Traction-control malfunction on a 2009 GS Adventure.

[Nick V]

Hi, peeps, Nick here.

I've got a problem with the ASC on my '09 GS Adventure, and I'm hoping that someone with previous experience of the same issues might recognize them and be able to offer advice.

Some background: the bike is a 2009-model hex-head. The engine-management and ZFE-high ECUs are standard 2009-vintage GSA, but the bike uses an engine and gearbox from an R1200S.

When changing gear and/or when moving from a small to large throttle opening and/or at high engine loads and speeds, the traction control cuts in, even when the rear wheel is obviously not spinning, and can sometimes stay active for almost as long as the throttle is open.
De-activating the ASC via the handlebar switch obviously makes the symptoms go away.
Strangely, this symptom is worse when the engine is at operating temp than when it's cold.

The only substantial engine modification is a de-catted 2-into-1-into-2 Afriflo stainless exhaust header, plus Tornado Developments can.

The bike also uses a K1200S rear wheel.
Current tyre makes and sizes are:
Front: 110/80-19 (Bridgestone Battlewing).
Rear: 180/55-17 (Michelin Pilot Road 3).

What I'm thinking is that there may be a substantial-enough difference in rolling circumference between the standard rear tyre, and the new one, to make the ECU think there is wheelspin when there isn't.
So far, I haven't tried experimenting with relative tyre pressures, or borrowing a standard rear wheel.

There is no effect on the bike's ABS, and no ABS fault lights are registering.
Could it be that even though they share the same wheel-speed sensors, the ABS has a greater built-in tolerance for rolling-circumference errors than the ASC?

Idea 1:
Ditch the current rear 180/55-17 in favour of a 190/55-17.
...Anyone...?

Idea 2:
Have a BMW dealership, or someone with a GS911, re-programme the ECU to accept the differing rolling circumferences (the owner's manual makes mention of this, but I don't know what's actually involved... can anyone say?)

 

[Ali-bear]

There may be a difference in the wheel speed sensor disks between the one you have fitted and the original. I am referring to the rotating steel disk with the slots in. This could easily make the computer miscalculate the wheel speed.

 

[Bendy toy]

I believe the computer compares front and back wheel speeds so if it sees the back as going faster than front it will think the wheel is spinning.

When new engine and gearbox were fitted did you also use the R1200S swing arm and FD? If so going back to the GS parts might solve the problem.

How about fitting the 1200S front wheel or at least its ABS sensor ring. Its probably the lowest cost way to see if it solves the problem.

 

[cookie]

I believe the computer compares front and back wheel speeds so if it sees the back as going faster than front it will think the wheel is spinning.

but every time you start the bike it does a comparison in the first few yards of travel, so it has a baseline.

 

[tanneman]

Is the wheel not spinning in the tyre?

 

[Bendy toy]

but every time you start the bike it does a comparison in the first few yards of travel, so it has a baseline.

Oh well one theory down the swannie. Also check the ABS sensors are lined up correctly with the wheel rings. After that it looks like the ECU will have to be interrogated.

 

[Nick V]

I believe the computer compares front and back wheel speeds so if it sees the back as going faster than front it will think the wheel is spinning.

That's the thing... I'm not sure whether the system gets it's 'baseline' value from the first few metres of travel, or whether it simply compares actual values against pre-set on-board values.

When new engine and gearbox were fitted did you also use the R1200S swing arm and FD? If so going back to the GS parts might solve the problem.

That's a good point.
I'm not sure - I'll have to ask the bloke who built the bike.
It DOES seem as though the engine is turning faster for the same vehicle speeds than my old (standard) GSA - so I'd bet on a lower-ratio final drive.
The funny thing is, my bike didn't used to do this...

How about fitting the 1200S front wheel or at least its ABS sensor ring. Its probably the lowest cost way to see if it solves the problem.

I can start by counting the number of teeth on both rings - and experimenting with tyre pressures.
I'll keep you all posted!

 

[Fanum]

That's the thing... I'm not sure whether the system gets it's 'baseline' value from the first few metres of travel, or whether it simply compares actual values against pre-set on-board values.

The first option.

Otherwise (and assuming it's sensitive enough) when you wear out a TKC , which is small but significant % of the radius of the tyre/wheel, it would be different from any set baseline.

There was an in-depth thread about it yonks ago here.

 

[Nick V]

when you wear out a TKC , which is small but significant % of the radius of the tyre/wheel, it would be different from any set baseline.

Thing is, though... surely any difference in rolling circumference which could make the ASC throw a wobbly would also affect the ABS?
In my case, the ASC is malfunctioning, but the ABS hasn't given a moment's trouble.

There was an in-depth thread about it yonks ago here.

Any pointers on the thread title? I'd be interested to have a squizz.

 

[Ali-bear]

Thing is, though... surely any difference in rolling circumference which could make the ASC throw a wobbly would also affect the ABS?
In my case, the ASC is malfunctioning, but the ABS hasn't given a moment's trouble.

Because the computer thinks the back wheel is going faster than it really is?

Because the ASC computation uses engine revs as well as wheel speed, where the ratio has changed because of your -ahem- hybrid drive train?

 

[Nick V]

Because the computer thinks the back wheel is going faster than it really is?

Because the ASC computation uses engine revs as well as wheel speed, where the ratio has changed because of your -ahem- hybrid drive train?

Now, that's entirely possible.

What I'm going to try, as soon as I have the time, is to measure any difference in rolling circumference by putting a tiny dab of Prussian Blue on the tread of the rear tyre, rolling the bike (with me in the saddle) through one revolution of the wheel, and measuring the length of the resulting track.
I'll then repeat the experiment with a 'control' GSA that has standard wheels and tyres, and compare the two values.

If I end up with disparate values, I'll try experimenting with tyre pressures (within reason!) and see if that doesn't help the problem...

 

[Bendy toy]

No need to sit on the bike just chalk mark the tyre and roll it forward one turn then do the same on the reference bike. My GSA with a new 150-70-17 tyre has a radius of 315mm (give or take 2mm or so).

 

[Nick V]

No need to sit on the bike just chalk mark the tyre and roll it forward one turn then do the same on the reference bike. My GSA with a new 150-70-17 tyre has a radius of 315mm (give or take 2mm or so).

Ta for the dimensions!

The reason for planning the method I am is that it more closely simulates real-world conditions - particularly tyre sidewall deflection with the mass of a rider aboard. (For all I know, the Pilot Road 3 tyre I'm using at the back may have more 'squash' than the standard 150/70-17, leading to an effective decrease in rolling diameter - and therefore, rolling circumference.)

If I really wanted to do this scientifically, I'd have to get both tyres - and those on the 'control' vehicle - up to full operating temperature, as well as rigging a way to measure rolling circumference at normal cruising speed, to factor in centrifugal tyre 'growth'...

 

[Bendy toy]

Ta for the dimensions!

The reason for planning the method I am is that it more closely simulates real-world conditions - particularly tyre sidewall deflection with the mass of a rider aboard. (For all I know, the Pilot Road 3 tyre I'm using at the back may have more 'squash' than the standard 150/70-17, leading to an effective decrease in rolling diameter - and therefore, rolling circumference.)

If I really wanted to do this scientifically, I'd have to get both tyres - and those on the 'control' vehicle - up to full operating temperature, as well as rigging a way to measure rolling circumference at normal cruising speed, to factor in centrifugal tyre 'growth'...

The important and easy to measure (= accurate) variables are tyre rolling radius via tape measure and final drive gear ratios - spec sheets.

Road bike tyres (correctly inflated) dont shift about on the side walls so one will be much the same as the other. But consider the confounding factors. None of the tests are scientific.

• Riders weight will shift as the bikes are punted along. No rider(s) no weight shift.
• Each bike will have different tyre wear.
• Tape measure and chalk marks on tarmac are hardly lab conditions.
• Traction control systems is built to cope with tyre wear which can reduce rolling radius by at least 6mm (2%) and considerably more with knobbly tyres.
• Traction control also built to cope with different load which as you say will reduce rolling radius.

 

[Nick V]

Got some experimentation time with the tyre pressures last night (trying to manipulate the effective rolling circumference of the tyres):

Front at 2.2 Bar, rear at 2.5 Bar (standard one-up pressures): Still misbehaving.
Front at 2.5 Bar, rear at 2.9 Bar (standard two-up pressures): Still misbehaving.
Front at 1.8 Bar, rear at 3.1 Bar: Still misbehaving.
Front at 3.1 Bar, rear at 1.7 Bar: Still misbehaving.

So, sad to say, altered tyre pressures made no difference to the ASC malfunction.

Tonight or tomorrow, I'll try unbolting the wheel-speed sensors from their mountings and seeing if they're overly dirty or contaminated, and check their air gaps.

If that doesn't work, I have another K1200S wheel available, to which I can mount a 190/55-17 ex-track tyre I can pick up cheaply.
If it is a case of ECU-thinks-rear-wheel-is-turning-faster-than-it-should, this will hopefully give enough extra rolling circumference to sort the problem...

 

[DrFarkoff]

Why don;t you get someone to read the fault codes

or check live data with the GS911 or similar??

 

[Nick V]

Why don;t you get someone to read the fault codes or check live data with the GS911 or similar??

It's a sensible thing to do on paper - and I plan to, at some stage.

But in my world, not as easy as it may at first seem:

• I don't own a car. I commute using my bike - it's not a 'lifestyle accessory' whose warranty and mileage count are jealously guarded, and that only sees the road on Sunday mornings.
• On principle, I stay away from BMW Motorrad dealerships whenever practically possible. I have no interest in being kicked in the balls and having them run off with my wallet the moment I walk through the door.
• My contact with a GS911 lives on the other side of town, and we both have disparate schedules and work hours which mean my time to see him is limited.

In any case, I haven't seen the yellow triangle except when it flashes rapidly to tell me the traction control is cutting in. If the display is giving me no visual warning that something is wrong, what are the chances that the ECU or ZFE have logged a fault code?

 

[Bendy toy]

My GSA is currently running a Maxxis SuperMax touring tyre on the back and a a 1/2 worn adventure trail tyre on the front. Its handles great on the road with no visible chicken strips. Im not good enough to take it off road so the smooth road tyre is fine.

The ABS and TCS work as they should.

 

[DrFarkoff]

In any case, I haven't seen the yellow triangle except when it flashes rapidly to tell me the traction control is cutting in.

If the display is giving me no visual warning that something is wrong, what are the chances that the ECU or ZFE have logged a fault code?

Live Data may be the answer and spot what is happening

 

[Nick V]

Live Data may be the answer and spot what is happening

Very true - I hadn't thought of that.
It's been a long, long time since I worked in a franchised motor dealer's workshop...