from photo, you can see the friction in the backing plate, which is pointed by red arrow. However, there is no friction in the drum part, see the part pointed by blue arrow in drum. where does this friction come from?

 

When brake is applied, there is grinding noise from this wheel. no this nosie when driving. Is it possible the brake shoe grinds on backing plate in other part?

 

What year Civic?

Are the brakes shoes and drum the correct ones for your Civic?

Were the brakes assembled correctly?

 

2001 Civic EX

The brake and drum are oringinal which ran fine and not re-assembled before. The problem happens after the wheel hit the potholes badly. The wheel is bent but tire is still hold on it. It is runable but I heard the noise. I replaced the wheel and tire last week, and then the sound is louder. It seems the break tries to keep pushing shoes intermittently but shoes do not move easily. If the brake is stepped hardly, no sound. Exchange the drum from another side, the problem still happens this side, but the other side is Ok. So it is not the drum problem.

 

Striking the potholes may have damaged/bent the spindle. If so, you'll need to replace it.

 

Thanks for your suggestion. I will pay attention to it.

How can the damaged/bent spindle cause the noise when braking?

Also, the wheel runs straight.

 

If the spindle is bent, the drum will not align with the other parts. So you will have some unusual rubbing. It may not be real apparent just looking at the wheel, but eventually you would also get abnormal tire wear.

 

The backing plate, which supports the brake assembly, is in the same spindle as drum's. The bent spindle will not cause the noise when braking. Am I right?

 

What makes you draw this conclusion? I don't understand the logic.

 

Only the shaft part is likely to bend. The brakes are attached to the cast part. So it will be out of line. You should be able to buy the whole thing (part #1) with the bearings, hub, and most of the brake parts still attached from a junkyard fairly cheap.