Very likely the Rolling Circumferences no longer match due to wrong tyres

 

^^ The man said it!! There is a reason why Mercedes recommends what it recommends

 

If the tire diameter between front and back exceeds 3%, abs etc will get triggered.

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Okay...yes, I intentionally have slightly taller tires on front P245/50 R18 for a better ride. They've been on about a year.
Previously had 265/45 R18 in back, but got tired of having ZERO protection from even the slightest curb scuff chewing into the rims! So I went with a slightly wider tire, but it also happens to be slightly shorter than the previous.

According to Tire Size Chart
Front: 245/50R18 = 27.6x9.6R18
Rear: 295/35R18 = 26.1x11.6R18

So you're telling me because I now have a front/rear tire height difference of 1.5", which results in a different rolling circumference, the computer cannot adjust it's processing to handle this?

Other than replacing tires, can I do something to mitigate this via SDS?
By the way, SDS says "Speed signal from control module ESP implausible" which supports what you've shared.

And I take it since the front/rear wheel speeds aren't congruent, the speedometer won't work at all?
Where's the logic in that?
(Face-Palm)

 

Wait!
I just figured another piece out... they put the wrong tires on the car.
I ordered 295/35 R18.
They put on 275/35 R18 = 25.6x10.8R18.
And that's a whole 2" shorter than the front!
Still... Computer should be able to adapt.
[emoji14]

 

Nothing is going to solve the problem other than getting like circumference tires on the car.

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Basically, your wheel speed sensors are causing the ABS/ESP errors due to mis-matched and incorrect tires. Oft times speed sensitive variable power steering will also tighten up in this type situation.

 

I spoke with the tire shop and they've agreed to get the correct tires ordered and put on.

I understand why the computer would complain about there being a difference in speed between the front and rear wheels, I just think it's complete shite MB choose to write the code to turn off the speedometer instead of defaulting to using the rear wheel as a the speed when things don't agree. After all, the speedometer works just fine, until I go faster than 35 mph. Then it turns off and throws the complaints. The cycle repeats when I next start the car.
But that's the German engineers for you, trying to control too many things.

 

Well, I suppose you could buy a Kia if you're unhappy with German engineering.

 

I'm curious if BMW, Porsche, Audi, and any of the other manufacturers from the same time, coded their engine management systems to disable the speedometer in the same scenario.

Kia? That's the sound I make during some of the martial arts movements. :-D

 

Forget the german cars, even american cars will throw a shitstorm if the tire size are too different. Had a 2012 Camaro not too long ago, same story. Turns out owner didn't tell us that he installed staggered 26" rims prior to us checking it out.

The ABS/ESP is tied to the drivetrain and half of the suspension, so yes the car will complain if the tire sizes are too different.

Your tires have a difference of 11%, a massive difference from the allowed 3%, so yes the car thinks shits about to hit the fan.

 

Every newer car will have an issue with different diameter tires front/rear. Some far worse than a warning message.

Some do kill the speedo, my buddie's Audi shuts down the WHOLE CAR! When the ABS sensor failed on his wife's new Q7, the car stopped moving, wouldn't shift into drive (totally electronic selector), wouldn't budge. It had to be put on a flat bed.

Because the car couldn't read the wheel speed on one wheel.

 

Audi

How dare you swear on Forum 🤣

That V.A.G. sh!t is some seriously screwed up these days

Sadly, because there are more of them in NW Highlands than there are MB's I get the pleasure of sorting a lot of the bloody things out

 

My buddy was not particularly happy when his two year old car did this.

He was even less happy when the dealer said, "Your car is fine, we can't find the fault" and two days later, it happened a second time.

So, he insisted that the service manager go for a drive in the car, with the Audi version of SDS, and sure enough, right rear wheel sensor speed was intermittent. New sensor fixed the problem.

Can't really tell you about stored codes or any of that, it wasn't my car, but we were in the middle of doing the intake flap actuator on his 2007 E350 (M272 V-6) when he told me the story...

By the way, we fixed that intake flap actuator for about $150 in parts, made by Pierburg, the OEM for lots of intake/sensor parts for MB. Dealer quote was about $2,000, for an entire new manifold + labor.

SDS to the rescue once again!

 

It just amazes me some car manufacturers basically design their vehicle to tell the driver "go fu¢π yourself" rather than to help the driver.
I'm okay with the vehicle complaining about something, but I'm not okay with it totally quitting its primary function: transport.
No ABS? Fine, keep going. I didn't have ABS 30 years ago either.
Can't tell which wheel is going the correct speed? Fine. Pick the faster one.
Just keep going.
That drive may the one to the emergency room to save your child's life! Having the car stop just because it doesn't like the tire size difference?
Utterly effing unacceptable!

I will be adding that little item to the checklist for future vehicle purchases.
If all Audis do that, totally shut down, then I'll never own an Audi again.

 

The school of hard knocks is not a tuition fee institution! That said I had a 2007 E350 Sport with staggered rims/tires.I ordered a set of tires to raise the rear of the car, and was warned by the tire store that it might affect ABS/ESP etc. They were right!!!!! Fortunately I was able to sell them with less that 5 miles on them for a $200 loss. What you are trying to do won't work until you get all 4 tires within specs for circumference to give you a dashboard that isn't all lit up like a Christmas tree. BTW any vehicle with ABS will cause issues with mismatched tires. Get tires to match the circumference needed, and your problems will go away.

 

Good luck.

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I didn't have ABS 30 years ago either.

I did.

My 1990 Mercedes-Benz 350 SDL was equipped with ABS, and that was 30 years ago. Many of today's standard automotive safety systems that are used globally were pioneered by Mercedes-Benz decades ago.

 

Okay, I'm curious. My buddy's 2002 S430 had staggered wheels/tires with run-flat tires when he bought it. He discovered some negatives in that setup, such as a rough ride and very short tire life. He found two of the larger wheels that matched, and put on standard Michelins that were the same size all-round. His car never complained at all. Were the staggered tires within 3%?

You can adjust for tire size in the instrument cluster, but AFAIK, that is for all four...

 

A little off topic, and the master minds are well above my knowledge here, but want to share last winter I pulled the staggared S500 OEM wheels off, and replaced them with four unstaggard wheels for the winter (snow tires). Essentially went from the staggard wheel setup to the 4matic wheel setup.

No issues, no errors, did not have to program or change a single thing, worked flawlessly. When I went back to the summer staggard setup, no issues again.

 

@4DGeorge .................

So you decide not to follow the manufacturers recommended tyre sizes, and now you blame that manufacturer because the Tyres dont work on your car 🤣

OK, so never mind MB recommended Tyre sizes .........................

It doesn't matter what Tyres you fit as long as the Rolling Circumferences are within 3%, and the closer the better, but even if they match each other but are way off the recommendations things like your Speedo and Fuel Mileage computer will be off, of course they will

@wallyp ..............

Mercedes use Staggered set ups, I have them on my W220, W212 and on my R170, but if you use one of the standard sizes quoted for the vehicle then yes you can adjust some in the Cluster, others by Version Coding. The car in Wally's question either had one of the stock recommendations or they were within 3% of each other, but just because he had no issues, (if they were not recommended sizes), his speedo and trip computer etc would have likely been inaccurate !!

 

@MikeKerr

That is because your Tyres matched in rolling circumference, and if your speedo etc was still spot on that is because they were the same Rolling Circumference as the Tyres taken off, without going into too much more time, it is called the U Number in your Version Codings, which basically means how far the Car travels per revolution of the Wheels

 

This is the Dynamic Rolling Circumference (Tyre) Version Codings, (U Numbers) in an ME ECU



To quote from another choice post on this forum today "Gobbledegook" .....................

Which to those of us who understand how these Cars actually work means "Important" stuff

 

The staggered tires set-ups that Mercedes chose are dead on for diameter. e.g. 245/45R18 and 265/40R18 for an AMG package have the exact same diameter, so no ABS/warning issues...

 

The staggered tires set-ups that Mercedes chose are dead on for diameter. e.g. 245/45R18 and 265/40R18 for an AMG package have the exact same diameter, so no ABS/warning issues...

Just another example of fine German engineering...

 

@Dave2302 I'm not the one who put the wrong sized tires on the car. The tire shop did that by misreading a 9 as a 7 which resulted in an inch shorter tire. An easy mistake on anyone's part. But I had specifically selected a tire that was very close to the OEM height as well as matching the existing front tires. I won't be in this predicament after the correct tires come in.
My only blame or rant towards MB or other manufacturers is their decision to completely disable the vehicle for something that is technically trivial in the grand scheme.
And no, my vehicle doesn't get disabled, but the speedo does turn off after a while each time. There's no NEED for them to do that. Even if the speedometer is wrong, all they should do is throw an error flag and leave it working as is. Even if they made it read 30 mph FASTER just to make it clear to the driver it is no longer accurate, it would still be available as a "guage" to judge speed with.

And as for the piece where they completely disable the vehicle?!? I mean think about the potential consequences of that? You get a flat driving on the freeway, pull over and put on a spare tire, only to have the car shut off just as you're getting up to speed and back on the freeway! Accident waiting to happen - lives at stake - over a misreading of speed between front and rear tires? That's a horrific design decision!
What if I decide to "light'em up" and go drifting a little bit, spinning the rear tires wildly, the car doesn't totally shut down then, it just keeps on sliding and spinning. And yet the front tire speed doesn't match the rear speed by a huge margin.
Can you imagine that kind of design decision process onboard an aircraft? "Oh crap! The #1 engine's RPMs aren't matching the #2 engine's RPMs, we're not going to be able to accurately judge yaw thrust input. Okay...shut off the aircraft!" (plane falls from sky)
I can think of numerous other pieces where it would be appropriate to shut the engine off to prevent it from cratering and destroying itself. But not just because there's an error within a non-life-support-critical system.
If I unplugged the oil pressure gauge connectors, would the vehicle shut itself off and require being towed? Air bag connectors? Brake pad wear sensors?

I guess I'm just in a mood today.

I have a funeral to attend in a few hours. My Mother-in-law passed away last weekend. COVID is suspected as the trigger culprit.
My two sons (10 and 7) haven't yet realized what it all means. But I'm sure by the end of the day, it'll hit them. And I'm dreading that for them.

 

You get a flat driving on the freeway, pull over and put on a spare tire, only to have the car shut off just as you're getting up to speed

You'll find out that nearly all manufacturers account for that.... In cars that come with spare tires, anyway. Every single one, from Honda up all the way to Porsche, the spare tire is carefully selected based on the current tire size.

Ever wonder why trucks like F150's and Tahoe's basically had full size spare tires? This is why. Space saver spare tires don't really exist at that size needed.

Audi and Subaru take it a step further, depending on the AWD setup, the spare tire is meant to go to either front or rear to minimize the difference in rolling circumference. Audi recommends the front, and if a rear tire gets flat, you're supposed to swap a good front tire into rear, and then install spare to front.

Same with Subaru, except it's to the rear and you're supposed to disable the AWD with either the knob or pulling the fuse.

The days of having full size spare tires are long gone. I think my car is the last MB with full size spare.... To put it in a German mindset, I can drive at 150mph, get a flat, pull over, swap with spare, and then continue at 150mph to my destination.

Can't do that with space saving spares nowadays.

 

My condolences to you and your family.

MB's don't completely disable the vehicle though. You can still complete whatever journey, unlike the dumb arsed V.A.G. vehicles.

And the correct MB Spare Wheel is the correct Dynamic Rolling Circumference

I am actually using 275 / 40 x 18 rears and 245 / 45 x 18 fronts with no issue on my staggered AMG Set up because they are close enough and I have made certain all the U figures are correctly coded for that (factory) set up

Those Tyres that were fitted by a so called Pro Tyre Shop are a mile apart, and they should have known that

This isn't something that has just happened, ABS / ESP systems have been around for at least 30 years and over the last 20 the Electronics have become more sophoisticated, so much so that my 2015 W212 wagon doesn't need TPMS Valves fitted, it's factory TPMS, (now dubbed "Run Flat") is now done by measuring the minute difference in rotational speeds when a Wheel / Tyre starts losing air ...............

That my friends is a sensitive system

The ESP doesn't work like that when drifting BTW, it knows how much intervention to give by a whole heap of parameters, Road Speed, Pitch and Yaw inputs from the G Sensors, Throttle Position, Steering Angle etc etc.

Drive Safely later on

 

Thank you for the thoughts. They are appreciated.

Got to learn a few more things today, during the 86 mile, each way, trip.
After the the few minutes required before the ESP system turns off the speedometer, I noticed another utter failing in MB's decision logic:
The odometer does NOT increment while the speedometer is turned off.
Although I drove over 177 miles, only a few have registered on the odometer. Now my mileage is officially wrong.
I'm sure this particular issue, mismatched tire sizes, is not a highly common problem for most drivers, but it really chaps my a$$ MB would make such a crappy decision to turn off the speedo, and the other systems, instead of merely flagging the problem and leaving the other pieces operable. Especially when they don't make it possible for us to change that setting within SDS.
(Unless I misunderstood that it IS possible to change it?)

 

Thank you for the thoughts. They are appreciated.

Got to learn a few more things today, during the 86 mile, each way, trip.
After the the few minutes required before the ESP system turns off the speedometer, I noticed another utter failing in MB's decision logic:
The odometer does NOT increment while the speedometer is turned off.
Although I drove over 177 miles, only a few have registered on the odometer. Now my mileage is officially wrong.
I'm sure this particular issue, mismatched tire sizes, is not a highly common problem for most drivers, but it really chaps my a$$ MB would make such a crappy decision to turn off the speedo, and the other systems, instead of merely flagging the problem and leaving the other pieces operable. Especially when they don't make it possible for us to change that setting within SDS.
(Unless I misunderstood that it IS possible to change it?)

Hmmm it’s way too late for a w220 lease , but that could be an interesting quirk to take advantage of to keep recorded mileage low!!