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Old 12-03-2012, 05:43 PM   #1
Mad Kaw OP
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Joined: Sep 2010
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Electronic Cruise Control installed! GS

Well I finished the second GS install of the venerable Rostra Cruise Control. This is actually the 4th bike I've installed it on and the third R series BMW. It works well considering it is an automotive cruise control adapted to a motorcycle.

I bought the "kit" from Murph at You can check out his hardware there.

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I’ve installed a Rostra Electronic Cruise Control on several bikes but most recently on my 2005 R1200GS. The project went well enough I agreed to install a second one on a friend’s 2006 model GS. This thread will document that installation.

The first R series I installed one of these systems on was a 2004 R1150RT. It was a huge PITA but worth it. However the mods I made to the Bowden Cable Distributor Box on the 1150 were painstaking compared to the GS. AND there is no VSS sensor on the 1150 RT so I had to install a magnetic wheel speed sensor...another PITA. Still it was worth the effort. Here's a link to that document for additional reference: R1150RT Cruise Install

The 1200 is much easier due to the fact that the 1200GS and 1200RT platform shares the same cable box so no serious surgery to the cable box is required to make it work. As you know the RT comes from the factory with cruise….the GS does not. So one only needs to order the parts from the RT to make this project a breeze.

Please don’t ask if the OEM cruise is a candidate for transplant from the RT to the GS platform. First – I do not know but I did some preliminary costs and personally I would not consider trying it on that point alone. I believe it would easily exceed $1500….maybe $2000. The Rostra on the other hand will set you back $300 tops.

I’m going to try and lay this document out in a straight forward step by step installation fashion. To my knowledge this particular install will work on 2005 – 2008 GS. But the later ones may not because of the absence of a VSS signal in the bike’s wiring. Next year we will attempt to do this install on a 2011 1200GSA. There may be a way to tap a VSS on the computer module but that remains to be seen.

The first section will address the mechanical aspects of this project. The second will address the electrical wiring.


1- I removed the seat, skin and tank from the bike in order to access the Bowden cable box and appropriate wiring.
2- I removed the OEM horn and mounted the Rostra servo to same bolt. I then re-mounted the horn on top of the same fairing frame member. (fig 1). Then I mounted the Rostra servo module in place of the horn bolt. I used the included bracket and bent it to fit. (figure 9).

3- I fashioned a bracket from a “L” support using this to mount the control pad above the left turn signal control. There are a million ways to do this….I’m sure you can figure something out that fits your ergos. (figure Fccp2 and Fccp3)

4- Referring to the right side throttle body; release the TB cable from the cable wheel on the under side of the TB. Then pop the retainer and pull the TB cable out. This will allow you to remove the Bowden box in the next step. (fig 2-2a)

5- Pry up release tab on the Bowden box and slide toward the left side of the bike. Gently remove cable box door. At this point you can either completely replace this cable box with an RT cable box OR you can save your self a few bucks and mod this one like I did. We simply drilled a 3/8 hole as shown (fig 3)

6- Clean cutting from inside the box then simply screw a ¼ brass compression X 1/8 NPT coupling into the newly drilled hole. This will act as the slack tube cable guide/fastener. The 1/8 NPT will cut threads into the plastic box as it is screwed in. Then insert cable sheathing into compression ferrule and tighten to fasten cable sheath to ferrule. A standard bicycle brake cable from WalMart will work fine here. *** However the cable itself was to stiff and would drag inside the box. I simply replaced it with a 1/16 piece of cable from a hardware store that was more supple and proved to work well for my application. YMMV. (fig 4)

7- This is how I modified the cable for the OEM cruise cable wheel. I drilled a hole through the side of a cable fitting and soldered it in place. (Fig 5-5b)

8- After fitting the cable into the OEM cruise guide wheel (fig 5b) place in the Bowden box (fig 6 and 6a). Install the wheel spring as shown. Slip the cable outside the box through the hole on the right side of the box you just drilled.

9- Pop the door back on the box. You can either use your stock door and trim it to accommodate the newly installed cruise control cable wheel or you can buy the RT door that is already the correct length. (Fig 6c)

10- Re-install in the retainer groove adjacent to the airbox. Guide the cable from the box into the cable sheath. Slide a ferrule onto the cable sheath then the compression nut. Now compress the ferrule onto the cable. (fig 7 and 7a)

11- Now re-attach the TB cable to the BMW’s right side TB wheel.

12- The other end of this intermediate cable serves a “slack tube” (a 6 inch tube of PVC with end). This tube allows for the required 40mm of slack between the servo cable and the throttle action for the Rostra to work properly. However with the OEM BMW cruise cable guide wheel you'll need a fraction of that slack. roughly 1/8" will do just enough not to hold tension on the TBs at idle.

Some have suggested the system needs NO SLACK TUBE on an R series with a Bowden Box. If you concur be my guest. However I have installed many of these CCs on R series BMWs and personally I would not install one without a slack tube if for no other reason than ease of adjusting the slack tension between the servo and the throttle engagement. (figure 8-8a)

13- I used a piece of clear plastic to fashion a “window” across the slack tube’s opening so I could see the ball chain and cable if needed for future troubleshooting. You don’t have to use this “window” and can use any material to cover the rectangular hole in the tube. (figure 8b)

14- As you can see the Rostra servo cable serves the opposite end of the slack tube. You can use the ball chain and other connectors that are included in the Rostra kit to attach the servo cable to the intermediate cable.

• TIP: You should “water proof” the handle bar control pad. Simply pop the cover off the switch …remove the rubber cover…and put a thin bead of RTV silicone around the base of the cover…then re-install. I also fill the seam around the cover of the switch and the hole where the wires exit. To date I’ve never had a problem with the switch failing during rain/washing.


This is the part I dislike! The mechanical aspect are straight forward in my mind. But “lecterck” stuff confuses me. I can’t see those little electrons flowing down the wires! AC/DC and Tesla are rock bands damn it! But some how I managed to wire this bee-otch can it worked.

In reality there are just a few circuits to complete and this project will shine like a new penny. In addition the Rostra comes with an installation manual and wirig instructions / diagram. However there will be a few detours we make in order to adapt this speed control system to a motorcycle…specifically a BMW motorcycle.

The wiring loom harness that plugs into the servo consists of these:

Orange – enable/engage light
Light green – clutch safety
Dark blue – tach signal (not used on this bike)
Dark green – set/coast
Gray – VSS sensor (vehicle speed sensor)
Brown- ignition switched power
Yellow – resume/accel
Black – ground
Violet – negative side of the brake switch
Red – positive side of the brake switch
Light blue and black on separate plug (for aux wheel speed sensor not used in this app)

The handle bar mounted control switch/pad:

Red, brown dark green, and yellow. These wires plug directly into the main harness off the servo.

Regarding ground: Make sure all black wires are grounded properly. An excellent ground is required for this system to work flawlessly. A compromised ground will cause all sorts of headaches and make it very difficult to troubleshoot the system. Make sure you ground is clean and has LOW RESISTANCE.

ORANGE WIRE – I highly recommend the use of an “engagement light” . All this light does is tell you the Rostra has engaged and is applying tension to the servo cable. This light can be very useful for troubleshooting. If the control pad lights up but the engage does not then you know your wiring/electrical is at fault. But if all lights illuminate and the Rostra still does not work then you know it is something on the mechanical side…likely a cable problem.

To install this little light just get a small 12v dash indicator light at Radio Shack or NAPA (etc). I mounted mine in the side panel under the right handle bar. Wire one side of the light to the Rostra’s orange wire and the other side to a 12v+ accessory power.

Light Green- clutch safety disengagement

This wire acts to disengage the Rostra when the clutch lever is pulled in. This is an additional safety release to the Brake release. Just splice the light green wire into the ground side of the clutch safety switch that plugs into the clutch lever on the right side of the handle bar. It will be a black wire with a green stripe. You can solder this or even use a barrel crimp connector. **** But don’t connect this wire until the last step!!! You can not have this circuit wired up and do the final diagnostics on the system.

Dark green on the Rostra soldered directly to the dark green on the switch pad

Brown – ignition switched power 12v+

Yellow on Rostra soldered directly to the yellow on the switch pad

Black – ground *remember to have a good clean ground!

Violet – negative side of brake switch
Red – positive side of brake switch OR and 12v+

**** The violet can be tapped into the wiring harness on the GS under the passenger seat. The OEM wire is coded grey/black/yellow.

**** This system is being adapted to a motorcycle but was designed for a car. A bike has two triggers for brake. The pedal and the right lever. The practical place to “monitor” these functions is at the common point…the brake light. We must set it up so that the Rostra will disengage when either pedal or lever triggers the safety. We use a 5 pin relay to accomplish this. The Rostra must sense ground in order to engage. If it senses 12v+ it will disengage…this is how the brake safety release works. The ground circuit for this leg must be solid and should not exceed 3 ohms of resistance in order for the Rostra to reliably engage. The instant Rostra senses anything else it will disengage. I installed the relay under the rear seat. I routed the violet wire to the relay’s 30 pin. Then I wired the gray/black/yellow wire from the GS to the 87 pin and 86 pin. I grounded 87a and 85.

Grey wire – VSS. The grey wire on the Rostra can be taped directly to a wire found under the tank up near the “yoke” on my GS. You’ll see a plug (refer figure 9) below the serial number plate and above the left side of the bikes ZFE Module (computer). The coded wire is blue/green Simply tap the grey wire of the Rostra into this blue/green wire. Apparently this is a digital signal from the rear wheel speed sensor that the Rostra can read directly! All I can figure is this is the same plug used on the RT and it’s electronic cruise control. BMW never put a cruise in the GS but seems they left the optional accessory plug on the GS. Maybe they planned on offering a GS cruise in the future? In any case it works! That’s all I care about.


The final stage is setting the dip switches under the rubber plug door on the body of the Rostra. I recommend doing this before you even install the module to the bike. But if you don’t it’s no big deal as you can see the switches by laying under the front fender and looking up into the servo.

These are switch settings I found to be most suitable for my GS: ALL SWITCHES SET TO THE OFF POSITION EXCEPT FOR 4, 9, 10, and 11. You can read the Rostra manual to understand these switches. I will not explain them here.

DIAGNOSTICS – In order to put the system in diagnostic mode you must have the clutch safety unplugged. Turn the key on then press resume/accel while simultaneously holding the power button (on the control pad). Next to the dip switches under the rubber plug door there is a diagnostic light. It will light up under a variety of conditions. Refer to the manual to fully understand it’s function.

It took me about 8 hours to install this system on a 1200GS going about it this way. If you come up with something better PLEASE share your info here. I’m certain there are many who’ll have a much cleaner and efficient install than I have presented here. I encourage you to share your tips with the community. This system has transformed my long trips especially on the slab. It makes tarmac cruising sooooo much more enjoyable. I’ve tested this system from 45 mph all the was up to 120 mph and it works as prescribed.

Total cost about $300. Enjoyment of use PRICELESS.
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Mad Kaw screwed with this post 12-03-2012 at 06:07 PM
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