Found on the internet. A Shimano Ice Tech disk.

from 2002, sorry.

Found on the internet. A Shimano Ice Tech disk.

My brother in law is a bike mechanic. He told me, it's possible, but it usually happens to newbies. It usually is the back wheel (and nobody, really nobody ever - besides some stupid newbies - uses the back brake more than the front brake)

Ever been on a tandem going 60+? Try snd stop that.

Sure. No problem. I have 205 mm disks, they can make it easily.

The point is: They won't stand it, if you brake all the way down. But they stand sudden hard brakes from 90 km/h to 30.

"Found on the Internet" isn't a terribly reliable source. For all we know, someone could have used a blowtorch to do that. Or it could have been one of those guys who put a disc on an industrial lathe.

The reality is that everyone LOVES to talk about melted discs, but I can't find a single credible instance where it seems to have actually happened in real-world riding conditions. On the contrary, I have found a couple of videos (like the one on GCN) where people attempt to melt discs on long descents but fail. On an anecdotal note, I have also descended some VERY long and steep roads and trails, and never had a problem--although I do, admittedly, use good technique. The Avid BB7s on my tandem do get very hot on rides like Independence Pass (both sides), Guanella Pass, Pikes Peak, Mt. Blue Sky, etc., but I've never had one fail or melt. Yes, I get nervous, especially when I have to apply them frequently to maintain a reasonable speed on very steep switchbacks, but, again, nothing has ever melted.

If poor technique caused discs to melt, I expect that there would be MANY credible stories and photos out there. Especially with the number of heavy ebikes being ridden up and down mountain passes by inexperienced and clueless riders these days.

All of that said, I absolutely use and recommend good braking technique--which mostly means not dragging a brake for very long. With moving air, discs cool off amazingly quickly when they are released. I also "air brake" as much as possible by sitting up and letting wind resistance do its thing at higher speeds. It's worth noting that most of these techniques aren't possible when descending with my MTB tandem because slower speeds are necessary on technical descents, and I've never had an issue with my Magure MT5 brakes either.

In short, I wonder if we're all just paranoid!

I've never pushed 60 miles per hour on a tandem, but I have done 50. Probably not a great idea, in hindsight! But I've never had an issue with my BB7s slowing me down or melting.

If I could devise a SAFE way to test stopping hard at 60 mph, I'd do it! But I'm not willing to put the safety of my team on the line...

What's hot? If you can't toch the disk? Ok. 60°C (what ever this is in fancy units). That's way too hot for my fingers, but absolutely nothing for steal or alloy. Problems begin at 500 °C, alloy gets softer then. Steal at 700 °C. It would glow in the dark.

I see Tadej Pogača going down quite fast (at least, that's what I would expect to be fast). Wikipedia says, he is 66 kg. His bike 7, some tools (dress, shoes, Garmin,...), let's say: 75 kg. That's a bit more than what my wife and I, together with our tandem are (135 kg). His disks are small, their surface is way less than half of my 205 mm disks. I would say: If disks don't melt with him, they won't melt with us as well, as long as I don't behave too stupid.

I'm not sure I understand your math--but I don't disagree with your point.

Well, Bill is right about melting the brakes if you follow his braking techniques.

that is true

and that there is how you are supposed to use a brake, rim or disc.
I’ve seen more than one bb-7 with melted red knobs.

Live in Sonoma County long enough you might find quite a few decents that, if you let a tandem run 60+ is easy.

I'd like to see a picture. The one I posted is 20 years old, a technology that actually doesn't exist anymore.

Pros go down with more than 100 km/h (which is approx 60 in fancy units). Their total weight is 75 kg, so the kinetic energy is round about (100x100x75/3.6) 210 kW. They use 140 mm disks for long 10-15 % descents. We use 205 mm, which is way more than double surface, for double weight. That has to be more than enough.

No pics sorry.

I once bought a fancy looking 203mm rotor that was front mounted. A retro fit with a modded hub and a Hayes cable/ hyd caliper. That bike could stop with a proper rotor up front. The fancy rotor warped so bad we had to remove it to get home.

There are huge decents in Sonoma county, miles long. Trinity grade, Rockpile, Geysers to name a few. 15% some spots even more. We stopped doing that stuff. A word to the wise.

Keep your speed in check. Asphalt likes skin and it’s not far to the bone.

Very true but keep in mind they have much shorter wheelbase and can easily carve a much tighter turn around the switchback at higher speed than you are likely be able to on a tandem. You will likely need to slow down more. We use 205mm rotors but we don't try to go anywhere near the speed of the pros on downhills.

Other than compressionless housing, I found mechanical disks works fine as long as you can take out all the slack out of the long brake cable. I do that with the standard cable adjuster on the TRP Spyre plus a Shimano inline cable adjuster (SM-CB90). The latter is what makes the Spyre satisfactory as rear disc brake. The cam on the SM-CB90 removes a lot of slack.

Most of the slack can be removed without the aid of an adjuster.

And a tandem goes downhill faster than a’pro’ on a half bike. This is where weight is your friend. I’ll race anybody down hill in a coasting race eith our tandem. Pro’s don’t pedal going 60 mph.

I did say tight corners on switchback Colour me surprised if a singe bike with shorter wheel base can't carve a tighter corner faster than a tandem with longer wheel base on same corner if the riders are good bike handlers.

On a straight downhill road, I agree tandems can go faster than a single bike due to physics. We did 107KPH on a very nice downhill run once but I decided the risks just wasn't worth it so we've never went that fast again.

I’ve yet to a switchback on a paved road that was so tight that the wheelbase of the bike limited how fast you get around it.

we can out corner the vast majority of single bikes on the tandem. 40 years of racing, including a lot of crits, even a crit on the tandem, helps.

At the margin a pro cyclist on a single bike will dust us in a corner, but the cornering limitations of a tandem are dimenimis compare to the factors of skill and how risk adverse you are.

We’ve descended major European climbs with some excellent cyclists, including former pros, and they struggle to keep up. You don’t have to descend slowly or corner slowly on a tandem; it’s just that most teams choose to.

I recabled our braking yesterday on the tandem. I don’t think both pucks are live as a matter of fact I’m positive. They do work well and this makes me want to try the TRP hy over cable caliper. Both pucks are live and should offer superior stopping power.

All these braking systems (rim or disc) will properly stop a typical tandem bike on mostly level grades. If the brakes do not stop “well” it is likely that the brake/cables/hydraulics are out of tune. However, as the total mass increases, the brakes will be become insufficient for a tandem on more prolonged downgrades because all of these braking systems were designed for single riders, the extra mass is pushing the envelope of gear engineered for single bikes.

I think most tandem riders realize this.

I used to ride a Cannondale tandem it came with Avid bb7s and 205mm brakes, I found towards the end of long Audax rides 100miles + my hands would start to cramp and I managed to turn the rear disc brown with heat after getting stuck behind a car on a long down hill. I upgraded the brakes to a 225mm hole rotor on the front and a better ventilated rotor on the back. And went for Shimano GRX shifters with a four piston caliper on the front and the cheap MT 200 on the back. Once set up they were great and required no maintenance compared to the BB7s which I had to adjust frequently. The new owner is very very pleased with this set up.

This is a super helpful quote. Thank you.

I'm picking up Spyre's and compressionless housing to give it a whirl.

Thanks all for the tips & suggestions.

Do give the Shimano cable adjuster a try. The cam on the adjuster was key for me. I found otherwise there is just too much slack for the normal cable adjuster to take out. Use as a little cable housing as you can get away with, even with compressionless housing.