Effect of servo removal

[Hubs]

Hi, having had the 4 hz warning light, residual braking at the rear, no servo at standstill when starting for about a year, I removed the servo system with the revised removal process which uses a relay to fix e electrics easily.

The true test is how the brakes feel afterwards, which is not as easy to find as the approach to removal!

Here's my take.

Rear brake - short pedal travel, loads of power, having to watch for rear lock ups now. No noise in use, brake lights working fine.

Front brake - loads of power, needs a strong pull to get it working hard, but perfectly acceptable. There is more travel at the lever for the initial braking point, but it modulates nicely, feels more controllable. Also, at standstill / engine off, still have a working brake. Brake light works fine. Also, silent in use, no whining at traffic lights.

Note: did 50 miles today, have in mind to check brake temperatures to make sure both sides ok. But that's it. Sweet modification, cost me £19 for a new rear hose and £3 for connectors.

Bike is a 2002 1150GSA

Any other views?

 

[sockpuppet]

2002 gsa? I thought that servos were from 2003?

 

[Hubs]

2003 model year, available in 2002. 52 plate. Big lump of useless abs servo on the floor in the shed now.

 

[DollyRocket]

Big lump of useless abs servo on the floor in the shed now.

You should make the new filtering aid (see the show us your ... thread..)

For me,

Back Brake - Brilliant, can lockup and rear wheel slide - far better than before - you really notice the bike hunker down when you use the brake which you never noticed before.

Front brake - No initial bite, and more lever travel, still good performance but not quite as much as before. I will have a fiddle to see if I can take out the lever travel.

On the whole - I am relieved to have got rid of the servo having had two go on me (both on the motorway slip roads!), the brakes without the servo are no worse than on my ktm even though it is a heavier bike.

I do notice that you do need to use both brakes at all times (as they are no-longer linked) to stop swiftly, but I still can't get over how powerful the rear brake is (i used to think it was a a token effort with the servo assist) but it really is good. Love it.

 

[se7en]

Rear brake does take a bit of getting used to

It's an easy adjustment to shorten the link rod that has the effect of lowering the brake pedal so you have to move your foot a little more before the brake bites - you may find this suits you better.

On the front, I haven't found any less power - it just doesn't have the initial grab of the servo brakes. Personally, I find this gives me much better feel over the braking.

 

[(RIP) Mark H]

Re the rear brake comments (Easy to lock the wheel, worse and somewhat dangerous in the wet I guess) The problem might be resolved by fitting a rear pedal cylinder with a smaller piston, this would require more foot pressure to get the same braking force and make it harder to lock the rear wheel, I guess a bit of research would be needed to find a suitable sized cylinder and fitting it but not difficult to do, would make the brake less fierce, Just a thought

1/2 hour later
Done a bit of research, Master cyl (Rear) piston Dia for 1100 R,RS,RT models 12mm, GS models 13mm, this from my R850/1100 Haynes manual, so if a R1100RT master cylinder could be fitted to a 1200gs the rear brake should be less fierce

 

[Myke Rocks]

Before you get yourself killified!

Re the rear brake comments (Easy to lock the wheel, worse and somewhat dangerous in the wet I guess) The problem might be resolved by fitting a rear pedal cylinder with a smaller piston, this would require more foot pressure to get the same braking force and make it harder to lock the rear wheel, I guess a bit of research would be needed to find a suitable sized cylinder and fitting it but not difficult to do, would make the brake less fierce, Just a thought

1/2 hour later
Done a bit of research, Master cyl (Rear) piston Dia for 1100 R,RS,RT models 12mm, GS models 13mm, this from my R850/1100 Haynes manual, so if a R1100RT master cylinder could be fitted to a 1200gs the rear brake should be less fierce

Before you get yourself killified!,
A smaller diameter master cylinder will make matters worse. Considerably worse. A larger diameter cylinder will mean you have to apply more pressure before rear wheel locks.

Bike is obviously dangerous as it is, and I woudl not like you to make it worse.
Remember, the danger occurs not in normal braking, but in an emergency, when, by the time you get your toe back off the pedal, you are already up the road on your arse!

Myke

 

[(RIP) Mark H]

Before you get yourself killified!,
A smaller diameter master cylinder will make matters worse. Considerably worse. A larger diameter cylinder will mean you have to apply more pressure before rear wheel locks.

Bike is obviously dangerous as it is, and I woudl not like you to make it worse.
Remember, the danger occurs not in normal braking, but in an emergency, when, by the time you get your toe back off the pedal, you are already up the road on your arse!

Myke

Not sure thats correct, a larger rear master piston needs less pressure to lock rear wheel imho

for a 1200gs;
Rear brake master cylinder - piston diameter

1200GS non abs 13 mm,

14.29 mm
Variant, BMW Integral ABS (partially integral)

as you can see the abs equipped bikes have a larger piston diameter, take the abs off and leave the original master cyl gives a fierce rear brake, I now know that a 13mm rear cylinder should be available and fit straight on

I cant find out what piston diameter is used on a R1150GS perhaps someone knows? but a R1100RT rear master would fit and is likely to be smaller diameter

 

[Myke Rocks]

You may not trust my view, but:

Not sure thats correct, a larger rear master piston needs less pressure to lock rear wheel

Rear brake master cylinder - piston diameter

1200GS non abs 13 mm,

14.29 mm
Variant, BMW Integral ABS (partially integral)

as you can see the abs equipped bikes have a larger piston diameter, take the abs off and leave the original master cyl gives a fierce rear brake, I now know that a 13mm rear cylinder should be available and fit straight on

I have worked on race car brakes for years, so I have a lot of experience balancing brake circuits.

Alternatively, change the slave cylinder at rear for one with smaller bores.

Alternatively alter geometry of brake pedal so that master cylinder pushrod moves more for same distance pedal moves, or shorten brake pedal.

Myke.

 

[Hubs]

Hi, not sure I'd describe the rear brake as dangerous. It has a different bite point than it used to have, and is at about the level of fierceness of a z550 I used to have. I've been riding my usual south devon commute which involves a fine mix of singletrack roads with gravel in the middle, and I felt it was fine now i've done a few more miles on it. I've also been doing a bunch of emergency stops, and the back is a little looser than with ABS, but only in a non-ABS brake sort of way. The big difference for me is that, after a year of no effective back brake, I now have one. Lots better..

My general observation is that the learning process involved in managing effective hard braking is quite complex, as we have to adapt to different bike characteristics - initial bite, dive, tyre condition, road condition, effect of and recency of rain, likelihood of inducing a lock; removing the servo has an effect on the overall balance across the bike, but it is different, rather than worse.

After 4 years on servo bikes, I notice I am very gentle with initial application, as the servo bikes have little initial response, then a hard bite. My braking approach has adapted to this and I now need to get back to a harder initial pull, which will then be easier to modulate - more travel but more progressive on the front.

I also note that I am braking a lot harder at the moment, as I get used to the system. Give it a few days and I'll be back to hardly braking at all, which is my preferred style.

My reaction right now is that it feels different, it brakes fine, it is a factor of many more reliable, and, wonder of wonders, it has brakes with the engine and ignition off. May seem like a small thing, but the immediate topography round our house makes that a thing of joy (bottom of Hothill Lane for those riding the South Devon unmetalled roads!) It also makes no noise at traffic lights.

Interestingly, one noise I thought was the servo system (a sort of resonant whine - very odd) under very hard braking at lower speeds, is still there, suggesting I'm hitting the same pad pressures as before, with a bit more effort.

 

[(RIP) Mark H]

I have worked on race car brakes for years, so I have a lot of experience balancing brake circuits.

Alternatively, change the slave cylinder at rear for one with smaller bores.

Alternatively alter geometry of brake pedal so that master cylinder pushrod moves more for same distance pedal moves, or shorten brake pedal.

Myke.

BMW balance the brake system by varying the master cylinder piston size on both front and rear, so theres more scope using available parts to balance the system if the abs is removed, it appears on non abs bikes the piston size is smaller so logically to the piston size needs to be reduced, I believe the same caliper is used on abs & non abs bikes

 

[ducatiparts.110mb]

BMW balance the brake system by varying the master cylinder piston size on both front and rear, so theres more scope using available parts to balance the system if the abs is removed, it appears on non abs bikes the piston size is smaller so logically to the piston size needs to be reduced, I believe the same caliper is used on abs & non abs bikes

Easy - whilst you're right about this, you're wrong in your statements above about piston size and the effect it has on the braking force.

However having removed the servo on mine, I'd say just get use dto the different feel of the brakes and the amout of force needed. No need at all to change components as BMW uses the same parts on the servo and non servo bikes.

I also have poor initial braking bite on mine now, but I put that down to the Goldfren pads I fitted which are universally acknowledged to be shite (which I found out after buying mine )

 

[Steptoe]

Here's my take.

Any other views?

And here's my take.

Servo removal make the bikes feel exactly the same as bikes that don't have servo fitted. Hope that's not too complicated.

Plus, bare in mind that the brakes of any two bikes which are more than a couple of years old never feel the same anyway.

 

[Hubs]

And here's my take.

Servo removal make the bikes feel exactly the same as bikes that don't have servo fitted. Hope that's not too complicated.

That made me laugh! Thanks.

Reminds me not to over analyse!

 

[DollyRocket]

Re the rear brake comments (Easy to lock the wheel, worse and somewhat dangerous in the wet I guess) The problem might be resolved by fitting a rear pedal cylinder with a smaller piston, this would require more foot pressure to get the same braking force and make it harder to lock the rear wheel, I guess a bit of research would be needed to find a suitable sized cylinder and fitting it but not difficult to do, would make the brake less fierce, Just a thought

I personally, like to have control of the brakes again in my hands (and feet). I like the fact I can lock the wheels up - but then I am used to it when riding off-road as it is a standard method of descending steep hills and taking tight turns at speed by locking the rear wheel.

I think it is great, I don't understand why should be perceived as being more dangerous now than it would be with the servo in place. People just get used to their bike before they push it to its (and their) limits.

 

[Myke Rocks]

Just an aside which may be helpful

With all brake pads, regardless of manufacturer, the closer you get to racing pads, the more pressure it takes with cold brakes before you get any noticible "Bite".
I would suggest, therefore, fitting very hard use/race type pads in the rear brake.
This will take the initial grabiness out of the brake, but, with hard use, they will revert to normal "bite" levels as the pads warm up.
It is a cheap and easy way to make your bike safer in the circumstances.

Myke

 

[Hubs]

Ref. The sharp rear brake; adjusted the pedal down, now takes more movement to actuate brake, problem gone.

After a few weeks commuting, very happy with servo removal. Added bonus, battery seems a lot happier on cold starts....

 

[Timolgra]

And here's my take.

Servo removal make the bikes feel exactly the same as bikes that don't have servo fitted. Hope that's not too complicated.

Thank you Steptoe, my last 3 1150's have had their servo's removed, any change in braking and 'feel' is minimal, if there is, it's an improvement