How much should brake pads drag on the rotor?

[DangerMice]

I changed my front pads on the weekend and I've noticed that the pads are dragging on the rotor. I read that dragging lightly is ok, but I'm not sure how light is lightly. If I spin the (10 inch) wheel it rotates twice before coming to a stop. Is that dragging too much? It seems to me like it might be.

I gave the whole assembly a light clean and put a few drops of brake fluid on the piston for some lube. Do I maybe need to clean it better? Not sure if it means anything but I couldn't push the piston back in with my fingers, I had to lay a metal ruler across it and then it pushed in easily enough.

DM

(sorry if this has been asked before, my search mojo may be malfunctioning)

[bogan]

I've had the same problem recently. Yes you should get more than 2 spins, though for a scoot the smaller wheel may mean you don't get as many as a bigger bike. Another check is to ride for a while then stop using the other brake, if they rotor is hot, theres a lot of drag.

Firstly, whenever you replace the pads (more often the better in between pads too), the pistons must be cleaned, warm water and dishwashing liquid is good for this, and by giving the lever a few pumps you can expose more of the piston to ensure you clean it all.

Secondly, previous owners can be numpties, often a full rebuild of the caliper is required, I've had to buff up 10 brake pistons in the last 6 months on mine! and replace seals, lube floatey bits for the floating caliper style ones.

[DangerMice]

Thanks for the response Bogan, I went for a 10 km ride after fitting them, using them gently. When I got home I could hold the disc between thumb and finger for about 3 seconds before the heat made me let go. I'll give the piston a really good clean this weekend and see if it makes a difference.

[Subike]

When you cleaned the brakes, did you clean the slider pins the calipers "float" on, These are the slider pins that allow the calipers to stay centralised over the discs. If they are dirty, your clipers can drag on the discs. These are very often overlooked when a brake overhaul is done. Remove, clean lube with light grease and replace.

[DangerMice]

I did, but in hindsight, probably not well enough. I scrubbed them with a toothbrush and water, but they weren't spotless. I'll give it another go. Thanks for the response.

[Max Preload]

If it is a floating caliper, thoroughly clean the slides and guides (holes in caliper) and and lubricate with a rubber grease. NOT an antiseize.