Boiling the billy

Well, not exactly the billy. Just the brake fluid in the Piaggio.

You guys just didn't pull you weight enough. Ok. It was obviously enough
to stop a MAJOR mechanical failure, but I expect better from my fellow
austmotoians.

Partly my fault, I suspect, for taking a novice over Mt Glorious.

Between being very hesitant, and the auto-transmission on the Piaggio
providing very little engine braking, Carol sat on the brakes virtually
the whole way down - well, as far down as it took for the heat from the
brakes to transfer to the brake fluid. Instant brake fade. Thank heaven
the front right disc was there as a back up. I reckon she did pretty
well to pull up with front brake only, on the downhill surface.

We let things cool down, and the brakes came good again. By that stage,
though, Carol was virtually in tears - so I parked the FJR on the side
of the road, and took the X9 down to the outskirts of Samford. Charles
came down with the Suzuki and took me back up the Carol and the FJR.
Geez! I hate riding pillion. I think he enjoyed putting the fear of the
devil into me.

All's well that ended well, though. Had a good visit with friends at
Samford, and then came back to Toowoomba via Enogerra and Ipswich Rd.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

What the ****? Riding downhill with the weight biased towards the front
of the bike the front brake will do even more than it's usual share of
the braking (which is 70% for the average bike). I don't know how much
this changes because of the design of scooters -front:rear weight bias
etc- but surely riding the rear brake only down a hill is going to cause
said overheating problems, not to mention being an extremely inefficient
way to slow down the bike. Why wasn't the front brake being used?

Nev..
'04 CBR1100XX

 

The front disk as a back up says it all, some training is really required in
braking techniques.

Boxer

 

you would expect better from a 500cc sports scooter designed to go through
twisties and highway use etc wouldnt ya.

might wana chuck some top notch brake fluid with a higher boiling point in
it, im using motul 5.1 - havnt taken the wifes yp250 over long twisties yet,
but it didnt go to bad.

 

With the Piaggio, there are two discs in front and one disc at the back.

The left hand lever operates both the rear disc and the left front disc
- with a roughly 60/40 rear/front split. The right hand lever operates
the front right disc.

Two issues here: first, Carol is still very much a learner and has a
morbid fear of the front brake (past bad experience on a motorcycle a
few years back). I'm working on that.

Second, I don't think that total braking potential was a concern. As far
as I can see, she simply rode the left lever all the way down, not
exerting a lot of pressure, but simply dragging it and thus not giving
it any chance of cooling off. Again, we're now working on the 'brake a
bit harder before you get to the corner, and then let go of the brake as
you go around the corner' principle.

In hindsight, it was probably good that she was NOT using both levers
because brake fade, when it came, would've been when BOTH levers were
useless. At least this way she still had the front right disc to pull
her up, when the others just gave up the ghost.

Actually, she's a bit of a shocker. She quite likes riding on the open
road (as we all do), but is very reluctant to practice those things
which are of concern - stop/start; low speed maneuvering etc.

I've been trying to get her to a car park to practice these things, but
I may have to hand over to a riding school. She's probably more prepared
to accept some degree of bullying from them.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

Amen to that. Still at the learning stage, but I've seen blokes who've
been riding for a long time STILL keep that right hand well away from
the front brake lever. I sometimes wonder how they've managed for so
long.

Saw a bloke on a cruiser a few years back. He had his foot on the brake
lever coming up to the traffic lights. As he got slower, he got to the
stage where balance was a problem, so the foot came off the brake lever
and onto the ground. The hand still never touched the front lever. He
did a pretty good impersonation of Fred Flintstone, in bringing the bike
to a halt.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

on the guzzzi V50 they have linked brakes , the front lever is a cable that
goes to the brake
master cylinder, because of the cable system it works SFA , not enough full

the rear is linked with the front , stomp on it and its stops rather well[1]

[1] well as good as an old guzzi can

 

Seemed to do alright when I took it the rest of the way down. Some
braking, but not a lot. And I found that the engine WOULD do some
braking if you got it up to revs first and then wound off the throttle.
The original problem was undoubtedly due to inexperience, fear, and
incorrect braking technique.

It's due for a major service now, so the higher spec brake fluid is one
of the things that will get done. I want to see if changing the
viscosity of the oil in the fluid drive will lower the rpm at which the
drive engages too.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

I don't understand how you can get brake fade
1. On a scooter with three discs
2. With disc brakes. (never had a disc "give up the ghost")

Theo

 

I have had disk fade on the race track many times, to the point of having to
pull into the pits and stop riding.

Boxer

 

Doesn't matter how many discs. If you drag the pads long enough,
friction will create heat. Enough heat transmitted through the
components will cause the brake fluid to overheat (boil) and the
resultant gaseous bubbles WILL impair hydraulic efficiency.

I've had "brake fade" happening in the car after some very spirited
driving requiring constant application of the brakes.

Why would you not expect it to happen?
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

I had total brake fade on my GTR1000 after hooning through the hills two
up for an hour.

That was... errmm... interesting.

G-S

 

let me know on the rear diff oil, coz I was thinking of that too.

I find the gear box when you wind off the throttle will engine brake, but
not like compression braking in a manual.

 

Just because you haven't experienced it yourself doesn't mean it doesn't or can't happen. Fade does occur if the brakes are
over-worked. I've had it happen on both cars and bikes in the past.

 

I inadvertently did similar on the K100 - and managed to warp the rear
disc as well. Believe it or not, I was riding in a different pair of
boots than I normally wear, and the inside lip of the sole was
depressing the brake lever to the extent where it was just just
dragging. I never noticed, until I went to use the rear brake (in
preparation for using the front) and noticed the lack of initial drag in
braking.

My brother confirmed it all when we pulled up, and he said "Did you know
that your brake light has been on for the last half an hour?"
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

Ca you really get a scooter's brakes hot enough to do that? Assuming you
don't have water in the fluid.

If you have water in the fluid, yes. Brake 'fade' used to be described as
what happens when you heat up your drums to the extent that they expand
enough for the brakes to be ineffective. Expansion by heating will have the
opposite effect with discs.
I've never had 'fade' with discs but then I don't ride/drive that
spiritedly. I would consider water in the fluid turning to gas being failure
rather than fade.

Theo

 

See my reply to Peter C. Please explain what you mean by 'fade' and what are
the mechanics of it.

Theo

 

Brake fade can be caused by the brake fluid boiling, but also from a loss of friction between the two surfaces. The brake pedal
would feel as firm as usual, but braking performance would be greatly reduced.

Sure it's harder to do on a disk/pad setup than a drum/shoe arrangement, but it's still possible if heat buildup is sufficient to
melt the binding glues in the pads and cause what's commonly known as "glazing".

Given that many scooters these days can do highway speeds, but have a smaller wheel and much smaller brake disks than a regular
bike, there would be less overall surface area to dissipate heat. Plus to cover the same distance as a larger bike at 100km/h the
wheels are travelling faster. If you were to mark a spot on the disks, it would be touched by the pads far more frequently than a
larger bike with larger wheels and disks.

So if someone is riding the brakes or riding very spiritedly, then the disks and pads don't get enough chance to sufficiently lose
heat and brake fade can occur.

Now if we were talking carbon/carbon brakes, then they need a massive amount of heat to be effective. The cooler they are, the less
efficiently they work.

 

What I am calling brake fade, in this case, is where the lever ends up
by coming right back to the handlebar, with absolutely no backpressure.
That, as far as I can tell, is caused by vapour bubbles in the brake
line. For that to happen, it MUST mean that the brake fluid boiled.

I would guess that having a contaminant such as water, in the brake
line, would cause that vapour bubble to occur at lower temperatures than
normal.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181

 

What an odd brake setup up.
No wonder she is not keen to use the front brakes because depending on what
she is doing with the rear brakes the front ones will react so differently.
(Just guessing)
I imagine your friend has almost got her rear braking down pat, shame that
the rear brake is a minimal part of the stopping. Also with the front brake
coming on at slow speeds this wouldn't make me feel confident in the rear
brake.
Just sounds weird to me though never ridden one.
I'd be looking at setting the bike up standard, Foot rear, hand both
front... Then she can learn how to brake properly.