Mechanical disc brakes are toilet!

Don't buy Shimano ones. They are proper 5h1te, I binned them after trying to adjust them time after time. I lost all braking one day....scary. I invested in 105 hydraulic and they are light years apart 

BB5 basic.

BB7 better but pain to keep adjusted for full bite. 

Spyre, same braking force as BB7 but much easier to keep good braking (occasional tweak of the cable adjust as the pads wear down). 

Hy-Rd brilliant best of cable operated world. Serious step up of braking force over the others. 

Yes, pad have to be properly bedded in.

Another point is that mechanical disc brakes work best with compressionless outers and decent cables - recently swapped out the cables on my (new to me) Pinnacle Arkose and the difference was massive (TRP cables if you are wondering). Even with the cheapo Tektro Mira calipers, the improvent was huge. A pal of mine uses TRP spyres on his gravel bike and he feels they are pretty impressive - and hes a big guy - 6'5"! - and is quick with it, so don't just discount them out of hand. As a comparison, he rides a rim braked road bike and has several MTB's as well (which are all hydraulic braked) so he knows what all the different options feel like. Yep - hydraulic are better (arguably, in most situations), but cable disc brakes can be very good, and you can still use your existing brifters etc, if changing over, without going to the expense of hydraulics.

fwiw, i really rate *all* the mechanical discs i've got/used.

avid bb5's - yup, really good, the manual pad-adjuster is handy. 

spyres - nicer, lighter feel, i prefer a hard, crisp bite point, and these feel a bit more nuanced (maybe i could say 'flexy', but that's not quite the right word)

shimano r317 - i love these, so much i've even bought some spares, just in case i want to build another bike in a few years. They've got a nice hefty / crisp lever feel, and great performance.

i've no idea what some people are doing to their brakes so that they need adjusting every couple of days. 

Anyone looking at this thread, I did buy the GTP calipers, they are awesome, 10/10 now I can pop the back wheel braking from 40kph.

I bought a genesis Day One with mechanical brakes.  Understanding that they would likely be poor, my god they were shite. 

I immediately ordered a full set of shimano Di2 levers and calipers.  Instant perfect performance with nice ergo hoods being di2 and the bike being single speed.

I ordered my hydraulic full brake system from german website, significantly cheaper than elsewhere. I had to shorten hoses and swap left to right being foreign wrong setup

Hate my mechanic disc brakes on my winter bike. Ironically I have hydraulic on my Summer best bike. Will definitely be replacing them this Autumn with 105 hydro. 

Only reinforcing the above but if you get the cheaper end of the bike market in terms of brakes, you're going to feel it.

I have mechanical discs on one winter bike and cable hydraulics on the other and the difference in huge. Then i bought an e-mtb with hydraulics and wow, it really loves to stop - but then it is a lump with huge grippy tyres too!

A lot depends on the installation. I have the bb7sl and the performance is decent. After having researched a lot, however, my best bet for the best breaking mechanical disc brake (far better than any normal mechanical system, according to users) is juin tech gt - which I have just received (so cannot report on performance yet). They seem very light and well made though.

I've got spyres mechanical discs on my bike & I thought they were toilet when I first had them,it was only when I swapped pads to something half decent, that they actually worked as good as decent rim brakes,they'll never be as good as hydraulic & you have to keep on top of the constant adjustment as they wear else you'll just find you are grabbing a handle full of air

Rim brakes - Great

Hydraulic Disc Brakes - Great

Mechanical Disc Brakes - The worst of both worlds. You have the extra half a kilo weight of disc brakes but none of the extra stopping power or modulation that hydro disc brakes give you.  They're a hell of a lot more faff in terms of maintenance than the above two systems, note the commentor above saying they need adjusting "every couple of days". 

They're an evolutionary dead end and will probably go the way of cantilever brakes soon. 

For every type of brake there are good ones and bad ones, and BB5s are not one of the good ones. I swapped mine for a pair of Spyres and the difference was remarkable.

Having said that, you can quite probably improve things with a better set of pads.

BB5's aren't great (in my opinion see end) disc brake pads take a bit of bedding in and heating up whatever hydraulic or cable  - worth googling for best way but my  summary is down a long hill and drag them after picking up speed x 3 to 4   - out of the box not impressive but will grow to love them in the wet other than their noisy howls and the need to adjust every couple of days 

They all take proper setting up to really get them in the sweet spot, but some are certainly better than others. The problem with the avids is that only one pad moves, so the static piston has to be set very close to the rotor by aligning the caliper very carefully... Then the moving piston needs winding in so you get plenty of bite. Otherwise all that happens is the rotor just gets flexed.

Spyres are great mechanical calipers and Avid can be found the sweet spot...if it's a new bike then get it back into the workshop to get it sorted. I have many coming in here hydraulic and mechanical citing poor performance....but down this way there is little need for discs ( you can all argue the disc /rim debate) and many have glazed disc pads...swap out with softer pads...bingo it's okay.... It does vary area to area but like I say if it's new....get it into the mechanic

You indeed get what you pay for but I used to ride with a pair of Spyres and they were very good, on par  with the very top end rim brakes in terms of performance and the latter wore out my rims right quick. 

Hydraulics are better but come with their own drawbacks where maintenance is concerned.

Are you certain they're mounted correctly?