Hello everybody!

Recently I have noticed that my braking has gotten bad. It takes very long to come to a full stop or even slow down a little. I have cleaned my rims which helped a little but not too much. I wanted to know if sanding the braking surface is a good way to improve braking. It sound like it will help, but will I ruin my rim? Is there a special way I should sand them?(wet or dry). Thanks!

By the way I have kool stop dual compound pads on both front and rear.

kool stop dual compound pads: Are they new pads?

You should not sand your rims. All you'll do is wear away some metal and the pads will soon have the surface right back where it is right now.

If your brakes have gotten poor over the past short while it has to be due to something that is interferring with the brake arms. On V brakes if you're using fenders be sure to check that the arms are not hitting the fenders.

Another possible issue may be that you ran your wheels and pads through puddles with an oil slick on it and your rims and pads got contaminated. So clean the rims again with a strong dish or laundry detergent and also clean the pads well to remove any oil.

Awesomness, I just had this problem yesterday. If you look on the braking system, you'll see a bolt on each side of the pads. If you tighten them alittle bit it'll tighten your brakes. Thus, stopping super fast ^^

The pads only have a couple hundred miles on them. All on flat land with little braking.

Thanks. I will try that today to see if it helps!

Scuff the pads with rough sandpaper/file.

Sounds like your brake pads may be glazed.

That would be my opinion as well. When "scuffing" the brake pads, remove the wheel and use a sanding block of some sort to make sure the sanding surface stays square with the pad. Don't remove a lot of material... You just want to break any glaze.
Inspect to make sure the pads are not wearing unevenly; that they are not hitting the rim squarely.
Also, make sure there's no "slop" in the system from kinked cables, worn housing... All that.

I think you're mistaken on that. Unless you had loose screws on your brakes there's no "bolts" that you can tighten on any of the systems that will make the brakes suddenly stop better. If you tightened something and got better performance then it is only because something had come loose and it needed to be corrected. Also with all the various brakes found on bicycles it doesn't do any good to just say to tighten something. You need to specify what brakes you have.

There are several factors that can contribute to poor braking. Cable can stretch on a newer bike. The brake pads can become glazed and/or contaminated. Pads wear down. Cables can slip if not tighten properly. Wheels can be dirty which contaminates the pads.

If the cables are stretched, you'll notice it in the lever. The lever may move further when you are applying the brakes than it used to. There are barrel adjusters on most brakes to take up the cable stretch.

If the pads are black and oily looking on the braking surface, they may be glazed or contaminated. You can clean them with a solvent...rubbing alcohol works well. Clean the rims at the same time.

If the pads are worn, you have to pull more cable to get the brake pads to engage the wheel. You can use the barrel adjuster to take up the slack or, if the pads are very worn, install new pads.

Cables can slip in the anchor bolt but this usually only happens upon new cable installation. Once set, the bolts usually stay tight.

My guess is that this is something that has happened gradually. I'd suspect cable stretch or pad wear over the other causes. Try tightening the cable and see if that brings back the braking.

What I use is 380 grit wet sandpaper and do it with a mild soap and water mixture.

Does it wear out the rims? In theory yes - about as much as braking over a distance of about 30ft in wet gritty conditions ONCE might. And the material removed is insignificant compared to whats removed when brake walls are CNC machined for uniformity.

The reality is pretty simple. Aluminum gets polished by the brake pads particularly if the pads are glazed. And rough surfaces have more friction. So as well as removing any brake pad glazing with a 280 grit sanding block, I also refresh the surface of the braking surface on the rims with a 380 grit wet sandpaper. Yeah - it does make a noticable difference and no - I`ve yet to have to change a rim thats been worn out for any reason on any bike that wasn`t used for extended touring.

I sanded the brake pads today and braking is way better than before. I also cleaned the rims and pads with some cleaner. The pads felt slippery before I sanded them but a couple seconds of sanding with 220 grit sand paper made them feel like new again. Thanks for the help guys!

And I am gonna stay away from sanding my rims right now, but if I upgrade rims later I will sand my current ones and see if the braking is improved.