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Anyone ever rebuilt entire brake system off the bike?

3K views 26 replies 11 participants last post by  1Slowrider 
#1 ·
I've been fixing up my 2002 GSXR here and there, it is low miles, but the brake lines are 14+ years old. And, the back brake is squealing. And, the top of the rear master cylinder reservoir hose looks a bit moist, although in 500 miles the reservoir does not appear to have dropped the level any, and the brakes still work well. Other than the squealing....

I'm thinking, rear brake overhaul may be the next project I take on. I've got a few questions for you gents:

1) I've never had braided steel lines before on a bike. Is there any chance the brakes will work too well? I know that sounds crazy, but, I'd not want the back brake to become a toggle switch.. Do braided steel lines eliminate "feel"?
2) I know the factory service manual recommends inspection/replacement of old brake lines. And, I want to replace the caliper piston seals, polish the pistons, inspect calipers, etc. BUT- should I also rebuild the master cylinder, and replace it's seals? Again, low miles, and everything is working, but- this stuff is getting old, and I like to be able to stop....
3) Anyone ever built like a 2x4 fixture to mount caliper, master cylinder, lines, reservoir, put an old disc rotor on it, and rebuild/bleed the brakes on the fixture? Seems this would eliminate any worries about spills, and could be mounted on a bench for comfy mounting/cleaning/bleeding.

Thoughts?
Jason
 
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#2 ·
Well I haven't done the brakes on my gixxer yet but have on my other bikes and it's not that bad. Any old bike could use it despite miles - rubber o rings and lines harden and degrade with time. It's a very doable job. Not sure where to get a good rebuild kit for the calipers so I'd be inclined to pull all the exact part #'s from the fiches and order OEM.

Some people let a tiny bit of air in the system, especially on rears, to get rid of the bite and provide a little bit of squish if you want a more progressive feel.

Hopefully some others can chime in who have more experience on your bike!
 
#3 ·
Ok, first off, no one I know of, or have ever met, leaves air in the brake system. That is just bad and dangerous advice.

Rebuilding the brakes is easily done on the bike, cleanly as well. No need for a brake jig.

Braided lines give you more feel and feedback, but also more stopping power and consistency. So if you are confident you aren't ham-fisted (or footed in this case), braided lines will be an improvement.

No, don't bother rebuilding the m/c unless you are leaking from it.
 
#6 ·
I know a lot of AMA and MotoAmerica pro racers. Not a single one (or their mechanics) would leave air in a brake system.
 
#8 ·
Well I wouldn't take my "advice" over more experienced riders. I never leave air in the brakes ever - only shared that in response to the concern about locking up the rear, passing along something I heard. Of course most racers don't touch their rear brakes, but I don't see the danger in softening up the rear to avoid locking it up in a corner if you do use it, since obviously you aren't relying on the rear for braking power but to stabilize the bike a bit.
 
#9 ·
Again, untrue. Every fast pro racer uses their rear brake. It is especially important as you get faster and need to be competitive. Using the rear brake to control your line mid-corner, or to settle the chassis is key.
 
#10 ·
DO NOT POLISH THE PISTONS.

I hope I made myself clear. The pistons have low friction coatings or anodising at a minimum. They only need to be cleaned or replaced.

The stock calipers are shite as they flex too much resulting in poor feel. A set of good condition 4 piston 750 calipers would be a significant upgrade. Or Honda 929, 954 Nissin calipers. They require some modification for clearance though.

Braided lines are a must and are becoming standard OEM equipment on many new bikes now.

Air in the braking system is just plain stupid as others have said. If there is a braking issue, it needs to be sorted out with some engineering knowledge. Friction materials, master - slave ratios, lines etc.
 
#11 ·
DO NOT POLISH THE PISTONS.

I hope I made myself clear. The pistons have low friction coatings or anodising at a minimum. They only need to be cleaned or replaced.
Thank you! Yes- I'm in the research phase so far, and collecting parts too. I will be reading up more and more- there's a good sticky here too that I've just started reading. But, this will go in my notes- just clean.

The stock calipers are shite as they flex too much resulting in poor feel. A set of good condition 4 piston 750 calipers would be a significant upgrade. Or Honda 929, 954 Nissin calipers. They require some modification for clearance though.
Is the 4 piston 750 caliper retro-fit a plug and play? Or is there a bit of work to do to get it all to match up?

Jason
 
#14 ·
Or ANY Suzuki for that matter. :lmao

But yeah, those gold 6 Pots from the K1 - K2 1000 definitely suck. I put them on my K1 750 back in the day. Biggest, ass backwards mod I've ever done in my life. I even stripped a banjo bolt in the process. :facepalm
 
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#16 ·
I've done a full overhaul (wouldn't call it a rebuild) of the brake system on my K4 as well as an 02 SV650. I would say off the bike because brake fluid is bad for anything other than brakes. You just need to be sure you know what you're doing... like using compressed air instead of pliers to get the pistons out and not polishing the coatings off the pistons. It's not hard to do if you take your time and pay attention to detail. Keep everything super clean and you're good to go.
 
#24 ·
I rebuilt both of the front calipers on my 2002 600 and it was a surprisingly easy job. The Tokico calipers are put together in a very intuitive way. The seals were in flawless condition as were the pistons (minus some grime on the exposed parts) so I don't know how necessary replacing them would be. The biggest issue I had was solidified brake fluid that got stuck inside the caliper. I had to use a vacuum to dislodge it.

Not to hijack your thread, but my rear brake is not holding pressure. If I bleed it, it works well for a few days and then slowly returns to being useless. Air is getting into the line somehow. There is no leak as the fluid level is unchanged in the rear reservoir. Anyone have any idea what the hell it could be? I bought a new SS brake line but I wonder if the issue is related to the master cylinder assembly as a whole.
 
#25 ·
Pull the little boot off the MC that protects the plunger. Does it look dirty? I've seen systems that had worn seals on the MC allow air in. Usually, if that's happening a little fluid will seep out too and make this area look dirty, which it shouldn't because of the boot.
 
#26 ·
So, I don't have compressed air, and would like to avoid taking the calipers to a shop to ask those guys to push my pistons out for me. I've heard of guys using a grease gun to push the pistons out, and then using solvent to remove the grease. Seems doable to me with what I have here, but, thought I'd ask here first.. Grease give anyone heartburn? As long as I clean it all out of the caliper and pistons when I'm done- should be no big deal, right?

Also, I'm thinking I'd like to try my vacuum bleeder when it is time to get the fluid out and back in to the system. I've seen a LOT of people not so happy with the vacuum setup, but, I bought this thing years ago, and I'd really like to try it to justify its existence in my toolbox, and if it does OK bleeding the brakes- it will be an easier job for me.

Watching youtube vids of dudes using these tell me that problems/hatred/mess when using these vacuum bleeders come from the fittings leaking. I'd like to use a grease around the fittings to block any leaks if needed. As near as I can tell, this stuff (Permatex Ultra Disc Brake Caliper Lube: https://www.permatex.com/products/l...kes/permatex-ultra-disc-brake-caliper-lube-4/) should be OK to use, and not contaminate the DOT4 system, correct?
 
#27 ·
If they aren't disassembled yet you can use the lever to get the pistons most of the way out. use wooden wedges / spacers till they are almost out. then take off the lines...... should be able to remove them if they are far enough out.
 
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