eduskator

There is always a maximum any given system can withstand until it fails (pressure, temperature, etc.). These are probably isolated cases...

Disc brakes are clearly a must when riding steep hills that requires lots of braking for this reason. I think there is no debate here.

Kontact

Yeah, no one rode down steep hills on bicycles until disc brakes came along.

eduskator

I'm not talking about the past, I'm talking about the present and the helpful and unexpensive technologies we now have.

OP is blowing his tire because of the heat generated by the friction between the pads and the rim. A viable solution is to generate the friction required to brake somewhere else than on the rims.

Lombard

They all died a fiery death when they tried.

Kontact

You know what else discs have that rim brakes don't?

Brake fade.

Lombard

Fixed. Granted this is true, mechanical disc brakes suck. And brake fade won't happen if you know how to use your brakes just as tire blow-offs won't happen with rim brakes if you know how to use your brakes.

Kontact

Brake fade can happen with mechanical discs. Get the pads and rotors hot enough and they stop acting like they have friction on each other. That doesn't happen with rubber rim brake pads because the rubber just wears off instead of holding the heat.

Lombard

And eventually the brake track on the rim wears too.

Don't get me wrong, I'm don't honestly believe in the rim vs. disc brake debate than one is any better than the other. There are good and bad points to each type. There are good rim brakes and good disc brakes. There are also crappy rim brakes and crappy disc brakes.

My point is if you know how to use your brakes properly, either of these options will serve you well.

Kontact

I wasn't suggesting rubber pads prevent rim wear. I was only suggesting that pad ablation is the trade-off that prevents the pad/rim contact from getting hot enough to lose friction.

Barrettscv 

Most professional riders depend on tubular tires and rims when rim brakes were used on long descents. With the tube encased and sewn-up in the tire, blowing a tire off the rim becomes nearly impossible.

Tubulars are also safer in the event of a blowout.

Kontact

So did you have an internal tube failure or did the bead blow off the rim?

terrymorse 

Wearing away rubber from the surface of a brake pad seems to be a very inefficient way to dissipate heat. Unless you're scrubbing away a bunch of material, but then the pad would not last long at all. The entire thermal capacity of a typical rim brake pad is (very roughly) 12 Joules per Kelvin.

Or is this trade-off process you refer to this:

1. pad surface gets soft from heat
2. soft pad material gets scrubbed away (ablated)
3. harder pad material contacts rim
4. repeat

terrymorse 

The braking heat-induced failure mode with tubulars is rolling the tire off the rim. This can occur after the high temperature softens the glue holding the tire to the rim.

Then again, pros usually descend so fast in races that they are not at risk of heat-induced tire failure.

georges1

I never had a blow out in the past on my road bikes. But for my bike upgrades and next builds,I will use slime tubes and continental grand prix 4 seasons.I used michelin tires the performer and the hilite comp as well as the axial in the past on my road bikes and never got a flat

Maelochs

Of course, the tire blowing off also eliminates the pad/rim contact from getting hot enough to lose friction.

Just messin' around. I don't care about any of this stuff. Ride what works for you, and if it doesn't work, ride something else or ride what you have differently. Your mileage Will vary.

Maelochs

And happily for all, tubular glue won't melt at the sort of rim temps experienced by pros riding at max pace down steep mountains .... and I am sure that in the cases where I saw riders in a broadcast race lose a tire and the announcers---themselves ex-pros---said that due to extreme heat of the pavement and the heat from braking, that the tubular glue melted, they were lying ... in the pocket of big Tubeless, for sure.

https://www.velonews.com/gear/techni...res-rims-oman/

Kontact

Pretty much. Add on the much higher leverage and surface area of a 622mm "disc" and you have a very heat resistant system, overall.

rsbob 

Happened upon a YouTube today, and of course can’t find it again, which discussed rim brake overheating of carbon rims on some long descents overheating the carbon and slowly breaking the molecular bonds which bind/bond the rim leading to eventual rim failure. Will keep looking…

OK, just search on You Tube Carbon Rim Brake Failure - there are a bunch of them.

terrymorse 

It’s not the carbon that fails at high temperature. It’s the resin.

This was a fairly common problem in the early days of carbon rims. Manufacturers have since then switched to resins with a higher softening temperature.

rsbob 

Yes indeed. I stand corrected unless you want to start an argument about it in the finest BF tradition.

terrymorse 

I came here for a good argument.

Maelochs

"That was never five minutes .... "

rsbob 

What?

“{SHUT YOUR FESTERING GOB, YOU TIT! YOUR TYPE MAKES ME PUKE! YOU VACUOUS TOFFEE-NOSED MALODOROUS PERVERT!!!”

Absolutely love MP. Been a fan since the start of the Flying Circus. The ridiculousness of it all is, shall we say, hauntingly familiar.

eduskator

Brake fade or a blowout, which is better?

Maelochs

Lol .... debating disc vs rim brakes is like debating how flat the Earth is. +No one is listening to anything but their own voices .... and the voices in their heads.

The only reason racers sometimes blow tires is because they have to go all-out to the very limit of safety, because they guy behind them will. On the road, there are a lot of options. If I have to descend a Really long, steep hill and I am worried about my brakes because I am riding them... I can pull to the side and let them cool a minute. Disc or rim or drum, tubular or clincher or tubeless, I do not have to hold the brakes for minutes at a time .... I am not on the clock with my career hanging in the balance.

Similarly, i can brake almost to a stop, then roll off, hitting the brakes intermittently, a little harder as I build speed, then slow way down and proceed downhill cycling through hard and gentle braking, to keep the brakes cool.

If I choose, I can ride the brakes hard the whole way and risk dying to a blow-out or blow-off or whatever. I am pretty sure if I die I won't be debating proper terminology.

It is great having the freedom to live my own life by my own lights, which usually, while cycling, i get to do a fair amount.