rdna

Extremely well explained My rear disc on my RTR feels useless and I'm really not comfortable doing these kind of DIYs. Is there anything in particular I should ask the service center guys to do/check when I give it to them? How long does it take? I'm not comfortable leaving the bike with them for a whole day just for this.

Old Fox

Tell them to check for air in the brake system. There's a procedure for bleeding air from the system. Also get the brake pads checked for wear. Pads worn too thin can damage the disc surface and don't provide good braking.

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kaynmantis

This thread encouraged me to change my disc pads. Actually the service center was too busy at the time and I didn't have time so when I reached home, I read the original post again and off I went to change the pads for the first time.

It was pretty straight forward. I just followed the instructions here. No hassle. Got the old pads removed in no time. The "fun" started when I had to put the new pads.

You see, this problem was not specifically mentioned in the original instructions. And as a novice, I had to find out the hard way . I hope my experience can add some value to this thread.

Now the problem. Since my old pads were so worn out, almost scraping the metal, the pistons were pushed out quiet a bit. This is inherent to hydraulic system compensating as the pads gets thinner. This means the new pads which are considerably thicker were not able to fit in, let alone making space for the disc to fit without pushing back the pistons. Bare hands were not going to help here (I tried). Seems people uses "C-clamp" to push back the pistons. I didn't have one. By this time it was too dark to continue. Decided to continue in the morning. In the mean time, I googled how to push back the pistons. C-clamp seems to be the preferred method. Another method I found is to bleed the fluid. Since I don't have a c-clamp, I thought I'd try this.

Next morning, I unscrew the bleeding nuts a bit and at the same time, using a 'monkey plier' pushed back the pistons. Voila, it went back without much effort. I re-tightened the bleeding nuts. Now both new pads were in with sufficient space for the disc to slide in. I put back everything back and everything is fine.

Yes, I'm aware of the danger of air getting in the system using the bleeding method to push back the pistons. Its no big deal as I can bleed the braking system again and filled new fluid which anyway is very easy.

Next on my shopping list. Get a c-clamp.

Old Fox

You did find a way though there is a better option without resorting to using the bleed-screw, risking air leakage into the system and loosing some brake fluid. Just open the top lid of the reservoir (mounted next to the front brake lever) and gently...very gently push back the pistons. The fluid needs space to go back and opening the reservoir lid gives it just that. Though this needs a few precautions vis a vis covering the tank and other painted surfaces with a cloth or something to avoid brake fluid spills from damaging it. Also, if you're a trifle quick in pushing back the pistons, a jet of brake fluid will shoot upwards from the reservoir . This is the famed Brahma Press in the reverse you see. Grabbing the pistons with a C-clamp and Slowly screwing it in would do the job pretty well.

One imp note here: Never push the pistons in against the pressure of the hydraulic fluid. Give the fluid some space to expand by either opening the lid of the reservoir or slightly loosening the bleed-screw. Liquids don't compress and using undue force will only end up in damaging the system components (the piston seals in particular).

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roshan3440

I got a doubt regarding new brake pads.... Other than pushing back the pistons, Do we need to prepare the new pads as in using emery on it before first use or is it to be installed directly without any preparation ?

Old Fox

No, you can usually use the pads as they are in the packing though if possible, very light polishing with 180 or 220 grade emery will just take off the production sheen and give you gripper brakes from the outset. That sheen does get rubbed off in a few kilometers of road use though.

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