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

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TheReal Houdini
05-05-12, 06:59 AM
I was disappointed to discover that I chewed nearly all the way through a set of v-brake pads on a single rainy descent off Skyline Drive in Shenandoah National Park. Furthermore, my stopping power subsequently went to crap, presumably due to glazing of the brake pads - after the descent, not during.

My Novara Safari is set up to run either v-brakes or discs.

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?

Thanks!


Chris Pringle
05-05-12, 08:38 AM
Quite controversial issue here in the forums, So I will try to remain impartial.

For V brakes, try some different pads first before you go through the expense of switching to disc brakes: Kool Stop salmon compound. See how those work for you.

Yes, disc brakes will also overheat on a long descent and you'll wear your pads quickly, too. You can minimize that with putting a larger rotor up front (e.g. 180mm), but the ones that come stock should work really well. You may have to play a liitle with that after a few tours. An advantage that many point out is that with disc brakes (besides amazing stopping power) you don't wear out your rims. It's usually easier and cheaper to change a rotor than an entire rim.

fietsbob
05-05-12, 08:56 AM
No one uses anything but friction for brakes. as you watch meteor showers
that is friction in action..
Rims on the bike, are very big disc brakes..
Toured for a few decades in summer on rim brakes,same pads fine at end of any trip
now have BB7 on my wet weather commuter.[160 on 20" wheels]
if there are worries, rim brake inserts, or disc spare pads in the bag take up little space .

technique matters. if you brake hard for a short period of time then let go ,
heat will not build up, like holding the brakes on and constantly dragging them.


Cyclebum
05-05-12, 09:00 AM
Compromise. Disc on back, V on front. Less weight and fiddle factor than two disc, stopping power when needed. Switch to Kool pads.

VT_Speed_TR
05-05-12, 09:02 AM
I have bikes with v-brakes, Avid BB7's, and hydraulic disk brakes. As far as stopping power and modulation, the hydraulics are the best. However, they are on my mtn bike, and I don't think I'd want them on a touring bike because of the difficulty with bleading the brakes and the potential for a damage line. The BB7's are great brakes, never had any issues coming down steep roads, lots of power, and simple to set up and adjust. For general riding v-brakes have served me well, but after having the power of disk brakes I prefer them.

I'd try different pads, I use Kool Stop, and find them far better then the crap that comes with most bikes as standard equipment.

sstorkel
05-05-12, 09:46 AM
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?

The longest descents I've done are probably in the 3-4 mile range with an average grade of -7 or -8%. I've never had a problem with overheating on my BB7-equipped touring bike. On long descents, I do concentrate on proper braking technique (alternate front and back brakes, brake hard when needed then release pressure rather than having brakes constantly engaged, etc).


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

I suspect that it's possible to get any brake pad to glaze if you treat it poorly enough. I also suspect that stock brake pads are optimized for low price rather than best performance; there may be replacement pads that work better. That said, I haven't had a problem with glazing on my BB7s.

djb
05-05-12, 11:44 AM
On long descents, I do concentrate on proper braking technique (alternate front and back brakes, brake hard when needed then release pressure rather than having brakes constantly engaged, etc).
I suspect that it's possible to get any brake pad to glaze if you treat it poorly enough. I also suspect that stock brake pads are optimized for low price rather than best performance; there may be replacement pads that work better. That said, I haven't had a problem with glazing on my BB7s.

all very good points, especially about not having brakes constantly engaged. This is common behaviour with some people and really does cause more problems that alternating and hard applications when needed.

also, as someone who has also toured loaded in very mountainous areas (and has experienced brake fading and/or hand tiredness requiring a stop to let things cool down) I do question that you went through a "set of pads" on one descent. One possibility is that you never clean your rims or pads and lots of abrasive has accumulated over time (or did in that section) . Even if it did accumulate during that descent, it doesnt make sense to have gone through that much pad material in such a short time--again, not an accusation but from my experience going down hills with a load.

do try diff braking techniques and you will see that brake fade will be less of an issue.

Carbonfiberboy
05-05-12, 12:13 PM
Brake hard, one rim at a time, and keep your speed up. Don't feather the brakes. Let the bike run as much as you can. You'll need both brakes before hairpins. When lever pressure to get the same effect increases, stop and let your pads and rims cool. This procedure works for 350+ lb. tandems. It will work for you. On a mass tandem descent of Mt. Ventoux, the only bikes that had big brake problems were running discs. Rim and drum brake bikes did fine. This probably can be laid to overconfidence on the part of the disc-equipped teams.

However that may be, you won't like it if you warp a rotor or melt all the plastic parts off your calipers in the middle of a tour. You also won't like it if you blow a tire off a rim. Historically, the only tires known to have been blown off tandem rims by heat were wire bead, FWIW. I always carry two sets of spare pads for rim brakes. They're small and light - ditch the packaging, bag them with their pins. I always carry a mini Leatherman, mostly for this purpose. Yes, Koolstop salmon, KS-LPVBSA for V-brakes. Google, they're rare to find on the shelf.

If you have an alcohol stove, wipe the rims with alcohol in the morning before a section with a big descent, or every morning. If you don't, consider carrying a small bottle of alcohol for this purpose. This makes a very big difference both in braking and in the life of your rims.

As all that may be, your rims will last a lot longer if you run discs. OTOH, they're a heavy addition and you already have rims. It can be argued 5 ways from Sunday.

Cyclebum
05-05-12, 02:12 PM
Yeah, modulation is the key for long down hills. Never had any trouble doing that. Have stopped occasionally to let rims cool. Pad wear was never a problem. Longest decent was 8 miles, 5%.

Bacciagalupe
05-05-12, 04:58 PM
This guy here talks about his encounter with brake fade on discs. (http://www.bikerumor.com/2012/02/14/road-bike-disc-brakes-are-coming-but-will-they-work/) 180-200mm rotors should not have the same issues, but the author of the article thinks discs on road bikes will be smaller.

It doesn't sound to me like discs would help much on massive descents, at least not enough to justify the upgrade costs. If the descent wrecked a pair of v-brake pads, it'd probably wreck disc pads as well. I'd go with discs if you have some other compelling reason, e.g. cycling in bad conditions.

seeker333
05-05-12, 05:00 PM
...My Novara Safari is set up to run either v-brakes or discs.

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?

Go ahead and take the plunge to BB7s (road or mtb version depending on your lever type/budget), you probably will be glad you did.

I've never had my BB7 discs overheat or glaze. The only thing bad that's happened to my BB7s was a rotor got bent, when something was moved in garage into bike leaning against wall. I was able to straighten the disc with an adjustable wrench while still mounted to hub. I think the pads do wear slower on BB7s than Avid SD7s (rim brakes I used for many miles), so replacement is less frequent and easier, since it's not necessary to carefully reposition or toe-in disc pads - they just drop into place.

Barrettscv
05-05-12, 05:09 PM
My take on Disc brakes is simple. If you ride in the rain often, use disc brakes. If your riding is in dry weather 90% of the time, disc brakes may not offer enough of an advantage.

Portland, OR or Seattle: Disc brakes
Tucson: Rim brakes

seeker333
05-05-12, 05:39 PM
That's a pretty good "rule", Barrettscv.

I'd modify slightly and say "or, if you roll down mountains with a heavy (rider+gear) load".

I'm sure there's a lot of fair-weather flatlander bicyclists who are completely puzzled by some folks seeming obsession with disc brakes.

JoeMan
05-05-12, 06:06 PM
I have a 2007 REI Safari. I changed over to BB-7s. I sometimes have my BoB trailer on this bike. I can say I have noticed improved braking with discs going downhill. I keep my loads on the light side and my body weight also low.

Barrettscv
05-05-12, 06:39 PM
I'm sure there's a lot of fair-weather flatlander bicyclists who are completely puzzled by some folks seeming obsession with disc brakes.

I have two bikes that have both Disc tabs and Canti bosses. I have never felt the need to install a system that is;

Heavier
More Costly
Requires special hubs and a very strong wheel build
Requires an extra stiff fork to avoid twisting forces.

Only in winter do I think I might be missing something. But then, I have never had a situation where the rim brakes failed to do it's job well.

If I lived in a rainy region with hills, I would install discs.

TheReal Houdini
05-05-12, 06:40 PM
Thanks, especially to those with BB7s. A few notes:

1. In retrospect, it was probably only half of the brake pads, not the whole thing, but still a lot.
2. My braking technique is good. The Houdini moniker was actually bestowed by fellow cyclists for on-bike behavior. However, it was raining and the reduced visibility and traction for both me and the motorists inspired me to brake harder and more frequently than I otherwise would have.
3. If I recall, the catastrophic failure of disc brakes on long descents was actually due to boiling of the hydraulic fluid - not an issue with bb7s.

Bekologist
05-05-12, 06:58 PM
rim brakes, loaded bike. no worries.


http://www.youtube.com/watch?v=F6cRrtFEu2w&feature=plcp

nubcake
05-05-12, 09:21 PM
:deadhorse2:

If you search for something like disc brakes on a touring bike you will read pages and pages of back and forth over which is better for a touring bikes. When it really comes down to it though, both systems have proven themselves and each has its minor quirks but when set up properly they both can work quite well in any situation.

Carbonfiberboy
05-05-12, 10:09 PM
rim brakes, loaded bike. no worries. 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.

Carbonfiberboy
05-05-12, 10:11 PM
Thanks, especially to those with BB7s. A few notes:

1. In retrospect, it was probably only half of the brake pads, not the whole thing, but still a lot.
2. My braking technique is good. The Houdini moniker was actually bestowed by fellow cyclists for on-bike behavior. However, it was raining and the reduced visibility and traction for both me and the motorists inspired me to brake harder and more frequently than I otherwise would have.
3. If I recall, the catastrophic failure of disc brakes on long descents was actually due to boiling of the hydraulic fluid - not an issue with bb7s.My anecdote was with BB7s. The plastic parts simply melted, which impaired the functioning of the brakes. Not the usual thing, though.

hopperja
05-05-12, 11:01 PM
I prefer disc brakes on any bike I own. Yes, I am biased, I just wanted to state that up front.

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 (http://en.wikipedia.org/wiki/Brake_fade), much like in a very aggressively driven motor vehicle. With the cable actuated BB7, there is no fluid to overheat, so it shouldn't be a problem.

I don't like the Avid hydros (Juicy line specifically). I'd steer clear of them. If you go with hydros, I have found the Hayes 9s to be virtually maintenance free in roughly 5,000 miles of commuting/utility/mountain biking. Given the choice between V brakes and BB7s, I'd choose BB7s. Between BB7s and other disc brakes, I'd choose Hayes 9s.

hopperja
05-05-12, 11:08 PM
Compromise. Disc on back, V on front. Less weight and fiddle factor than two disc, stopping power when needed. Switch to Kool pads.

I don't get your suggestions. Since most stopping power comes from the front brake, if you were only going to buy one new brake, why not put a disc on the front?

fietsbob
05-06-12, 12:21 AM
If you use the rear as a drag brake, its some what like a typical tandem use.
in a similar situation..

Or,
Door #3 Magura HS 33 .. the hydraulic rim brake. V brake boss mounted..

azesty
05-06-12, 01:13 AM
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

Bacciagalupe
05-06-12, 05:14 AM
If I recall, the catastrophic failure of disc brakes on long descents was actually due to boiling of the hydraulic fluid - not an issue with bb7s.
The brake pads can also glaze.

In the article I linked, the author talks to several manufacturers; mechanical vs hydraulic for discs makes no difference for brake fade. Conditions hot enough to boil the hydraulic fluid would just melt other components in the brakes.

I don't think discs offer any real advantage for descents like this.

Bacciagalupe
05-06-12, 05:19 AM
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 (http://en.wikipedia.org/wiki/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
05-06-12, 07:10 AM
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
05-06-12, 07:12 AM
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
05-06-12, 07:30 AM
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
05-06-12, 07:47 AM
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
05-06-12, 09:49 AM
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
05-06-12, 10:07 AM
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
05-06-12, 08:04 PM
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
05-07-12, 09:06 AM
Oh hey what's going on in this thr-

http://i.imgur.com/OMPZQ.gif


-oh.

Werkin
05-07-12, 09:20 AM
...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
05-07-12, 10:03 AM
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
05-07-12, 03:06 PM
A first generation mechanical to hydraulic converter known the have issues with air ingress was also on the author's brake failure bike.

fietsbob
05-07-12, 03:11 PM
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'
05-07-12, 03:41 PM
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
05-07-12, 04:26 PM
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
05-08-12, 06:23 AM
I would hardly say he "cooked the crap out of them"....
When was the last time you saw bike rims with that much discoloration? :D

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
05-08-12, 09:57 AM
...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
05-08-12, 10:55 AM
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:
http://wp-content.rpmware.com/wp-content/uploads/2009/04/dba-4000-5000series-580x561.jpg
http://www.socalevo.net/gallery/albums/userpics/10991/TECH%20ARTICLE%20brake%20rotor%20engineering20.jpg

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
05-08-12, 10:39 PM
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
05-09-12, 12:47 AM
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
05-14-12, 05:51 AM
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
05-14-12, 12:22 PM
Or you cannot buy hardware to make up for poorly thought out riding skills.

Burton
05-15-12, 05:58 AM
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.