Is is good or bad idea to ride with just one break, say with a front? Or related question instead two v-brakes have one disk brake on the front wheel?

What would be the point?

And no, I don't think it would be an especially good idea. Especially not going downhill, fully loaded.

In this situation, redundancy is good.

Well, usually we use two v-breaks, wich is not as strong as disk brakes, then the efficiency of breaking front wheel is much more then rear wheel.

This is not a good idea. The reason for two brakes is redundancy. If you have only a front brake, and the cable breaks or slips through the pinch bolt, you are in trouble.

V-brakes or disk brakes makes no difference. For safety reasons, you need two independent brake systems.

Yes. Only one brake is not good. Although the front is the most important, 2 brakes front/rear are not redundant, I use them both.

Disc/V at the front/rear is fine.

Some people prefer discs because you won't overheat the rim and risk a tube blowout in a looong descent. If that happens in practice I don't know. Some say rim brakes are more serviceable are parts are more common. A disc brake requires tight tolerances between rotor and pad but isn't affected by disaligned wheels.

I think you mean BRAKE and the only bike that's ok with a single brake is a fixed gear

+1. If you want better braking, then replace the front v with a disc, and keep the back. Redundancy is good.

In addition, with only a front brake, it's possible to skid the front tire if you're heavily loaded, or on sketchy surfaces, which is a bad thing.

Then again, I wouldn't want to go on a tour with only one break either.

When I read the subject line, that is exactly what I thought!

One break, two breaks, three? Guess it depends on the terrain, load and how far you are going.

How many breaks you take on your ride is up to you.

I would only ride with one brake on very flat terrain.

I try to avoid taking breaks at all, except to sleep at night.

Yeah, just in case you haven't realized how painfully obvious the answer to your question is, imagine this:

You're going down the biggest hill you'll be riding on (for me, this is probably something to do with the Alps). Not only is the grade in excess of 10%, but you're going downhill at over 40 MPH without a guard rail. Suddenly a fleet of soccer moms in SUVs start driving at random, hitting eachother, blocking your path. You must stop to avoid the fiasco, and stop fast, so you pull hard on your only brake, harder than you ever have, and suddenly the cable slips. You pull again, but you just go faster. Three seconds to decide whether you plummet off a cliff or get launched head first into an SUV. Two... One... ... This isn't choose your own adventure, you know... no takebacks.

I think it is a better question than it's getting an answer.

There is a purpose to a front and a rear brake, the front brake stops you when you really need to be stopped, the rear brake shares the loads, and there are loose terrain advantages where dragging the rear wheel helps straighten you out or on extrem terrain where the front brake may not be useable.

If one takes seriosly all weather stopping, cable slipeage, Suvs, wheel failure, etc... Then one is currently really running a single brake system with a pair of front and rear brakes. There is a reason why high performance motorcycles have double front brake systems. That is real redundency, in parallel, compared to having a forward and rear brake which is just serial brakes that do different things. That's why I am going for three brakes.

Three brakes can probably be done for a very similar weight compared to two brakes with in-line x-cross levers. That's a system that is widely popular and doesn't improve redundency or performance one whit.

^^^ +1
That's what I was saying. Two brakes are NOT redundant. Each have different purposes and I use them both. I run an interrupter cross lever for the front brake to relax on the tops.

Tandems often have a drum brake at the rear on top of two regular brakes. And that's not even redundant because it has a specific use on descents.

Hehe you could set up a bike with 4 brakes: 2 rims brakes and 2 disc or drum brakes. Like in here

I usually like to ride a good 4 hours before my first break. But, if I pass a decent bakery, then, a quickie break is always nice...load up for the afternoon haul. The low in my day is between 2-4pm. And at night, of course.

"I run an interrupter cross lever for the front brake to relax on the tops."

A lot of people like that. My preference (until I actually try it anyway ), is to run an extra lever on the tops and an extra brake on the front. Hardly any difference in weight vs. those who do run two top interupters. I have the hand positions covered and an extra brake system.

That's interesting, and very safe
What is the combination? Disc/drum + rim or V + caliper ? (this one seems though, one on each side of the fork )

Brake cables sometimes break. That's a good enough reason to have two brakes on your bike, imho.

You know, I'm going to forward this idea to Mythbusters and see if they'll find out how hard it would be to blow up a tire with rim-brake friction.

You can do it ofcourse you'd be much better off with F&R brakes.
Probably not a good idea if you've got a loaded rig. Hard enough to stop as it is.

"That's interesting, and very safe
What is the combination? Disc/drum + rim or V + caliper ? (this one seems though, one on each side of the fork )"

The current project has a front fork disc and Paul Vs. I am using a Paul e lever for the disc.

https://www.paulcomp.com/frmbrklev.html

I find the disc brake really heavy, another time I would probably just go for a sidepull, afterall it is a backup.

huuum. V brake and side pull. Yeah maybe a long reach caliper mounted on the other side of the fork... Some time trialists back in the days used to mount their front brake like this.

Yeah! Put the bike on a threadmill, lock the brakes, put weight on the handlebars and put a fan to simulate wind. But I doubt it happens in practice... you need significant pressure to blow a tire. However a friend was touring in the mountains and he confirmed his rim got pretty hot .

NO ITS A REALLY BAD IDEA!!!!