Front brakes query

[Kendo]

I just bought an R1100 RT 1998,  beautiful bike.  But been trying to bleed the front brakes. Was a bit nasty and brown, but flushed it through with fresh. Prev owner replaced the tyres, battery, and pads along with an oil and filter change. However front brakes are a bit spongey. Ie they are until the lever is pulled, then they firm up. They work fine in any event, but normally I would have said classic signs of air in the fluid. They improved a bit after new fluid, no signs of air in the fluid, but if you leave it for a couple of minutes even after one squeeze, they go soft again.

I don't want to have to remove the fuel tank and bleed it on the tower, but if that's what's needed. So be it. Just looking for some advice really. I'm going to change the fluid in the rear too during the week, but don't relish taking all the panels off along with the tank. 

[dirtrider]

17 minutes ago, Kendo said:

I just bought an R1100 RT 1998,  beautiful bike.  But been trying to bleed the front brakes. Was a bit nasty and brown, but flushed it through with fresh. Prev owner replaced the tyres, battery, and pads along with an oil and filter change. However front brakes are a bit spongey. Ie they are until the lever is pulled, then they firm up. They work fine in any event, but normally I would have said classic signs of air in the fluid. They improved a bit after new fluid, no signs of air in the fluid, but if you leave it for a couple of minutes even after one squeeze, they go soft again.

I don't want to have to remove the fuel tank and bleed it on the tower, but if that's what's needed. So be it. Just looking for some advice really. I'm going to change the fluid in the rear too during the week, but don't relish taking all the panels off along with the tank. 

 

Afternoon Kendo

 

Did you push the front caliper pistons back into their bores then hold them there during the bleed? If not then try prying the brake pads back off the rotor then use some sort of shim to hold them there during the bleed process.  

 

If still spongy then you will probably have to bleed the bleeder fitting on the ABS module (usually a little air gets trapped there).

 

OR- possibly try riding the bike for a short while THEN re-bleeding (sometimes the riding & brake usage will allow the air-in-the-fluid  to free up to point that you can then bleed it out).   

 

The other possibility is that you don't have actual air in the system but have old degraded brake hoses (somewhat common on older BMW bikes). As you squeeze the lever the hoses can swell up  & the lever feels spongy  like air in the system. After a few pumps the hose swelling stops then you get a firmer lever feel.

 

On older BMW 1100/1150 bikes the brake hoses REALLY should be replaced if original/

[Michaelr11]

Along with everything that DR said to you, try pumping the lever so it’s firm and then put a couple of rubber bands there to hold the lever in that position. Leave it that way overnight. If the problem was a small air bubble, this should push it out.

 

[Paul De]

21 hours ago, dirtrider said:

The other possibility is that you don't have actual air in the system but have old degraded brake hoses (somewhat common on older BMW bikes).

 

Kendo,  On a 21 year old bike I was leaning toward brake lines if they are still the original OEM rubber hoses. The OEM lines gave a touch of a spongy feel even when new and time would only make that worse.  I waited a little too long on my '99RT and had one line start to leak a few years back, so it is prudent to replace OEM brake lines now regardless of air in the system or not. There are very high quality made to fit kits available from either Galfer or Spiegler.  They are comparable quality so you should buy the best deal you can find.  Both offer kits using vinyl covered braided stainless steel hoses which is a nice upgrade to the OEM hoses used on that bike.  The braided SS lines will  also noticeably improve brake feel over OEM as well.

[Kendo]

Thanks folk, I will try all of your suggestions, the last being to replace the hoses. I'll let you know how I get on in due course. In the UK I use Hel brake lines on my other bikes. Usually superb.   But I'll try the easy stuff first. 😁 

[AndyS]

13 minutes ago, Kendo said:

 In the UK I use Hel brake lines on my other bikes. 

 

 

Motorworks supply Goodridge hoses for your model.

[Lowndes]

Kendo,

 

You REALLY are living on borrowed time with those OEM brake lines.  DOT4 degrades them over time (NOT miles).  Replace ALL of the "rubber" lines including the clutch lines.

 

The front brakes on my '99 R1100S locked up from decomposing OEM brake lines.  The other failure mode is the aneurysm DR describes above.

 

We have Galfer and Spiegler brake line kits over here that are PTFE with SS braided and sheathed and very well made.  My complete kit, clutch lines and all, was about $210 USD several years back.  ZERO issues since then.

[James in OK]

Hoses should be first.  That's a ticking time bomb.  And you'll be happy with the brake feel after it's done!

[Selden]

On 6/20/2019 at 10:09 AM, Kendo said:

Thanks folk, I will try all of your suggestions, the last being to replace the hoses. I'll let you know how I get on in due course. In the UK I use Hel brake lines on my other bikes. Usually superb.   But I'll try the easy stuff first. 😁 

 

Not what you want to hear, but on a 20-year old bike, replacing the rubber brake line hoses should be the first thing you do. Those OEM hoses are living on borrowed time.

[Kendo]

Thanks, will be ordering new lines next month. 😁 Weather's good, so back on the Harley for now. 

[Kerlaan]

Check your lower left hose to the brake calliper before you ride next, prior to the new lines.  Pump the brake lever and then look for a bulge at the top of the flexible tube as in connects to the solid line.  This has happened on a couple of R1100RT that passed my eye and also existed on the 130,000km one I just bought.  I would have videoed and posted of the phenomena were it not for me stripping the brakes down yesterday.  I am fitting new Goodrich lines.  Make sure you use DOT4 fluid.