Heat dispersal issues with Bicycle brakes

I ride down Hill a lot (full story below) and occasionally get a smell
of burning rubber which until now I always assumed was probably the
pads, however my rear tyre just blew at the point where the tyre touches
the wheel rim and could easily have taken me with it so how do I either
fit disk brakes to a bicycle that wasn't designed to take them, or can
you think of another solution?

As some may know I'm currently living in Hong Kong, you may also be
aware of the fact that we have a hill hear abouts, from which on a nice
clear balmy night like tonight you get a fabulous view of central and
Kowloon. I've just returned from an evening photographic section on the
peak, [1] and as I've done 3 times before I took my fold up bicycle [3]
as riding down is a hoot, the vertical decent is over 500 meters and
there are 2 routes you can take, either Old Peak Road [4] and Magazine
Gap and I decided to take the later.

Having taken a load of photos I climb on the bike and head off, slowly
gathering speed, I'm quickly overtaken buy a pizza delivery boy on a
50cc moped but 2 minutes later I sail past him glancing on the way past
at his speedo which reads 50 Kmph. It's a lot of fun as you can imagine
but can't last forever and about 15 minutes later I arrive at the place
just before the bottom of the hill where I have to haul on the brakes
[5] and turn into a car park to get home, this all goes according to
plan and I get off the bike to push it up the short hill back to my
block [6] but as I'm pushing the bike the rear tire blows taking about 3
seconds to deflate fully, "**** me" thinks I "nice of it to do it now".
Any advice on how to continue riding down hill like a nutter but avoid
this potentially lethal side effect of using the brakes too much would
be great fully received.

[1] nothing serious, I'm an armature but I get some good [2] photos
[2] in my opinion
[3] this time in the back of a cab but I have used the bus and the Peak
Tram in the past
[4] the word road is misleading as it's preposterously steep, it's no
longer open to vehicular traffic as we now have the very long but not so
steep Magazine Gap, I went down it on the push bike a couple of months
ago and when I arrived at the bottom I noticed this smell of burning
rubber and realised that I had tested the endurance of the brakes on the
bike to the limit. I have vaguely asked about fitting disk brakes to the
rear wheal as I use these to control my speed and only use the fount to
stop and been told that is is not possible.
[5] not that I didn't have the brakes partially on most of the way anyway
[6] It's not possible to approach it from above

--
Bob
Currently borrowing a black and red Yamaha XJ750 with fuel injection
Present: Honda XL125RF (FS)
Past: Honda CG125
bob at homeurl tomato dot co dot uk
remove the red fruit if you’d like to email me.

 

Is there a link to them? Could generate some interest.

 

If not I'm sure it could be rectified.

 

It might take several people. Working on a rotor basis.

 

The Older Gentleman wrote

If current theories hold true.

 

Nah, he's winding us up.

 

Sounds like the brake is badly adjusted and the block is rubbing the
tyre on braking.

But anyway, you can get brackets that will allow fitting of an
International Standard caliper to a non-disc frame but they aren't too
good. They flex a lot. You could probably get a good framebuilder to
braze a mount on though, if it's a steel or ti frame.

As far as forks are concerned it'd be cheaper an easier to replace the
fork with one that already has a disc mount.

Disc brakes do rock, I wouldn't be without them now.

 

I think he's gone ohm now.

 

Well, don't start coiling him names
--
Catman MIB#14 SKoGA#6 TEAR#4 BOTAFOF#38 Apostle#21 COSOC#3
Tyger, Tyger Burning Bright (Remove rust to reply)
Alfa 116 Giulietta 3.0l (Really) Sprint 1.7
Triumph Speed Triple: Black with extra black bits
www.cuore-sportivo.co.uk

 

On the 18:15 ex-Victoria with all the other commutators.

 

Watt's that?

 

Do you leave the breaks on for a long time? It's better to repeatedly apply
them hard for a short while then release them for a bit to give them chance
to cool down rather than keeping them on at a low pressure for a long time.

 

It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember
(The Older Gentleman) saying
something like:

He's given us the brush off, slipring away like that.

--

Dave

GS 850 x2 / SE 6a
SbS#6 DIAABTCOD#16 APOSTLE#6 FUB#3
FUB KotL OSOS#12? UKRMMA#19 COSOC#10

 

Just checked, there is a full 1.5 ~ 2 millimetres of clearance so 'snot
that.

It's an aluminium frame as sadly titanium would be nice but wasn't on
offer, one of these
http://www.yeahbikes.com/yra062.htm
I don't mind if the brakes flex a bit, particularly on the back as this
is the one I drag to control my speed so the brackets sound ideal, any
idea who makes them (URL?) as when I asked in a shop for precisely that
all I got was blank looks and then when I had explained my self I was
told it was impossible?

Don't think I'll find forks to fit my frame with disk fittings.

Certainly the difference going from drum to disk on the Motorbike was
huge but the current V-brakes have got plenty of stopping power, the
power on the front brake is very lumpy as the wheel rim is not smooth
but that's not the end of the world, if I can find forks with disk
fittings I'll change over but it's not as important as the rear.

Oh and thanks for the non "Oh look here's a wanker who can't spell"
response.

--
Bob
Currently borrowing a black and red Yamaha XJ750 with fuel injection
Present: Honda XL125RF (FS)
Past: Honda CG125
bob at homeurl tomato dot co dot uk
remove the red fruit if you’d like to email me.

 

They don't.

Cos the power on the front brake is very lumpy as the wheel rim is not
smooth and as the hills f'in' steep, I've got to use some braking.

Ah but you guys are so much more intelligent.


--
Bob
Currently borrowing a black and red Yamaha XJ750 with fuel injection
Present: Honda XL125RF (FS)
Past: Honda CG125
bob at homeurl tomato dot co dot uk
remove the red fruit if you’d like to email me.

 

But the hill is steep and if I want to go down it at a controlled speed
I have to convert the same amount of kinetic energy into heat [1] as I
have a fixed amount of gravitational potential energy and doing it in
short bursts would mean the temperatures would be even greater.

[1] I know that air resistance increase with the square of velocity but
I'm going to ignore it

--
Bob
Currently borrowing a black and red Yamaha XJ750 with fuel injection
Present: Honda XL125RF (FS)
Past: Honda CG125
bob at homeurl tomato dot co dot uk
remove the red fruit if you’d like to email me.

 

Looking at the bike I don't think you'll be able to. There's simply
not enough room for them at the back and you won't be able to fit them
to the forks.

Also I dunno how much the folder cost, but ones I've seen haven't been
that expensive and mtb disc brakes run to around 60 quid per brake for
cable operated ones and 100 plus per brake for hydraulics. Probably
be more cost effective to buy a new bike with them fitted.

And beat in mind cheap disc brakes are worse than v-brakes.

 

You really need to sort the front brake. It's much more powerful than
the rear, meaning you can use it less and still slow down the same
amount.

Dragging the rear all the way down a hill is bad news, as you've
found.

 

Nope, you are all missing the point. (Or I am just about to)

Your tyre blew because the wheel rim heated up because of brake
application over a long-ish period of time.

A fault of naff rims and/or a badly fitted tyre. The hot wheel rim
expands and the tyre beading loses grip.

Either get yourself a proper wheel with smooth beading and better heat
dispersion properties or do as Dave(? sorry fucked attributions) said
above and apply the brakes in short bursts that allow the wheel rim time
to cool a bit between applications.

 

It's got to take the same amount of energy out so I'd have thought it
would get just as hot, if I used both brakes that would distribute the
energy and reduce the heat. I tried to sort the front brake but the lump
is where the wheel rim is joined and the shop didn't think there was
anything they could do, got any suggestions?

--
Bob
Currently borrowing a black and red Yamaha XJ750 with fuel injection
Present: Honda XL125RF (FS)
Past: Honda CG125
bob at homeurl tomato dot co dot uk
remove the red fruit if you’d like to email me.