GSXR brake caliper rebuild

[JimClark49]

Hi all,

Was cleaning my Tokico calipers today. Pumped lever, and one troublesome piston's rubber seal came part way out. I ended up opening the entire caliper and will do a full replacement of seals.

Two pistons were rather troublesome in getting out, and I ended up scratching the surface with my mole grip. Picture attached below. Is this damage OK, or will I need new pistons? I am assuming that because the seal sits lower, the scratch shouldn't matter too much and they will not leak.






Also, on recent MOT, I was advised brake pads need changing. Looking at them, it seems they have quite a lot of material left....I am a fast road rider, and use my brakes hard....do you think these need replacing or could I get another 500 - 1000 miles?

[JimClark49]

Ok thanks mate.

And how would I put them back in, just push them in with my fingers?

Also, are there any special considerations for bleeding the system of air, or do I just put the caliper back together and bleed as normal?

[JimClark49]

Why do we fall? So we can learn to get back up again!

The other pistons are fine, they popped out easy, but these two were stuck and only came a quarter of the way out on pumping the lever.

I have ordered new pistons and a seal set today. I am enjoying working on the calipers and its an easy enough job. The bike is on 28k and calipers were in good nick, so this rebuild should hopefully see another 28k.

Also bought the brake bleeder. If I am right, do I just crack open the caliper bleed nipple and suck through until brake fluid comes out into collecting jar?

[JimClark49]

kev b said:

When you have all the seals removed, clean out the grooves perfectly with something soft enough not to scratch the alloy.

If you don't clean all the furry corrosion and gunge out, your new pistons will soon stick like the old ones, also, use plenty of rubber grease when fitting the seals, this will help assembly and protect from corrosion for a while.

Thanks for the tips mate.

I tried to clean grooves best I can with brake cleaner and toothbrush but couldn't get rid of all the corrosion.

Will castrol red rubber grease suffice for the seals? Do i just coat seals and push these in place on the caliper?

[JimClark49]

Thanks for further suggestions.

I am quite happy that most of the caliper grooves are cleaned and I don't think the little bit of corrosion will negatively effect anything. After all - the calipers were working nicely before I decided to strip them.

New pistons and seals arrived today - so I will coat seal with red grease and slot them in place. I will then put some brake fluid around piston and push them in - should they be ALL the way in or does it not really matter?

Also - whats the deal with cable tie-ing the brake lever following a brake bleed?

[JimClark49]

Hi All,

Pistons are in, calipers joined back together, and vacuum pump to bleed brakes is here.

Is the procedure for using pump to bleed brakes as follows:

1) suck old fluid out of reservoir using vacuum pump
2) add new fluid to reservoir
3) Go to caliper opposite the reservoir (i.e nearside), attach bleeder hose, create 10 - 15mmHg vacuum, and then crack open bleed nipple to allow fluid to come out into container
4) keep doing this until fluid comes out clear with no air bubbles
5) Repeat process on offside caliper.
6) Finally use vacuum to bleed at master cylinder until clear fluid (with no bubbles) comes out.
7) Check lever is nice and firm and put the reservoir cap back on

Am I listing the steps correctly? Anything I have missed?

[JimClark49]

gwm said:

https://www.youtube.com/watch?v=MPL7bpgcmVI

Basically that's it, though I would start at the master cylinder and work towards the furthest away caliper. Just don't let the fluid in the reservoir drop below minimum and keep the vacuum pressure up.

Thanks mate.

The reason I thought master cylinder is last is because air rises, and the cylinder is at the highest point.

[JimClark49]

I tried to bleed the system today with vacuum pump but there is still air in the system as lever is still very soft.

I am not sure what I am doing wrong, how much fluid should I take out of each caliper and M/C? Instruction manual for pump says about 2 inch of fluid.