Well, maybe not ‘unbreakable’; but I was left stranded yesterday when my fan belt broke. Fortunately, I had a spare in the ‘boot’. Are there any brands/constructions of fan belts that are more resistant to breaking than your typical $5 auto shop ones?
Also, any opinions on emergency fan belts?
Fans still have belts?
They did in 1966. 
Ooooo I remember something from a few years back now. MG?
What kind of car do you have?
The serpentine belts used in most cars in the past 20 years are pretty damn near indestructible. Usually they only break if the tensioner breaks or one of the belt-driven accessories seizes up. A lot of car manuals don’t even call for periodic replacement anymore, just occasional inspection. I once put around 200,000 miles on a belt on my old 80’s Buick when I was commuting a long distance-- I had a replacement belt in the car and it was easy to change, but I held off on actually doing it out of perverse curiosity as to when the belt would actually go. It ended up outliving the car.
The old style V-belts are another story. The key really isn’t the brand of belt or anything like that, but keeping the tension adjusted. If you’re having regular problems, you might want to invest in tension gauge and learn to check it yourself. Learning how to check and adjust the tension yourself also means you shouldn’t have too much trouble changing the belt itself, and so you can carry application-specific spare belts instead of a rinky-dink emergency belt.
ETA: Oh, also, a bad pulley will drastically shorten the life of V-belts as well, so you might want to give those a look over.
I suppose they’ll get you from the side of the road to your driveway, or a nearby mechanic. I wouldn’t trust it further than that.
Or, you can just use panty hose
Once drove 60 miles, at night, with no alternator. Cruised into the driveway with my headlights just beginning to fade out. Honestly, I was just trying to get nearer to home before calling a tow, and somehow made it all the way.
1966 MGB. No tensioner. FWIW, the belt that broke and the replacement are Flennor AVX10 X 900 LA A5105. Not flat like modern belts, but V-shaped in cross-section.
I did watch the mechanic replace the belt. There are three bolts holding the generator. Loosen them all, replace the belt, use two hands to tighten the lower bolt and one hand to pull a crowbar to tension generator, tighten the other two bolts using three hands. I just need an assortment of wrenches I can carry with me (which I should do anyway).
Alas, I don’t wear panty hose.
The new batteries are stronger than the Lucas replicas. Unfortunately, the fan belt drives the fan (and thus, the water pump) as well as the generator.
I’ve never heard anyone complain about Gates belts, so if they have the right size*, they’d be a good pick.
The original Volkswagen Beetle (rear) engines tensioned the generator/alternator by inserting or removing shims between the two halves of the alternator’s pulley. Maybe your MG was *supposed *to be done this way and they just used a ‘shortcut’… 
And if you have an unbreakable belt and the fan bearing rusts solid?
What happens when the unbreakable belt meets the immovable fan? 
The unbreakable belt, ah, breaks! Or more precisely it quickly heats up and starts to melt (and smoke and stink, a lot!) from the incredible friction of being dragged across an unmoving pulley. Then it breaks.
The advantage of having a serpentine belt though, is that all you need to replace it is a tensioner tool (usually just a half inch breaker bar), a new belt, and about 45 seconds!
There are emergency belts made from plastic links that can replace a broken V belt without any tools. Flat belts can wear out, stretch, or break eventually, but I think that’s usually the result of improper tensioning. They certainly outlast V belts though.
Does anyone remember an old MAD magazine item on car repair? There was an illustrated guide on fan belt problems:
“If your fan belt looks like this [drawing of belt with multiple cracks], it indicates dry rot. May cause eventual breakage.”
“If your fan belt looks like this [drawing of belt with hazy black spots], it indicates grease rot. May cause eventual slippage.”
“If your fan fan belt looks like this [drawing of belt with buckle], indicates brain rot. May cause eventual embarrassment when your pants fall down.”
Gates: more money. Worth it.
I ended up getting two belts of the same (German) brand as the one that broke. I’ll carry them both.
Something else happened on that trip, and I thought I’d mentioned it but can’t find it. The car stalled twice. It was a warm day, and I was stuck in traffic. When I asked the mechanic about it after I got to work, he asked if it was a fuel-related stall or an ignition-related stall. Since the car just died – no sputtering – I told him the latter. Also, he’d just cleaned the fuel system. I have an ‘invisible’ Pertronix ignition in the car. He said that when the electronic ignition is about to fail, it is susceptible to heat and just quits. He mentioned I needed a ‘coil’. But I can’t imagine the (new-ish) coil failing. Is there another component of the Pertronix ignition that is called a ‘coil’?
Other than that, the car runs great. We drove it out to dinner Saturday.
I had a coil fail under heat in a Chevy. So it can happen. I assume the wire expanded enough to cause a short somewhere. The car failed several times on very hot days. Replaced a lot of parts before it wouldn’t restart after cooling down anymore. The coil had shorted out permanently then. I don’t have any way to prove it was the coil and not some random events initially, but it never happened again with a new coil, so that’s pretty close to positive.
ETA: Oh yeah, also had a problem starter solenoid like that. Don’t know what went wrong, but that has a coil too.
I just did one on a Toyota Camry. Royal PITA. Had to remove an upper engine mount, and there was not room for a standard socket to de-tension the idler. Had to use a pry-bar to shift the engine in the mounts enough to get a wrench on it. This is indicative of FWD more than serpentine belt though. A stack of V-belts would have left even less working room.
Another vote for Gates. Best belt out there IMHO.
About the stalling. If it is ignition, the tach will drop like a stone to zero. If fuel it will coast down with engine speed.
While coils do fail, it isn’t common.
With an MGB my first thought is do you still have a points type SU fuel pump? If so, I have $5 that says the pump is going away. The common mode of failure for an SU pump is stop working, works fine for a couple weeks, stops again, and then finally fails.