Looking for some input, thoughts and comments concerning our new build. We're a 290lb tandem team that rides pretty quick. We usually go out with the 21mph Saturday single group at our club ride. We climb very strong and aren't afraid to hit 50mph on good, safe, clear vision downhills. We live just west of Portland, Oregon at the base of the coast range so we have some serious clinmbs right out our front door.
Anyway, I'm building a new bike for us and have the choice of using an XTR V-brake(?) or Avid road disc on the rear. Previously our bike had XTR's front and rear and they worked pretty darn good but that was our only option as the frame wasn't disc compatible. I'm using either a Campy Record or Mavic front caliper and the rear is undecided.
I've never ridden a disc bike and haven't read much good or bad about their performance on tandems. Just curious what folks think that have been where I am with making this choice. Also, I already own both brakes so cost/investment plays no part of the decision.
Thanks a bunch, great group with an amazing amount of useful info. We're new here and look forward to becoming active participants in this forum.
As soon as I figure out the photo posting thing I'm provide pics of our current ride and provide a blow by blow photo essay of the new build. It's currently at the paint shop for a custom spray and will return in 11 days for the "operation" to begin...
It'll make it's debut at the Monster Cookie Metric century on April 29th in Salem, Oregon.
Ride safe!
KRhea
PortlandVelo.net
The BikeForums Team
-adv-
This is an archived thread, you can find the full version of this thread, with images, links and more content here.
IMHO, go with the Avid mech disc but have your builder include the necessary drilled brake bridge and cable guides to support a rear caliper just to keep your options open for the future, e.g., fitting a rear caliper wired to your brake lever and adding a bar-con to control the disc for European switchbacks, etc...
FWIW: We have one road tandem with dual Record calipers and the other has the hybrid system with a Campy caliper up front and the Avid mech disc on the rear. This gives me a frequent reminder of how much added control and utility the rear disc provides vs. a rear caliper. The only thing that a rear disc can't do for you is alleviate hand cramps from prolonged braking on very long, high-brake demand descents which is where the alternative configuration mentioned above comes back into play.
zonatandem
For a team in your weight class and agressive/hilly riding would agree with rear Avid disc + the option of also putting on a rear V-brake.
Have test ridden one tandem with discs front and rear (an Avid rear and Hayes front). Stopping power was awsome, however this was on a fast/short descent (just under 40 mph) riding the tandem solo. Didn't want to put stoker Kay through full speed descent then hit the brakes scenario.
Discs tend to present their own issues, and some folks still prefer the Arai drum for prolonged descents.
We use a D/A front caliper and Tektro Mini V-brake on our tandem and are a sub-250 lb. 'older' duo. However, we no longer are in the go-fast/climb/descend any nountain full-tilt league. Been there, done that.
Pedal on TWOgether!
Rudy and Kay/zonatandem
dsmyers
TandemGeek,
I thought it was unsafe to use disc brakes as drag brakes (i.e., constantly applied) due to excessive heat build-up. Is this not true?
Thanks,
Daniel
IMHO, go with the Avid mech disc but have your builder include the necessary drilled brake bridge and cable guides to support a rear caliper just to keep your options open for the future, e.g., fitting a rear caliper wired to your brake lever and adding a bar-con to control the disc for European switchbacks, etc...
FWIW: We have one road tandem with dual Record calipers and the other has the hybrid system with a Campy caliper up front and the Avid mech disc on the rear. This gives me a frequent reminder of how much added control and utility the rear disc provides vs. a rear caliper. The only thing that a rear disc can't do for you is alleviate hand cramps from prolonged braking on very long, high-brake demand descents which is where the alternative configuration mentioned above comes back into play.
cornucopia72
We have the setup that TandemGeek describes. We use the disc brake to give my hand and the rim a brake on prolonged/steep descents. As soon as I find some time I will add a bar-mounted in-line lever to the disc brake. That way we will use it to modulate speed while turning also. If the disc proves that is enough to slow our rig down to safe speeds coming down 10% + laberiths, we may remove the rim brake then. We are a 300 lb. team and droping!
stapfam
Thoughts to me are that rim breaks wear out rims and disc breaks wear out---Not much really except pads. Both brakes are good so will be effective but if taking in long descents, there could be an advantage to having the "V" brake fitted as an extra brake.
I have discs on our Mountain tandem and they are effective. Top end hydraulics though so can't say a great deal about the Avids. Only suggestion is to get a Large Disc, at least 180mm, as this will give more effective braking and stay cooler. We have 200mm discs front and rear, and you want to hear the Solo riders gasping for breath with envy when they see them.
As to using Disc brakes as a drag brake- There is a technique for using them on downhills- but we have never had an overheating problem and that was even after getting them to a dull orange glow on one particular steep downhill.
Retro Grouch
TandemGeek,
I thought it was unsafe to use disc brakes as drag brakes (i.e., constantly applied) due to excessive heat build-up. Is this not true?
Thanks,
Daniel
I have some personal friends who melted tha plastic parts on their Avid caliper while riding in Italy last summer. They have switched back to using Santana's Formula hydraulic brake.
dbohemian
I have some personal friends who melted tha plastic parts on their Avid caliper while riding in Italy last summer. They have switched back to using Santana's Formula hydraulic brake.
I have heard of this happening. On my recent tandem, I fitted Avids front and rear. The stopping power is excellent (380 lbs team, going 40+ no problem)
I look at the Avids as being a disposable product in times of emergency. Rarely do I ride super steep, switchback roads where I have to ride the brakes. I figure, that if it becomes absolutely necessary I will just cook the Avids and purchase new ones or rebuild the calipers (they really are quite inexpensive). I have heard that they melt but will continue to function. They may even have a higher heat tolerance compared to some hydraulics that will just boil over and stop functioning.
I am a motorcycle rider and brakes are a similar consideration. At this point motorcycle brakes are so good that it is a none issue, they can dissipate heat at an amazing rate. Hopefully, someday we have a great road hydraulic option too. Until then the Avids seem to be the ticket.
cornucopia72
I have some personal friends who melted tha plastic parts on their Avid caliper while riding in Italy last summer. They have switched back to using Santana's Formula hydraulic brake.
Just in our backyard, while coming down into Bass Lake at the Grissly Century, we had to stop because our Arai drum brake was smoking.... go figure
Hermes
I have some personal friends who melted tha plastic parts on their Avid caliper while riding in Italy last summer. They have switched back to using Santana's Formula hydraulic brake.
That information is consistant with Santana's published article on tandem brake testing. I have posted on this before, but we have Santana's Winzip Disc which has the 10 inch rotor. See below:
We have one high speed 5 mile > 5% grade descent using the brake as a drag brake to control speed. It worked fine with no fade. Took it to the LBS for inspection afterword and decided to replace the pads. The brake had ~1000 miles. We are going to Tuscany this year and I will report back the brake experience. I am taking a couple of sets of extra pads.
TandemGeek
I thought it was unsafe to use disc brakes as drag brakes (i.e., constantly applied) due to excessive heat build-up. Is this not true?l
Only if the operator is completely oblivious to or ignores all of the very obvious signs that they are exceeding the heat capacity of their brake system, which is true for all rim, disc, and even drum brakes.
Here's the deal: In the case of disc brakes, as the rotor approach the upper-end of the caliper & rotor heat capacity the operator will begin to hear and feel the distinctive effects of brake pad outgassing and glazing which will only get worse and is accompanied by the loss of braking power, aka. heat induced brake fade. The same thing happens with rim brakes, except that unlike the mechanical discs which limit the heat build up to the rotor, hub, caliper and cable/housing, rim heating migrates into the tires and tubes and can create a situation where a tire "blows off" a rim: a catastropic failure mode. If anyone is struggling to understand what I mean by the sound and feel of brake's outgassing most teams have probably experienced it on any hilly, regular ride where they apply maximum braking near the bottom of a steep hill: it's that 'griding' sound and vibration that occurs just before you've finally got it slowed down enough to either finish the stop or move on. It's not a bad thing near the bottom of a hill that you're familiar with; however, it is a problem when you're 1/2 way down an 5,000 ft descent that you're unfamiliar with.
The only way that I know of to create a catastropic failure mode with a mechanical disc brake is to continuously apply both front and rear brakes to the point where both brakes are allowed to acheive heating points where they can both suffer nearly compete brake fade before the tandem is safely brought to a stop. Again, this suggests that the captain was unaware of how to properly use his braking systems or of the warning signs associated with a brake system exceeding its heat capacity and the need to bring the bike to a stop so that the brake system can cool-off before resuming the descents.
IMHO, continuing to make a long and challenging unfamiliar descent on any brakes after there are obvious signs of fade is analogous to riding with tire that is going flat; you either figure out "something's not right here" or end up skidding around on a metal hoop with a tire jamed in your fork or rear stays. However, I suspect that many captains may not have received sufficient instruction or taken time to appreciate what brake fade is and how it works and assume that "discs" will simply work under all conditions... which is simply not true of discs or any brake system.
Since they were mentioned, let me note here, hydraulic brakes are different in that as they overheat they can transmit the heat into the fluid as well as the non-metallic hydraulic lines. As hydraulic fluid heats it expands and even in an open system you can reach a point where the expanding fluid will no longer allow you to release the pads from the rotor. In off-road conditions the affected wheel / brake simply lock up and drag you to a stop in the dirt. However, the high friction roads will keep that wheel turning on the outgassing, fully glazed-over brake pads (to no effect other than heat generation) and at some point a hydraulic line or seal will let go: that is a catastrophic failure mode, i.e., your brake is now inoperable. I bring up this little problem with hydraulic brakes to underscore that to my knowledge the only tandem disc brake systems in recent times to suffer catastrophic failures have been hydraulic systems, not mechanical. Yes, there have been all kinds of profound warnings and cited test results that suggested the Avid brakes were "not safe for tandems" but despite asking for real world examples over the past 4 years I have yet to hear of anything other than melted plastic knobs. Santana's introduction of the all metal WinZip mechanical disc caliper is, in fact, the solution to their Formula disc. The Formula, to its credit, when set up properly and given the necessary attention to routine adjustments, is an outstanding brake. However, in the real world, most owners neither had the knowledge or access to mechanics who knew how to work on those brakes and therein was the weakness in that system. The Avid is a no-brainer, the Winzip, from most accounts, is far easier to set up and adjust than the Formula, but not a no-brainer.
So, getting back to Avids, yes you can melt the red plastic knobs (they're replaceable and cheap, by the way), probably the nylon seal/cap, you can even melt the plastic cable housing and teflon liner but not the metal inner housing, you can end up with a warped disc, and although I haven't heard of it happening with a rotor, I suspect you might cook the grease out of your rear hub's bearings as has been reported a few times with drum brakes that were severely overheated. But, other than "losing both your brakes" due to rider-induced brake fade while still underway, the mechanical brake will not come apart UNLESS there is some type of plastic part sitting in the reaction arm, cams, or retention screw and nut that holds the whole thing together that I'm not aware of.
The combination of the Avid's excellent performance and higher-than-rim-brake heat tolerance with non-catastrophic failure mode is why disc brakes have become very popular as a rear brake alternative for teams that don't need or want a drum brake on their tandem for any one of a variety of reasons. As for your original question about their use as a drag brake, let me be the first one to suggest that almost anyone with one of these Avid rear discs is already using it as a drag brake... it's hard not to because it just works so darn well. What I mean is, because a rear disc is so much more effective than a rear rim brake I know that I find myself biasing my downhill braking to 75% rear / 25% front, using the front only for more aggressive braking action in combination with the rear, particulary when it's wet. Now, while I'm not doing the "set-it-and-forget-it" drag brake operation normally associated with an Arai drum brake, in many cases and on very steep, twisty descents the effect is the same: that rear brake is on A LOT... as in a lot more than it would be if it was a rim brake as I still remain ever mindful of rim heating given that we run very high pressure, narrow tires. As the terrain gets steeper and more challenging, the brake use goes into alternating front on / back off then front off / back on brake use to make sure that neither brake is allowed to climb into unchecked brake fade, thereby ensuring that I always have sufficient brake capacity to bring our tandem to a stop if needed.
This then brings us full circle to the Avid as a drag brake. No, I wouldn't recommend the rear rim / Avid as a defacto "default" set up on any tandem or for any team that truly needs a drag brake: that's the realm of the Arai drum brake and always will be until something better comes along. However, what what you describe about yourself and the way you ride, the rear Avid with front caliper will be all you need for nearly all of your domestic riding. However, if you should happen to venture into the mountains where some type of supplemental braking system is recommended by the tour leaders or anyone familiar with the route, prudent use of a dual caliper braking system with an Avid disc judiciously employed as a "supplemental" brake should allow you to make the most challenging descents in a safe and controlled, non-stop manner if you so choose. Add 100lbs to your team weight or cut your experience level as a cyclist by 75%, and the recommendation quickly changes, as would steering someone who is rather large away from the authentic Chippendale side chair.
P.S. With regard to XTR V-brake vs. Caliper, while linear pull brakes have more stopping power it's almost a moot point on the rear wheel since either a caliper or linear pull brake will lock up the rear wheel under near panic braking with the front brake fully applied and heat capacity is the same for either. My take is, if you have caliper front, have caliper rear. If, however, you have linerar pull / bosses on the front, go with linear pull / bosses on the rear.
TandemGeek
I have some personal friends who melted tha plastic parts on their Avid caliper while riding in Italy last summer. They have switched back to using Santana's Formula hydraulic brake.
Did the Avid's fail catastrophically, require immediate replacement after the descent, or did they continue to work through the end of the tour with perhaps some maintenance after the overheat?
Why do they believe the Formula would have been any less resistant to overheating than the Avid?
bikeriderdave
We're a 270-280 lb team. We had two tandems when we lived in Beaverton: One with cantilevers and, later, one with NOS Campy sidepull brakes with Kool-Stop pads (have since changed to standard reach dual-pivot caliper brakes, but that' not part of this story). We had NO issues riding the West Hills (Skyline down Johnson/Logie), coast range, Laurel Mountain, or Mt. Hood on either bike. The only descent that gave me pause was Blooming-Fernhill, south of Forest Grove. Not for lack of braking power, but fear of overheating a rim/tire. [FWIW, I also stopped briefly to cool the rims when descending Mt. Ventoux a couple of years back -- auto traffic necessitated more braking than the mountain did.]
We have since moved to the Midwest, adopted a child, and acquired a triple, which has a rear Avid disc. I love the way the disc feels and stops the bike. We have kept a rear cantilever installed for safety (it's a triple after all, and my stokers are the most important people in my world). IMO, you can trust what Tandemgeek has to say about the Avid and discs in general.
Also IMO, If you want a light, fast, uncomplicated bike for a 290 lb team in all terrain, specify dual-pivot caliper brakes front and rear. If you appreciate the feel and extra security of a disc on the rear, go with the Avid.
dbohemian
I agree, dual pivot brakes are very good. My previous tandem, which I did not manufacture was a cannondale with dual pivots. I was a good bit lighter than now, but never had any issues with those brakes whatsoever.
I am heavier now, the team is heavier (heck, some of you guys are featherweights:D ) So I put the disks on the first tandem I have built for myself. They seem to work really well too. I love the front, I am luke warm about the back, the feel is not as good.
Can't go wrong either way IMHO. I would make a recomendation based on team weight really.
P.S. I could absoutely design a road lever with integrated hydraulic master cylinder but I wonder if the market is there. I would have to design with a certain group of calipers in mind (maybe only similar ones like the Gustav and Hope or something similar). I don't know if the road tandem crowd is ready to go dual hydraulic disk.
Also, if a certain company, lets say hope (I like Hope, I think any issues with Hopes are typically bicycle mechanics unfamiliarity with disc systems) was approached with enough orders in hand, I know they could be convinced to redesign a lever for this purpose. Same with Magura. It just would take some consensus of buyers, and that could be like hearding cats when it comes to cyclists.
All the best,
Dave Bohm
Bohemian Bicycles
Retro Grouch
Did the Avid's fail catastrophically, require immediate replacement after the descent, or did they continue to work through the end of the tour with perhaps some maintenance after the overheat?
Why do they believe the Formula would have been any less resistant to overheating than the Avid?
They survived the experience with a cool-down stop and finished the tour with the Avid brake. They replaced it with the new Formula hydraulic brake after they returned home.
The fellow in question is a retired engineer and an excellent bike mechanic. He has extensive experience with the Formula disc brake. He originally got away from the Formula due to the slave pistons cocking after a period of wear. When they cock, they lock up the back wheel which can be solved by pushing the bike backward. He says the caliper has been redesigned to solve the problem.
My wife and I have a week long tour scheduled with them in August but we'll be riding in northern Wisconsin and are not anticipating any excess heat generating descents.
KRhea
Thanks for all the great info. I think I'll go with my original idea of dual pivot caliper front with the Avid rear disc.
Really appreciate all the informative responses.
KRhea
PortlandVelo.net
zonatandem
If discs start 'glowing' it's time to stop and dump some of that excess water and create some steam! "Hiiiissss!"
Does that constitute a cheap way of heat-treating the disc?
Trsnrtr
IMHO, go with the Avid mech disc but have your builder include the necessary drilled brake bridge and cable guides to support a rear caliper just to keep your options open for the future, e.g., fitting a rear caliper wired to your brake lever and adding a bar-con to control the disc for European switchbacks, etc...
I understand the European switchback comment, but what about the Colorado Rockies. My wife and I are taking our flatlander V-brake equipped tandem out this Summer for some riding including Vail Pass. Seeing as how our total weight including tandem is just under 400#, are we going to shoot over a cliff or something?
Seriously, is it time that i started looking for a disc?
TandemGeek
Seriously, is it time that i started looking for a disc?
Probably a good question for it's own thread, i.e., Anyone ridden Vail Pass on their Tandem? I have not and can't offer any advise in this regard and, with a 320 lb ride-away weight, we would likely have different impressions on what the threshold is for using rim vs. rim + supplemental vs. rim + drag brakes.
However, as a generic response let me note that it is this very question -- should we fit a supplemental brake for this tour? -- that folks in the light and middle weight classes always tend to have when headed off to new places with potentially steep descents in variable weather conditions that have given rise to the popularity of a mechanical disc as a primary rear brake. While it lacks the heat capacity of the Arai drum, the mechanical disc does trump the rear rim brake when pressed into service on challenging descents in dry or wet conditions and does so in a relatively lightweight, easy to service, and somewhat stylish package when compared to the Arai drum and earlier mechanical discs.
So, if like us, you've ever found yourself on a descent where you really needed that supplemental brake that you decided to leave at home, the mechanical disc is a welcome addition. And, as already noted in my first post, it can alternate duties as a primary rear brake without your rim brakes, or be pressed into service as a "supplemental" brake with your rear rim brake installed.
zonatandem
Team weight/steep terrain/your nerves will dictate if a 3rd brake is mandatory.
Nobody says you have to descend full speed without stopping while descending a long pass.
Alternately applying front/rear brake, steadily, and not letting your speed build up too high can get most (but not all) couples down most descents.
We are a light team (sub-250 lbs) and have descended Kitt Peak in Arizona (altitude about 7,000+ ft, with 11 miles of curving 6 to 7% grade) with only one stop at mid-descent. Reason for the stop? Pilot's fingers were starting to cramp up from very fast alternating application of front and rear Mafac canti brakes. Felt the rims, and they were warm, but not hot. It had been predicted by 'experts' that we could not make that descent on our tandem without a 3rd brake and would suffer failure/blowout/overheated rims.
Have done many descents in mountainous terrain (as high as 9,200', but never Vail Pass).
Twisty descent down the Mogollon Rim near the town of Strawberry, AZ in a rain storm with us pedaling in fog/clouds. We out-braked a tandem that had 3 brakes. Experience/confidence/and knowing how to brake is a +.
That's our experience; yours may vary, so go with your gut instinct. If pilot/stoker want a 3rd brake for the Rockies, then do it.
Be safe and enjoy the scenery!
Pedal on TWOgether!
Rudy and Kay/zonatandem
Trsnrtr
That's our experience; yours may vary, so go with your gut instinct. If pilot/stoker want a 3rd brake for the Rockies, then do it.
Be safe and enjoy the scenery!
Pedal on TWOgether!
Rudy and Kay/zonatandem
My thoughts at the moment are not to worry about it. We've been down some smaller mountains with no problems and most of the roads that I've driven in the Rockies look like little braking would be required due to reasonable curves and road geometry. My stoker is pretty fearless. :)
Big H
We just installed Hope Mono 4 disks with 180mm rotors on our MTB tandem. We live in Lagos Nigeria now and the bike is still in South Africa but it will come home after our home leave at the end of the month. These are four pot brakes and they are awesome!!!!!!!!
merlinextraligh
Probably a good question for it's own thread, i.e., Anyone ridden Vail Pass on their Tandem?
Haven't ridden it on a tandem, but I've done it several times on a single bike. It's actually not very steep (It essentially follows the same grade as the interstate) and the descent on either side is not technical. It is about 4,000 vertical feet, so it goes on a long way. I wouldn't think it would put a particular hurting to your brakes.
K&M
KRhea - We are a team of about your weight and speed. We have ridden tandems with rim brakes front and back, but certainly would not give up the Avid mech. disc we are now running. We think it is far superior to any rim brake we've tried. We have descended some of Northern California's steepest, most technical and most prolonged grades and still have not managed to melt the Avid's knobs. I can't imagine what a team of our weight would need to do to accomplish that! And even if the knobs did melt, as Tandemgeek points out, that's a lot better than blowing a tire off a rim (which is not at all uncommon when fast teams take on serious descents with only rim brakes - check the recent history of the Terrible Two Double Century!) or bursting a hydraulic seal (I was a certified brake mechanic in a former life and I wouldn't trust hydraulic brakes on my tandem - there's a reason cars are required to have dual hydraulic systems). Go with the mechanical disc. It's worth it for the peace of mind alone.
zonatandem
In 200,000+ miles of tandeming without disc/drum brake and lots of long/steep descents we have never blown a tire/tube due to heat build up in the rim. Never melted pads either. But again, we are a light team. Have heard of (but not personally witnessed) folks blowing tires due to heat buildup. Have also heard of disc locking up due to excessive heat build up.
You make your choices! So far ours have all been good!
cornucopia72
In 200,000+ miles of tandeming without disc/drum brake and lots of long/steep descents we have never blown a tire/tube due to heat build up in the rim. Never melted pads either. But again, we are a light team. Have heard of (but not personally witnessed) folks blowing tires due to heat buildup. Have also heard of disc locking up due to excessive heat build up.
You make your choices! So far ours have all been good!
First time I hear of a disc locking up due to heat build up. Once, I locked the back wheel because I had the disc brake engaged with the bar end lever and a moron cut us off and I had to apply both rim brakes. My intention was to slow down but once our momentum was low enough the back wheel skidded, no big deal but my wife got a big scare. On the other hand, a front tire blow out while turning because of excessive heat is common place and has happened to people we ride with... very nasty.
dbohemian
Have heard of (but not personally witnessed) folks blowing tires due to heat buildup. Have also heard of disc locking up due to excessive heat build up.
O.k. someone has to call the MythBusters!!:D
TandemGeek
In 200,000+ miles of tandeming without disc/drum brake and lots of long/steep descents we have never blown a tire/tube due to heat build up in the rim. Never melted pads either. But again, we are a light team. Have heard of (but not personally witnessed) folks blowing tires due to heat buildup. Have also heard of disc locking up due to excessive heat build up.
You make your choices! So far ours have all been good!
Heat induced tire blow-offs: None personally experienced to date, on or off-road. However, have spoken to others who have shared their personal accounts of tire blow-offs and watched one rear tire blow-off immediately after the team came to a stop 1/2 day down a steep descent to allow their rims to cool... Funny thing about stopping a tandem with really hot wheels: once the cooling airflow goes away the rim, tube and tire temps will momentarily rise before they cool, sometimes with a loud rapport.
Melted brake blocks: Yes; MT3000 with XT V-brakes descending fire road in Georgia back in 2000. It was one of those stupid things where I allowed the tandem to accelerate to a speed that was right at the ragged edge for the road conditions and the lower we went the more twisty the road became, limiting the use of the front brake due to the probability of a front wheel wash-out. Given our weight and speed, the rear brake quickly heated up to a point where it could no longer lock up the rear wheel or afford much useful braking and as the pads overheated, glazed and faded they finally reached a temperature when they started to melt, depositing black strings of rubber goo on Debbies seat tube, stays and legs. Fortunately, the road began to straighten out as we got closer to the bottom where the front brake could finally be fully pressed into service. The rear brake pads were pretty much gone and the rim was scored by the metal pad holders. I sold that tandem and purchased a new tandem that I fitted with dual hydraulic discs 6 months later.
Hydraulic brake lock-up: Yes, been there and done that too. To be fair, the brake fluid in our Hope 04DH hydraulic brakes was old and the master cylinder probably had too much fluid, both of which exacerbated the problem. However, despite being an open system that allows for some amount of fluid expansion, we were the last ones to leave the lodge at Bear Creek and the road out was a very steep, gravel descent. As we approached the riders in front of us we were travelling much faster and needed to slow down... a lot. That sent the brake temperatures way up which, by itself, wasn't a problem. However, our friends were all riding prudently and at a careful pace which meant that our very hot brakes were being "ridden" to keep our speed in check and, although I was alternating brake usage front to back I noticed that the back brake stayed on when I released the lever... Well, as you can imagine, with the brake pads now being pressed up against the rotor by heat expansion in the hydraulic system, the overheat condition increased exponentially in short order, with the rear brake locking up the rear wheel and dragging us to a stop. I siphoned off a few cc's of hydraulic fluid from the master cylinder and as the system cooled we were on our way. It locked up once more later in the ride on another fast technical descent and once we were home I immediately replaced the old DOT4 brake fluid with the same higher boiling point Motul 600 I used on my motorcycles.
Mechanical disc cookout: We've only "cooked" the rear disc on our road tandem once. And, for those of you who are headed to or have been to the 3 State 3 Mountain Challenge, want to guess which turn on which road caused me to "burn it up"? Yup: that big old hairpin at the bottom the really fast, straight descent down Suck Creek Road (satellite photo below, downhill is from east to west across the photo). The disc did it's job, but those pads were screaming before, during, and for some time after that turn. Now, relative to full disclosure, there is a down side to having a rear disc on a road tandem that is similar to having discs on your off-road bikes: they allow you to push your bikes that much harder and further into threshold braking situations where you would have likely exercised a bit more prudence and caution had you only had rim brakes at your disposal. So, lesson learned here is, be mindful if you using up that added safety margin that a supplemental brake can provide because if you use it, you lose it.
The moral of this story? Given the right conditions, poor judgement, and/or equipment set-up and maintenance issues you can use up just about any brake system.
While we haven't been behind or along side anyone descending a hill when a tire "let go" under heaving braking, I've heard enough accounts and seen a couple shredded tires including one with a blown out rim (note here: rim failure under hard braking probably caused that tire to go) to conclude that it does happen. While I'm not exactly sure of the mechanics involved, i.e., does the air in the tire expand, does the tire soften and become more pliable, or is it a combination of both, I do believe it's a concern for larger teams or loaded touring teams who can really generate a lot of brake energy.
Moreover, keep in mind that the friction generated between your tires and the road under hard braking is also where I suspect a goodly amount of the tire heating comes from vice just the friction between the brake pads and rim: road temperatures and tire compounds definitely come into play in the tire blow-off equation. However, all of that said, IMHO if someone rides any brake long enough they can cook it: there's only so much brake energy that a system will handle before the limits of the brake pad material -- usually the weakest list in terms of heat capacity -- will be reached, so gooey pads, smoking drum brakes, and disc brake rotors that can sear flesh in an instant are all very real and not confined to urban legends and myths.
Trsnrtr
Haven't ridden it on a tandem, but I've done it several times on a single bike. It's actually not very steep (It essentially follows the same grade as the interstate) and the descent on either side is not technical. It is about 4,000 vertical feet, so it goes on a long way. I wouldn't think it would put a particular hurting to your brakes.
Thanks for the info. I talked to a guy (who also happens to own my bike shop) and he doubted that I would really need any more brakes in light of his experiences. Like ZonaTandem, he said to just alternate the brakes and stop occasionally if I felt the need.
I also talked to a guy tonight that used to live near where I'm going and said he used to ride Vail and also told me not to worry about my brakes and worry more about my lungs. We live at 750' elevtion. :)
mandd
Okay, so...
Given all of that (above discussion), does anyone have any recommendation for (v-brake) pads if they are going to be seeing heavy use. Certainly in the automotive world (different, I know) pads can make all the difference. Are there a variety of pad compounds out there that work better for specific conditions?
Thanks,
Damien
robmitchell
Hi,
I suggest front rim and rear disc at the least.
You can't have enough braking!
Both people, both incomes, both peoples health etc...
Keep it fun but safe.
I have melted down and blown a rear tube descending Molas pass in Colorado with a rim brake.
We had stopped once to cool the rim, and maybe I was over braking or not letting off enough between slow downs but feel lucky to have learned the lesson without crashing us both.
I now, never go much over 40 unless it's a straight long run out, even with the rear disc.
Always test the brake early in the descent to make sure it's working.
Rob
mandd
At some point down the road I will look at a drag brake (no disc mounts) but it isn't an option for right now. So at this point, I need to maximize what I have (Linear pull rim, road levers with travel agents). We aren't racers or close to it, but we are probably big for a team compared to everyone here (probably 400lbs for team, bike and load). I'll be careful, and I'm sure we'll be fine since we're in no hurry and will do what we need to. All the same though, I would like to have the best set up that I can with regard to the pads.
Thanks again,
Damien
TandemGeek
Are there a variety of pad compounds out there that work better for specific conditions?
Yes, there are... but unless you have really specialized needs or equipment, the key to getting the most out of your brake system is making sure that:
1. Your brake pads aren't too old. After just a couple seasons brake pads begin to lose their grip as they dry-out and become hard. Even if you're not wearing through your brake blocks in just a couple seasons consider replacing your old ones if your brakes are loosing their bite, chatter or grind on the rims. You can usually squeeze out a little extra life by lightly sanding brake blocks to remove the top layer of glazed rubber but once they're dried out they really need to be replaced. New brake blocks are really a treat after riding on ones that are tired.
2. Your brake pads are properly adjusted up against the rim: you want to be sure your pads are flush and squarely aligned with your rim's braking surfaces with just enough toe-in to stop any brake squeal. It's easy to go overboard with toe-in and, frankly, it's a short-term proposition since the application of your brakes will eventually wear-down the ends of your brake pads but, for really noisy brakes, it's still one of the best remedies.
3 Your rim's braking surfaces are in good shape. Having a little brake pad material embedded in your rims isn't all that bad until it starts to get old to begins to collect other junk. Making a point of cleaning your rim side walls with a Scotchbrite pad and some mild abrasive cleanser, e.g., Softscrub or Bonami every now and again. I usually put two small pieces under the brake blocks and apply the brake just hard enough to keep the pads from coming out as I rotate the wheel to make quick work of it.
4. Make sure your brake cables are only as long as they need to be to prevent binding when doing a full left-lock to right-lock turn of your handlebars. Same goes for the housing length between the rear cable stop and brake caliper, hanger, or "noodle". Any extra brake cable housing will degrade the performance of your brakes, as will cruddy old brake cable housing and cables. Like brake blocks, even the brake cables and housings will need periodic replacement. How often will depend on the conditions in which you ride your bike.
OK, now that that stuff is out of the way, here are a couple links that may be of interest...
First: Just how much variability can there be with different rim brake compounds? Here are some test results from a bunch of years ago that did a pretty good job of quantifying it:
http://www.bicyclesource.com/bike/choosing/brake-pads.shtml
Probably the most varied line of brake pad materials come from Swissstop:
http://www.swissstop.ch/index.php?content=aboutus_test&lang=en
KoolStop also offers a variety of compounds:
http://www.koolstop.com/brakes/Compound.html
However, at least for me, I've never had any problems with the stock Campy compounds on our tandem rim brakes and I believe Shimano also has a pretty good compound, as does Avid as I've had no problems with their stock pads on my solo mountain bikes. Again, keeping the pads fresh is often times the key.
stapfam
One of the reasons we went hydraulic disks was hand fatigue on long rides. After 65 miles offroad the pilot was having difficulty in applying enough pressure to the lever with V brakes. Now whether this was hand fatigue or brake blocks going off- I would not like to say but hand fatigue is no longer an issue. One recommendation I would make though is that you go for the largest disc it is possible to fit on the Tandem- Better braking and better cooling. We have 200mm discs front and rear and like the feel of them.
For those that have them- There is a technique for long downhills with disc's. You do not use them as a Drag brake, even if it is your 3rd rear brake. You let your speed build up and you brake sharply to bring your speed down. Release the brakes and let the speed build up again- then brake. This can can also be done alternating front and rear brake so The brake pads and discs should never overheat. I have had the discs glowing a dull orange on one ride, with no effect on the Discs or pads- but I do use the sintered pads that are harder.
With rim brakes- I would make certain that the rims are in good condition, but you already do that, don't you!!! No thin braking area and properly tensioned wheel to take the strain of a few corners at a higher than normal speed. If you are worried about the wheels getting too hot- or think you are losing brake efficiency- Then you can always stop and admire the view for a couple of minutes. There is always time for a photo shot- or a stop for refuelling or just to give the butt a rest from sitting in the saddle for too long.
RickinFl
I *have* blown off a tire from heating on a long descent of Mary's Peak in Oregon. The irony involved was that I had been repeatedly warned by experienced riders in the area (we were newly arrived from Florida), but I didn't really believe that blow-off due to heat was real. Fortunately, we didn't crash since we were in a straight stretch, but we had just exited a bend, and years later I still cringe when I think of what might have happened had the tire blown when we were turning.
I installed an Arai drum brake the very next day, and it stayed on the bike the whole time we lived in Oregon, and I was glad to have it.
There's one thing I think is superior about a drum brake, and that's that you can set it to maintain your speed in a descent at whatever you (or more often your stoker) think is safe (usually about 50-55 mph for me depending on conditions at the moment) and just use your hand brakes to feather the speed for curves and so forth. Your hands can get really fatigued trying to accomplish the same thing with the regular brakes, be they rim or disc. I know this from experience. The drum brake under these conditions adds a safety and comfort factor, and it's cheap insurance.
Yup- they are heavy, goofy looking and make dealing with a flat on the rear more of a hassle. Still worth the extra margin of safety IMO.