Need help with front brakes

  #1  
Old 07-26-2018, 05:13 PM
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Default Need help with front brakes

I bought a 2009 cbr600rr with about 15k miles that had 1 owner and was never crashed but apparently dropped in the garage and has minor scratches. The only real issue with the bike is a spongy front brake lever. I bled all 3 nipples using an air compressor but that method didn't work. I decided to try it manually to see if that would help but it didn't work either. Here's the issue. After I bled the brakes it was fine until I rolled the bike backwards a few feet or forwards a few feet. I've done my research and my conclusions are either one or both rotors are warped or the master cylinder needs to be rebuilt or replaced. I guess the brake lines could be the issue too because they appear to be original. I was thinking about taking the master cylinder off the bike to bench test it but I'm not sure how to check for warped rotors. It seems logical that a rotor got bent when the bike was dropped or that the master cylinder needs to be rebuilt but I'm not sure what to do next. Please help.
 
  #2  
Old 07-27-2018, 06:58 PM
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If your only issue is a spongy feel to your front brake, then by either bleeding the brakes or adjusting your lever or both, you would normally be able to achieve the feel of response you want and have full stopping power. However, if a component is failing somewhere you’ll have to dig a little deeper to solve your problem.
If you have a warped disc you will know about it. Your braking performance will be noticeably poorer than when everything is working properly. This tends to be more noticeable at lower speeds coming to a stop. It will feel notchy and you might feel pulsing at your lever. There are a few ways to actually prove this but a front wheel paddock stand is essential.
A simple spin with the wheel raised would be the first thing. Use your lever and listen. Now you could have binding pads caused by the caliper pistons binding or a master cylinder issue but if you think it’s a disc, you can prove which one and where.
Either get a marker fixed (taped or cable tied etc) so it sits almost touching your disc and spin the wheel. Or just scribble over the disc and spin. Your looking for marks appearing or disappearing depending on the method you use.
Why not remove your calipers and give them a clean up ? Pads out and some soapy water with an old toothbrush followed by some aerosol brake cleaner. Then use some fresh fluid to replace the old. It’s the same principle as a bleed and only takes a little longer. This also takes another possible culprit out of your issue.
Sure you’ll sort it but post how your getting on. Best of luck mate.
Btw.... what do you mean by “ after I rolled it forwards or backwards a few feet” ?
 

Last edited by wes 17; 07-27-2018 at 07:01 PM.
  #3  
Old 07-28-2018, 03:33 PM
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I'm going to be ordering a triple tree from amazon today but it will take a week to get here. I looked at the brakes again and it looks like the front pads need to be replaced. If the front pads are worn down beyond the requirements would that lead to a spongy front brake? Could it be possible that if I change both front brake pads and bleed the brakes again that might solve my problem?
 
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Old 07-28-2018, 03:39 PM
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Also I found 2 different types of brake pads but I can't tell which one is correct. I found EBC brakes FA390HH disc brake pad set and EBC brakes FA436HH disc brake pad set. They both claim to fit a 2009 CBR600RR but I can tell visually they are different. The 390 has a line down the middle almost making it 2 pads and it has a more square shape. Without taking the pads off I think the 436 would be the type that I want, correct?
 
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Old 07-28-2018, 06:37 PM
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If your pads are heavily worn then changing them and flushing your fluid would definitely help, and more than likely remove the spongy feel at your lever.
Minimum thickness should not really be below about 2mm.
Sorry but I can’t help you with your pad replacements but sure a fellow owner of your model will be along to help you out.
Best of luck mate.
 
  #6  
Old 07-28-2018, 07:05 PM
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I checked out a video on youtube and realized a triple tree is not required to remove the brakes. I took off the front left caliper and removed both brake pads. The one side has maybe 1-2mm and the other side has like 2-3mm so I am definitely replacing them. I can also tell now which pads to buy and it's the FA390HH. I am going to order new pads and some more dot 4 fluid and see if this fixes the issue. Hopefully the pads were just so worn that somehow that was resulting in the spongy feeling. Thanks for your help.
 
  #7  
Old 07-28-2018, 07:15 PM
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This is a more technical question but I'm hoping to understand the brakes a little better. If the pads are worn down significantly then the piston has to travel out farther which results in the brake fluid dropping correct? If the reservoir is full or topped off would you still have a spongy feeling from significantly worn pads? Do the pistons on the caliper only come out a certain distance? Is the spongy brake feeling because the piston is extended all the way but since the pads are so worn they are not making proper contact with the rotor to stop the wheel from rotating? I'm just trying to understand the mechanics. Thanks again for your help.
 
  #8  
Old 07-29-2018, 05:16 AM
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Good thoughts mate. Now your starting to understand your issue.Your caliper pistons are capable of squeezing your pads down to the metal backing plate so get those new pads on ASAP.
 
  #9  
Old 07-31-2018, 04:10 PM
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Alright so I just replaced the front brakes and then bled them but I'm still having issues. The brakes were good but after I took the bike down and tried to move the bike backwards I noticed the pads were catching and creating friction preventing the bike from moving naturally. Then the brakes went spongy again. I also noticed when I took the pads off the left side that they were significantly more worn than the right side. I'm thinking I have a warped disc but I'm not sure. Thoughts?
 
  #10  
Old 08-02-2018, 10:11 AM
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From my initial post I enquired about your “rolling cowards and backwards” statement.
When I reseat my calipers after removal I pull my lever in and hold it there, then tighten the bolts up.

One thing at a time to resolve you problem mate.
The caliper pistons need proving so it’s pads out time, some pipe attached to your bleed nipple and work that lever, bleed nipple and get those pistons moving in and out freely. Keep an eye on your fluid levels at this stage and cover paintwork etc..Check your seals whilst your doing this. The pads retaining pin should also be checked showing that the pads slide freely through it.
Once your happy, reseat as discussed and flush/bleed the system.
I imagine that during this, if you have a warped disc it will become apparent or use one of the methods described earlier. If all this fails then maybe it’s time to look further back than discs and calipers.
Best of luck mate
 

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