Hey To All...

I have an '05 RKC with about 12K miles on it. Back when I had the 10K service done I also had both tires replaced. When I picked up the bike I noticed the front brake lever had a LOT of travel in it, certainly more than it had before the service. I found this out when I left the shop and found myself having to do a pucker move because I grabbed the brake lever, squeezed, and nothing was happening. I spun around and headed back to the shop. Of course the story was "We didn't do anything with the hydraulic system. All we did was remove the calipers to remove the wheel. The way they feel now is the way they are suppose to be. If they were harder than it is now then there was something else wrong to begin with and we 'fixed' it by removing the calipers". Ummmm......yeah. I went 'round and 'round with the owner and finally said "screw it, I'll take it to a shop that knows what they're doing"

Being an auto mechanic since way back when, I do have the tools and mechanically inclined. The brake lever will get tight after I pump them about 3 - 4 times. So, I have since bled the system in different ways using different methods. I can say there is no air in the lines. So I went to the next step. I put the bike on the jack and spun the front tire...it had a good resistance from the pads contacting the rotor. I removed the right caliper and I had to wiggle it to get it removed...good contact from the pads to the rotor. I now spin the tire and it spins free. I remove the left side caliper and it all but falls free from the rotor.....hardly any contact from the pads to the rotor. So...I install the right side caliper and squeeze the brakes to get the pistons to extend out a bit in the left caliper and reinstall it. I had to work it on to get the rotor to fit between the pads which tells me I now have good contact between the pads and rotor. This did the trick...I grabbed the brake lever and it was tight. However that only lasted a few days. I double checked everything again and the left caliper seems to lose its contact pressure with the rotor as if the caliper pistons are retracting too far back into the caliper. This would account for the reason I can pump the brakes and get a hard lever but when I let go the pistons suck back into the caliper bores and I'm back to square one. I'm tired of having to pump the front brakes so I can use them. There are no other problems such as noise, squeeling, vibration, warpage, etc.

So....now I'm looking for any ideas. Replace the caliper? Replace both calipers? Hit it with a big hammer? (jk)


Thanks much,
Brian

 

Sounds like the left one needs to be rebuilt. I know I have seen a post in here somewhere about calipers that stick and the fix for it. You might try looking in the DIY section. Good luck.

 

I don't think the calipers need rebuilding. Normally I replace pads when I replace tires. Check the fluid level in the master cylinder, it may be low. When you replace tires, you have to spread the pads a tad when you slip the wheel off. When you go back on with the wheel, you need to slip the rotor between the pads. Before you go anywhere, you have to pump the brakes up to reseat the pads against the rotor.

If you have one side giving you trouble, they may have left the rotor on the wheel and during the tire mount operation warped the rotor. The only way to check this is with a dial indicator against the rotor surface and eliminate any steering play to check while rotating the wheel. Warped rotors on a bike will make you think that you have lost all brakes. it takes about three pumps to pump them up.

 

Well I can say that the fluid is not low as I made sure everything was as it should be while bleeding the system and topped it all off. From the auto industry it's fairly common the have the pistons stick in the bore and keep too much pressure on the pads which will result in premature pad wear. However I've never seen a problem where the pistons retract too far back into the caliper.

Any other ideas out there? I just did some work on an '06 RKC and I couldn't believe how tight his front brake lever felt compared to mine.....the way mine use to be.


Thanks,
Brian

 

Still sounds like there is air in the lines. The brakes are notoriously hard to bleed.

Did you use a power bleeder? Also, isn't there a proportioning valve under the steering head? Maybe its been tampered with.

I wonder if they cracked a line when they let the calipers hang from the hose while changing your tire.

 

Hey Adam...

I used a power vacuum bleeder and went through quit a bit of fluid just to make sure all was well. I also removed the brake line "T" that is under the steering head (in the triple tree area) from its mount so I could tap on it, and the hard lines, as I was bleeding the brakes. Up to this point I have lost no fluid which would be the case if a line was cracked. It just seems strange that it has been isolated down to just the left side caliper.

Thanks for the reply.


Brian

 

I have no idea whether you have any air in the brake line or not. But, here's a tip that helped me when I replaced the front brake lines recently. I was having a difficult time getting all the air out of the lines. I pumped until I had ran a bottle of brake fluid through the system so I quit. Next day, I pick up another bottle and got to thinking about something I read on this forum so I tried it.

I pulled the front calipers off one at a time, opened the bleeder on each one at a time and forced the caliper pistons back into the caliper as far as I could get them by pushing on the brake pad. After I went through that process, I bled the brakes using the coventional method and after pumping and bleeding each caliper twice, I had a full pedal.

It appears that there may be a small amount of air that had been trapped somehow behind the caliper pistons and by forcing them all the way back, the air was pushed out.