Originally Posted by DangerousDanR

Reading the OP's description of the new tandem it will be a disc brake bike. I am more than fine with rim brakes for a solo road bike. But when my wife was looking at a new solo bike in 2014-2015 I made sure that she got one with disc brakes. She mostly uses it for short trips to visit friends or go shopping. Disc brakes work better in the rain, and sometimes rain storms come in very fast here on the north plains.

My road bikes are all rim brakes. My MTBs are all disc brakes. Our tandem is disc. The only one that has had heat issues is the tandem, and that has been solved. For our bulk, MTB downhill brakes are, in my opinion, the best way to go. Lighter teams will probably have a different set of parameters, but even if my wife and I both got down to our ideal weight, we would be around 350 lbs. Add in the bike and gear for touring and we are in the 400 to 450 lbs. range.

Mine are Hope, SRAM, Formula, TRP, Trickstuff, and a whole lot more companies make very good downhill specific brakes. I prefer to use DoT 4 fluid because I know that I can get fluid anywhere that I am likely to travel without having to wait for it to be shipped to me. Others will prefer mineral oil fluids, used by companies such as Magura or Shimano. Drum drag brakes are mostly unavailable for new bikes. My setup as it sits today has been shown to work as both a drag brake to keep speeds below our tolerance level on descents, and as a fast stopper from high speeds.

If I am running my tires at the tire and rim manufacturer's upper limit for pressure (I do) and the PV=nRT thing pushes them up by 10 PSI I am running out of range. Probably safe, but not certified. I wouldn't want to have to stop on a steep downhill with a strong tailwind traveling 45 MPH with a rim brake bike.

Originally Posted by LV2TNDM

The leverage of a larger rotor means less energy. Remember, Archimedes said "If I had a lever long enough, I could lift the earth." In other words and for experiment's sake, if you had a REALLY large rotor (much larger than your wheel), you could easily stop your wheel with your fingers. Again, if the rotor were large enough. So a larger rotor will require less energy to stop. At least that's my interpretation! (Granted 20mm difference isn't much, but it's still something. That combined with additional surface area makes a difference.)

Originally Posted by headasunder

any thoughts on which pads manage heat better, resin or sintered, we have ice tech 203 rotors with resin pads that suffer on the long steep descents. We are off on tour soon so would like to improve heat management if possible

Originally Posted by Alcanbrad

I realize this is getting into the weeds and does not change your point, however, it would be interesting to have and equation that would allow us to plug in some real world scenarios to see where disc braking falls apart. Just throwing it out there to see if someone is game

Originally Posted by bakerjw

Anyway, we are on the verge of getting our new custom road tandem built and delivered. When I say built, I mean that Doug Curtiss at Curtlo Cycles is preparing to be build the frame and I will assemble on it once it is in hand.


Lolly, our mountain tandem, shown below, was also built by Doug and I completed the build with my list of components. With Lolly, I used TRP Spyke brakes with larger disks. As you can see, the rear rotor is like a 220mm. Fully loaded with gear, food and water on our Tour Divide Ride a couple of years back, Lolly weighed in at around 90#. The Spyke brakes and rotors were solid as can could be regardless of load or descent and as the captain, I couldn't be happier.


We are going to be running a Shimano 105 3x10 drivetrain which has readily available components.


My initial thoughts are to go with TRP Spyre calipers and a 203mm rotor in front with another large one in the rear. The build will also have a caliper mount on the rear in case I would ever want to mount a supplemental rim brake.


The wheels will be built on Onxy hubs and Sun Ringel Rhyno Lite rims as I've never had any trouble with them and they can utilize rim braking.

Originally Posted by LV2TNDM

From what I understand, you are nowhere near "running out of range" with a 10psi "overpressure" in road tires. I understand blowoff pressure is determined by inflating a tire on an industry-standard hook-bead rim and inflated. Blowoff pressure is divided in two to determine "max pressure" for the tire. So, a tire with a 120 max pressure rating will blow off at 240psi.* This safety margin of 100% makes sense. Bicycles do regularly heat up rims, so the tire should be able to withstand pressure increases by heat, per the PV=nRT relationship.

Originally Posted by mtseymour

For even better braking, think about full hydraulic brakes (eg. Shimano Ultegra). Unfortunately, this option is more expensive because you have to use hydraulic shifters in in 2x11 drivetrain (eg. Ultegra ST-R8020). However, a 2x11 drivetrain will shift better than a 3x10, and a large cassette should allow you to handle steep climbs.

Originally Posted by mtseymour

Does any good quality mtn or road bike come with the Spyre?

Originally Posted by mtseymour

The other advantage of using a disc-specific rim is that you can use wider aluminum rims (with minimal weight gain), or carbon rims. Wider rims and tires are more popular now because they provide more comfort without sacrificing rolling resistance. For example, it's common to see a high-end single road bike (eg, Giant TCR) with 25mm or 28mm tires. We use carbon rims with 28 & 32mm tires on our Calfee road tandem.

Originally Posted by diabloridr

All the higher-end Co-Motion tandems spec the Spyre, that was a good enough recommendation for us when were building our Macchiato.

Originally Posted by Msteven

We also had Hy/Rd brakes on shimano 203mm rotors, and they failed due to overheating on a longish downhill in traffic. The pistons never let go after that. had to remove that night after limping home.
We returned to the Spyre cable pull calipers, but the effort required to pull these is very difficult after a few minutes.
After a bit of internet research and concluding that our spare road Di2 hydro Brifters will work with Saint 4piston calipers. (I picked up XT/XTR front and rear derailleurs)
The saint hose has a long brass banjo fitting to help dissipate heat.
WIth the LARGE caliper and LARGE metallic pad with heat sinks, this combination works far better than I expected.
Finally, I changed the rotors over to Magura MDR-P e-bike full float 203 rotor. these don't warp nearly as much as standard rotors. so not much chattering after hard use.

in summary- oversized calipers, oversized pads, over-designed rotors = confident braking for extended periods. Metallic pads don't seem to wear as fast as organics, nor do they "grab" instantly, so progressive stopping power.

Originally Posted by headasunder

So you run shimano calipers and magura rotors any issues with pad clearance given the magura rotors are 0.2mm thicker. I'm underwhelmed with the icetech offering and would like to change the front out

Originally Posted by mtseymour

If you're investing in a custom tandem, it's not a good idea to skimp on brakes. The price difference between the Spyre and Hy/Rd is only about $40 per wheel, but the latter is more powerful due to the hydraulic calipers. if you're really confident about the Spyre, why bother with supplemental rim brake? Does any good quality mtn or road bike come with the Spyre?

Originally Posted by bakerjw

As fate would have it, the pound is over/under valued to our advantage against the dollar so a pair of HY/RD calipers delivered was around $200.00.

I was only considering the Spyre because the Spyke was absolutely rock solid on our mountain tandem (90# fully loaded) and they handled every descent on our Canada ride beautifully.