were terrible. I think they were Kenda
> brand and they would unseat and blow without provocation.
>
>
> >Also, for a good and amusing tutorial by Sheldon about folding steel
> >bead tires, see "http://www.sheldonbrown.com/video/tire-folding.html".
> >Remember, red is the only color that works, LOL.
> >
> >On tandems, there was (or is) often a drum brake to use as a drag break
> >when descending steep hills. A disc brake doesn't work well as a drag
> >brake, as the rotor will warp and the pad will quickly be worn down.
> >
> > I have an old panasonic but keep the tires and
> >> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
> >> not the best in the world but a heck of a lot better than what my LBS sold me.
> >> It is a 27 inch rim and I could not find any better quality tires). But is it
> >> the tire/wheel quality at issue? I have been thinking about getting a new bike
> >> rather than trying to upgrade this one for a number of reasons (I don't think
> >> it's even possible to switch to the current wheel size) but the blow-outs are
> >> my biggest justification of expenditure to my wife.
> >
> >It's a good justification. Get a road bike with disc brakes. It will
> >eliminate the blow outs, but if you ride with the brakes constantly on
> >you'll go through a lot of pads and rotors.
>
> I didn't know they made road bikes with disk brakes, I was thinking of something
> like a Giant OCR C3..hmm I will have to look around some more. It is only this
> one steep hill that gives me problems because of the hazards that I must keep
> speed down, and of course I tend to keep it braking even harder for fear of
> going too fast if I do have a blow out. My assumption, based upon the square of
> velocity for kinetic energy is that it would generate less heat if I kept the
> speed down to 10mph rather than 20mph (i would be going close to 50 mph without
> braking).

Best to get going fast so that convective cooling is greatest.
Convective cooling increases linearly with temperature difference
and much more rapidly than linearly with speed.

Get up to high speed, brake rapidly to low speed. Stop altogether
if you feel hinky. On a regular route you could stop at different
times and check rim temperature. Use the _back_ of you hand, and
swipe it across the rim.

--
Michael Press

 

[Tom Sherman]

datakoll aka gene daniels wrote:
>
> btw. BEN, do you know what reconditioned Panasonics are fetching on
> Ebay?

$795 for a 2007 "packable" Panasonic touring frameset, including
headset, fenders and racks: <http://www.yellowjersey.org/posd7.html>?

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

 

[Ben Kaufman]

On Sat, 29 Mar 2008 13:06:22 -0700, Michael Press <[email protected]> wrote:

>In article <[email protected]>,
> Ben Kaufman <[email protected]> wrote:
>
>> On Fri, 28 Mar 2008 12:47:50 -0700, SMS <[email protected]> wrote:
>>
>> >Ben Kaufman wrote:
>> >> Is it normal to have blow-outs on a road bike from prolonged hard braking going
>> >> about one mile down a steep hill or should superior wheels and tires be able
>> >> to deal with the generated heat?
>> >
>> >It's normal. Pump your brakes rather than having them on all the time,
>> >and stop occasionally to let them cool. That said, it does vary with rim
>> >and tires. It's not the air in the tube expanding because of the heat
>> >that causes the blow out, it's the rim getting too hot.
>> >
>> >Are your rims straight side or hook edge? What kind of bead does the GT2
>> >tire have (steel or kevlar)? Sheldon's shop sells some 27" steel bead
>> >tires. See "http://www.sheldonbrown.com/harris/tires/630.html"
>>
>> Wow, I see they do still have some name brand 27" tires. Thanks.
>> >
>> My rims are straight. The tire has a wire bead, I just checked the specs.
>> When I get them from performance they were "folded" but they spring back when
>> unleashed. The tires that my LBS put on were terrible. I think they were Kenda
>> brand and they would unseat and blow without provocation.
>>
>>
>> >Also, for a good and amusing tutorial by Sheldon about folding steel
>> >bead tires, see "http://www.sheldonbrown.com/video/tire-folding.html".
>> >Remember, red is the only color that works, LOL.
>> >
>> >On tandems, there was (or is) often a drum brake to use as a drag break
>> >when descending steep hills. A disc brake doesn't work well as a drag
>> >brake, as the rotor will warp and the pad will quickly be worn down.
>> >
>> > I have an old panasonic but keep the tires and
>> >> tubes up to date (PerfomanceBike GT2 Kevlar, rated at 105 lbs, 26TPI, which are
>> >> not the best in the world but a heck of a lot better than what my LBS sold me.
>> >> It is a 27 inch rim and I could not find any better quality tires). But is it
>> >> the tire/wheel quality at issue? I have been thinking about getting a new bike
>> >> rather than trying to upgrade this one for a number of reasons (I don't think
>> >> it's even possible to switch to the current wheel size) but the blow-outs are
>> >> my biggest justification of expenditure to my wife.
>> >
>> >It's a good justification. Get a road bike with disc brakes. It will
>> >eliminate the blow outs, but if you ride with the brakes constantly on
>> >you'll go through a lot of pads and rotors.
>>
>> I didn't know they made road bikes with disk brakes, I was thinking of something
>> like a Giant OCR C3..hmm I will have to look around some more. It is only this
>> one steep hill that gives me problems because of the hazards that I must keep
>> speed down, and of course I tend to keep it braking even harder for fear of
>> going too fast if I do have a blow out. My assumption, based upon the square of
>> velocity for kinetic energy is that it would generate less heat if I kept the
>> speed down to 10mph rather than 20mph (i would be going close to 50 mph without
>> braking).
>
>Best to get going fast so that convective cooling is greatest.
>Convective cooling increases linearly with temperature difference
>and much more rapidly than linearly with speed.
>
>Get up to high speed, brake rapidly to low speed. Stop altogether
>if you feel hinky. On a regular route you could stop at different
>times and check rim temperature. Use the _back_ of you hand, and
>swipe it across the rim.

Unfortunately, I have to keep the speed down on this particular hill due to the
curves, unpredictability of cars and road debris, including fallen rock. It is
also so steep that coasting speed gets back up very quickly so there is little
time before I have to reapply the brakes, especially towards the bottom where it
is steepest and there is the greatest danger of cars blowing a stop sign.
However, I do what you suggest on another hill (Harriman St. Park, NY) where I
can coast up to 40mph and not have to worry about anything (other than a crazy
deer) until a hairpin turn and then back up hill.

Ben

 

[datakoll]

Tom, do you work for the State?

 

[Tom Sherman]

datakoll aka gene daniels wrote:
>
> Tom, do you work for the State?

I do not have the connections to even get interviewed for a government job.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful