Disc vs. Caliper continued - How about both?

[muz]

Originally Posted by cmbicycles

Belt and chain + disc and v-brake = they cant make up their mind about anything... probably a mix of Campy, Sram and Shimano there too.

Any tandem can use a belt drive for the timing chain. There is really no downside other than the cost. You need a purpose built rear triangle (and drivetrain) for full belt driven system.

[merlinmurph]

Originally Posted by Davist

Don't tandems typically have the cranks synched? These are outta phase by a couple belt links or whatever they're called..

I saw that, too. It has to be intentional.

Originally Posted by muz

I am guessing this tandem doesn't ride anywhere where the drag brake is actually needed.

Doubt it. These guys ride a lot and ride everywhere. While in the area, they climbed Mt. Battie which is a relatively small climb but with 15% grades. I have no doubt they push the limits of braking. Their business is dead right now because, well, you know, but they told us all about the trips they've done all around the world.

[slowpoke]

Originally Posted by cmbicycles

Belt and chain + disc and v-brake = they cant make up their mind about anything... probably a mix of Campy, Sram and Shimano there too.

I know you're joking, but carbon timing belts are not uncommon nowadays. Co-motion uses it for many of their tandems (e.g. the Speedster).

[Brian Smith]

Originally Posted by muz

Any tandem can use a belt drive for the timing chain. There is really no downside other than the cost. You need a purpose built rear triangle (and drivetrain) for full belt driven system.

I'd agree if you changed the "can" in that statement to "could."
The belts are only available for a certain small range (some say unfortunately chosen) of boom tube lengths.

[Brian Smith]

Originally Posted by pdmtong

Mech discs make it easier to travel but work poorly compared to hydro especially in a tandem. The bb7 203 I had was ok and spongey compared to the one finger stopping of the six piston hopes I have now on our full suspension mtb tandem

That v brake in the rear...Why bother? What would that contribute relative to the rear disc?

The hydraulic brakes are probably nice to have on a mtb tandem, but for long road tandem descents, tandem heat and fluid isn't necessarily best. I trust that the specialist tandem builders would all be supplying them if they were. It's not as though the driving factor here is minimizing purchase price. As far as what the brake controlled by the stoker would contribute...perhaps your stoker has never mounted a strong protest to your choice of speed?
It doesn't have to actually produce greater deceleration in order to deserve a place on the bike, and in fact being only slightly effective may just make it...the perfect choice.

I say "fix" the crank timing difference present there. It probably came about unintentionally due to insufficient belt tension. Unless the stoker is doing the shifting, why give the captain another thing to consider when timing shifts?

[pdmtong]

Originally Posted by Brian Smith

The hydraulic brakes are probably nice to have on a mtb tandem, but for long road tandem descents, tandem heat and fluid isn't necessarily best. I trust that the specialist tandem builders would all be supplying them if they were. It's not as though the driving factor here is minimizing purchase price. As far as what the brake controlled by the stoker would contribute...perhaps your stoker has never mounted a strong protest to your choice of speed?
It doesn't have to actually produce greater deceleration in order to deserve a place on the bike, and in fact being only slightly effective may just make it...the perfect choice.

I say "fix" the crank timing difference present there. It probably came about unintentionally due to insufficient belt tension. Unless the stoker is doing the shifting, why give the captain another thing to consider when timing shifts?

good point...we are not doing 3+ mile 8% descents...more like 15% down a root/rock garden for a yards not miles.

a placebo v-brake? my point is why bother when choosing the disc will be much more effective.

my stoker has a lot of complaints about my captaining, but speed is not one of them. usually it has to do with line choice and over caution.

[jpw]

Continentals.

[Ozz]

Needs a Routewerks bag.....I hear they are all the rage now!

[smead]

I sure as heck would not want my stoker controlling a back brake?! Braking in a turn is gonna change your line big time, the one with the bars that turn should have full control over braking unless the team has been together a long long time.

Funny about the out of sync cranks too. That would be hell on out of the saddle climbs.

Goofy rig all around from my take!

[zap]

In this day and age, good discs are all you need.........and don't drag any brakes unless it's a drum.

For years we would launch down steep descents (max 18%) off Blue Ridge Parkway in VA and NC on our old tandem......with canti brakes. We were pushing the limits! Plus not for touring with packs either.

When we acquired our travel tandem we moved to disc F & R. You can do a search in this forum about our recent move to Paul Klampers.......wonderful brakes. Also moved on to belt drive/rings on the timing side.

Personally, I could not deal with cranks out of sync. I don't know if the riders in the op did this intentionally or not but some teams do go out of phase a bit.

[smead]

I have some experience with out of sync cranks. About ten years ago my stoker and I were just about ready to shut the lights off in the motel the night before a fast double century. He calmly says to me - "dude, look at the tandem". "What. What?" I say. "Oh, oh ****!". The day before I "tuned" 'er up - greased both hubs, adjusted the shifting, dialed in the fit, and replaced the chains. Well I forgot one thing - didn't sync the cranks when I pinned in the timing chain! Was off by about 120 degrees . We were lucky to get it fixed without having the right tools for the concentric BB.

Then earlier this summer when I replaced chains, I did it again! Noticed the last month or so that when my wife would stand, the pedals kept wanting to stop 3/4 through my stroke. My knees started to hurt. I of course blamed my stoker - what is wrong with you? This went on for a few more rides til' one day in the garage was having a beer and happened to notice the cranks were off by about 20 degrees. What a dumb-ass! I guess in another ten years I'll do it again

[zap]

Originally Posted by Ken Robb

Wouldn't a relatively "fade-proof" front disc reduce the importance of the rear brake? BTW, I don't think a tandem has double the aero drag because the stoker is in the draft of the rider up front.

We have 203 rotors.....they are most certainly not fade proof. You really want to keep the front rotor heat down as much as possible by using the rear brakes more-but not dragging. You want to conserve the front brake for that oh shxt double turn blind hairpin corner. All steel rotors do a good job of heating up hubs as well. Best to use rotors with al spiders.

[Mark McM]

Originally Posted by smead

I sure as heck would not want my stoker controlling a back brake?! Braking in a turn is gonna change your line big time, the one with the bars that turn should have full control over braking unless the team has been together a long long time.

Drag brakes aren't controlled like normal brakes. Instead of being momentarilly applied, released and modulated like standard brakes, they are more typically applied and left on at a constant drag level.

If you take a look at the first photo, you'll see what looks like a bar-end shifter at the end of the stoker's handlebar. But instead of being attached to a derailleur, the lever's cable is attached to the drag brake. On a downhill, the stoker will set the drag brake control setting to a fixed position and leave it there (instead of shifting to a specific gear, the lever with "shift" to a specific drag force). For speed modulation, the tandem captain adds additional brake with his standard levers as necessary.

As I mentioned earlier, this was a common system when the "shift" lever controls a special drum brake, in conjunction with rim brakes controlled by standard brake levers. These drum brakes were designed for continuous heat dissipation, just for this purpose. But rim brakes usually aren't designed for as much heat dissipation as those drum brakes work, so I don't know that this is a wise set-up.

[slowpoke]

Originally Posted by zap

All steel rotors do a good job of heating up hubs as well. Best to use rotors with al spiders.

Generally, aluminum conducts heat better than steel. But I'm guessing depending on how the rotors are attached to the spider, the heat transfer is not as efficient as if it was one continuous material.

[flying]

Aside from the cool tandem....I have often wondered why the industry didn't go this route anyway

Think about how many cars even now have disc front & drum rear

Same for many motorcycles.

So for bicycles the industry maybe missed a level of profit...That being introduce disc capable forks & let road rider keep a rear rim brake.

Save them having to buy a whole new frame set to try disc
They could even offer a complete upgrade kit to fit most bikes etc

Then again they probably feared the obvious.... that folks would half try disc & say forget it