I only recently noticed my discs at the front are a bit warped as when taking the wheels off for my recent forks and tyre jobs, when the calipers were off the wheel ran smooth as anything But once I put the calipers back on, it was far more harder to turn the wheels, although it turned, wasn't as smooth. I know there is some friction but this seems way to excessive for my liking.
So I had a real close look at the pads and they seem to be wearing at an angle
Back one isn't as bad but if I'm doing the front, may as well do the back one too.
Checked them with a laser pen and the discs aren't true So on a hunt now for a decent set.
Looks like I'll stay away from the wavy & Chinese etc would like to stick to original I think
Slow down a bit.
They wear at whatever angle is necessary, even more likely when you have floating discs and 2 pistons in each caliper that will adjust in and out accordingly.
"Warped discs" is a term used too loosely and not always the case.
If you used crappy cheap pads for example and had heat transfer causing parts of the pad to transfer to the disc, then that would cause a "hot spot" which in turn can cause a grabbing sensation every time the pads hit it, as it is part raised on the disc, and can give a similar feeling to a warped disc.
Another silly one but very easily done is when you buy new discs they have a sticky oily film on them for protection.
This needs totally wiping off with brake cleaner before using otherwise that can cause a sticking effect too. It "should" just burn off eventually, but by then you may have contaminated your pads so will still get a shitty feel on the brakes that won't quite feel as good again as they were.
I had a problem a few years back where i virtually ended up changing the front end of my bike due to a juddering "warped disc" feeling, a bit like braking on cobble stones, and the culprit eventually turned out to be the only possible thing left that i hadn't changed, which was the brake lines.
If they had been standard lines i would've thought about changing them much earlier, but they were upgraded braided ones and as there were no leaks or visual damage i totally overlooked them.
Lesson learned. As for the pads being at an angle, i would look more into your calipers, there is a possibilty that you may have issues with sticking pistons, and now is a good time to learn how to clean them up while there is reasonable weather, 'cos unless you have a decent garage or cover, it's a shit job out in the cold.
I've cleaned mine so many times i can do them on the bike without removing the calipers or fluid, just for a general clean up and for fresh rubber grease.
Do that a couple of times a year and not only do you get good at it, but it keeps piston trouble at bay for much much longer.
Other reasons for your pads rubbing when putting back on are firstly because you've simply disrupted them, even a fraction of a millimetre will change the angle of the pads so the lines on the discs and the pads will now not line up causing friction.
This is made much worse if you take the pads out and put them back in different places, they will need bedding in again and much more resistance will be felt and heard.
If you ever do get new discs, which i doubt very much you need anyway, then make sure the surface of the wheel hub is TOTALLY free of any built up crud or dirt, it needs to be spotless so the new discs lay perfectly flat on the wheel.
And use a torque wrench on the wheel nuts, that's very important.
Good luck with the rear caliper bolts, be prepared for disaster as they tend to weld themselves to the wheel hub,and can be a complete and utter bastard to remove. Heat seems to be the main weapon of choice, i personally had to buy another wheel last time.
Just an important pointer though, if you really did have a warped disc(s), then with these decent calipers that are on these bikes if you grabbed a handful of front brake you would find yourself doing your very best Superman impression when it totally locks up!
The fact you haven't mentioned anything of the sort, or even moaned about a juddering or pulsing feeling when braking suggests to me that your calipers are due for at least a personal clean up by yourself, or possibly even an overhaul.
Brake discs are one of the more expensive things to buy, along with the rear shock, but if you don't need it then no point in wasting money, 'cos if your piston still doesn't function as it should then you won't be gaining anything whatsoever, and could even score the new discs which you really don't want.
For the record, if you do put new discs on then ideally you want new pads too, and a perfectly functioning caliper so they all work in harmony straight from the off.