ABS/DSC faults - advice from the trade!

A

andyfanshawe

Member
 Chesterfield UK
Just a quick bit of feedback for you all from the repair side of this business!
I am having an influx of BMW's with driveshafts where the toothed wheels (Reluctor or phonic or....) have bulged outwards due to corrosion getting underneath. This results in the ABS sensor being gradually eaten away to a point where it fails. As this develops, i am getting "wheel speed sensor interpolation" on my scan tool.

For the uninitiated, interpolation is the science of guessing what data was if it is missing. As I tried to explain to one of my sons for his degree work......If you take the temperature everyday for 7 days, but lose the data for Wednesday, it is possible to guess (or more accurately "intelligently determine") the missing one from the others. Yes, there are formulas for interpolation, but not going to bore anybody!! Having a maths degree certainly helps me with modern day cars!! But my Wife says its boring!!! Blah, blah, blah....she says.

As the sensor hits the distorted toothed wheel, the signal changes instantaneously (reduced air gap) and produces an implausible signal (or one that is different to the rest). The computer disregards this and substitutes a value to complete the calculation.

So, what am I saying? If you get the interpolation word, it is highly likely the driveshaft and sensor needs changing.

On the other hand, when a single speed sensor fails, the 3 lights will light up on the dash, and also the tyre pressure warning light. Obviously because the frequency of the signal from the speed sensor varies as the diameter changes. So the computer knows the tyre is going down by sampling the waveforms from each wheel and looking for an increased frequency (shorter "period" for the scientists out there!

All this is not concrete but will give a guide as to what may be wrong.
Just some secrets from the trade :wink: .

Andy.
 
I dont think you need to replace the whole driveshaft, you can get seperate reluctor rings.
 
GuidoK said:
I dont think you need to replace the whole driveshaft, you can get seperate reluctor rings.
Click to expand...

In some cases, yes, but try ordering the right one, with the right number of teeth and diameter, and getting the old one off and the new one on! Nightmares! Faster to get new shafts. And surprisingly cheap. Most customers want the car back asap (yesterday!). Not had much luck with new reluctors I'm afraid.

IMAG1160_zpsdjepqmb7.jpg


Closest ABS sensor is the one where the stone has cut a groove in it. Other one is from a 2008 320D that has been worn away by a rusty reluctor wheel.

M1's are starting to appear with these problems.
Andy.
 
andyfanshawe said:
In some cases, yes, but try ordering the right one, with the right number of teeth and diameter, and getting the old one off and the new one on! Nightmares!
Click to expand...

I think these will fit the e85:
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-124.html
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-125.html

Getting them on/off is very simple. Snip/dremel the old ones in one spot (and they spring off immediately), or tap with a chisel.
Use a steel brush (if needed on drill) and clean off the rust (or use some sandpaper or whatever)
Tap the new rings on, with a straight piece of metal until they hit the sholder.
Can be done in 15-30 min if you have the axle out. Its no big deal imho, especially the rear ones.

Faster to get new shafts. And surprisingly cheap.
.
Click to expand...
Yes, no name AFTERMARKET ones are cheap.
BMW uses special hollow large diameter shafts (especially the manual 2.5i/3.0i, they have the largest diameter: 38mm hollow (the lighter engines have thinner hollow shafts), and they are BMW only.
They are £350+, so not exactly cheap, unless you can get them used.

This is an OEM BMW driveshaft:
s-l1600.jpg

This is an aftermarket driveshaft:
?id=7206417&lng=en&n=0.jpg

Making the twin tapered hollow shaft is obviously a much more complicated process, so BMW must have thought to get some gain out of it one way or another otherwise they wouldnt have bothered with such a more expensive production procedure.

So yes, cheaper in price, but not made to OEM specs so not the same product.
Lots of aftermarket products from quality suppliers like febi are made to exactly the same design (and very often are rebadged OEM products where I've seen the bmw logo even sanded away), but regarding the driveshafts (the ones I've seen) they are not the same design.
Normally I dont mind aftermarket products, and they can even be of an improved design, like meyle HD bushings or an aluminium thermostat housing instead of the plastic ones, but with aftermarket driveshafts I dont see an improvement in a smaller diameter solid driveshaft, so I would rather look for a used one in decent condition over a cheap new one if I would need a new driveshaft (I had to change 1 out once on my car)
 
GuidoK said:
andyfanshawe said:
In some cases, yes, but try ordering the right one, with the right number of teeth and diameter, and getting the old one off and the new one on! Nightmares!
Click to expand...

I think these will fit the e85:
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-124.html
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-125.html

Getting them on/off is very simple. Snip/dremel the old ones in one spot (and they spring off immediately), or tap with a chisel.
Use a steel brush (if needed on drill) and clean off the rust (or use some sandpaper or whatever)
Tap the new rings on, with a straight piece of metal until they hit the sholder.
Can be done in 15-30 min if you have the axle out. Its no big deal imho, especially the rear ones.

Faster to get new shafts. And surprisingly cheap.
.
Click to expand...
Yes, no name AFTERMARKET ones are cheap.
BMW uses special hollow large diameter shafts (especially the manual 2.5i/3.0i, they have the largest diameter: 38mm hollow (the lighter engines have thinner hollow shafts), and they are BMW only.
They are £350+, so not exactly cheap, unless you can get them used.

This is an OEM BMW driveshaft:
s-l1600.jpg

This is an aftermarket driveshaft:
?id=7206417&lng=en&n=0.jpg

Making the twin tapered hollow shaft is obviously a much more complicated process, so BMW must have thought to get some gain out of it one way or another otherwise they wouldnt have bothered with such a more expensive production procedure.

So yes, cheaper in price, but not made to OEM specs so not the same product.
Lots of aftermarket products from quality suppliers like febi are made to exactly the same design (and very often are rebadged OEM products where I've seen the bmw logo even sanded away), but regarding the driveshafts (the ones I've seen) they are not the same design.
Normally I dont mind aftermarket products, and they can even be of an improved design, like meyle HD bushings or an aluminium thermostat housing instead of the plastic ones, but with aftermarket driveshafts I dont see an improvement in a smaller diameter solid driveshaft, so I would rather look for a used one in decent condition over a cheap new one if I would need a new driveshaft (I had to change 1 out once on my car)
Click to expand...

Thanks for your input.
Excellently put and all good.
Personally i have never had a problem with an aftermarket driveshaft, and have been fitting for 20 years +.
I know the procedure for fitting the reluctor wheels very well thank you. But good advice to others. I have never been lucky enough to get a reluctor wheel to fit any driveshaft properly. And with durability. And with the correct waveform. And I haven't got time to repeatedly send back or redo a job because the signal is not quite correct to the ECU.
About a year ago, I tried to order a reluctor wheel for a humble 2007 fiesta. I was advised by the aftermarket suppliers (Minorfern, euro, andrew paige, etc) that they needed to know how many teeth, the diameter etc, and they couldn't guarantee any of them working.

As a DIY'er working on my own car, I will risk the chance of having to remove a driveshaft again and again, but as a business owner that is a BIG NO NO. Customers are very happy, and thats good enough for me. i can get cars out on time and have good faith in minimal comebacks. None so far.

i think we are coming from different perspectives here. Each to his own.
i may go down this route again one day though.
But I value your input and advice.
Thank you.

Andy.
 
GuidoK said:
BMW uses special hollow large diameter shafts (especially the manual 2.5i/3.0i, they have the largest diameter: 38mm hollow (the lighter engines have thinner hollow shafts), and they are BMW only.
They are £350+, so not exactly cheap, unless you can get them used.

Making the twin tapered hollow shaft is obviously a much more complicated process, so BMW must have thought to get some gain out of it one way or another otherwise they wouldnt have bothered with such a more expensive production procedure.
Click to expand...

The tubular shaft will have much better resistance to torsional twisting (polar motion of inertia) twisting isn't a good thing particularly if shafts are unequal length, hollow are less likely to distort or bend and are much lighter reducing mass/vibrations and lowering vehicle weight. Better all round which is presumably why BMW specify them over solid shafts.
 
Have a look at this superb video on YouTube. https://youtu.be/33T1b4alccY

Brilliant. Sometimes replacing a reluctor wheel is impossible because the drive shaft has to be intact to be able to do it! Beating it out of the hub is sometimes the only option.
Good exercise too!!
Gotta love the corrosion in the UK ( and new york by the looks of things!).
Andy.
 
Ewazix said:
The tubular shaft will have much better resistance to torsional twisting (polar motion of inertia) twisting isn't a good thing particularly if shafts are unequal length, hollow are less likely to distort or bend and are much lighter reducing mass/vibrations and lowering vehicle weight. Better all round which is presumably why BMW specify them over solid shafts.
Click to expand...

Yes I also think in that line. The driveshafts are indeed unequal lenght.
Especially on high speeds (faster rotations) I can imagine it reduces vibration, especially when the center of the axle is sitting a bit off center, which is possible.
I had an aftermarket shaft, ordered one when I needed a replacement (because a bmw one is so expensive), but I immediately noticed the difference in thickness and weight, so I didnt even bother to put it in, sent it back (opted luckily for mister-auto's no hassle free return service) and got a low mileage used one in extremely good nick (and even cheaper than the new aftermarket one, so as far as costs go there are good alternatives).
Especially with a performance car on the autobahn, I'm not going to cheap out parts where I get the feeling that corners have been cut.
The z4 is already a car with a very very short wheelbase that can do pretty good speeds (mine runs ~175mph with the mods
), so any part that sacrifices stability without any other significant gain might not be the best choice for me :wink:

andyfanshawe said:
Have a look at this superb video on YouTube. https://youtu.be/33T1b4alccY

Brilliant. Sometimes replacing a reluctor wheel is impossible because the drive shaft has to be intact to be able to do it! Beating it out of the hub is sometimes the only option.
Good exercise too!!
Gotta love the corrosion in the UK ( and new york by the looks of things!).
Andy.
Click to expand...

SMA is a nice channel, but I cant help thinking that he is a bit too much in love with his air tools. He started wacking on that cv joint because his air hammer wasnt capable to turn the thread, but after the wacking he finally tried a breaking bar, and you can immediately see how much more torque you can apply with the breaker bar than with his (probably good quality/snap on) impact. I would have first tried the breaker bar instead of getting a huge sledgehammer (and god knows inflicting unseen damage on other parts), and I suspect he may have gotten it loose without the wacking and damaging the cv joint.
I guess mechanics become blunt objects themselves if they're constantly exposed to cars rusted by salt on the roads, and foremost cars made out of very inferior materials compared to european premium cars. Materials used in US cars are utter crap. Thats why they are cheap.

Good example why it is important to keep your car (that is the underside of your car) in shape; you avoid the mechanics to go all caveman on your car.
So pressure wash the underside of the car frequently and thorougly (getting rid of salt and mud), NEVER park on gras or under a tree (constantly damp, the bottom wont get the chance to get dry) etc etc. (garaged is obviously best). How the underside looks is maybe more important than how the body looks. Most people seem to be really into polishing and detailing the outside with the most exotic named and smelling expensive cosmetic stuff, totally unaware of the turd growing underneath :lol:
 
I have done loads of rear shafts due to the reluctor ring rotting...
They have been having this trouble for years now

Shafts are about £80... not bad at all considering you get new CV joints and boots..

Might as well once the shaft is out, we did fit just rings in the early days....hardly seems worth it now
 
GuidoK said:
andyfanshawe said:
In some cases, yes, but try ordering the right one, with the right number of teeth and diameter, and getting the old one off and the new one on! Nightmares!
Click to expand...

I think these will fit the e85:
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-124.html
https://www.ukpartsdirect.com/abs-reluctor-rings/bmw-abs-reluctor-rings/abs-reluctor-ring-125.html

Getting them on/off is very simple. Snip/dremel the old ones in one spot (and they spring off immediately), or tap with a chisel.
Use a steel brush (if needed on drill) and clean off the rust (or use some sandpaper or whatever)
Tap the new rings on, with a straight piece of metal until they hit the sholder.
Can be done in 15-30 min if you have the axle out. Its no big deal imho, especially the rear ones.

Faster to get new shafts. And surprisingly cheap.
.
Click to expand...
Yes, no name AFTERMARKET ones are cheap.
BMW uses special hollow large diameter shafts (especially the manual 2.5i/3.0i, they have the largest diameter: 38mm hollow (the lighter engines have thinner hollow shafts), and they are BMW only.
They are £350+, so not exactly cheap, unless you can get them used.

This is an OEM BMW driveshaft:
s-l1600.jpg

This is an aftermarket driveshaft:
?id=7206417&lng=en&n=0.jpg

Making the twin tapered hollow shaft is obviously a much more complicated process, so BMW must have thought to get some gain out of it one way or another otherwise they wouldnt have bothered with such a more expensive production procedure.

So yes, cheaper in price, but not made to OEM specs so not the same product.
Lots of aftermarket products from quality suppliers like febi are made to exactly the same design (and very often are rebadged OEM products where I've seen the bmw logo even sanded away), but regarding the driveshafts (the ones I've seen) they are not the same design.
Normally I dont mind aftermarket products, and they can even be of an improved design, like meyle HD bushings or an aluminium thermostat housing instead of the plastic ones, but with aftermarket driveshafts I dont see an improvement in a smaller diameter solid driveshaft, so I would rather look for a used one in decent condition over a cheap new one if I would need a new driveshaft (I had to change 1 out once on my car)
Click to expand...
I bought a pair of these from UKparts direct based on our recommendation and they fit perfectly. Thanks.
 
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