I was dropping down a steep, high traction pitch slaloming through some bushes using the rear brake quite a bit when after about 50 yards of this my rear brake lever pulled to the bar. I was going pretty slow so was able to stop with my front. The rear disc was hotter than hell as expected but neither the hose nor the reservoir were even warm.
It doesn't feel like I have any air in the system as the brake works fine elsewhere. In fact, the entire rest of the ride it was trivial as usual to lock up the rear brake. Any ideas why it pretty much failed in the above situation?
In article <[email hidden]>, getnews1 @dslextreme.com says...
Quoted message said:
I was dropping down a steep, high traction pitch slaloming through some bushes using the rear brake quite a bit when after about 50 yards of this my rear brake lever pulled to the bar. I was going pretty slow so was able to stop with my front. The rear disc was hotter than hell as expected but neither the hose nor the reservoir were even warm.
It doesn't feel like I have any air in the system as the brake works fine elsewhere. In fact, the entire rest of the ride it was trivial as usual to lock up the rear brake. Any ideas why it pretty much failed in the above situation?
Greg
Well if it didn't come back then it simply has a leak. If it did come back then you did boil the fluid. What brake are we talking about here.
Avid Juicys. Shouldn't the hose have at least been warm?
In article <[email hidden]>, getnews1 @dslextreme.com says...
> I was dropping down a steep, high traction pitch slaloming through > some bushes using the rear brake quite a bit when after about 50 > yards of this my rear brake lever pulled to the bar. I was going > pretty slow so was able to stop with my front. The rear disc was > hotter than hell as expected but neither the hose nor the reservoir > were even warm. > > It doesn't feel like I have any air in the system as the brake works > fine elsewhere. In fact, the entire rest of the ride it was trivial > as usual to lock up the rear brake. Any ideas why it pretty much > failed in the above situation? > > Greg > >
Well if it didn't come back then it simply has a leak. If it did come back then you did boil the fluid. What brake are we talking about here.
Avid Juicys. Shouldn't the hose have at least been warm?
Greg
Not sure, but I don't think so. That plastic line isn't a good conductor of heat.
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
That's disappointing as this was just a short pitch, although I was using my rear brake more than usual because the traction was incredible. I sent an email to Goodridge to see if they're working on hose kits for the Avids.
"Slacker" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
G.T. said:
Slacker said:
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
That's disappointing as this was just a short pitch, although I was using my rear brake more than usual because the traction was incredible. I sent an email to Goodridge to see if they're working on hose kits for the Avids.
Greg
While the Goodridges are very nice, I don't think they'll help heat induced lever fade.
There are a few other things you might want to look into.
Larger rotors will dissipate heat much better than smaller ones.
Not all brake fluids are created equal - look for higher boiling points. I've seen them range from around 300F to 600F for racing (not DOT approved) fluid, which is what I'm using for the Turner. The downside is the racing fluid is 7x the cost.
Also, maybe try a different brake pad compound if they're available?
None of that is relevant even if correct - his problem is, he didn't fit Hopes.
Shaun aRe - I have Hopes. WTF is 'brake fade' ',;~}~
"Chris Phillipo" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
Quoted message said:
Quoted message said:
>situation? > >Greg > >
Well if it didn't come back then it simply has a leak. If it did come back then you did boil the fluid. What brake are we talking about
here.
Quoted message said:
Quoted message said:
Avid Juicys. Shouldn't the hose have at least been warm?
Greg
Only the caliper has to be to cause a problem. I'm surprised you've been having trouble with those the engineering in them really impressed me, I'm going to get a set my self.
"Shawn Curry" <[email hidden]> wrote in message news:lvW9c.122577$1p.1726610@attbi_s54...
Quoted message said:
G.T. said:
I was dropping down a steep, high traction pitch slaloming through some bushes using the rear brake quite a bit when after about 50 yards of this my rear brake lever pulled to the bar. I was going pretty slow so was able to stop with my front. The rear disc was hotter than hell as expected but neither the hose nor the reservoir were even warm.
It doesn't feel like I have any air in the system as the brake works fine elsewhere. In fact, the entire rest of the ride it was trivial as usual to lock up the rear brake. Any ideas why it pretty much failed in the above situation?
Possibility: Brake fluid can absorb water from the air. That's why the car stuff says "Always close tightly" or something like that on the label. That water can boil long before the fluid. Steam brakes don't work well. :-) Can't really see how water can get into the system otherwise, unless you hit a really deep stream crossing while descending. the sudden cooling could conceivably decrease the pressure in the system sucking water into it (I doubt it though-just avoiding what I need to do right now :-) ). Although this can allegedly happen with hubs and BBs (but that's air contracting not fluid). I'd put in better fluid and bleed well.
I'm going to look into different fluid. The fluid that's in there is what came with the Avid bleed kit so I'd think it should be ok. And I haven't ridden any stream crossings yet this year.
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics? -- PeteCresswell
I'm going to look into different fluid. The fluid that's in there is what came with the Avid bleed kit so I'd think it should be ok.
I've got Hope C2's on my FS and Avid mechs on my hardtail.
I'm thinking of swapping them around so I have a Hope C2 on the front wheel of each bike and an Avid mech on the rear of each.
Reasons-up-until-now: 1) The mechs are cheaper/lighter and I don't perceive any significant performance diff between the mech and the Hope when used on the rear wheel.
2) The mech is a little grabby/unpredictable on the front wheel (180 mm rotors). Probably a pad composition issue but but the Hope is sooooo much more controllable/predictable...
Now maybe there's third rationale:
3) The mech isn't prone to any hydraulic-specific failure, so there's an ace in the hole in whatever situation provokes same. -- PeteCresswell
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics?
Maybe, but it can be designed around. Airliner brakes can get hot enough to catch fire in emergencies, but still work. Various motor racing uses have tremendously greater loads on the brakes than mountain bikes, e.g. Formula 1 car and motorcycles. Their brakes keep working.
I'm going to look into different fluid. The fluid that's in there is what came with the Avid bleed kit so I'd think it should be ok.
I've got Hope C2's on my FS and Avid mechs on my hardtail.
I'm thinking of swapping them around so I have a Hope C2 on the front wheel of each bike and an Avid mech on the rear of each.
Reasons-up-until-now: 1) The mechs are cheaper/lighter and I don't perceive any significant performance diff between the mech and the Hope when used on the rear wheel.
2) The mech is a little grabby/unpredictable on the front wheel (180 mm rotors). Probably a pad composition issue but but the Hope is sooooo much more controllable/predictable...
Now maybe there's third rationale:
3) The mech isn't prone to any hydraulic-specific failure, so there's an ace in the hole in whatever situation provokes same.
Try again on reason #1. The Avids may be cheaper, but they are anything but lighter. Prove it to yourself- take off the lever, cable/housing, caliper and rotor from each and weigh them... I'm betting that Avid setup is at least 100gm heavier. The thing that propogates the fallcy that mechaicals are lighter is the claimed weights. For the Hydraulics, the entire system is weighed. The mechanicals? Just the caliper and rotor. They don't include the cable and housing (much heavier than hose and fluid) or lever.
In article <[email hidden]>, [email hidden] says...
Quoted message said:
RE/
Quoted message said:
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics?
Open systems will fade in this way, closed systems should go the oposite way and the lever will become stiff.
When you're talking closed systems that would mean a solid reservoir rather than the expandable one of the Juicys?
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
Yes. Too much heat is the enemy of any brake systems.
Quoted message said:
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
Actually, on that particular DH course I mentioned, both of my brakes did fail. It was a fairly steep and super loose section, so I was relying on the rears. When the rear went I switched to the front brake, which soon after, also failed. I was faced with two options: dump the bike now before I hit critical mass speed or ride it out without any brakes praying that they come back before the next turn.
Quoted message said:
If so, does the failure mode involve something specific to hydraulics?
That trail is the only one Ive every experienced over heating my Hayes. I confirmed it two other times. Same trail, same exact section... no frig'n brakes. Needless to say, I hate that trail! -- Slacker
In article <[email hidden]>, [email hidden] says...
Quoted message said:
RE/
> Chris is correct about the lever coming back as the brake cools > down. I've had this happed a couple times up at Big Bear with my > little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics?
Open systems will fade in this way, closed systems should go the oposite way and the lever will become stiff.
When you're talking closed systems that would mean a solid reservoir rather than the expandable one of the Juicys?
What's the difference between Open and Closed hydraulic systems?
The difference here is simply that an open system has a brake fluid reservoir and a closed system doesn't. The Hope C2 is the only closed system disc brake on the market. All other disc brakes have open systems which means they have a reservoir for oil expansion (due to heat) and oil supply (for automatic pad pad wear adjustment). The Hope C2 has a manual adjuster knob on the lever which adjusts a piston for fluid expansion and pad wear.
"G.T." <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
I was dropping down a steep, high traction pitch slaloming through some bushes using the rear brake quite a bit when after about 50 yards of this my rear brake lever pulled to the bar. I was going pretty slow so was
able
Quoted message said:
to stop with my front. The rear disc was hotter than hell as expected but neither the hose nor the reservoir were even warm.
It doesn't feel like I have any air in the system as the brake works fine elsewhere. In fact, the entire rest of the ride it was trivial as usual
to
Quoted message said:
lock up the rear brake. Any ideas why it pretty much failed in the above situation?
Was it on another thread here about brakes? Someone was talking about the reservoir outlet hole gets covered up by the piston on the Hayes brakes if you keep the lever (and therefore the piston) compressed. That would mean that you effectively convert your closed system to an open system - or whatever. Solution? Pump the brakes where possible to allow the fluid to flow to and from the reservoir. May not appy to your brakes of course. Might not even be the problem either :-) -- Westie
Open systems are actually open to the outside air through a little vent hole, this hole is blocked under braking but it is open when the levers are in the open position. Fluid doesn't normally leak out because there's a labyrinth it would have to travel to get out but if you hang the bike upside down or heat up the fluid it will come out the hole.
My Hope disk brakes aren't like this, there is a piston which moves in the reservoir which seals the fluid from the air. Which is just as well as the fluid absorbs water (and performance suffers when that happens).
I guess the open end of the chamber is probably not air-tight.
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics? -- PeteCresswell
This time with Shimano XTR Disk system. Rode SCREEMING FAST down 6,000 , about 13 miles. Stopped MANY times on the big downhill run just to catch my breath, take a few pictures and clear my ears. No brake problems there.......... I got those disk REAL HOT no doubt. I rememeber thinking to myself..........." I hope these brakes don't go out or else I'm DEAD".
G.T., I don't know what happened to your brakes, but mine just rock in all situations and filled with mineral oil!!!
"James Annan" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
Chris Phillipo said:
Open systems are actually open to the outside air through a little vent hole, this hole is blocked under braking but it is open when the levers are in the open position. Fluid doesn't normally leak out because there's a labyrinth it would have to travel to get out but if you hang the bike upside down or heat up the fluid it will come out the hole.
My Hope disk brakes aren't like this, there is a piston which moves in the reservoir which seals the fluid from the air. Which is just as well as the fluid absorbs water (and performance suffers when that happens).
I guess the open end of the chamber is probably not air-tight.
James
Uhhmm, which Hopes would they be?!? All the ones I've seen, and I'm sure other open systems too, for obvious reasons, have a diaphragm between the fluid and air. This allows fluid expansion and auto pad wear adjust without allowing the fluid _ANY_ contact with the air. Allowing the fluid to have contact with the air at regular intervals would be utter stupidity.
"James Annan" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
My Hope disk brakes aren't like this, there is a piston which moves in the reservoir which seals the fluid from the air. Which is just as well as the fluid absorbs water (and performance suffers when that happens).
I guess the open end of the chamber is probably not air-tight.
James
Uhhmm, which Hopes would they be?!? All the ones I've seen, and I'm sure other open systems too, for obvious reasons, have a diaphragm between the fluid and air. This allows fluid expansion and auto pad wear adjust without allowing the fluid _ANY_ contact with the air. Allowing the fluid to have contact with the air at regular intervals would be utter stupidity.
um..I think if you re-read my post you will see that we are not in disagreement. It was Chris Phillipo who said that fluid could leak out...
On Tue, 30 Mar 2004 00:24:26 GMT, "(Pete Cresswell)" <[email hidden]> blathered:
Quoted message said:
RE/
Quoted message said:
Chris is correct about the lever coming back as the brake cools down. I've had this happed a couple times up at Big Bear with my little 6" rotors.
Is that to say that any hydraulic disk brake can effectively fail from too much heat?
I'm thinking stupid-long-steep hills (like coasting down the Mt Washington access road or the road from Hale Akala observatory)... Could *both* brakes fail in this manner?
If so, does the failure mode involve something specific to hydraulics?
A German bike mag tested a whole bunch of disk brakes not so long ago. One of the tests involved bolting each brake system onto the test rig, with the same rider riding it each time down a long, steep alpine road and jamming the brakes on. The hoses on the Avid Juicy 7s melted, as they did on the Hopes. All the other brakes were fine.
Damned efficient, those Krauts.
I think Avid upgraded the hose spec after seeing the test results - but I'm not *sure*.......
