Brakes

[TheBeastie]

I guess the other part I should mention.. I am thinking with my next build I will get hydraulic brakes with a geared MAC build with thumb throttle and not even worry about ebike levers/sensors and just remember to remove throttle when braking.

I was thinking this is the method used on cars and motorbikes so why isn't it good enough for ebikes? Is it that ebrake levers are typically much more important for DD motors because of regen and the fact they give a large amount of resistance when power is cut. This is unlike geared based motors as they automatically behave just like a freewheel when there is no power.

 

[friendly1uk]

Prolonged use can burst the tyre off the rim

Hows that work then? Are you saying the rim gets so hot the tyre softens, so tyres with no decent bead may pop off? Or that if you use a wheel till it wears out there is nothing left to sit a tyre on?

 

[-dg]

Prolonged use can burst the tyre off the rim

Hows that work then? Are you saying the rim gets so hot the tyre softens, so tyres with no decent bead may pop off? Or that if you use a wheel till it wears out there is nothing left to sit a tyre on?

Air pressure increases with temperature.

 

[Hillhater]

.. I am thinking with my next build I will get hydraulic brakes with a geared MAC build with thumb throttle and not even worry about ebike levers/sensors and just remember to remove throttle when braking..

I have been riding that way for years ( except not hydraulic) with no issues.
The key i believe is the thumb throttle which allows independent control of power whilst the fingers are operating the brake .

 

[friendly1uk]

Prolonged use can burst the tyre off the rim

Hows that work then? Are you saying the rim gets so hot the tyre softens, so tyres with no decent bead may pop off? Or that if you use a wheel till it wears out there is nothing left to sit a tyre on?

Air pressure increases with temperature.

Oh I see. Bit outside my box that was.
To quantify this, air at 23c expands 25% by the time it reach's waters boiling point. That is a 25% increase in pressure, if no expansion is possible.

I have decent sized rims and tyre's and pressure on the comfortable side. This is not an issue for me personally. This is an issue for the extreme circumstances of hot days, big hills, skinny rims and tyres, using pressure already close to bursting. You can substitute the big hills for high powered motors though. Both lead to more braking

.. I am thinking with my next build I will get hydraulic brakes with a geared MAC build with thumb throttle and not even worry about ebike levers/sensors and just remember to remove throttle when braking..

I have been riding that way for years ( except not hydraulic) with no issues.
The key i believe is the thumb throttle which allows independent control of power whilst the fingers are operating the brake .

Why would you want anything other than 'power off' while braking? Automating this with brake levels is a real important part of my build, and iirc a legal requirement.

 

[Hillhater]

Why would you want anything other than 'power off' while braking?

.. because its not necessary in practice !
..and why over complicate things
Ask any motor bike rider why they dont have a "power cut" interlock on their brakes ?
Legally ??... if you are really going to be legal, you only have 250W to handle so no problem for brakes anyway. :wink:

 

[TheBeastie]

Why would you want anything other than 'power off' while braking?

.. because its not necessary in practice !
..and why over complicate things
Ask any motor bike rider why they dont have a "power cut" interlock on their brakes ?
Legally ??... if you are really going to be legal, you only have 250W to handle so no problem for brakes anyway. :wink:

OK great, knowing that some one else does do this doesn't make me feel like I am a weird freak.
Do you have geared or DD bike?
Good to know your from aus, I don't think I have noticed your location before. I have always noticed your alias though because every time I see it at the corner of my screen my brain always interprets it into "HeilHitler" until I look more carefully. :lol:

 

[Toorbough ULL-Zeveigh]

I guess the other part I should mention.. I am thinking with my next build I will get hydraulic brakes with a geared MAC build with thumb throttle and not even worry about ebike levers/sensors and just remember to remove throttle when braking.

I was thinking this is the method used on cars and motorbikes so why isn't it good enough for ebikes? Is it that ebrake levers are typically much more important for DD motors because of regen and the fact they give a large amount of resistance when power is cut. This is unlike geared based motors as they automatically behave just like a freewheel when there is no power.

it also saves the motor from smoking so you can't hold it stalled.
axe dis guy wye he's gone the other way.

Also tonight I decided it's time to install an e-brake cutoff switch. Honestly that switch would have been a whole lot more useful when the bike was new and I did a couple "unintentional burnouts" by laying on a little throttle at a stop and responding by applying brakes instead of dropping the throttle. But whatever - an e-brake cutoff can be extremely useful in a split second, should my throttle ever short or something else go wrong.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=37207&start=275#p738534

 

[bzhwindtalker]

Good luck doing a good wheelie with ebrakes cutof! They are only usefull on grandma's bike IMO. You can use a hybrid throttle setup if you are concerned with unintentional burnouts, with a pushbutton inline with your throttle line, so that you need to push the button and twist the throttle at the same time to get power.

To quantify this, air at 23c expands 25% by the time it reach's waters boiling point. That is a 25% increase in pressure, if no expansion is possible.

I saw a bike tire (a kojak IIRC) brust from pressure sitting on hot pavement in Colorado while it had been pumped to 120 psi in colder weather. But would the heating from rim brakes create the same effect? I bet an AL rim has more than enougth surface to shed the energy.

 

[Chalo]

Prolonged use can burst the tyre off the rim

Hows that work then? Are you saying the rim gets so hot the tyre softens, so tyres with no decent bead may pop off? Or that if you use a wheel till it wears out there is nothing left to sit a tyre on?

Air pressure increases with temperature.

The changes in the rubber and casing materials have a greater effect than the change in adiabatic pressure, which isn't much.

A good sized rim can shed a LOT of heat, but it has to have a good sized temperature gradient to ambient to do it. On a hot day, that means a hot rim.

 

[-dg]

The changes in the rubber and casing materials have a greater effect than the change in adiabatic pressure, which isn't much.

A good sized rim can shed a LOT of heat, but it has to have a good sized temperature gradient to ambient to do it. On a hot day, that means a hot rim.

Ok, this should have been obvious, but I am out of practice at thinking in Kelvins. Assuming a tire initially filled to 100 psi on a 68 f day (293 K) that heats to almost the boiling point of water (393 K) then the pressure will have increased to 127 psi. Which doesn't help, but yeah, probably is not the main problem.

I left off the calculation just before boiling to avoid having to think about water vs steam which probably does not matter but it would require more research to be sure it doesn't.

Any idea of what temperatures are actually reached in practice?

 

[Chalo]

There are anecdotal accounts of trapped water steaming out of rims on long downhills on mountain roads. I don't have particular reason to disbelieve that, but the hottest rims I have observed on my own bike were only just a little too hot to keep my fingertips on. Maybe 60C? Hard to tell.

 

[Chalo]

I'm changing up a couple of my bikes at the moment, to better suit my circumstances and to keep things interesting.

I have a Redline Monocog 29er that I originally set up with a Sachs 7-speed gearhub and an X5305 front hub, but which I later de-electrified by adding a Marzocchi Bomber XC Comp fork, a 48 spoke disc brake wheel with a touring bike rim, and a Hayes disc brake with 203mm rotor and EBC Gold metallic pads. It has served me in that latter configuration for something like seven years now. It's a good suspension fork with a very respectable brake.

Both the original rigid fork and the Marzocchi suspension fork support rim brakes and disc brakes, but as it happens, the rigid fork for the bike was still set up as before with a V-brake (Shimano Deore), Tektro booster arch, and dual compound Kool Stop pads. I decided to build a non-disc front wheel with a wider rim, and use the rim brake after switching back to the original fork.

Today I had the day off of work, so I swapped the forks on the Monocog. After the switch, I noticed two things while test riding: One was that I had to dramatically lower the front tire pressure to have the same perceived ride comfort on broken pavement-- where 40 psi worked great before, and kept the 60mm front tire stable on the 24mm wide rim, I had to lower the pressure to 25 psi to yield equivalent ride quality with the rigid fork. But the new wheel's 38mm wide rim fattens the tire and keeps it stable at very low pressure, and the new setup is 2-1/2 pounds lighter even with the much bigger, heavier rim.

The second thing I noticed (and this is where things get back on topic) was that the boosted V-brake was much more powerful and somewhat more sensitive than the big-rotor Hayes HMX-1 brake upgraded with HH+ rated sintered metal pads. Like the brakes I machined to my own design, these rim brakes offer more power than any discs I have tried. Unlike the brakes I made, this one uses commodity parts, with only setup to distinguish it from brakes anyone can own after a session on eBay. The fact that they cost a fraction of what decent discs cost is just a bonus.

The rear brake on that bike is a drum brake built into the 7-speed gearhub. It's as consistent as any drum brake, but not particularly powerful. However, while sorting out the bike's other issues, I took the time to replace the cable and housing with good stuff, make sure the lever and brake arm were lubed, and set it up just right. That brake has been transformed. It's still a drum with soft engagement and gradual bite, but it's strong now if I give it a firm grip. Years of wear & tear, dirt, corrosion and minor kinks in the cable housing had deteriorated the brake's performance so gradually that I didn't even notice it was feeling tired. Now it's back up to snuff, and while it's no match for either the front disc or the front V-brake, it feels up to the job.

 

[amberwolf]

Any idea of what temperatures are actually reached in practice?

According to this page:
http://cozybeehive.blogspot.com/2008/05/rim-heating-during-braking.html

In a chapter on 'Braking', in the book Bicycling Science (Gordon,MIT), there is a nice graph of rim temperature above ambient vs speed for a few cases consisting of different bicycles, drag co-efficients, combined masses and wheel diameters.

I don't have the book, but it might be available via google book search:
http://www.google.com/search?q=book+Bicycling+Science+%28Gordon%2CMIT%29


Then this page may have other info:
http://www.iosrjen.org/Papers/vol2_issue8%20(part-5)/G0284044.pdf

Key words: - Brake Rotor, Heat Transfer,Temperature distribution,Graphs . I.
Introduction. To get objective statements about the behavior of brake rotor under ...

 

[cal3thousand]

I guess the other part I should mention.. I am thinking with my next build I will get hydraulic brakes with a geared MAC build with thumb throttle and not even worry about ebike levers/sensors and just remember to remove throttle when braking.

I was thinking this is the method used on cars and motorbikes so why isn't it good enough for ebikes? Is it that ebrake levers are typically much more important for DD motors because of regen and the fact they give a large amount of resistance when power is cut. This is unlike geared based motors as they automatically behave just like a freewheel when there is no power.

There's not always time to "remember' when traveling at speed. If you plan to go past legal, I would get motor cut working. It's not that difficult at all!

I was dreading the installation of the Bionx pressure switches, but after I got on it and bought the right female receptacle from radio shack (Type K if you are wondering). Some speaker cable wired from the 2 terminals on the receptacle directly to the 'e-brake' connector on the controller. ( I used a multimeter/ohmmeter to determine which of the 3 wires were completing a circuit on lever pull). Then, I ended up just running another parallel circuit for the other lever right on top.

One thing to think about if you do this is that the Bionx switches rely on hydraulic pressure to actuate. I realized this when testing the setups without fluid and noticed that the side with the integrated switch in handle (I bought 2 different ones on this bike; Auriga e-sub and the Bionx press switch) would cut the motor while the side with the pressure switch did not. Makes me happy that I decided to run 2 different switch styles on 2 bikes rather than one style to each bike. Now, in a complete fluid loss situation (not that it will happen), motor cut will still happen.

 

[cal3thousand]

Btw, I have one suggestion to add to the list that isn't mentioned.

The bike I built for my wife is to be considered a "show"-type bike. Cosmetics are VERY important to this particular ebike . I had the rims powdercoated to match the frame, basket, etc. before building the wheels. EVERYTHING is purple.

The frame originally carried rim brakes and started life as a street legal ebike. (Giant Suede-e) But rim brakes would just eat at the beautiful rims. So disc was the ONLY way to go. Since the frame is fairly long and I changed the handlebars to a cruiser style, finding cable brakes of sufficient length was a problem. She was already complaining about the poor lever feel of her previous bike with BB5s, so hydraulic was the ticket. It will also be faster than legal (35mph+) so e-brakes were a safety requirement in my book.

 

[full-throttle]

I know what you mean.

Velocity print colour rims, for example, are available in both versions.

I know which one I'd go for :wink:

Even the common all-black disc-specific rims look so much better.

Good luck finding a tubeless-compatible or UST rim for rim brakes too.

 

[Electric Junk]

Avid BB7 or Juicy 3, simple, powerful and reliable

 

[Chalo]

She was already complaining about the poor lever feel of her previous bike with BB5s, so hydraulic was the ticket.

That's because BB5s are terrible. BB7s are not terrible, and not hydraulic.

When aesthetics count, it's much easier to get cable length and routing just right than it is to trim, reseal, and bleed hydraulic brakes. That's why hydraulic hoses almost always look like a bad haircut, with ugly excess length poking out in front.

 

[bzhwindtalker]

it's much easier to get cable length and routing just right than it is to trim, reseal, and bleed hydraulic brakes. That's why hydraulic hoses almost always look like a bad haircut, with ugly excess length poking out in front.

That's true, and cable are easyer to set up for amateur bike mechanics, but are usualy set up quite bad too. I used BB5 on my custom velomobile build and they worked great, my friend had sturmey archer drum hubs in 90 mm and they were brillant, sharp and powerfull, maintenance-free. But this was in 20" wheels.

 

[Chalo]

it's much easier to get cable length and routing just right than it is to trim, reseal, and bleed hydraulic brakes. That's why hydraulic hoses almost always look like a bad haircut, with ugly excess length poking out in front.

That's true, and cable are easyer to set up for amateur bike mechanics, but are usualy set up quite bad too.

That's often the case. When manufacturers supply too-long cables with new bikes, they usually get installed that way without being trimmed to length. Most bicycle shops in my area don't grind the housings flat on the ends, either. There are a lot of things to get wrong, or at least not quite right, when setting up brake and shift cables.

I used BB5 on my custom velomobile build and they worked great, my friend had sturmey archer drum hubs in 90 mm and they were brillant, sharp and powerfull, maintenance-free. But this was in 20" wheels.

My experience with BB5 discs is that the stock pads wear quickly and lack bite. There are few replacement pads available other than the stock Avid pads. If good sintered metal pads were available for BB5, I would probably not have such a low opinion of the brakes.

Drums can be very good, even in smaller sizes. They take a very long time to break in and deliver their best performance, though. When you try out a new drum brake, it's easy to be disappointed. And they tend to be finicky about what kind of lever works best with them.

 

[full-throttle]

That's why hydraulic hoses almost always look like a bad haircut, with ugly excess length poking out in front.

"Almost always"? Is that right? Care to prove your claim?
And cable actuated brakes almost always look better?

You are simply hydrophobic :lol:

Besides, comparing cable length to a haircut while wearing some dead cat on your head is stupid.

 

[friendly1uk]

Why would you want anything other than 'power off' while braking?

1 .. because its not necessary in practice !
2..and why over complicate things
3 Ask any motor bike rider why they dont have a "power cut" interlock on their brakes ?
4 Legally ??... if you are really going to be legal, you only have 250W to handle so no problem for brakes anyway. :wink:

I numbered your points for a more succinct reply.

1, But it is, people have burnt there bike's out, and why waste power when your trying to slow down. You should be thinking regen, not waste.
2, The automatic control is too complicated, you would rather have a procedure to follow whenever you brake? Here is my procedure, I pull the brake to stop, then let it go to carry on.
3, Don't you have the answer? Modern management systems cut the fuel under many conditions.
4, It's a regulation because it is considered wise for more reasons than brake efficiency.

I really can't imagine how your bike works without one. There must be a number of procedures. You can't even pause motor power over jumps, as I can't imagine your using pedal assist if your not using the cut-off switch's.

I can't see a single advantage to not having them. Perhaps it is a motorcycle thing, but I don't ride a motorcycle.

 

[cal3thousand]

I guess I'm one of the exceptions, chalo. I cut and resize ALL my hydraulic hoses. And it's absolutely necessary when adding a pressure sensor to a non-ebike hydraulic set.

And I actually find that it takes more bike-specific tools to handle cable routing/sizing/fitting properly. (4th hand & cable cutter, crimper)

I was able to handle everything for the hydraulic hoses with tools that I already have for automotive maintenance. Only bike-tool I used was the cable cutter on the hose. I could have done that with my wire loppers too. ( I guess you can say you need bleeding tools to offset that, but I already have that)

EDIT: Oh, and another thing you can flame on about. I like to be wasteful and use ATE super blue brake fluid in DOT 4 applications (Not really wasteful, I use what I have left from car work )

 

[Hillhater]

Why would you want anything other than 'power off' while braking?

1 .. because its not necessary in practice !
2..and why over complicate things
3 Ask any motor bike rider why they dont have a "power cut" interlock on their brakes ?
4 Legally ??... if you are really going to be legal, you only have 250W to handle so no problem for brakes anyway. :wink:

I numbered your points for a more succinct reply.

1, But it is, people have burnt there bike's out, and why waste power when your trying to slow down. You should be thinking regen, not waste.
2, The automatic control is too complicated, you would rather have a procedure to follow whenever you brake? Here is my procedure, I pull the brake to stop, then let it go to carry on.
3, Don't you have the answer? Modern management systems cut the fuel under many conditions.
4, It's a regulation because it is considered wise for more reasons than brake efficiency.

I really can't imagine how your bike works without one. There must be a number of procedures. You can't even pause motor power over jumps, as I can't imagine your using pedal assist if your not using the cut-off switch's.

I can't see a single advantage to not having them. Perhaps it is a motorcycle thing, but I don't ride a motorcycle.

1.. anyone who who burns out a motor against a brake is a moron ! This is basic hand-brain-hand coordination. and within minutes it becomes muscle memory !
2.. " automatic control is too complicated" ..and unnecessary !.. Do you really ride with your throttle pinned and rely on your brake sensors for control ?? ..That sounds like a recipe for an accident !
How do you remember to stop pedaling when you brake ?
3.. I have never come across any management system that cuts power when i brake..Care to give an example ?
4.. A regulation ?...so is 250 watts !! :lol:

A singe advantage ?...
How about,.. less components to fail,... less to buy and install, ...wider choice of controllers, ..etc etc.