What's a rear disc brake worth?
 

I was on the phone today with Co-Motion discussing a future strip & repaint of our bike. As an afterthought, I inquired about a braze-on for a rear disc brake. I was informed that a braze-on isn't an option (owing to the thickness of the chainstay wall), but that the rear triangle -- seat tube, chain- and seat stays -- could be swapped out (along w/ a new cable routing for the disc). Price: $600 (plus the disc and brake hardware)(rear hub isn't really a factor as I'll be going to a new wheelset anyway [I'd be specifying a disc hub instead of one threaded for a drum]). Is the added braking capacity cost-effective?

If you live in a state where you might ride in the wet, it could be worth it.

I did not see it clarified, the cost is $600 for the frame rework alone or $600 for rework and the paint work?

PK

It depends on whether you plan to travel. Isn't the big hill there something called the Acosta Bridge?

Not without a clear and recurring need.

Frankly, given the cost of the repaint, rework of the frame and cost of new wheelset and other hardware that you're looking at for this "refresh" I'm surprised you're not considering a complete tandem upgrade, i.e., buying a new or newer/2nd hand model that has the more current components and selling your current tandem to defray part of the cost.

Case in point: We just "refreshed" a used triplet with new paint and just a few component upgrades and are considering a new wheelset merely for the sake of color change. With all that taken into account we wound up being a stone's throw away from what it would have cost to have a new base-model aluminum triplet built to order. That wasn't the original plan, as the original intent was to leave it "as it was". One thing led to another and, well... there you go. It's an awesome and fairly unique triplet frame, but it was not the most cost-effective way to go about adding a triplet to the stable. That said, and as a bonified equipment freak... the process and friendships developed along the way are things I value the most, I tend to prefer unique bikes, and I rarely work to a budget when it comes to bikes unless that's one of the project goals.

So, where are you trying to go with this project and is the path you're considering going to get you where you want to be?

I've only experienced disc brakes on a mountain bike. Before that I used direct-pull "V" brakes. For a mountain bike were the rims get dirty and wet, this may be a benefit but on a road bike it is just a different way of doing the same thing. Good rim brakes work just fine. On the road I try to use my brakes as little as possible. They are literally a waste of energy. In my opinion disc brakes are a solution looking for a problem.

Hey, you can bandit the Dames Point Bridge, at least twice as much vertical.

While we had our tandem built to accept a rear disc, we've never installed one.

For us, with a team weight of 350lbs, we haven't felt the need for a disc. Dura Ace calipers stop the bike fine.

The reason to want a disc would be heat dissipation. However, we've done some long fast descents without a disc. The closest to Jacksonville are Six Gap, and Brasstown. Coming down Brasstown, which is very steep, and too twisty to bomb down, is the only place I felt like I wanted a disc. The descents on Six Gap, including Hogpen, are all manageable without a disc.

To some degree, this is a matter of riding style. If your style is to descend fast,off the brakes, and then brake hard for the corner, and repeat, you'll have much less problem with overheating rim brakes, than if you descend in a more speed controlled manner hitting the brakes frequently.

Living in Jacksonville, unless you're going to go to the Mountains frequently, and you want to descend slowly, I would pass on $600 of frame rework.

Loaded touring might be another reason to want a disc.

You may want to consider adding a disc brake on the front only and keeping your current rim brake on the rear. It is much less expensive to add a disc compatible fork and you will still have the stopping power of the disc on the front.

I'd +1 to all the comments above regarding the need for a disc brake in the first place.

Then, FWIW, if you really feel like you wanted one for whatever reason, I'd ask them about adding a "doubler" onto the chainstay as an alternative to the extensive work proposed. A "doubler" being a piece of metal, perhaps 3" long and wrapping around say 1/2 of the diameter of the chainstay, brazed or welded over the existing tube. It spreads the load out over a much bigger area of the chainstay material. The chainstay obviously is engineered to carry a good deal of strain already, and a doubler might be enuf to enable it to safely carry the braking load as well. It's impossible to "tell from here" whether it's a workable solution, but I can't help but wonder (think) that it might be, and it is certainly less complex and might be less expensive than the proposal. FWIW.

Wow. It's known on the other side of the country?

I passed on the front disc-thing last year before I bought our new carbon fork.

I'd reflected on my original question not long after I'd started the thread and had pretty much come to the same point as everyone who'd commented. Upgrades are one thing, but there does come a point of gilding the proverbial lily. FYI, Co-Motion quoted $600 for just the framework change.

I thought the caliper / canti brakes on my tandem were no good (they would only just lock the wheel if squeezed really hard) until our ex pro racer friend came for a ride on his single bike with us. He told me that every time we stopped, he would have to go round us as he could not brake hard enough. He uses Dura Ace 7800 and Ksyriums, so his equipment should brake as well as anything. It took a bit of tinkering to get the rear cantilever brake in particular to work that well, but they're really good now. So I have to agree with others - using properly setup caliper brakes the tandem can stop faster than a well-ridden single bike.

The complication and weight associated with discs is not really worthwhile unless you like riding slowly down steep hills, ride in the rain a lot or insist on using the latest newfangled carbon rims. Whether I would to spec a new bike caliper brakes is not clear. I just moved to Switzerland and live on the side of a 400 metre vertical drop hill, which is about as big as the biggest hill I'd ever ride down in the UK, plus we need to ride in snowmelt for a few months of the year, so I need to test the current solution a bit first. My sense though is that we like to ride downhill fast and use relatively heavy Bontrager aluminium rims, so heating shouldn't be an issue I hope.

We us Dura Ace caliper on front, Tektro Mini-V on the rear for the past 34,000+ miles on our Zona tandem.
We live in AZ which has not many flat spots like FL.
Asides of brakes/pads, much is on how you brake on long or steep descents.
Have done both lots of times. Descended 11 mile long 6% twisting mountain (Kitt Peak) with only old Mafac cantis decades ago
Yes, have ridden a tandem with front and rear discs.Bit of overkill for our type/style of rid
However, having said that, do whatever you like that fits your comfort level.

$600 for just the frame upgrade to discs without paint, not worth it. It's obvious from the replies that a disc rear system is most times not mandatory. There are some areas where they are preferred, but still tandems rolled those roads prior to discs.

Comparing your Florida to our Florida, suffice to say that our Co-Motion with discs front and rear is way more brakes than needed locally. We are the second owners, and it had discs when we got it. Actually the fork has no rim brake provisions and the frame is "V" brake posts.

The few times the discs were welcome was at events far from home. Save your money.

I'm assuming the Speedster uses a "V" brake style rear assembly. FWIW, Paul Components just released some nice looking short pull cyclocross brakes. Pretty much a high end short pull "V" brake for brifters. These may be an effective upgrade instead of discs. Especially if you run Travel Agents or a similar conversion of pull device. These are a new brake, just released this month.

http://paulcomp.com/minimoto.html

PK

Another vote for 'sell and upgrade' *if* you think you *need* a rear disk.

Our first tandem (Cannondale, below) only has rim brakes. Last year we wondered "what if" we traveled and needed another rear brake? We addressed that unlikely scenario by buying our second tandem (Santana, below) which has a drum brake.
We have not yet *needed* the extra brake. But we're not complaining.

Total invested in *both* bikes: <$3
Choosing which to ride today: Priceless!

Time to suit up and enjoy another beautiful day....

Ok... where do I begin... first off, with all the due respect, those that are questioning the validity of disc brakes do not have disc brakes. For us it wasn't a conscious decision. Our 2005 Raleigh Coupe came with disc brakes as standard equipment. Avid BB7 mechanicals. Complexity? They are no more (or less) complex than a rim brake except that they don't use your rim as a rotor. This has certain advantages... wet weather braking is superb and you don't have to remember to change to Kool Stop Salmon pads at the start of your rainy season. Broken spokes and a serious wobble in the rim aren't ride ending.

We have a LOT of experience riding our V-Brake equipped beach cruiser style tandem in town as that bike is our only car. We have a lot less experience riding the Raleigh on club rides out in the country. But that's where we were yesterday... there was another couple that just bought a used Co-Motion tandem with disc brakes. 8" discs. Ours has 6" discs. After we just about killed ourselves climbing this mountain it was time to come down. They were nursing their way down the mountain and we were behind them. The other thread about getting stokers used to speed comes to mind because with a blind stoker... ... good thing... I got scared only once... got the levers to touch the bars(!) to get enough ****** to get through the corner alive. The brakes were pinging and popping and clearly not happy. Within seconds they had recovered and worked like new. After some time the rest of the couples came down the hill and the first thing "L" said to me was "man I love my disc brakes!". A v-brake equipped bike would need a drag brake to keep from blowing up the tires on a descent like that.

One thing I noticed about "L's" disc was that the rear caliper was mounted inside the rear triangle on the chainstay. Ours is mounted outside on the rear dropout. It seems to me that a front-line tandem builder could change the dropout or dropouts to disc brake compatible ones without scrapping the entire rear triangle. I'd have to second the opinions to just start over with a disc brake equipped bike otherwise. Discs are awesome and are clearly the future. They aren't worth taking a loss on your present ride (unless they are) but if you actually have the choice! Definitely go with the mechanical disc. Hydraulic discs are an entirely different beast and if someone used the word "complexity" when talking about hydraulics I wouldn't really be able to disagree. FWIW.

H

Your friend cannot stop as well as you because the wheelbase of his single is less than half of your tandem. That said, I think I have my v-brakes adjusted about as well as is possible and while I would happily ride anywhere (and have) without the rear brake working I could (would) never do that if it was just the rear brake working! On the disc brake equipped tandem the rear brake alone is sufficient to get some serious stopping done. I've addressed the issue of disc brake "complexity" in another post.

H

I have disc brakes on my mountain bike and rim brakes on the tandem. I have never ridden a tandem with disc brakes. However, we have descended some very steep hills and I never found myself wishing I had disc brakes. We have ridden almost all of the mountain passes in Colorado. We have ridden up & down Mount Evans - the highest paved road in north America. We have ridden up & down Mt Haleakala on Maui - 10,000 vertical feet. If rim heating were a problem, I think a disc would get hot enough to have problems as well. We almost never ride in wet conditions. It just doesn't rain that much in Colorado.

I think the only ones who can compare the advantages and disadvantages of disc -vs- rim brakes is someone who has ridden both under similar circumstances and can somewhat objectively compare the two. There is no "best". Just which compromises each is willing to live with.

...those that are questioning the validity of disc brakes do not have disc brakes. Validity or necessity? They are two very different things. Disc brakes work, but so do rim brakes as do drum brakes. The biggest variable in any braking situation is rider judgement, experience and the amount of care that went into the selection, set-up and maintenance of a given bike or tandem's brake system.

Complexity? They are no more (or less) complex than a rim brake except that they don't use your rim as a rotor. Complexity is related to conversion, more so than anything else, particularly if you are considering dual discs. Discs require disc-compatible hubs as well as a frame and fork that will accept the disc. For manufacturers/consumers, there is the added cost of making a frame compatible with discs, disc-specific components and the added weight of those components assuming a tandem doesn't require a drum brake. Bear in mind, the installation of a rear disc still precludes the installation of a drum/drag brake... which can be yet another consideration for some teams under the heading of "complexity" if they are borderline drum brake candidates.

[discs have] certain advantages They also have certain disadvantages, in that 700c disc compatible wheels still aren't something that are readily available in the event of a disc wheel failure, front disc wheels in particular. They also use-up their brake pads at a much faster rate than rim brakes for folks who ride in challenging terrain where brake use is heavy. Therefore, brake pad adjustments and changes need to be made more frequently. Some captains may also get a false sense of security that causes them to push their tandem and its discs to a point where they simply create the risk of brake fade at higher speeds than they would have with only rim brakes if they're not mindful that even discs can be over-used.

A v-brake equipped bike would need a drag brake to keep from blowing up the tires on a descent like that Perhaps. Not all rim-brake equipped tandems blow-off tires and the likelihood that someone will over-use their rim or disc brakes to the point where brake fade makes them nearly useless can be the same. Again, the most important part of the "brake system" is the operator, to include selecting the correct brakes for how they will use their tandem as well as how to use and maintain those brakes. For some of the most challenging, long descents a drag brake may still be the best choice for many riders as they have the added benefit of reducing the hand-fatigue that can come from constantly applying brakes for extended periods of time.

One thing I noticed about "L's" disc was that the rear caliper was mounted inside the rear triangle on the chainstay. Ours is mounted outside on the rear dropout. True. A tandem or bicycle can certainly have the rear triangle designed around a disc brake installation. Our '98 and '02 Erickson tandems had their mechanical discs mounted between the stays with an attachment point on each to distributed the loads. daVinci has used a similar placement for many years, as has Santana vis-a-vis their very nifty chainstay-mounted brake adapter that supports either a pac-man for a drum or a caliper for discs. Co-Motion finally switched to the between the stay position a couple years back after mounting theirs up and behind the rear drop-outs. While I prefer the between stay installation, I can also appreciate why builders like Calfee stick with the other approach. Both work just fine.

It seems to me that a front-line tandem builder could change the dropout or dropouts to disc brake compatible ones without scrapping the entire rear triangle. It all depends on how the frame's rear triangle was originally designed and fabricated. As an OEM, Co-Motion will rework their frames to an OEM standard: very prudent. However, a custom frame shop might opt to go about it a different way, i.e., swapping out the original left stay for one that is beefier with an I.S. mount and appropriate clearances for the desired rotor size. Again, this is a decision a tandem owner must make when considering changes to accommodate different braking systems.

Discs are awesome and are clearly the future. Discs do work well, but they are merely an option: not the future. V-brakes were also heralded as the "future" for tandems, yet many enthusiasts still find that either standard cantilever or caliper brakes are more than adequate for their needs and expectations.

They aren't worth taking a loss on your present ride (unless they are) but if you actually have the choice! Definitely go with the mechanical disc. No, only consider discs as another option and factor them into your decision process. Talk with a qualified dealer or builder and be honest about your needs and expectations. Some teams may find that they'll be better served by discs, whereas others may still need rim + drum/drag, and others may only need rim brakes, but would benefit from having the ability to fit a rear-only disc or perhaps a drum "just in case" they need or want added flexibility in the future.

Hydraulic discs are an entirely different beast and if someone used the word "complexity" when talking about hydraulics I wouldn't really be able to disagree. I've used hydraulics on our off-road tandems since the late 90's. They're only complex if you don't have any experience with hydraulic brake systems. The issue with hydraulics is their suitability for road use vs. off-road. Again, you'll find a few teams that have used them on road tandems with great success... one team in particular who circumnavigated the globe and put them through some very demanding descents.

Frankly, having ridden tandems with just about every type of brake system in a variety of different road and off-road conditions for many years... I'm just thrilled that we have a number of options, of which discs play a part.

Bottom Line: It's all about having options and understanding which one is best for you.... or finding someone with the knowledge and experience who can help you figure out what might be best if you're unsure.

So based on all of the experience and knowledge you have of the various braking systems that are available for tandem use what would you use on a new tandem that you were going to build today.

Suggested uses:

1. Road - Team weight around 300 pounds - 25-27 pound tandem, flat to rolling terrain, team likes to ride at a fairly decent speed. Most rides in dry conditions.

2. Road same as above but with steep climbs, descents. Dry conditions.

3. Same as 1 above but in a wetter environment.

4. Same as 2 above but in a wetter environment.

All of the above scenarios would be using aluminum rims.

Any of the above but consider loaded touring.

Thanks,

Wayne

Have ridden in 30-some states.
Climbed/descended up/down to 9,200 ft.
Descended long (11 mile, 6%) mountain curves.
Been told "you can't do that without 3rd brake" and managed just fine.
There is no secret ultimate brake.
It's more in 'how' you brake.
Have utilized Mafac cantis, V-brakes, center/sidepulls, U-brake, drum and yes 2 disc brakes.
Good quality brakes and pads that are adjusted properly + pilot's confidence/knowhow are key.
We prefer rim brakes.
Whatever works and makes you comfortable . . .
Pedal on TWOgether!
Rudy and Kay/zonatandem

1. If you will use tires no wider than 28mm and have no need for mud guards, dual pivot calipers, front & rear with the ability to add a disc for future flexibility. If you plan to use 28mm tires or wider or have a need or desire to use mud guards, then cantilevers... Linear pull for simplicity or something like Paul Neo Retro if they'd look better to you and you are willing to learn how to set-up true canti's.

2. Same as above. If you find you tend to ride your brakes a lot on these hills or just want more braking power, swap out the rear rim brake for the rear disc with a 203mm rim. This is where rider preferences begins to come into play and why you leave your options open. (Note: If you have a nervous stoker, either the rim or the rear disc can be set-up as a supplemental brake that they can control; mostly for piece of mind and to clue you in on when they are hitting their threshold for descent speed, bearing in mind that most stokers will eventually figure out that if they pull up on the brake cable running along side the top tube that'll also activate the brake and get your attention... analogous to that pull cord on trains and trolleys.)

3. Front rim and rear disc to cut down on rim wear while also providing a little more rear braking power to compensate for the degraded performance of your front rim brake in wet conditions.

4. If you're talking all-weather riding in the PNW, then this is where dual discs start to become an attractive option for a variety of reasons: improved wet weather performance without excessive rim brake track wear, tire size and mud guard clearance becomes dependent on the fork crown opening and rear stay / brake bridge placement and very good performance when mud and windchill induced ice build-up on rims could become a factor.


5. [Any of the above but consider loaded touring] Canti's for #1 - #3, but with rear disc for #2; rear canti's & drum for #3. Dual discs or front disc with rear canti & rear drum for #4 in the touring will be here in the US. Overseas, canti's with rear drum.

Agree essentially with your entire post, TG, with following observations:
1) One can in fact install mudguards on bikes with standard short-reach dual-pivot caliper brakes, (the only kind that really work.) It takes some ingenuity and creativity because an intact mudguard will not pass under such a brake and still clear a 25mm tire, so you have to craft a way of mounting each one of them in two sections, afore and abaft the brake. There are many postings on the web about doing this -- it does help to have never thrown away any of one's thirty years' worth of left-over brackets and mounting hardware. But the message is that a need for mudguards does not rule out caliper brakes and carbon forks, AND they can be made easy-on, easy-off for traveling. Extra bonus: a pavement-skimming mudflap on the front mudguard keeps the stoker's feet dry.

2) Another advantage of both the two-caliper-plus-rear-disc and the two-disc-plus-rear-caliper setups: Setting aside the argument about whether discs are "better" than calipers, whichever of these you choose still gives you three brakes. Yes, you have to train yourselves as a team in the proper and safe use of brakes controlled by two people but in extremis when gravity is about to get the better of you, having a nice cool rim that hasn't been braked yet might be just what it takes to get you out of trouble. Even though we do have three brakes, I have to confess that it's mostly to keep our favourite Europe tour purveyor happy; I'm mostly with ZonaT who says two is all you need when you are featherweights.

I smile to see that the disc-brake bandwagon is showing signs of being more like a carousel -- it comes full circle as enthusiasms and fashions come and go.

They can, but it's definitely a geek's only type of project that usually entails coming up with a way of also mounting the fender stays to forks and rear drop-outs that don't have mounting eyes. I've done this on our singles and the tandems and while it works, the clearances are very tight and it takes a lot of attention to detail to get a good installation that doesn't vibrate or shift during use. Again, if I planned to use mudguards all or a lot of the time I'd probably be running larger diameter tires as well, so a good set of canti's would likely be my choice for brakes vs. my beloved calipers.

Our Calfee in its credit card "touring" configuration with both front & rear mudguards using an aluminum brake bridge that joined the front & rear halves at the front & back of the calipers:
http://www.thetandemlink.com/Images/Calfee/touring2.jpg

Our Erickson with mudguards using a similar front brake bridge arrangement but a more normal rear mudguard installation:
http://tandemgeek.files.wordpress.co...3/sdc10742.jpg

This is a photo taken from the underside of our Calfee's front fork where you can see the piece of aluminum that passes through the caliper to bridge the front & rear half of a mudguard together. Note that the fender stays are connected to the front fork with zip ties that have molded-in eyes:

http://bikeforums.net/attachment.php...hmentid=253728

For those of you who don't want to go through the trouble of crafting your own fender adapter, here in Portland, rivercity bikes make the 'reach around' adapter. They work great!

That's a clever + handy lil thing! And bonus they're selling it online as well for the rest of us not hangin' around PDX.

Necessity being the mother of invention you gotta know Portland is where you're gonna come up with this stuff! Not diss'ing it - it's beautiful but Lord knows it's gonna be wet once in a while. Keep on riding!

TandemGeek mentions tight clearances. How much space do you have between fenders and tires in your winter fender setup?

Just a couple millimeters in some spots, perhaps 5mm at the most.

Not ideal for riding over freshly paved roads, but given we ride slicks and don't ride off paved surfaces with these particular tandems it's enough. The front mudguards have break-away stays as well, so if some wayward stone did get picked up by the front tire and make its way between the tire and mudguard, the mudguard will pop loose before the wheel's rotation is affected.

Again, this underscores why mudguards needs to be installed in such a way that they don't have any slop or movement.