Tyre Monitor algorithm Two flats

[1afc]

Hi New to MB and new to forum so sorry if dumb question. (Have searched but not found answer)

I have a 2007 ML320 CDI which uses the ABS sensor to compare rotational speeds and therefore determine variations in rolling radius.

However, I ran the right hand tyres over an obstacle in the road and staked both front and rear tyre. Both tyres deflated over about 8km (5 miles) but the tyre monitor did not indicate a flat. Luckily I caught the problem before wrecking the rims.

I took the car to the MB dealer asking to check the sensors and they said all ok. I know the system works for a single flat and it it highlighted a problem over about 1.5 miles.

I asked about the program to compare and they said it compared all four tyres not across an axle or one side to the other.

Two tyres going flat out of four I would have thought would have been enough of a problem.

They then said that it may take time (certain distance) for the system to work out the problem but had no real idea how it worked.

Can anyone shed light on how two flats on one side was not detected.

Thanks for you rforum.

Regards
1afc

 

[kth286]

what warning lights came up on the dash ?

Is tyre deflation warning an option on your car or is it a standard feature?

If it is an option how do you know you have that option ?

ABS is antilock braking and ESP is a development onto ABS.

It would be ESP part that is used.

 

[1afc]

Hi kth286

what warning lights came up on the dash ? - None

Is tyre deflation warning an option on your car or is it a standard feature? - Standard

If it is an option how do you know you have that option ? Has shown deflation of other tyres.

Hope this helps

 

[kth286]

how was the warning shown on previous ocassion ?

 

[1afc]

Red text in screen between main instruments.

 

[1afc]

Red text in Odometer screen between speedo and tacho.

(Sorry double post)

 

[kth286]

did that reset itself when tyre replaced OR was it reset via star diagnostics ?

Perhaps they turned the function off via star diagnostics by mistake.

we need a star expert on here for this - one will probably be along shortly.

 

[1afc]

Reset

It was reset via the "R"eset button top centre of dash. and the indication actually happened before (when I changed tyre pressures on one axle) and after when I limped home from the double puncture as I only had one spare and had to inflate the least damaged tyre.

 

[donubenz]

If you have the tyre pressure read out system then look at the rims. The tyre pressure sender has a much more rigid bolted down valve instead of the standard rubber pushed in valve.
The standard warning uses the cars computer to count the revs of the tyre/mile. If you have a flat then it counts more and flags up the warning.
I would have thought that you should get some warning particularly with 2 flats! Hope your rims are OK
Don

 

[1afc]

Thanks Don
No pressure sensors just the revs/mile.

Yes I would have thought it would show up as well and MB dealer here has no idea so I thought I'd ask the question.
Alan

 

[markjay]

The only (and very general) input I can offer is that the EPS-based tyre monitong system is rather crude and not as accurte as the valve/sensor based one. However, it cost nothing as it is already there (although in the past dealer used to charge £50 to have it activated on the computer), and as such it is better to have it than not to, but I would not be surprised if it can not be 100% relied on to correctly identify flats in every situation.