Seems like I have a buckled back rotor. There is brake rub at certain points when I rotate the wheel yet it is fine at other points and when spun you can see the buckle.
Can you fix a buckled rotor any way? Or is it a case of just either living with it or buying a new rotor?
replace, ideally.
how did you bend it? if you did try to straighten it, you have more chance if it was bent through impact, although i suspect it was warped with heat rather than impact
Bend it back into shape with an adjustable spanner.
pull it as straight as you can then brake with it to get it really hot. It MAY go straight.
What kong said
thought that may be the case. I think it was from a rock smashing into it but not 100% sure?
OMG loads of posts whilst I typed a response.
Such a small buckle that it is hard to notice with the wheel off but I will give it a shot if the only other option is to buy another rotor then no loss if i f*ck it up.
use an adjustable as sdb says - you'll find you have to bend the disk [b]way[/b] more than you'd think, as it just bounces back, but with patience you can get it quite straight 🙂
6" adjustable spanner with tape on the jaws to prevent marking. I have a pair of bottle openers from MBUK with a slot in the back which is just too perfect for this job for it to be an accident. I had to do my SS's rotors on Sunday, had an annoying ticking noise when riding, after a phaff getting the front wheel back in while trying a 29er front wheel. The rotor was hitting the pads, so a ten minutes bending the rotor violently cured the problem. You don't have to replace unless the rotor is really bent, in which case the wheel won't be rotating anyway. If it turns, it's fixable. You do have to put more force into it than you might imagine; rotors are stainless steel, and pretty springy, and much more difficult to break than you think..
bending the rotor violently
Violence? I spent literally HOURS taking the disc off, putting it in the vice, bending it this way and that, marking the rub-points with black marker, re-fitting the disc, etc etc etc. Figured out that i was just over-bending it one way then the other. In the end i ditched the vice and spanner and just left the disc on the wheel and coaxed it into line with my FINGERS. worked a treat!
Mind you about 1/3 of the disc was rubbing the pad, i can imagine if its more of a short sharp kink you might need a spanner to get it straight but if its just a gentle warp then try with ur hands first otherwise you risk making mincemeat out of it!
Straightening rotors is routinely done even to new bikes, there's even a Park tool for the job.
I have a lovely park tools' rotor truing tool. Very effective. Also Morning Star Tools in the US do a marvellous set of tools for the purpose.
Dogsby
Is this the tool you got? http://www.sjscycles.co.uk/product.asp?pf_id=12923&src=froogle
There is no big kink but there is a mark on the rim of the rotor where a rock hit it. Will try with the fingers tomorrow but the rotor tool may be a worthy buy as cheaper than a new rotor and less faff than the vice/spanner option.
Buy a new one, i've tried for hours to get rotors straight again with no luck. Once you get one part straight, the bits at 90 degrees to it just bend.
ajf,
That's the one. I find it is fine for fixing small bends.
Dogsby
Well, 'violently' is a relative term, I push the rotor or pull it fairly sharply a centimeter or so a couple of times, check it then move to the next bit. I never bother taking the wheel off, as I use the gap either side of the rotor between the pads as a guide, with a piece of white paper behind. I don't use my fingers 'cos I don't want greasy finger prints on the disc that I have to clean off with alcohol. A bit of masking tape stuck on the spanner takes ten seconds to do, and is hardly a faff. Hell, I've even done it sitting outside a pub during a bheer stop. It's not difficult.
If I replaced rotors every time I found a bent one, I'd have to sell my bike to pay for it 
It's really not difficult to straighten a rotor out, it doesn't have to be perfect.