The back brake on my road bike is playing up, probably due to being ignored after years of faultless service, so not something I’ve had to tinker with before tbh.

The calipers squeeze the wheel happily enough, but then won’t let go – have to physically pull them apart, not ideal when riding along! Before I leap in mindlessly, does the Hive Mind think this is likely to be due to the caliper being awkward or the cable? Before I pull the wrong bit to pieces…. 😳

Shimano 105, in case it makes any difference

Try slackening the cable and unhooking it from its stop, then squeeze it manually to see if it returns. If it doesn’t it’s not the cable. There are a couple of online tutorials (Park do one I think) that will guide you through the process. My Ultegra brakes seized the same way and its a bit of a faff with little grub screws and what not, so best to take them apart on a sheet of some kind. They just need a good clean at the pivots probably.

Sounds like the caliper is seized. Take it apart, clean and grease the pivots.

Been riding in the wet without mudguards?

Disconnect the cable as said earlier,if the caliper springs back fine then you know that the cable is the culprit and needs replacing.

If the caliper is still stiff/reluctant to return with no cable attached then as Al said it probably needs a good clean and lube,make sure you lube the return spring on the rear as well as the pivots.

If you can’t work out if it’s the cable or the caliper you can’t fix it. Pay someone to do it.

Cheers guys – my initial thought was that it was probably the gunk from riding without mudguards getting in the caliper. Looking at the weather forecast, Wednesdays night ride may become a garage fettling night….