I've now gone and pretzeled my disc brake rotor after trying to stamp on my rear wheel late last night in a desperately futile attempt to pull it back into some sort of round-ish shape. 🙄

It has about 2-3mm of sideways play across 1 third of its circumference now.

Can I bend it back into some sort of ridable shape to get me through today's ride – and how should I do this?

Or should I just forget about it and find something else to do today instead?

I got some clean cardboard (back of an A4 pad) and made a U to cover disc, the clamped a large adjustable spanner over U and used it to lever disc. You have to overbend to get the required bend if you see what I mean, go slow and steady till you get a feel for how much force and pull it takes to make a change to the rotor.

Try (very very hard) not to touch any 'brake' part (pad faces, disc) with hands or anyhing else oily,greasy etc etc.

Park even do a tool for it!

Yes you can if you are patient. Use an adjustable spanner, making sure the jaws are il/grease free and a fairly tight fit on the disc, gently tweak it back into shape. It takes time and should be done with the wheel in place. Keep rotating it back/forth, and have a gentle lever with the spanner, best to have a light touch and not too heavy handed. may take a while, especially if it is well out of shape. Good luck.

One of these should just about do it….

Cheers… thanks for all the tips – disc rotor now almost perfectly true. I think the trick is to try to also gently bend the rotor arms as well as the braking surface if at all possible, otherwise things go skewiff.. 🙂