Soft front brakes

[jimbo]

Can anybody offer me any advice on why my front brakes remain so 'soft'?
The MOT guy warned me that the front pads were wearing unevenly, so I dicided to strip the calipers down.
When I took it apart I discovered that the pads were wearing fine, but decided to clear things up anyway.
So I popped out the pistons and cleaned things up then fitted new pads.

Since then the lever has been soft. I've bled it through multiple times. Its just about ride-able with the abs on a dry road cutting in as the level hits the grips.

there is some pump-up, so I used a cable tie to hold the pressure up overnight. Next day better, but it gradually went soft again (hours not minutes).

So what have I done? I can think of 2 options:
- Either I have not seated the pistons properly somehow?
- I have knackered the brake pipes by leaving them clamped for a few days while I did the calipers? I guess the pressure over night 'pushes' out any dent in the flexible pipe? odd it doesn't stay OK?

Anyway the second seems to make more sense, but I don't really want to buy new pipes unless I'm fairly sure it'll do the trick.

Any other ideas?

 

[Packer]

You haven't told us which model but I'm assuming that it's servo assisted.

You have removed the tank to refill the servo/ABS system haven't you?

If the brakes work and the calipers aren't leaking fluid then I would think that the pistons must be installed correctly.

Also, the front lever activates the rear brake on these models so you may need to look at the rear as well.

There are pictures of the ABS unit and how to top it up in here and on Advrider.com

 

[robc]

Hi Jimbo,
I sometimes get this. If I remove the front wheel and forget to tie the calipers to the mudguard and leave them to hang then I get a soft front brake too. Obviously, some air gets in. Like you, I can pump the lever once or twice then get a normal lever. It then goes soft again.

Over time - a few days of commuting - seems to purge all of the air out of my brake leaving me with a firm lever again.

I've learned to accept is as a characteristic of my bike. It's an 02 non servo GS.

Regards

Rob C

 

[jimbo]

Sorry - its an ABS non-servo brake system 2001 bike.

I did lift the tank (and filled my shoes with petrol as a bonus) and bled through the nipple on the ABS unit.

 

[Boxergs]

Blebs on hoses

Have you checked the hoses to see if there are any blebs?...mine did same, had to replace hoses.

 

[robc]

Bleb. Now there is a word from my childhood. I grew up in County Durham and it was a common word. I've never heard it since I move daaan saaarf.

Regards

Rob C

 

[andy white]

Sounds like air in the fluid to me, there only needs to be a tiny amount of bubbles to give a poor feel. Did you use a Mityvac or speed bleed, or did you bleed the system the traditional way?

 

[John Armstrong]

On my 100GS I found the front brake a bit soft at times. After going up and down a few Dolomites passes two up, the feel at the lever seemed to be quite a bit harder. Whether it was the fluid getting very hot and dispersing any air back to the master cylinder, or the reduced air pressure at the top of the passes doing the same, or a combination of the two, I don't know.

 

[dancerdave]

are they still the original hoses? That was the problem on my 2000 non servo abs bike. Braided hoses fitted by Jaythro, and problem solved