Partial ABS-ectomy

[Boffin]

My iABS system recently decided to die. The unit passed start-up and ride-away self tests but failed under braking. The symptoms I had were, on use of the front brake lever only, General Warning lamp on and Brake Failure flashing at 4hz (which indicates at least one brake in residual braking mode) but servos OK. If, as normal, I also touched the rear lever the brakes both went into residual mode - which in traffic is terrifying.

At home, I found that as I slowly increased lever pressure, the general warning lamp would start to flicker and if i then released the pressure would go out again. If however, I continued to increase the pressure then the brake failure light started to flash and the fault latched until next restart.

 

I got a quote for a new iABS unit of £1450 - about $2100 at current rates. Used units cost around £300-£400 but I could find none available in the UK - both of the major UK BMW specialist breakers say good units are rare as hens-teeth - so I decided to go for an ABS-ectomy.

 

There is an added complication in the UK now, in that if ABS is fitted to the bike, then the warning lights must follow normal start-up sequence and not indicate a failure to pass the annual MoT test (mandatory safety inspection). In theory, if I remove _all_ ABS components, then that is ok, but it relies on the tester being sensible.

 

What I have done is to cut and seal the hard lines coming from the iABS pump.

I then fitted bypass loops to connect the two master cylinders to the callipers and bled them through. The front bypass has two different sized pipe unions (M10 and M11 I think) - I bought a ready-made pipe from a UK supplier (Motorworks). The rear has standard m10x1.0 unions and so I made my own pipe - though I am told the pipe from a non-abs GS fits.

 

This now gives me normal function of the brake/tail lights and powerful brakes with good feel. The bonus is that the ABS lights go through their normal start-up sequence and do not indicate failure. Even the servo-pump motors start when the brake levers are operated, but with no input pressure there is no output pressure.

 

All-in-all this was a quick and easy job.

 

Pros:- Smooth, powerful brakes with good feel and no risk of "residual" braking.

Easy to do, with no changing of brake-light switches or wiring looms.

For the UK, MoT friendly ABS lights.

 

Cons:-

No ABS (obviously)

No weight-saving by ditching the large, heavy ABS unit.

No handy extra space under the tank.

 

 

I informed my insurance company, who had no problem with the modification, so no increase in premium.

 

My bike is back on the road and I am a happy chap again.

 

Andy

 

[dirtrider]

Afternoon Andy

 

Is the ABS controller still full of brake fluid? If not the pumps will burn up in short order as the brake fluid is the lubricant.

 

[Boffin]

Yes, I made sure they were topped off before I sealed the cut pipes.

 

Andy