V-brake vs. BB7 for long, loaded, fast descent.

[Bacciagalupe]

As for Avid BB7s, I don't see how cable actuated brakes would overheat. The big issue with disc brakes theoretically overheating is that the brake fluid can get too hot causing brake fade, much like in a very aggressively driven motor vehicle.

BIKERUMOR: Mechanical versus hydraulic discs for road, any performance or safety difference with regards to brake fade?
Shimano: There’s absolutely no difference in brake fade. The benefit to hydraulics is better modulation, there’s a more linear progression of braking power. Plus, the hose won’t get contaminated like cables and housing.

Magura: Mechanical disc brakes will not suffer from boiling oil, but from melting of other components, spongy feeling and bad modulation from mechanical cable and housing. If mechanical disc brakes would be top, then MTBs and cars still would use them!

[Bekologist]

Iron Horse trail descent? Beautiful country. Looks like you're descending into western WA, reverse of the usual. That is pretty fast for that surface.

Quilcene crossover, Sequim to Quilcene. gravel on the ascent, the road turns into blacktop at about 4,000 feet for a great descent.

[djb]

A couple of people have mentioned rim wear.

Most of my rides are flat, but there have been a couple of long descents, like one from 3900m to 1500 m, but my commuter has almost 17,000 km on the front wheel, and I can still see the front wear indicator....

Where I ride has a lot of grit on the road, so my bike is often covered with fine to coarse sand.

z

Z, are you pretty good for wiping down your rims of grit after riding in rain? My experience shows this to be a big factor in both rim life and braking power. I.just use a rag, which I feel is sufficient if done regularly after rain rides to keep the braking surface fairly clean and in good shape for long term.
It's obvious right away by feel and sound if everything has grit on it (rims, pads)

Again, for someone in rain often, I absolutely see the advantages of disks.

[djb]

BIKERUMOR: Mechanical versus hydraulic discs for road, any performance or safety difference with regards to brake fade?
Shimano: There’s absolutely no difference in brake fade. The benefit to hydraulics is better modulation, there’s a more linear progression of braking power. Plus, the hose won’t get contaminated like cables and housing.

Magura: Mechanical disc brakes will not suffer from boiling oil, but from melting of other components, spongy feeling and bad modulation from mechanical cable and housing. If mechanical disc brakes would be top, then MTBs and cars still would use them!

Excellent points these.

As for boiling fluid, melting plastic etc you really have to be constantly hammering the brakes. I've experienced boiling fluid on a motorcycle on a racecourse, where brakes really are being abused non stop. Back to touring, if one feels required hand pressure increasing and increasing, you just lay pfff it for a bit, you are not needing to keep consistent lap times like on track, you just pull over and let's things cool down for a bit. But again, can see the advantages of disks in cruddy conditions.

[Mr. Fly]

BIKERUMOR: Mechanical versus hydraulic discs for road, any performance or safety difference with regards to brake fade?
Shimano: There’s absolutely no difference in brake fade. The benefit to hydraulics is better modulation, there’s a more linear progression of braking power. Plus, the hose won’t get contaminated like cables and housing.

Magura: Mechanical disc brakes will not suffer from boiling oil, but from melting of other components, spongy feeling and bad modulation from mechanical cable and housing. If mechanical disc brakes would be top, then MTBs and cars still would use them!

Well, I don't know if cars are good examples of why hydraulics were used. Cars have a distribution issue that bikes typically do not suffer from. Things like a relatively long distances between pedal and caliper, plus the many moving suspension parts do not lend themselves to good transfer of force. Bikes, especially non-suspended ones, do not really have such high requirements.

[fietsbob]

Magura's rim brakes, the HS33, the nicer lever than the 22.
have thick rubber brake shoes, in plastic snap in holders, so don't heat the fluid.
They have been popular for touring bikes for a decade + , out of Germany.

They are dual slave cylinder, with a pressure balance tube, Rim brakes.
don't confuse them with disc brakes.
http://www.magura.com/en/products/rim-brakes-2012.html

[sstorkel]

Excellent points these.

As for boiling fluid, melting plastic etc you really have to be constantly hammering the brakes. I've experienced boiling fluid on a motorcycle on a racecourse, where brakes really are being abused non stop. Back to touring, if one feels required hand pressure increasing and increasing, you just lay pfff it for a bit, you are not needing to keep consistent lap times like on track, you just pull over and let's things cool down for a bit. But again, can see the advantages of disks in cruddy conditions.

Agree. It sounds like the guy who wrote the article that Bacciagalupe linked had very poor braking technique and that's what lead to his crash! He admits to dragging the brakes constantly while going 30mph. That's something that I wouldn't do regardless of which brake system I was using...

[Bacciagalupe]

Agree. It sounds like the guy who wrote the article that Bacciagalupe linked had very poor braking technique and that's what lead to his crash! He admits to dragging the brakes constantly while going 30mph.

He also admits that he used a setup that wasn't appropriate.

But he wasn't making a blanket assertion that "discs are always bad." Rather, his crash got him thinking, "how are the road discs going to actually work? Roadies aren't going to put up with 200mm rotors and multiple pistons, and sooner or later they'll do something that creates brake fade." Thus, he tried to get the manufacturers to divulge how they're going to set up road disc brakes (without much luck).

Plus, you can see how 2-3 minutes of light pressure dragging -- which really isn't that long -- cooked the crap out of the rotors.

One manufacturer reps openly says rim brakes are less likely to heat up than disc ("With rim brakes you already have the biggest possible rotor on a wheel: the rim!"), and Hayes Brakes pretty much punted.

Touring cyclists will be more willing to use larger rotors, beefier calipers and slightly heavier forks. But my best guess is that if you had a decent technique and still generated enough heat to glaze a perfectly good set of rim brakes, you'd also cook either a mechanical or hydraulic disc brake system.

I.e. it doesn't look to me like discs offer superior descent braking, and therefore that's not a great motivation to upgrade. A better reason is improved braking in rain and mud.

[TenThousandSuns]

Oh hey what's going on in this thr-




-oh.

[Werkin]

...I've read that disc brakes can overheat on long, fast road descents resulting in potentially catastrophic loss of stopping power. Can anyone confirm or deny this for Avid BB7s?

I've read that disc brake pads can glaze under similar conditions. Can anyone confirm or deny this for Avid BB7s?

Would disk break pads require substantially less frequent replacement than v-brake pads?...

I don't ride a loaded touring bike, but do have BB7 and V-brakes on bikes used on road climbs.

BB7 pads can overheat when used in prolonged braking, however, when bicycle disc pads glaze they make more noise, and lever effort increases, there is no "catastrophic loss of stopping power". Lever effort on glazed disc pads is nothing like the scary fade I've experienced with rim brake pads. I've glazed metallic Avid pads and aftermarket ceramic pad compounds while using 160mm front & 140mm rear G2 rotors. No glaze after switching to Swiss Stop pads on a 180mm rotor up front, and no glaze with a 200mm up front & 160mm rear using a pad pairing of Avid metallic inboard, Swiss Stop outboard. I will be installing a 180mm rotor on the rear this week, BTW.

Pad replacement intervals depend on the pad compound and usage. I've worn out soft ceramic disc pads quickly. I haven't worn through an Avid metallic pad, so I don't know first hand about its service life to the end. From the looks of the Avid V-brake pads on a bike that occasionally accompanies me (I ride it sometimes also) on my usual routes, I would say Avid's metallic disc pad will outlive Avid's V-brake pad used under the same conditions. The pads on my single pivot rim brake bike not only wear rapidly on the same descents, they pick up pieces of the rim also.

The disc brake configuration on my primary bike outperforms the rim brakes on my other bikes in dry conditions. The 40mph top speed descents I ride are short, but very steep, with either a rough surface, short radius turns, or a stop sign at the end, all reasons to use the brake hard, or at least drag for a while. One descent is so rough I must drag the brake for its entire length, keeping speeds extremely low; it's a rim brake destroyer.

[sstorkel]

Plus, you can see how 2-3 minutes of light pressure dragging -- which really isn't that long -- cooked the crap out of the rotors.

The brake rotors certainly got hot, but based on my welding experience I would hardly say he "cooked the crap out of them". In fact, I wonder if the pads were properly "bedded in" before the ride...

Interesting to note that one of the author's companions was also riding a disc brake-equipped cyclocross bike and didn't crash during the same descent. The buddy was using Avid BB5 mechanical discs while the author was using mineral oil-based hydraulic discs and swapped the stock brakes rotors for ones with significantly less thermal mass. Poor braking technique, poorly chosen rotors, and mineral oil (rather than DOT) hydraulic fluid seems to have led to a "perfect storm" that caused the crash. Rather than taking responsibility for his poor equipment choices, the author now wants to suggest that disc brakes and road bikes don't mix. That might make for good press, but it shades the truth a bit too much for my liking...

[Werkin]

A first generation mechanical to hydraulic converter known the have issues with air ingress was also on the author's brake failure bike.

[fietsbob]

Arai Drum brakes for drag brakes on tandems have been used so long
some Tandem hubs, like Shimano's are still threaded to take them.

add a disc hub in back, 3rd lever , for the drag brake,
and use V brakes for all the other braking needs

[Trikin']

I've been using the BB7's 2yrs with larger (Dia) rotors
I RIDE A CATrike Trail and I use a trailer when I tour (E-BOB).
The trike came with the BB5's.....the BB7's are great and are simple to adjust
The E-BOB has a 500W hub motor and the Li-Ion battery is mounted to trailer deck.....approx. 22lbs, plus camping gear and stuff, then the trike and me......250lbs+ ? I need the extra stopping power

I had Magura Hyd. brakes on another trike on a single lever, it failed once....resulting in a flip over on a hill. Got a larger reservoir (4 a tandem) never had an issue after that.

You can't ride your brakes(overheat) and you can't jam them on at the last moment and when they fail look out

[mikhalit]

I like V's for their simplicity weight and performance in dry conditions. They would be a good choice for 90% of situations I experience on tour. But last summer I had a nasty long descend in the rain with my kids in the trailer (that's +30 kilos , and the bike + rider + gear was about 140 kilos), I was super careful but sometimes had to push the brake levers really hard to maintain the right speed. Switched to BB7 after that and liking it a lot.

Still wish i had also a light sunny weather commuter with V's.

[Bacciagalupe]

I would hardly say he "cooked the crap out of them"....

When was the last time you saw bike rims with that much discoloration?

I'd hope you'd agree that while he did not warp the rotors, clearly he was generating a lot of heat in a fairly short time span. If he was using mechanical discs, maybe he'd get another minute or so. Maybe not.

Rather than taking responsibility for his poor equipment choices, the author now wants to suggest that disc brakes and road bikes don't mix.

That is not what the author is saying.

He does accept and openly states that his technique was off, and that the equipment turned out to be insufficient.

But his point is that his choices were typical roadie behavior -- choosing the lightest equipment available, assembling it himself, descending at high speeds, dragging the brakes. And it didn't take long for his brakes to completely fail.

Thus it's virtually certain that other roadies will make similar mistakes. We simply do not live in a perfect world where weight weenies will choose the heavier rotor; where riders who like speed will slow down because of the type of brakes they selected; where every single bike shop and home mechanic will set up and maintain disc brakes perfectly; where no one will drag their brakes.

Thus, the purpose of the article is not to say "discs are evil, never go near them." Instead, he's trying to get Shimano, Magura and TRP to 'fess up on the techniques they will use to minimize the aspects under their control (e.g. material choice, installation).

Nor am I saying "discs are instant death on a descent" or "no tourer should ever use discs." I'm neutral on the issue. I'm only saying that discs won't necessarily perform any better under the same conditions that the OP faced, and thus doesn't offer an advantage for that particular issue. Thus I on that specific basis it's not worth the upgrade.

[Werkin]

...I'm neutral on the issue. I'm only saying that discs won't necessarily perform any better...it's not worth the upgrade.

Do you Bacciagalupe, have or had BB7 disc brakes on a road bike?

[brandini]

Like others have said: try changing your braking method on descents. Bike rotors have a relatively small thermal mass and you should use the same method as cars when descending a mountain: don't drag the brakes, brake hard at times when you can, and let the brakes cool the other times. The idea to alternate front and back to give cooling time is also pretty smart.

A car known for it's ninny brakes, the Prius, even has hill descent mode for this reason. It drags the gas engine (unpowered) to help provide additional friction and prevent too much speed gain on descents. It can do this because it can circulate coolant to shed the generated heat.

Since you don't have an extra method to wick away heat, you have to be sure to let the brakes cool since the rotors are not vented.

Yes they are cross-drilled, but not vented like a car, which has 2 flat surfaces and cooling vanes between. This is one reason why car brakes are so good, surface area. They're even taking this farther and farther:



So happy braking!

The article posted does have many 'failures' of both method and equipment, but going with a solid system made for a mtb should get you where you want. The BB7 does have 2 versions: long (mtb) and short (road) pull to match the appropriate levers, so take that into account when choosing.

[nubcake]

Who else is still convinced people are greatly over thinking which brakes to use? I stand behind the fact both brakes will work just fine when properly set up.

The author from the article mentioned the brake levers going to the bar, a classic sign of fluid fade over pad fade, with mechanical brakes he would still have braking as it was not the pads over heating. He probably had fluid fade due to the fact the brakes were not properly bled or had some factory defect (very possible as it was a new system that was probably rushed out) My big problem with that article is the alarmist headline which really should have read "If you do not set your brakes up properly they will fail in a horrible way"

I have TRIED to overheat my hydro discs with no luck (?) 6 in brake rotors and dragging them down a somewhat steep fire road decent that lasted 5ish miles, even pedaling the flatter sections while still dragging the brake to try and heat it up more. My brakes are about 5 years old and have not been bleed in at least 2 years, also running knock off pads. These systems are not very fragile despite what some seem to want you to think, you just need to know how to set them up (which is true about anything)

[sstorkel]

The author from the article mentioned the brake levers going to the bar, a classic sign of fluid fade over pad fade, with mechanical brakes he would still have braking as it was not the pads over heating. He probably had fluid fade due to the fact the brakes were not properly bled or had some factory defect (very possible as it was a new system that was probably rushed out) My big problem with that article is the alarmist headline which really should have read "If you do not set your brakes up properly they will fail in a horrible way"

The article explains exactly why the author experienced brake fade. There's no mystery: 1) he used poor braking technique, 2) he replaced the stock rotors with ones that were significantly lighter which contributed to overheating, 3) he used a braking system that was designed for cyclocross (low speeds, relatively short descents) rather than road riding (high speeds, long descents).

One of the author's riding companions was on a bike equipped with Avid BB7 mechanical disc brakes and the article makes no mention of him crashing due to brake fade.

[TheReal Houdini]

I made the switch to BB7s. In addition to the issues discussed earlier in this thread I'll add:

You can't (its not safe to) overdrive your brakes. If you need 30 meters to stop you better be able to see 30 meters ahead. Likewise if you can only see 20 meters around the next curve you should slow to the point you can stop in 20 meters or less. Better brakes = shorter stopping distance = faster descents = more fun (for me). I can go faster, brake less, create less friction and heat, knowing the stopping power is there if I need it.

Summary:
Rim brakes are good enough;
Disc brakes are better.

[fietsbob]

Or you cannot buy hardware to make up for poorly thought out riding skills.

[Burton]

So what kind of V-brake pads are we talking about. Not all V-brake are created equal and neither are all V-brake pads. Top end Shimano pads completely embarass low end pads.

Pretty much the same story for disc brakes. Aside from recommending a larger rotor size for better cooling on hilly areas, top end pads will make a big difference.

Which is not to say you don't need good technique or shouldn't stop and let things cool down ocassionally is conditions warrant it. From my own experience, glazed brake pads on either result from continuously dragging the brakes without applying enough pressure to remove any surface material.

Long story short - I'd tour with either one.