Cycling is a very expensive hobby. So I tend to buy stuff not from famous brands like FSA and so on. But is it safe to do that? Cheap handlebars will send me flying like Superman one day. What parts of the bike I should never buy cheap?
There are potentially a lot of ins and outs to this question, as one could ask what discipline you're talking about, how aggressive of a rider you are, skill level, etc, as it all has an impact on how likely you are to be punished for going cheap, and how severely.
However, there's a really good axiom in cycling: "Cheap, light, and strong. Pick two." Your answer is pretty much right there.
An example would be comparing a bottom-end aluminum Shimano road wheelset vs super cheap, unreputable carbon wheels. The former is cheap and strong but not light, and the latter is cheap and light but not strong. For most categories of bike component, there are going to be choices that have a similar relationship. If you want to get by with cheap stuff, this is the angle you have to work. Light components at very low prices, especially ones new to the market, often turn out to be junk, sometimes in a way that can be dangerous (there have been numerous pedals, wheels, hubs, stems, brakes, and cranks in this vein in particular.) Conversely, being really successful at being a thrifty cyclist is usually all about either finding the stuff that's a little less flashy but more stalwart and able to get the job done or just finding good higher end stuff at low prices. Most attempts at "getting away with something" by buying the other kind of cheap stuff are bound to fail.
Some more particulars:
- There are a lot of flashy, cheap two-piece cranks running around these days that can have issues with pressed interfaces that are supposed to be permanent coming apart and creaking.
- There are some good offbrand carbon rims and some that have proved unreliable. It's a good place to be cautious.
- Rear hubs are a component where it's easy for manufacturers to put out something for cheap that has a high engagement rate, smooth bearings, and light weight that then proceeds to totally fail to be a reliable component. It's best to go for something that's either a known workhorse (XT and 105 for example) or true high end, and not roll the dice on anything else.
- Cheap, off-brand headsets and bottom brackets are almost always disappointments.
A final note: it's actually a really good idea to pay close attention to how long a given model of component has been on the market unchanged. Bike component manufacturers love having flashy new attention-getting things and often feel pressure to change up their lines at least every couple years if not sooner. More often than not, when they keep the same model kicking around longer than this it's because it's just a good design and has earned a reputation for it, and there are a lot of examples of cheaper components this applies to. PD-M520s, CR18s, and FH-M756s are some examples from the last couple decades.
Taking into account your
flying like Superman one day part in your question, I would like to nuance the last paragraph of Grigory Rechistov's answer.
In my urban cycling experience it's the parts in front of your center of gravity (front wheel, fork, headset, etc...) that should be super reliable as a failure of those elements would send you flying forward, which can be very harmful to you.
The same holds for tires and brakes (thanks cmaster for the comment) as a failure of one of them could make objects hard to avoid, also leading to a flight forward.
If e.g. your pedal or rear wheel fails however, the resulting damage to you is less extreme.
In bicycling componentry what applies is "cheap, light, reliable — choose two". To explain this, a cheap component may be reliable enough, but it will be heavy. Light top-tier parts will cost you a lot. It is when you see light and cheap stuff on sale you should become very careful.
Entry level components are typically made of steel and aluminum alloys and are typically manufactured with well proven but not bleeding edge technological processes. Steel is heavy but hard to break.
Mid range stuff has more aluminum in it, which is lighter but is still very reliable for everything from road to downhill.
Competition-level components tend to include as much carbon or other lightest exotic materials as possible, and they are made using finest technological advances to date. Carbon have had bad reputation in reliability in the past, which is no longer true if manufacturing quality control is adequate. All this is not free of course.
Off-brand or counterfeit stuff is made without regard to quality or tolerance control, which cuts down on the price, but also on performance, reliability and life expectation.
If I may reformulate your question "which bike parts may not be allowed to be less reliable?", then the answer would be "everything supporting your weight or participating in braking". Which is, basically, everything on the bike, including everything braking-related, handlebars, frame, pedals, crank, saddle, even chain. Shifting components do not carry your weight, so, theoretically, they may be less reliable (not that I would recommend it), as different bells and whistles, such as lamps, reflectors, fenders.
There are two classes of 'cheap' bike parts.
One that looks like a top end part but is cheaply made. And one that is sturdy and not fashionable, but which they can produce cheap because they do not need to change manufacturing every time.
That first class is the kind to avoid. Do not buy the cheap knock-off version of an expensive (and/or highly fashionable) part. But if you can use an old fashioned part, one that has proven its use, why not.
My current rides do not have anything fancy, sturdy steel and old fashioned parts, but I do not have to fear that anything breaks, as it is all proven tech. (The bike is almost thirty years old, I bought it second hand, but I think most parts are still the parts they build it with, solid and sturdy.)
An other point in keeping a bike from breaking is not asking to do things the bike is not build for.
You mention street jumping.
That is not something I am familiar with but I guess you need a reasonably sturdy bike for it. If your bike is designed for the job you use it for, or overly sturdy for what you use it for, you can get away with a lot. But a bike build to be as light as possible will not be as sturdy, it is more likely to break.
Good question. Another angle on this is longevity and ease of replacement. Really cheap parts can end up costing more if you do any sort of mileage. If it's a cassette then you can just try it and see but replacing a hub, bottom bracket or headset can be a bit more of a pain.
I think there's never really any particular reason to go higher end than about Shimano 105 (and FSA stuff is fine) unless you're really into shaving the grams.
Cheap handlebars will send me flying like Superman one day
Why should they?
Like everything else, a bike is as good as the weakest link. If the handlebars aren't the weakest link in your performance, leave them along. Or as the saying goes, "if it ain't broke, don't fix it!"
If you're putting high loads on your bars, for example with jumps, then you need bars that can take it. But before that, you need shocks that can take it and a frame that can take it. If you're trying to save the last few fractions of a gram on a track bike, maybe lightweight bars and headset will get you that little edge. But not unless you already have a super-tricked-out competition bike already.
In the real world, the most important place to spend money is your wheels. After that, a frame (and forks) which fit your needs - and most importantly which fit you, because bad ergonomics are your biggest energy sink.
For everything else, so long as it meets some minimum level of performance and reliability, you won't notice any difference past that. Or more accurately, you would need to reach a point where you could notice that difference before it's worth upgrading.
And beyond all that, the single biggest issue on bikes isn't the quality of bits, it's the quality of maintenance. It doesn't matter how good your cassette is, if your chain is rusty and slack. And what really will send you flying like Superman is loose bars, loose brake levers, or anything else which can come off and land in the wheels.
Beside the other good answers, I have two other suggestions for you, to help you with your decision where to save.
- Is it a "needs replacement frequently" part? If yes, buy cheap. Sure, the expensive part may last a bit longer until it needs replacement, but in most cases I have encountered, over a lifetime of a bicycle, buying cheaper expendables at a higher frequency pays off when compared to expensive expendables. An exception would be a case where safety would be compromised before the replacement moment comes - if you come across a set of cheap brake pads which don't hold from day one, obviously don't buy them.
- For non-expendable parts, try to gauge the production complexity of the part you are buying. Cheap producers typically have less R&D, less engineering know-how on the production floor, higher tolerance for variability in the finished product, and less quality control. This can lead to nightmarish quality in finicky high-complexity parts, but to perfectly good noncomplex parts. The internally geared inner hub mentioned by Nathan is a good example of a complex-to-produce part, so no wonder the cheap ones are a bad buy. But something like a handlebar grip is not complex, and producing a good one doesn't cost more than producing a bad one. So it is a perfectly good candidate for buying cheap.
These guidelines are obviously not perfect, since they are more of a tendency than always-valid rules, and of course there is no black-and-white division between expendable-nonexpendable and complex-noncomplex, it is a spectrum. But they have served me well so far.